# The XML C parser and toolkit of Gnome

# Note: this is the flat content of the website

# libxml, a.k.a. gnome-xml

"Programmingwithlibxml2 is like the thrilling embrace of an exotic stranger." MarkPilgrim

Libxml2 is the XML C parser and toolkit developed for the Gnomeproject(but usable outside of the Gnome platform), it is free softwareavailableunder the MITLicense.XML itself is a metalanguage to design markup languages, i.e.text languagewhere semantic and structure are added to the content usingextra "markup"information enclosed between angle brackets. HTML is the mostwell-knownmarkup language. Though the library is written in C avariety of language bindingsmake it available inother environments.

Libxml2 is known to be very portable, the library should build andworkwithout serious troubles on a variety of systems (Linux, Unix,Windows,CygWin, MacOS, MacOS X, RISC Os, OS/2, VMS, QNX, MVS, ...)

Libxml2 implements a number of existing standards related tomarkuplanguages:

- the XML standard: http://www.w3.org/TR/REC-xml
- Namespaces in XML: http://www.w3.org/TR/REC-xml-names/
- XML Base: http://www.w3.org/TR/xmlbase/
- RFC2396:Uniform Resource Identifiers http://www.ietf.org/rfc/rfc2396.txt
- XML Path Language (XPath) 1.0: http://www.w3.org/TR/xpath
- HTML4 parser: http://www.w3.org/TR/html401/
- XML Pointer Language (XPointer) Version 1.0: http://www.w3.org/TR/xptr
- XML Inclusions (XInclude) Version 1.0: http://www.w3.org/TR/xinclude/
- ISO-8859-x encodings, as well as rfc2044[UTF-8]andrfc2781[UTF-16]Unicode encodings, and more if using iconv support
- part of SGML Open Technical Resolution TR9401:1997
- XML Catalogs Working Draft 06 August 2001: http://www.oasis-open.org/committees/entity/spec-2001-08-06.html
- Canonical XML Version 1.0: http://www.w3.org/TR/xml-c14nandthe Exclusive XML Canonicalization CR draft http://www.w3.org/TR/xml-exc-c14n
- Relax NG, ISO/IEC 19757-2:2003, http://www.oasis-open.org/committees/relax-ng/spec-20011203.html
- W3C XML Schemas Part 2: Datatypes REC 02May2001
- W3C xml:idWorking Draft7April 2004

In most cases libxml2 tries to implement the specifications in arelativelystrictly compliant way. As of release 2.4.16, libxml2 passed all1800+ testsfrom the OASIS XMLTestsSuite.

To some extent libxml2 provides support for the followingadditionalspecifications but doesn't claim to implement them completely:

- Document Object Model (DOM) http://www.w3.org/TR/DOM-Level-2-Core/thedocument model, but it doesn't implement the API itself, gdome2 doesthison top of libxml2
- RFC959:libxml2 implements a basic FTP client code
- RFC1945:HTTP/1.0, again a basic HTTP client code
- SAX: a SAX2 like interface and a minimal SAX1 implementationcompatiblewith early expat versions

A partial implementation of XML Schemas Part1:Structureis being worked on but it would be far too early to makeanyconformance statement about it at the moment.

Separate documents:

- the libxslt pageprovidinganimplementation of XSLT 1.0 and common extensions like EXSLTforlibxml2
- the gdome2 page:a standard DOM2 implementation for libxml2
- the XMLSec page:animplementation of W3CXMLDigital Signaturefor libxml2
- also check the related links section below for more related andactiveprojects.

Logo designed by Marc Liyanage.

## Introduction

This document describes libxml, the XMLC parser and toolkit developed for theGnomeproject. XML is a standardfor buildingtag-basedstructured documents/data.

Here are some key points about libxml:

- Libxml2 exports Push (progressive) and Pull (blocking) typeparserinterfaces for both XML and HTML.
- Libxml2 can do DTD validation at parse time, using a parseddocumentinstance, or with an arbitrary DTD.
- Libxml2 includes complete XPath, XPointerand XIncludeimplementations.
- It is written in plain C, making as few assumptions as possible,andsticking closely to ANSI C/POSIX for easy embedding. WorksonLinux/Unix/Windows, ported to a number of other platforms.
- Basic support for HTTP and FTP client allowing applications tofetchremote resources.
- The design is modular, most of the extensions can be compiled out.
- The internal document representation is as close as possible to the DOMinterfaces.
- Libxml2 also has a SAX like interface;theinterface is designed to be compatible with Expat.
- This library is released under the MITLicense.See the Copyright file in the distribution for the precisewording.

Warning: unless you are forced to because your application links withaGnome-1.X library requiring it, Do Not Use libxml1,uselibxml2

## FAQ

Table of Contents:

- License(s)
- Installation
- Compilation
- Developer corner

### License(s)

1. Licensing Terms for libxml

   libxml2 is released under the MITLicense;see the file Copyright in the distribution for the precisewording

2. Can I embed libxml2 in a proprietary application ?

   Yes. The MIT License allows you to keep proprietary the changesyoumade to libxml, but it would be graceful to send-back bug fixesandimprovements as patches for possible incorporation in themaindevelopment tree.

### Installation

1. Do NotUselibxml1, use libxml2
2. Where can I get libxml?

   The original distribution comes from xmlsoft.orgor gnome.org

   Most Linux and BSD distributions include libxml, this is probablythesafer way for end-users to use libxml.

   David Doolin provides precompiled Windows versions at http://www.ce.berkeley.edu/~doolin/code/libxmlwin32/

3. I see libxml and libxml2 releases, which one should I install ?
   - If you are not constrained by backward compatibility issueswithexisting applications, install libxml2 only
   - If you are not doing development, you can safely installboth.Usually the packages libxmland libxml2arecompatible(this is not the case for development packages).
   - If you are a developer and your system provides separatepackagingfor shared libraries and the development components, it ispossibleto install libxml and libxml2, and also libxml-develandlibxml2-develtoofor libxml2 >= 2.3.0
   - If you are developing a new application, please developagainstlibxml2(-devel)
4. I can't install the libxml package, it conflicts with libxml0

   You probably have an old libxml0 package used to provide thesharedlibrary for libxml.so.0, you can probably safely remove it. Thelibxmlpackages provided on xmlsoft.orgprovidelibxml.so.0

5. I can't install the libxml(2) RPM package due tofaileddependencies

   The most generic solution is to re-fetch the latest src.rpm ,andrebuild it locally with

   `rpm --rebuild libxml(2)-xxx.src.rpm`.

   If everything goes well it will generate two binary rpm packages(oneproviding the shared libs and xmllint, and the other one, the-develpackage, providing includes, static libraries and scripts needed tobuildapplications with libxml(2)) that you can install locally.

### Compilation

1. What is the process to compile libxml2 ?

   As most UNIX libraries libxml2 follows the "standard":

   `gunzip -c xxx.tar.gz | tar xvf -`

   `cd libxml-xxxx`

   `./configure --help`

   to see the options, then the compilation/installation proper

   `./configure [possible options]`

   `make`

   `make install`

   At that point you may have to rerun ldconfig or a similar utilitytoupdate your list of installed shared libs.

2. What other libraries are needed to compile/install libxml2 ?

   Libxml2 does not require any other library, the normal C ANSIAPIshould be sufficient (please report any violation to this rule youmayfind).

   However if found at configuration time libxml2 will detect and usethefollowing libs:

   - libz:ahighly portable and available widely compression library.
   - iconv: a powerful character encoding conversion library. Itisincluded by default in recent glibc libraries, so it doesn't needtobe installed specifically on Linux. It now seems a partofthe official UNIXspecification. Here is one implementation ofthelibrarywhich source can be found here.
3. Make check fails on some platforms

   Sometimes the regression tests' results don't completely matchthevalue produced by the parser, and the makefile uses diff to printthedelta. On some platforms the diff return breaks the compilationprocess;if the diff is small this is probably not a serious problem.

   Sometimes (especially on Solaris) make checks fail due tolimitationsin make. Try using GNU-make instead.

4. I use the CVS version and there is no configure script

   The configure script (and other Makefiles) are generated. Usetheautogen.sh script to regenerate the configure script andMakefiles,like:

   `./autogen.sh --prefix=/usr --disable-shared`

5. I have troubles when running make tests with gcc-3.0

   It seems the initial release of gcc-3.0 has a problem withtheoptimizer which miscompiles the URI module. Please useanothercompiler.

### Developercorner

1. Troubles compiling or linking programs using libxml2

   Usually the problem comes from the fact that the compiler doesn'tgetthe right compilation or linking flags. There is a small shellscript`xml2-config`which is installed as part of libxml2usualinstall process which provides those flags. Use

   `xml2-config --cflags`

   to get the compilation flags and

   `xml2-config --libs`

   to get the linker flags. Usually this is done directly fromtheMakefile as:

   `CFLAGS=`xml2-config --cflags``

   `LIBS=`xml2-config --libs``

2. I want to install my own copy of libxml2 in my home directoryandlink my programs against it, but it doesn't work

   There are many different ways to accomplish this. Here is one waytodo this under Linux. Suppose your home directory is`/home/user.`Then:

   - Create a subdirectory, let's call it `myxml`
   - unpack the libxml2 distribution into that subdirectory
   - chdir into the unpacked distribution(`/home/user/myxml/libxml2`)
   - configure the library using the "`--prefix`"switch,specifying an installation subdirectoryin`/home/user/myxml`, e.g.

     `./configure --prefix/home/user/myxml/xmlinst`{otherconfiguration options}

   - now run `make`followed by `make install`
   - At this point, the installation subdirectory contains thecomplete"private" include files, library files and binary programfiles (e.g.xmllint), located in

     `/home/user/myxml/xmlinst/lib,/home/user/myxml/xmlinst/include`and `/home/user/myxml/xmlinst/bin`

     respectively.
   - In order to use this "private" library, you should first add ittothe beginning of your default PATH (so that your own privateprogramfiles such as xmllint will be used instead of the normalsystemones). To do this, the Bash command would be

     `export PATH=/home/user/myxml/xmlinst/bin:$PATH`

   - Now suppose you have a program `test1.c`that youwouldlike to compile with your "private" library. Simply compile itusingthe command

     `gcc `xml2-config --cflags --libs` -o test test.c`

     Note that, because your PATH has been set with`/home/user/myxml/xmlinst/bin`at the beginning, thexml2-configprogram which you just installed will be used instead ofthe systemdefault one, and this will automaticallyget thecorrectlibraries linked with your program.

3. xmlDocDump() generates output on one line.

   Libxml2 will not inventspaces in the content ofadocument since all spaces in the content of a documentaresignificant. If you build a tree from the API andwantindentation:

   1. the correct way is to generate those yourself too.
   2. the dangerous way is to ask libxml2 to add those blanks toyourcontent modifying the content of your document intheprocess. The result may not be what you expect. ThereisNOway to guarantee that such a modificationwon'taffect other parts of the content of your document. See xmlKeepBlanksDefault()andxmlSaveFormatFile()
4. Extra nodes in the document:

   For a XML file as below:

       <?xml version="1.0"?>
       <PLAN xmlns="http://www.argus.ca/autotest/1.0/">
       <NODE CommFlag="0"/>
       <NODE CommFlag="1"/>
       </PLAN>

   after parsing it with thefunctionpxmlDoc=xmlParseFile(...);

   I want to the get the content of the first node (node withtheCommFlag="0")

   so I did it as following;

       xmlNodePtr pnode;
       pnode=pxmlDoc->children->children;

   but it does not work. If I change it to

       pnode=pxmlDoc->children->children->next;

   then it works. Can someone explain it to me.

   In XML all characters in the content of the document aresignificantincluding blanks and formatting linebreaks.

   The extra nodes you are wondering about are just that, text nodeswiththe formatting spaces which are part of the document but that peopletendto forget. There is a function xmlKeepBlanksDefault()toremove those at parse time, but that's an heuristic, and itsuse should belimited to cases where you are certain there is nomixed-content in thedocument.

5. I get compilation errors of existing code like whenaccessingrootor child fieldsofnodes.

   You are compiling code developed for libxml version 1 and usingalibxml2 development environment. Either switch back to libxml v1 develoreven better fix the code to compile with libxml2 (or both) by following the instructions.

6. I get compilation errors about nonexistingxmlRootNodeorxmlChildrenNodefields.

   The source code you are using has been upgradedto be able to compile with both libxmlandlibxml2, but you need to install a more recent version:libxml(-devel)>= 1.8.8 or libxml2(-devel) >= 2.1.0

7. XPath implementation looks seriously broken

   XPath implementation prior to 2.3.0 was really incomplete. Upgrade toarecent version, there are no known bugs in the current version.

8. The example provided in the web page does not compile.

   It's hard to maintain the documentation in sync with thecode<grin/> ...

   Check the previous points 1/ and 2/ raised before, and pleasesendpatches.

9. Where can I get more examples and information than provided ontheweb page?

   Ideally a libxml2 book would be nice. I have no such plan ... Butyoucan:

   - check more deeply the existinggenerated doc
   - have a look at the setofexamples.
   - look for examples of use for libxml2 function using the Gnomecode.For example the following will query the full Gnome CVS base fortheuse of the xmlAddChild()function:

     http://cvs.gnome.org/lxr/search?string=xmlAddChild

     This may be slow, a large hardware donation to the gnomeprojectcould cure this :-)

   - Browsethelibxml2 source, I try to write code as clean and documentedaspossible, so looking at it may be helpful. In particular the codeofxmllint.c and of the various testXXX.c test programs shouldprovidegood examples of how to do things with the library.
10. What about C++ ?

    libxml2 is written in pure C in order to allow easy reuse on anumberof platforms, including embedded systems. I don't intend to converttoC++.

    There is however a C++ wrapper which may fulfill your needs:

    - by Ari Johnson <ari@btigate.com>:

      Website: http://libxmlplusplus.sourceforge.net/

      Download: http://sourceforge.net/project/showfiles.php?group_id=12999

11. How to validate a document a posteriori ?

    It is possible to validate documents which had not been validatedatinitial parsing time or documents which have been built fromscratchusing the API. Use the xmlValidateDtd()function.It is also possible to simply add a DTD to an existingdocument:

        xmlDocPtr doc; /* your existing document */
        xmlDtdPtr dtd = xmlParseDTD(NULL, filename_of_dtd); /* parse the DTD */

                dtd->name = xmlStrDup((xmlChar*)"root_name"); /* use the given root */

                doc->intSubset = dtd;
                if (doc->children == NULL) xmlAddChild((xmlNodePtr)doc, (xmlNodePtr)dtd);
                else xmlAddPrevSibling(doc->children, (xmlNodePtr)dtd);

12. So what is this funky "xmlChar" used all the time?

    It is a null terminated sequence of utf-8 characters. And onlyutf-8!You need to convert strings encoded in different ways to utf-8beforepassing them to the API. This can be accomplished with the iconvlibraryfor instance.

13. etc ...

## Developer Menu

There are several on-line resources related to using libxml:

1. Use the search engineto lookupinformation.
2. Check the FAQ.
3. Check the extensivedocumentationautomaticallyextracted from code comments.
4. Look at the documentation about libxmlinternationalization support.
5. This page provides a global overview and someexampleson how to use libxml.
6. Code examples
7. John Fleck's libxml2 tutorial: htmlorpdf.
8. If you need to parse large files, check the xmlReaderAPI tutorial
9. James Henstridgewrote somenicedocumentationexplaining how to use the libxml SAX interface.
10. George Lebl wrote anarticlefor IBM developerWorksabout using libxml.
11. Check theTODOfile.
12. Read the 1.x to 2.x upgrade pathdescription.If you are starting a new project using libxml you shouldreally use the2.x version.
13. And don't forget to look at the mailing-list archive.

## Reporting bugs and getting help

Well, bugs or missing features are always possible, and I will make apointof fixing them in a timely fashion. The best way to report a bug is touse theGnomebugtracking database(make sure to use the "libxml2" module name). Ilook atreports there regularly and it's good to have a reminder when a bugis stillopen. Be sure to specify that the bug is for the package libxml2.

For small problems you can try to get help on IRC, the #xml channelonirc.gnome.org (port 6667) usually have a few person subscribed which mayhelp(but there is no garantee and if a real issue is raised it should go onthemailing-list for archival).

There is also a mailing-list xml@gnome.orgfor libxml, with an on-line archive(old). To subscribe to this list,pleasevisit the associatedWebpage andfollow the instructions. Do not send code, I won'tdebug it(but patches are really appreciated!).

Please note that with the current amount of virus and SPAM, sending mailtothe list without being subscribed won't work. There is *far too manybounces*(in the order of a thousand a day !) I cannot approve them manuallyanymore.If your mail to the list bounced waiting for administrator approval,it isLOST ! Repost it and fix the problem triggering the error. Also pleasenotethat emails withalegal warning asking to not copy or redistribute freely the informationstheycontainare NOTacceptable for the mailing-list,suchmail will as much as possible be discarded automatically, and are lesslikelyto be answered if they made it to the list, DO NOTpost tothe list from an email address where such legal requirements areautomaticallyadded, get private paying support if you can't shareinformations.

Check the following beforeposting:

- Read the FAQand usethesearch engineto get information related to your problem.
- Make sure you are using arecentversion, and that the problem still shows up in a recentversion.
- Check the listarchivesto see if theproblem was reported already. In this casethere is probably a fixavailable, similarly check the registeredopenbugs.
- Make sure you can reproduce the bug with xmllint or one of thetestprograms found in source in the distribution.
- Please send the command showing the error as well as the input (asanattachment)

Then send the bug with associated information to reproduce it to the xml@gnome.orglist; if it's reallylibxmlrelated I will approve it. Please do not send mail to me directly, itmakesthings really hard to track and in some cases I am not the best persontoanswer a given question, ask on the list.

To be really clear about support:

- Support or help requests MUST be senttothe list or on bugzillain case of problems, so that theQuestionand Answers can be shared publicly. Failing to do so carries theimplicitmessage "I want free support but I don't want to share thebenefits withothers" and is not welcome. I will automatically Carbon-Copythexml@gnome.org mailing list for any technical reply made about libxml2orlibxslt.
- There is no garantee of support,ifyour question remains unanswered after a week, repost it, making sureyougave all the detail needed and the information requested.
- Failing to provide information as requested or double checking firstforprior feedback also carries the implicit message "the time of thelibrarymaintainers is less valuable than my time" and might not bewelcome.

Of course, bugs reported with a suggested patch for fixing themwillprobably be processed faster than those without.

If you're looking for help, a quick look at the list archivemayactuallyprovide the answer. I usually send source samples when answeringlibxml2usage questions. The auto-generateddocumentationisnot as polished as I would like (i need to learn moreabout DocBook), butit's a good starting point.

## How to help

You can help the project in various ways, the best thing to do first istosubscribe to the mailing-list as explained before, check the archives and the Gnomebugdatabase:

1. Provide patches when you find problems.
2. Provide the diffs when you port libxml2 to a new platform. They maynotbe integrated in all cases but help pinpointing portabilityproblemsand
3. Provide documentation fixes (either as patches to the code commentsoras HTML diffs).
4. Provide new documentations pieces (translations, examples, etc...).
5. Check the TODO file and try to close one of the items.
6. Take one of the points raised in the archive or the bug databaseandprovide a fix. Get in touch withmebefore to avoid synchronization problems and check that thesuggestedfix will fit in nicely :-)

## Downloads

The latest versions of libxml2 can be found on the xmlsoft.orgserver ( HTTP, FTPand rsync are available), there isalsomirrors (Australia(Web), France) or on the Gnome FTP serveras source archive,Antonin Sprinzl also provide amirror in Austria. (NOTE thatyou need both the libxml(2)and libxml(2)-develpackagesinstalled to compile applications using libxml.)

You can find all the history of libxml(2) and libxslt releases in the olddirectory. TheprecompiledWindows binaries made by Igor Zlatovic are available in the win32directory.

Binary ports:

- Red Hat RPMs for i386 are available directly on xmlsoft.org, the source RPM willcompile onany architecture supported by Red Hat.
- Igor Zlatkovicis nowthemaintainer of the Windows port, heprovidesbinaries.
- Blastwave provides Solarisbinaries.
- Steve Ballprovides Mac OsXbinaries.
- The HP-UX porting center provides HP-UX binaries
- Bull provides precompiled RPMs forAIXaspatr of their GNOME packages

If you know other supported binary ports, please contact me.

Snapshot:

- Code from the W3C cvs base libxml2 module, updated hourly libxml2-cvs-snapshot.tar.gz.
- Docs, content of the web site, the list archive included libxml-docs.tar.gz.

Contributions:

I do accept external contributions, especially if compiling onanotherplatform, get in touch with the list to upload the package, wrappersforvarious languages have been provided, and can be found in the bindings section

Libxml2 is also available from CVS:

- The GnomeCVSbase. Check the Gnome CVS Toolspage;the CVS module is libxml2.

- The libxsltmodule is also present there

## Releases

Items not finished and worked on, get in touch with the list if you wanttohelp those

- More testing on RelaxNG
- Finishing up XMLSchemas

The change logdescribes the recents commitstothe CVScode base.

There is the list of public releases:

### 2.6.26: Jun 6 2006

- portability fixes: Python detection (Joseph Sacco), compilation error(William Brack and Graham Bennett), LynxOS patch (Olli Savia)
- bug fixes: encoding buffer problem, mix of code and data in xmlIO.c(Kjartan Maraas), entities in XSD validation (Kasimier Buchcik), variousXSD validation fixes (Kasimier), memory leak in pattern (Rob Richards andKasimier), attribute with colon in name (Rob Richards), XPath leak inerror reporting (Aleksey Sanin), XInclude text include of selfdocument.
- improvements: Xpath optimizations (Kasimier), XPath object cache(Kasimier)

### 2.6.25: Jun 6 2006:

Do not use or package 2.6.25

### 2.6.24: Apr 28 2006

- Portability fixes: configure on Windows, testapi compile onwindows(Kasimier Buchcik, venkat naidu), Borland C++ 6 compile (EricZurcher),HP-UX compiler workaround (Rick Jones), xml2-config bugfix,gcc-4.1cleanups, Python detection scheme (Joseph Sacco), UTF-8 file pathsonWindows (Roland Schwingel).
- Improvements: xmlDOMWrapReconcileNamespaces xmlDOMWrapCloneNode(KasimierBuchcik), XML catalog debugging (Rick Jones), update to Unicode4.01.
- Bug fixes: xmlParseChunk() problem in 2.6.23, xmlParseInNodeContext()onHTML docs, URI behaviour on Windows (Rob Richards), comment streamingbug,xmlParseComment (with William Brack), regexp bug fixes (DV &YouriGolovanov), xmlGetNodePath on text/CDATA (Kasimier),one Relax-NGinterleave bug, xmllint --path and --valid,XSD bugfixes (Kasimier),remove debugleft in Python bindings (Nic Ferrier), xmlCatalogAdd bug(Martin Cole),xmlSetProp fixes (Rob Richards), HTML IDness (RobRichards), a largenumber of cleanups and small fixes based on Coverityreports, bugin character ranges, Unicode tables const (Aivars Kalvans),schemasfix (Stefan Kost), xmlRelaxNGParse errordeallocation,xmlSchemaAddSchemaDoc error deallocation, error handling onunallowedcode point, ixmllint --nonet to never reach the net (GaryCoady),line break in writer after end PI (Jason Viers).
- Documentation: man pages updates and cleanups (Daniel Leidert).
- New features: Relax NG structure error handlers.

### 2.6.23: Jan 5 2006

- portability fixes: Windows (Rob Richards), getaddrinfo on Windows(KoljaNowak, Rob Richards), icc warnings (Kjartan Maraas),--with-minimumcompilation fixes (William Brack), error case handling fixon Solaris(Albert Chin), don't use 'list' as parameter name reported bySamuel DiazGarcia, more old Unices portability fixes (Albert Chin),MinGW compilation(Mark Junker), HP-UX compiler warnings (RickJones),
- code cleanup: xmlReportError (Adrian Mouat), removexmlBufferClose(Geert Jansen), unreachable code (Oleksandr Kononenko),refactoringparsing code (Bjorn Reese)
- bug fixes: xmlBuildRelativeURI and empty path (WilliamBrack),combinatory explosion and performances in regexp code, leakinxmlTextReaderReadString(), xmlStringLenDecodeEntities problem(MassimoMorara), Identity Constraints bugs and a segfault (KasimierBuchcik),XPath pattern based evaluation bugs (DV &Kasimier),xmlSchemaContentModelDump() memory leak (Kasimier), potentialleak inxmlSchemaCheckCSelectorXPath(), xmlTextWriterVSprintf() misuseofvsnprintf (William Brack), XHTML serialization fix (Rob Richards),CRLFsplit problem (William), issues with non-namespaced attributesinxmlAddChild() xmlAddNextSibling() and xmlAddPrevSibling() (RobRichards),HTML parsing of script, Python must not output to stdout (NicFerrier),exclusive C14N namespace visibility (Aleksey Sanin), XSDdataypetotalDigits bug (Kasimier Buchcik), error handling when writing toanxmlBuffer (Rob Richards), runtest schemas error not reported(HisashiFujinaka), signed/unsigned problem in date/time code (AlbertChin), fixXSI driven XSD validation (Kasimier), parsing of xs:decimal(Kasimier),fix DTD writer output (Rob Richards), leak inxmlTextReaderReadInnerXml(Gary Coady), regexp bug affecting schemas(Kasimier), configuration ofruntime debugging (Kasimier),xmlNodeBufGetContent bug on entity refs(Oleksandr Kononenko),xmlRegExecPushString2 bug (Sreeni Nair),compilation and build fixes(Michael Day), removed dependancies onxmlSchemaValidError (Kasimier), bugwith <xml:foo/>, more XPathpattern based evaluation fixes(Kasimier)
- improvements: XSD Schemas redefinitions/restrictions (KasimierBuchcik),node copy checks and fix for attribute (Rob Richards), countedtransitionbug in regexps, ctxt->standalone = -2 to indicate nostandaloneattribute was found, add xmlSchemaSetParserStructuredErrors()(KasimierBuchcik), add xmlTextReaderSchemaValidateCtxt() to API(Kasimier), handlegzipped HTTP resources (Gary Coady), addhtmlDocDumpMemoryFormat. (RobRichards),
- documentation: typo (Michael Day), libxml man page (Albert Chin),savefunction to XML buffer (Geert Jansen), small doc fix (AronStansvik),

### 2.6.22: Sep 12 2005

- build fixes: compile without schematron (Stéphane Bidoul)
- bug fixes: xmlDebugDumpNode on namespace node (Oleg Paraschenko)i,CDATApush parser bug, xmlElemDump problem with XHTML1 doc,XML_FEATURE_xxxclash with expat headers renamed XML_WITH_xxx, fix someoutput formattingfor meta element (Rob Richards), script and styleXHTML1 serialization(David Madore), Attribute derivation fixups in XSD(Kasimier Buchcik),better IDC error reports (Kasimier Buchcik)
- improvements: add XML_SAVE_NO_EMPTY xmlSaveOption (Rob Richards),addXML_SAVE_NO_XHTML xmlSaveOption, XML Schemas improvements preparingforderive (Kasimier Buchcik).
- documentation: generation of gtk-doc like docs, integrationwithdevhelp.

### 2.6.21: Sep 4 2005

- build fixes: Cygwin portability fixes (Gerrit P. Haase),callingconvention problems on Windows (Marcus Boerger), cleanups based onLinus'sparse tool, update of win32/configure.js (Rob Richards), removewarningson Windows(Marcus Boerger), compilation without SAX1, detectionof thePython binary, use $GCC inestad of $CC = 'gcc' (Andrew W.Nosenko),compilation/link with threads and old gcc, compile problem byC370 onZ/OS,
- bug fixes: http_proxy environments (Peter Breitenlohner), HTML UTF-8bug(Jiri Netolicky), XPath NaN compare bug (William Brack),htmlParseScriptpotential bug, Schemas regexp handling of spaces, Base64Schemascomparisons NIST passes, automata build error xsd:all,xmlGetNodePath fornamespaced attributes (Alexander Pohoyda), xmlSchemasforeign namespaceshandling, XML Schemas facet comparison (KupriyanovAnatolij),xmlSchemaPSimpleTypeErr error report (Kasimier Buchcik), xml:namespaceahndling in Schemas (Kasimier), empty model group in Schemas(Kasimier),wilcard in Schemas (Kasimier), URI composition (William),xs:anyType inSchemas (Kasimier), Python resolver emmitting errormessages directly,Python xmlAttr.parent (Jakub Piotr Clapa), trying tofix the file path/URIconversion, xmlTextReaderGetAttribute fix (RobRichards),xmlSchemaFreeAnnot memleak (Kasimier), HTML UTF-8serialization, streamingXPath, Schemas determinism detection problem,XInclude bug, Schemascontext type (Dean Hill), validation fix (DerekPoon),xmlTextReaderGetAttribute[Ns] namespaces (Rob Richards), Schemastype fix(Kuba Nowakowski), UTF-8 parser bug, error in encodinghandling,xmlGetLineNo fixes, bug on entities handling, entity nameextraction inerror handling with XInclude, text nodes in HTML body tags(Gary Coady),xml:id and IDness at the treee level fixes, XPath streamingpatternsbugs.
- improvements: structured interfaces for schemas and RNG errorreports(Marcus Boerger), optimization of the char data inner loopparsing(thanks to Behdad Esfahbod for the idea), schematron validationthoughnot finished yet, xmlSaveOption to omit XML declaration, keyrefmatcherror reports (Kasimier), formal expression handling code notpluggedyet, more lax mode for the HTML parser, parser XML_PARSE_COMPACToptionfor text nodes allocation.
- documentation: xmllint man page had --nonet duplicated

### 2.6.20: Jul 10 2005

- build fixes: Windows build (Rob Richards), Mingw compilation(IgorZlatkovic), Windows Makefile (Igor), gcc warnings (Kasimierandandriy@google.com), use gcc weak references to pthread to avoidthepthread dependancy on Linux, compilation problem (Steve Nairn),compilingof subset (Morten Welinder), IPv6/ss_family compilation (WilliamBrack),compilation when disabling parts of the library, standalonetestdistribution.
- bug fixes: bug in lang(), memory cleanup on errors (William Brack),HTTPquery strings (Aron Stansvik), memory leak in DTD (William),integeroverflow in XPath (William), nanoftp buffer size, pattern "." apthfixup(Kasimier), leak in tree reported by Malcolm Rowe, replaceNodepatch(Brent Hendricks), CDATA with NULL content (Mark Vakoc), xml:basefixupon XInclude (William), pattern fixes (William), attribute buginexclusive c14n (Aleksey Sanin), xml:space and xml:lang with SAX2(RobRichards), namespace trouble in complex parsing (Malcolm Rowe), XSDtypeQNames fixes (Kasimier), XPath streaming fixups (William), RelaxNGbug(Rob Richards), Schemas for Schemas fixes (Kasimier), removal of ID(RobRichards), a small RelaxNG leak, HTML parsing in push mode bug(JamesBursa), failure to detect UTF-8 parsing bugs in CDATAsections,areBlanks() heuristic failure, duplicate attributes in DTDbug(William).
- improvements: lot of work on Schemas by Kasimier Buchcik bothonconformance and streaming, Schemas validation messages (KasimierBuchcik,Matthew Burgess), namespace removal at the python level(BrentHendricks), Update to new Schemas regression tests fromW3C/Nist(Kasimier), xmlSchemaValidateFile() (Kasimier), implementationofxmlTextReaderReadInnerXml and xmlTextReaderReadOuterXml (JamesWert),standalone test framework and programs, new DOM importAPIsxmlDOMWrapReconcileNamespaces() xmlDOMWrapAdoptNode()andxmlDOMWrapRemoveNode(), extension of xmllint capabilities for SAXandSchemas regression tests, xmlStopParser() available in pull modetoo,ienhancement to xmllint --shell namespaces support, Windows port ofthestandalone testing tools (Kasimier andWilliam),xmlSchemaValidateStream() xmlSchemaSAXPlug() andxmlSchemaSAXUnplug() SAXSchemas APIs, Schemas xmlReader support.

### 2.6.19: Apr 02 2005

- build fixes: drop .la from RPMs, --with-minimum build fix(WilliamBrack), use XML_SOCKLEN_T instead of SOCKLEN_T because it breakswith AIX5.3 compiler, fixed elfgcchack.h generation and PLT reductioncode onLinux/ELF/gcc4
- bug fixes: schemas type decimal fixups (William Brack), xmmlintreturncode (Gerry Murphy), small schemas fixes (Matthew Burgess andGUYFabrice), workaround "DAV:" namespace brokeness in c14n (AlekseySanin),segfault in Schemas (Kasimier Buchcik), Schemas attributevalidation(Kasimier), Prop related functions and xmlNewNodeEatName (RobRichards),HTML serialization of name attribute on a elements, Pythonerror handlersleaks and improvement (Brent Hendricks), uninitializedvariable inencoding code, Relax-NG validation bug, potential crashifgnorableWhitespace is NULL, xmlSAXParseDoc and xmlParseDocsignatures,switched back to assuming UTF-8 in case no encoding is givenatserialization time
- improvements: lot of work on Schemas by Kasimier Buchcik onfacetschecking and also mixed handling.

### 2.6.18: Mar 13 2005

- build fixes: warnings (Peter Breitenlohner), testapi.cgeneration,Bakefile support (Francesco Montorsi), Windows compilation(Joel Reed),some gcc4 fixes, HP-UX portability fixes (Rick Jones).
- bug fixes: xmlSchemaElementDump namespace (Kasimier Buchcik), pushandxmlreader stopping on non-fatal errors, thread support fordictionnariesreference counting (Gary Coady), internal subset and pushproblem, URLsaved in xmlCopyDoc, various schemas bug fixes (Kasimier),Python pathsfixup (Stephane Bidoul), xmlGetNodePath and namespaces,xmlSetNsProp fix(Mike Hommey), warning should not count as error (WilliamBrack),xmlCreatePushParser empty chunk, XInclude parser flags (William),cleanupFTP and HTTP code to reuse the uri parsing and IPv6(William),xmlTextWriterStartAttributeNS fix (Rob Richards),XMLLINT_INDENT beingempty (William), xmlWriter bugs (Rob Richards),multithreading on Windows(Rich Salz), xmlSearchNsByHref fix (Kasimier),Python binding leak (BrentHendricks), aliasing bug exposed by gcc4 ons390, xmlTextReaderNext bug(Rob Richards), Schemas decimal type fixes(William Brack),xmlByteConsumed static buffer (Ben Maurer).
- improvement: speedup parsing comments and DTDs, dictionnary supportforhash tables, Schemas Identity constraints (Kasimier), streamingXPathsubset, xmlTextReaderReadString added (Bjorn Reese), Schemascanonicalvalues handling (Kasimier), add xmlTextReaderByteConsumed(AronStansvik),
- Documentation: Wiki support (Joel Reed)

### 2.6.17: Jan 16 2005

- build fixes: Windows, warnings removal (William Brack),maintainer-cleandependency(William), build in a different directory(William), fixing--with-minimum configure build (William), BeOS build(Marcin Konicki),Python-2.4 detection (William), compilation on AIX (DanMcNichol)
- bug fixes: xmlTextReaderHasAttributes (Rob Richards),xmlCtxtReadFile()to use the catalog(s), loop on output (William Brack),XPath memory leak,ID deallocation problem (Steve Shepard), debugDumpNodecrash (William),warning not using error callback (William), xmlStopParserbug (William),UTF-16 with BOM on DTDs (William), namespace bug on emptyelements inpush mode (Rob Richards), line and col computations fixups(AlekseySanin), xmlURIEscape fix (William), xmlXPathErr on bad range(William),patterns with too many steps, bug in RNG choice optimization,line numbersometimes missing.
- improvements: XSD Schemas (Kasimier Buchcik), pythongenerator(William), xmlUTF8Strpos speedup (William), unicode Pythonstrings(William), XSD error reports (Kasimier Buchcik), Python __str__callserialize().
- new APIs: added xmlDictExists(), GetLineNumber and GetColumnNumberforthe xmlReader (Aleksey Sanin), Dynamic Shared Libraries APIs (mostlyJoelReed), error extraction API from regexps, new XMLSave option forformat(Phil Shafer)
- documentation: site improvement (John Fleck), FAQ entries(William).

### 2.6.16: Nov 10 2004

- general hardening and bug fixing crossing all the API based onnewautomated regression testing
- build fix: IPv6 build and test on AIX (Dodji Seketeli)
- bug fixes: problem with XML::Libxml reported by Petr Pajas,encodingconversion functions return values, UTF-8 bug affecting XPathreported byMarkus Bertheau, catalog problem with NULL entries (WilliamBrack)
- documentation: fix to xmllint man page, some API functiondescritpionwere updated.
- improvements: DTD validation APIs provided at the Python level(BrentHendricks)

### 2.6.15: Oct 27 2004

- security fixes on the nanoftp and nanohttp modules
- build fixes: xmllint detection bug in configure, building outsidethesource tree (Thomas Fitzsimmons)
- bug fixes: HTML parser on broken ASCII chars in names (William),Pythonpaths (Malcolm Tredinnick), xmlHasNsProp and default namespace(William),saving to python file objects (Malcolm Tredinnick), DTD lookupfix(Malcolm), save back <group> in catalogs (William), treebuildfixes (DV and Rob Richards), Schemas memory bug, structured errorhandleron Python 64bits, thread local memory deallocation, memory leakreportedby Volker Roth, xmlValidateDtd in the presence of an internalsubset,entities and _private problem (William), xmlBuildRelativeURIerror(William).
- improvements: better XInclude error reports (William), treedebuggingmodule and tests, convenience functions at the Reader API(GrahamBennett), add support for PI in the HTML parser.

### 2.6.14: Sep 29 2004

- build fixes: configure paths for xmllint and xsltproc,compilationwithout HTML parser, compilation warning cleanups (WilliamBrack &Malcolm Tredinnick), VMS makefile update (Craig Berry),
- bug fixes: xmlGetUTF8Char (William Brack), QName properties(KasimierBuchcik), XInclude testing, Notation serialization,UTF8ToISO8859xtranscoding (Mark Itzcovitz), lots of XML Schemas cleanupand fixes(Kasimier), ChangeLog cleanup (Stepan Kasal), memory fixes (MarkVakoc),handling of failed realloc(), out of bound array adressing inSchemasdate handling, Python space/tabs cleanups (Malcolm Tredinnick),NMTOKENSE20 validation fix (Malcolm),
- improvements: added W3C XML Schemas testsuite (Kasimier Buchcik),addxmlSchemaValidateOneElement (Kasimier), Python exceptionhierearchy(Malcolm Tredinnick), Python libxml2 driver improvement(MalcolmTredinnick), Schemas support forxsi:schemaLocation,xsi:noNamespaceSchemaLocation, xsi:type (KasimierBuchcik)

### 2.6.13: Aug 31 2004

- build fixes: Windows and zlib (Igor Zlatkovic), -O flag withgcc,Solaris compiler warning, fixing RPM BuildRequires,
- fixes: DTD loading on Windows (Igor), Schemas error reportsAPIs(Kasimier Buchcik), Schemas validation crash, xmlCheckUTF8 (WilliamBrackand Julius Mittenzwei), Schemas facet check (Kasimier), defaultnamespaceproblem (William), Schemas hexbinary empty values, encodingerror couldgenrate a serialization loop.
- Improvements: Schemas validity improvements (Kasimier), added --pathand--load-trace options to xmllint
- documentation: tutorial update (John Fleck)

### 2.6.12: Aug 22 2004

- build fixes: fix --with-minimum, elfgcchack.h fixes(PeterBreitenlohner), perl path lookup (William), diff on Solaris(AlbertChin), some 64bits cleanups.
- Python: avoid a warning with 2.3 (William Brack), tab and spacemixes(William), wrapper generator fixes (William), Cygwin support (GerritP.Haase), node wrapper fix (Marc-Antoine Parent), XML Schemassupport(Torkel Lyng)
- Schemas: a lot of bug fixes and improvements from Kasimier Buchcik
- fixes: RVT fixes (William), XPath context resets bug (William),memorydebug (Steve Hay), catalog white space handling (PeterBreitenlohner),xmlReader state after attribute reading (William),structured errorhandler (William), XInclude generated xml:base fixup(William), Windowsmemory reallocation problem (Steve Hay), Out of Memoryconditionshandling (William and Olivier Andrieu), htmlNewDoc() charsetbug,htmlReadMemory init (William), a posteriori validation DTDbase(William), notations serialization missing, xmlGetNodePath(Dodji),xmlCheckUTF8 (Diego Tartara), missing line numbers onentity(William)
- improvements: DocBook catalog build scrip (William), xmlcatalogtool(Albert Chin), xmllint --c14n option, no_proxy environment (MikeHommey),xmlParseInNodeContext() addition, extend xmllint --shell, allowXIncludeto not generate start/end nodes, extend xmllint --version toinclude CVStag (William)
- documentation: web pages fixes, validity API docs fixes(William)schemas API fix (Eric Haszlakiewicz), xmllint man page (JohnFleck)

### 2.6.11: July 5 2004

- Schemas: a lot of changes and improvements by Kasimier Buchcikforattributes, namespaces and simple types.
- build fixes: --with-minimum (William Brack), some gcccleanup(William), --with-thread-alloc (William)
- portability: Windows binary package change (Igor Zlatkovic),Catalogpath on Windows
- documentation: update to the tutorial (John Fleck), xmllint returncode(John Fleck), man pages (Ville Skytta),
- bug fixes: C14N bug serializing namespaces (Aleksey Sanin),testSAXproperly initialize the library (William), empty node set inXPath(William), xmlSchemas errors (William), invalid charref problempointedby Morus Walter, XInclude xml:base generation (William), Relax-NGbugwith div processing (William), XPointer and xml:baseproblem(William),Reader and entities, xmllint return code for schemas(William), readerstreaming problem (Steve Ball), DTD serializationproblem (William),libxml.m4 fixes (Mike Hommey), do not providedestructors as methods onPython classes, xmlReader buffer bug, Pythonbindings memory interfacesimprovement (with Stéphane Bidoul), Fixed thepush parser to be back tosynchronous behaviour.
- improvement: custom per-thread I/O enhancement (Rob Richards),registernamespace in debug shell (Stefano Debenedetti), Python basedregressiontest for non-Unix users (William), dynamically increase thenumber ofXPath extension functions in Python and fix a memory leak(Marc-AntoineParent and William)
- performance: hack done with Arjan van de Ven to reduce ELF footprintandgenerated code on Linux, plus use gcc runtime profiling to optimizethecode generated in the RPM packages.

### 2.6.10: May 17 2004

- Web page generated for ChangeLog
- build fixes: --without-html problems, make check without make all
- portability: problem with xpath.c on Windows (MSC and Borland),memcmpvs. strncmp on Solaris, XPath tests on Windows (Mark Vakoc), C++ donotuse "list" as parameter name, make tests work with Python 1.5(EdDavis),
- improvements: made xmlTextReaderMode public, small buffersresizing(Morten Welinder), add --maxmem option to xmllint,addxmlPopInputCallback() for Matt Sergeant, refactoring ofserializationescaping, added escaping customization
- bugfixes: xsd:extension (Taihei Goi), assorted regexp bugs(WilliamBrack), xmlReader end of stream problem, node deregistration withreader,URI escaping and filemanes, XHTML1 formatting (Nick Wellnhofer),regexptransition reduction (William), various XSD Schemas fixes(KasimierBuchcik), XInclude fallback problem (William), weird problemswith DTD(William), structured error handler callback context (William),reversexmlEncodeSpecialChars() behaviour back to escaping '"'

### 2.6.9: Apr 18 2004

- implement xml:id Working Draft, relaxed XPath id() checking
- bugfixes: xmlCtxtReset (Brent Hendricks), line number and CDATA(DaveBeckett), Relax-NG compilation (William Brack), Regexp patches(withWilliam), xmlUriEscape (Mark Vakoc), a Relax-NG notAllowed problem(withWilliam), Relax-NG name classes compares (William), XIncludeduplicatefallback (William), external DTD encoding detection (William), aDTDvalidation bug (William), xmlReader Close() fix, recusiveextentionschemas
- improvements: use xmlRead* APIs in test tools (Mark Vakoc),indentingsave optimization, better handle IIS broken HTTP redirectbehaviour (IanHummel), HTML parser frameset (James Bursa), libxml2-pythonRPMdependancy, XML Schemas union support (Kasimier Buchcik), warningremovalclanup (William), keep ChangeLog compressed when installing fromRPMs
- documentation: examples and xmlDocDumpMemory docs (John Fleck),newexample (load, xpath, modify, save), xmlCatalogDump() comments,
- Windows: Borland C++ builder (Eric Zurcher), work aroundMicrosoftcompiler NaN handling bug (Mark Vakoc)

### 2.6.8: Mar 23 2004

- First step of the cleanup of the serialization code and APIs
- XML Schemas: mixed content (Adam Dickmeiss), QName handling fixes(AdamDickmeiss), anyURI for "" (John Belmonte)
- Python: Canonicalization C14N support added (Anthony Carrico)
- xmlDocCopyNode() extension (William)
- Relax-NG: fix when processing XInclude results (William),externalreference in interleave (William), missing error on<choice>failure (William), memory leak in schemas datatypefacets.
- xmlWriter: patch for better DTD support (Alfred Mickautsch)
- bug fixes: xmlXPathLangFunction memory leak (Mike Hommey andWilliamBrack), no ID errors if using HTML_PARSE_NOERROR, xmlcatalogfallbacks toURI on SYSTEM lookup failure, XInclude parse flagsinheritance (William),XInclude and XPointer fixes for entities (William),XML parser bugreported by Holger Rauch, nanohttp fd leak (William),regexps chargroups '-' handling (William), dictionnary reference countingproblems,do not close stderr.
- performance patches from Petr Pajas
- Documentation fixes: XML_CATALOG_FILES in man pages (Mike Hommey)
- compilation and portability fixes: --without-valid, catalogcleanups(Peter Breitenlohner), MingW patch (Roland Schwingel),cross-compilationto Windows (Christophe de Vienne), --with-html-dirfixup (Julio MerinoVidal), Windows build (Eric Zurcher)

### 2.6.7: Feb 23 2004

- documentation: tutorial updates (John Fleck), benchmark results
- xmlWriter: updates and fixes (Alfred Mickautsch, Lucas Brasilino)
- XPath optimization (Petr Pajas)
- DTD ID handling optimization
- bugfixes: xpath number with > 19 fractional (William Brack),pushmode with unescaped '>' characters, fix xmllint --stream --timing,fixxmllint --memory --stream memory usage,xmlAttrSerializeTxtContenthandling NULL, trying to fix Relax-NG/Perlinterface.
- python: 2.3 compatibility, whitespace fixes (Malcolm Tredinnick)
- Added relaxng option to xmllint --shell

### 2.6.6: Feb 12 2004

- nanohttp and nanoftp: buffer overflow error on URI parsing (IgorandWilliam) reported by Yuuichi Teranishi
- bugfixes: make test and path issues, xmlWriter attributeserialization(William Brack), xmlWriter indentation (William), schemasvalidation(Eric Haszlakiewicz), XInclude dictionnaries issues (Williamand OlegParaschenko), XInclude empty fallback (William), HTML warnings(William),XPointer in XInclude (William), Python namespaceserialization,isolat1ToUTF8 bound error (Alfred Mickautsch), output ofparameterentities in internal subset (William), internal subset bug inpush mode,<xs:all> fix (Alexey Sarytchev)
- Build: fix for automake-1.8 (Alexander Winston), warningsremoval(Philip Ludlam), SOCKLEN_T detection fixes (Daniel Richard),fix--with-minimum configuration.
- XInclude: allow the 2001 namespace without warning.
- Documentation: missing example/index.html (John Fleck),versiondependancies (John Fleck)
- reader API: structured error reporting (Steve Ball)
- Windows compilation: mingw, msys (Mikhail Grushinskiy),functionprototype (Cameron Johnson), MSVC6 compiler warnings,_WINSOCKAPI_patch
- Parsers: added xmlByteConsumed(ctxt) API to get the byte offestininput.

### 2.6.5: Jan 25 2004

- Bugfixes: dictionnaries for schemas (William Brack), regexpsegfault(William), xs:all problem (William), a number of XPointerbugfixes(William), xmllint error go to stderr, DTD validation problemwithnamespace, memory leak (William), SAX1 cleanup and minimal optionsfixes(Mark Vadoc), parser context reset on error (Shaun McCance), XPathunionevaluation problem (William) , xmlReallocLoc with NULL (AlekseySanin),XML Schemas double free (Steve Ball), XInclude with no href,argumentcallbacks order for XPath callbacks (Frederic Peters)
- Documentation: python scripts (William Brack), xslt stylesheets(JohnFleck), doc (Sven Zimmerman), I/O example.
- Python bindings: fixes (William), enum support (StéphaneBidoul),structured error reporting (Stéphane Bidoul)
- XInclude: various fixes for conformance, problem related todictionnaryreferences (William & me), recursion (William)
- xmlWriter: indentation (Lucas Brasilino), memory leaks(AlfredMickautsch),
- xmlSchemas: normalizedString datatype (John Belmonte)
- code cleanup for strings functions (William)
- Windows: compiler patches (Mark Vakoc)
- Parser optimizations, a few new XPath and dictionnary APIs forfutureXSLT optimizations.

### 2.6.4: Dec 24 2003

- Windows build fixes (Igor Zlatkovic)
- Some serious XInclude problems reported by Oleg Paraschenko and
- Unix and Makefile packaging fixes (me, William Brack,
- Documentation improvements (John Fleck, William Brack), examplefix(Lucas Brasilino)
- bugfixes: xmlTextReaderExpand() with xmlReaderWalker, XPath handlingofNULL strings (William Brack) , API building reader or parserfromfiledescriptor should not close it, changed XPath sorting to bestableagain (William Brack), xmlGetNodePath() generating '(null)'(WilliamBrack), DTD validation and namespace bug (William Brack), XMLSchemasdouble inclusion behaviour

### 2.6.3: Dec 10 2003

- documentation updates and cleanup (DV, William Brack, John Fleck)
- added a repository of examples, examples from Aleksey Sanin,DodjiSeketeli, Alfred Mickautsch
- Windows updates: Mark Vakoc, Igor Zlatkovic, Eric Zurcher,Mingw(Kenneth Haley)
- Unicode range checking (William Brack)
- code cleanup (William Brack)
- Python bindings: doc (John Fleck), bug fixes
- UTF-16 cleanup and BOM issues (William Brack)
- bug fixes: ID and xmlReader validation, XPath (William Brack),xmlWriter(Alfred Mickautsch), hash.h inclusion problem, HTML parser(James Bursa),attribute defaulting and validation, some serializationcleanups,XML_GET_LINE macro, memory debug when using threads (WilliamBrack),serialization of attributes and entities content, xmlWriter(DanielSchulman)
- XInclude bugfix, new APIs and update to the last version includingthenamespace change.
- XML Schemas improvements: include (Robert Stepanek), importandnamespace handling, fixed the regression tests troubles, addedexamplesbased on Eric van der Vlist book, regexp fixes
- preliminary pattern support for streaming (needed forschemasconstraints), added xmlTextReaderPreservePattern() to collectsubdocumentwhen streaming.
- various fixes in the structured error handling

### 2.6.2: Nov 4 2003

- XPath context unregistration fixes
- text node coalescing fixes (Mark Lilback)
- API to screate a W3C Schemas from an existing document (Steve Ball)
- BeOS patches (Marcin 'Shard' Konicki)
- xmlStrVPrintf function added (Aleksey Sanin)
- compilation fixes (Mark Vakoc)
- stdin parsing fix (William Brack)
- a posteriori DTD validation fixes
- xmlReader bug fixes: Walker fixes, python bindings
- fixed xmlStopParser() to really stop the parser and errors
- always generate line numbers when using the new xmlReadxxxfunctions
- added XInclude support to the xmlReader interface
- implemented XML_PARSE_NONET parser option
- DocBook XSLT processing bug fixed
- HTML serialization for <p> elements (William Brack and me)
- XPointer failure in XInclude are now handled as resource errors
- fixed xmllint --html to use the HTML serializer on output(added--xmlout to implement the previous behaviour of saving it using theXMLserializer)

### 2.6.1: Oct 28 2003

- Mostly bugfixes after the big 2.6.0 changes
- Unix compilation patches: libxml.m4 (Patrick Welche), warningscleanup(William Brack)
- Windows compilation patches (Joachim Bauch, Stephane Bidoul,IgorZlatkovic)
- xmlWriter bugfix (Alfred Mickautsch)
- chvalid.[ch]: couple of fixes from Stephane Bidoul
- context reset: error state reset, push parser reset (GrahamBennett)
- context reuse: generate errors if file is not readable
- defaulted attributes for element coming from internal entities(StephaneBidoul)
- Python: tab and spaces mix (William Brack)
- Error handler could crash in DTD validation in 2.6.0
- xmlReader: do not use the document or element _private field
- testSAX.c: avoid a problem with some PIs (Massimo Morara)
- general bug fixes: mandatory encoding in text decl, serializingDocumentFragment nodes, xmlSearchNs 2.6.0 problem (Kasimier Buchcik),XPath errorsnot reported, slow HTML parsing of large documents.

### 2.6.0: Oct 20 2003

- Major revision release: should be API and ABI compatible but got alotof change
- Increased the library modularity, far more options can be strippedout,a --with-minimum configuration will weight around 160KBytes
- Use per parser and per document dictionnary, allocate names andsmalltext nodes from the dictionnary
- Switch to a SAX2 like parser rewrote most of the XML parsercore,provides namespace resolution and defaulted attributes, minimizememoryallocations and copies, namespace checking and specific errorhandling,immutable buffers, make predefined entities static structures,etc...
- rewrote all the error handling in the library, all errors canbeintercepted at a structured level, with preciseinformationavailable.
- New simpler and more generic XML and HTML parser APIs, allowingtoeasilly modify the parsing options and reuse parser context formultipleconsecutive documents.
- Similar new APIs for the xmlReader, for options and reuse, providednewfunctions to access content as const strings, use them forPythonbindings
- a lot of other smaller API improvements: xmlStrPrintf (AlekseySanin),Walker i.e. reader on a document tree based on Alfred Mickautschcode,make room in nodes for line numbers, reference counting and futurePSVIextensions, generation of character ranges to be checked withfasteralgorithm (William), xmlParserMaxDepth (Crutcher Dunnavant),bufferaccess
- New xmlWriter API provided by Alfred Mickautsch
- Schemas: base64 support by Anthony Carrico
- Parser<->HTTP integration fix, proper processing of theMime-Typeand charset informations if available.
- Relax-NG: bug fixes including the one reported by Martijn FaassenandzeroOrMore, better error reporting.
- Python bindings (Stéphane Bidoul), never use stdout forerrorsoutput
- Portability: all the headers have macros for export andcallingconvention definitions (Igor Zlatkovic), VMS update (Craig A.Berry),Windows: threads (Jesse Pelton), Borland compiler (Eric Zurcher,Igor),Mingw (Igor), typos (Mark Vakoc), beta version (StephaneBidoul),warning cleanups on AIX and MIPS compilers (William Brack), BeOS(Marcin'Shard' Konicki)
- Documentation fixes and README (William Brack), search fix(William),tutorial updates (John Fleck), namespace docs (Stefan Kost)
- Bug fixes: xmlCleanupParser (Dave Beckett), threadinguninitializedmutexes, HTML doctype lowercase, SAX/IO (William),compression detectionand restore (William), attribute declaration in DTDs(William), namespaceon attribute in HTML output (William), input filename(Rob Richards),namespace DTD validation, xmlReplaceNode (Chris Ryland),I/O callbacks(Markus Keim), CDATA serialization (Shaun McCance),xmlReader (PeterDerr), high codepoint charref like &#x10FFFF;, bufferaccess in pushmode (Justin Fletcher), TLS threads on Windows (JessePelton), XPath bug(William), xmlCleanupParser (Marc Liyanage), CDATAoutput (William), HTTPerror handling.
- xmllint options: --dtdvalidfpi for Tobias Reif, --sax1 forcompattesting, --nodict for building without tree dictionnary, --nocdatatoreplace CDATA by text, --nsclean to remove surperfluousnamespacedeclarations
- added xml2-config --libtool-libs option from Kevin P. Fleming
- a lot of profiling and tuning of the code, speedup patchforxmlSearchNs() by Luca Padovani. The xmlReader should do farlessallocation and it speed should get closer to SAX. Chris Andersonworkedon speeding and cleaning up repetitive checking code.
- cleanup of "make tests"
- libxml-2.0-uninstalled.pc from Malcolm Tredinnick
- deactivated the broken docBook SGML parser code and plugged theXMLparser instead.

### 2.5.11: Sep 9 2003

A bugfix only release:

- risk of crash in Relax-NG
- risk of crash when using multithreaded programs

### 2.5.10: Aug 15 2003

A bugfixes only release

- Windows Makefiles (William Brack)
- UTF-16 support fixes (Mark Itzcovitz)
- Makefile and portability (William Brack) automake, Linux alpha, MingwonWindows (Mikhail Grushinskiy)
- HTML parser (Oliver Stoeneberg)
- XInclude performance problem reported by Kevin Ruscoe
- XML parser performance problem reported by Grant Goodale
- xmlSAXParseDTD() bug fix from Malcolm Tredinnick
- and a couple other cleanup

### 2.5.9: Aug 9 2003

- bugfixes: IPv6 portability, xmlHasNsProp (Markus Keim), Windowsbuild(Wiliam Brake, Jesse Pelton, Igor), Schemas (Peter Sobisch),threading(Rob Richards), hexBinary type (), UTF-16 BOM (DodjiSeketeli),xmlReader, Relax-NG schemas compilation, namespace handling,EXSLT (SeanGriffin), HTML parsing problem (William Brack), DTD validationfor mixedcontent + namespaces, HTML serialization, libraryinitialization,progressive HTML parser
- better interfaces for Relax-NG error handling (Joachim Bauch, )
- adding xmlXIncludeProcessTree() for XInclud'ing in a subtree
- doc fixes and improvements (John Fleck)
- configure flag for -with-fexceptions when embedding in C++
- couple of new UTF-8 helper functions (William Brack)
- general encoding cleanup + ISO-8859-x without iconv (Peter Jacobi)
- xmlTextReader cleanup + enum for node types (Bjorn Reese)
- general compilation/warning cleanup Solaris/HP-UX/...(WilliamBrack)

### 2.5.8: Jul 6 2003

- bugfixes: XPath, XInclude, file/URI mapping, UTF-16 save(MarkItzcovitz), UTF-8 checking, URI saving, error printing (WilliamBrack),PI related memleak, compilation without schemas or without xpath(JoergSchmitz-Linneweber/Garry Pennington), xmlUnlinkNode problem withDTDs,rpm problem on , i86_64, removed a few compilation problems from2.5.7,xmlIOParseDTD, and xmlSAXParseDTD (Malcolm Tredinnick)
- portability: DJGPP (MsDos) , OpenVMS (Craig A. Berry)
- William Brack fixed multithreading lock problems
- IPv6 patch for FTP and HTTP accesses (Archana Shah/Wipro)
- Windows fixes (Igor Zlatkovic, Eric Zurcher), threading(StéphaneBidoul)
- A few W3C Schemas Structure improvements
- W3C Schemas Datatype improvements (Charlie Bozeman)
- Python bindings for thread globals (Stéphane Bidoul), andmethod/classgenerator
- added --nonet option to xmllint
- documentation improvements (John Fleck)

### 2.5.7: Apr 25 2003

- Relax-NG: Compiling to regexp and streaming validation on top ofthexmlReader interface, added to xmllint --stream
- xmlReader: Expand(), Next() and DOM access glue, bug fixes
- Support for large files: RGN validated a 4.5GB instance
- Thread support is now configured in by default
- Fixes: update of the Trio code (Bjorn), WXS Date and Durationfixes(Charles Bozeman), DTD and namespaces (Brent Hendricks), HTML pushparserand zero bytes handling, some missing Windows file pathconversions,behaviour of the parser and validator in the presence of "outof memory"error conditions
- extended the API to be able to plug a garbage collectingmemoryallocator, added xmlMallocAtomic() and modified theallocationsaccordingly.
- Performances: removed excessive malloc() calls, speedup of the pushandxmlReader interfaces, removed excessive thread locking
- Documentation: man page (John Fleck), xmlReader documentation
- Python: adding binding for xmlCatalogAddLocal (Brent M Hendricks)

### 2.5.6: Apr 1 2003

- Fixed W3C XML Schemas datatype, should be compliant now exceptforbinHex and base64 which are not supported yet.
- bug fixes: non-ASCII IDs, HTML output, XInclude on large docsandXInclude entities handling, encoding detection on external subsets,XMLSchemas bugs and memory leaks, HTML parser (James Bursa)
- portability: python/trio (Albert Chin), Sun compiler warnings
- documentation: added --relaxng option to xmllint man page (John)
- improved error reporting: xml:space, start/end tag mismatches, RelaxNGerrors

### 2.5.5: Mar 24 2003

- Lot of fixes on the Relax NG implementation. More testingincludingDocBook and TEI examples.
- Increased the support for W3C XML Schemas datatype
- Several bug fixes in the URI handling layer
- Bug fixes: HTML parser, xmlReader, DTD validation, XPath,encodingconversion, line counting in the parser.
- Added support for $XMLLINT_INDENT environment variable, FTP delete
- Fixed the RPM spec file name

### 2.5.4: Feb 20 2003

- Conformance testing and lot of fixes on Relax NG andXIncludeimplementation
- Implementation of XPointer element() scheme
- Bug fixes: XML parser, XInclude entities merge, validity checkingonnamespaces,

  2 serialization bugs, node info generation problems, a DTDregexpgeneration problem.

- Portability: windows updates and path canonicalization (Igor)
- A few typo fixes (Kjartan Maraas)
- Python bindings generator fixes (Stephane Bidoul)

### 2.5.3: Feb 10 2003

- RelaxNG and XML Schemas datatypes improvements, and added afirstversion of RelaxNG Python bindings
- Fixes: XLink (Sean Chittenden), XInclude (Sean Chittenden), API fixforserializing namespace nodes, encoding conversion bug,XHTML1serialization
- Portability fixes: Windows (Igor), AMD 64bits RPM spec file

### 2.5.2: Feb 5 2003

- First implementation of RelaxNG, added --relaxng flag to xmllint
- Schemas support now compiled in by default.
- Bug fixes: DTD validation, namespace checking, XInclude andentities,delegateURI in XML Catalogs, HTML parser, XML reader (StéphaneBidoul),XPath parser and evaluation, UTF8ToUTF8 serialization, XMLreader memoryconsumption, HTML parser, HTML serialization in the presenceofnamespaces
- added an HTML API to check elements and attributes.
- Documentation improvement, PDF for the tutorial (John Fleck),docpatches (Stefan Kost)
- Portability fixes: NetBSD (Julio Merino), Windows (Igor Zlatkovic)
- Added python bindings for XPointer, contextual error reporting(StéphaneBidoul)
- URI/file escaping problems (Stefano Zacchiroli)

### 2.5.1: Jan 8 2003

- Fixes a memory leak and configuration/compilation problems in 2.5.0
- documentation updates (John)
- a couple of XmlTextReader fixes

### 2.5.0: Jan 6 2003

- New XmltextReader interfacebased on C#API(with help of Stéphane Bidoul)
- Windows: more exports, including the new API (Igor)
- XInclude fallback fix
- Python: bindings for the new API, packaging (StéphaneBidoul),drv_libxml2.py Python xml.sax driver (Stéphane Bidoul), fixes,speedupand iterators for Python-2.2 (Hannu Krosing)
- Tutorial fixes (john Fleck and Niraj Tolia) xmllint manupdate(John)
- Fix an XML parser bug raised by Vyacheslav Pindyura
- Fix for VMS serialization (Nigel Hall) and config (Craig A. Berry)
- Entities handling fixes
- new API to optionally track node creation and deletion(LukasSchroeder)
- Added documentation for the XmltextReader interface and some XML guidelines

### 2.4.30: Dec 12 2002

- 2.4.29 broke the python bindings, rereleasing
- Improvement/fixes of the XML API generator, and couple of minorcodefixes.

### 2.4.29: Dec 11 2002

- Windows fixes (Igor): Windows CE port, pthread linking, pythonbindings(Stéphane Bidoul), Mingw (Magnus Henoch), and export listupdates
- Fix for prev in python bindings (ERDI Gergo)
- Fix for entities handling (Marcus Clarke)
- Refactored the XML and HTML dumps to a single code path, fixedXHTML1dump
- Fix for URI parsing when handling URNs with fragment identifiers
- Fix for HTTP URL escaping problem
- added an TextXmlReader (C#) like API (work in progress)
- Rewrote the API in XML generation script, includes a C parser andsavesmore informations needed for C# bindings

### 2.4.28: Nov 22 2002

- a couple of python binding fixes
- 2 bug fixes in the XML push parser
- potential memory leak removed (Martin Stoilov)
- fix to the configure script for Unix (Dimitri Papadopoulos)
- added encoding support for XInclude parse="text"
- autodetection of XHTML1 and specific serialization rules added
- nasty threading bug fixed (William Brack)

### 2.4.27: Nov 17 2002

- fixes for the Python bindings
- a number of bug fixes: SGML catalogs,xmlParseBalancedChunkMemory(),HTML parser, Schemas (Charles Bozeman),document fragment support(Christian Glahn), xmlReconciliateNs (BrianStafford), XPointer,xmlFreeNode(), xmlSAXParseMemory (Peter Jones),xmlGetNodePath (PetrPajas), entities processing
- added grep to xmllint --shell
- VMS update patch from Craig A. Berry
- cleanup of the Windows build with support for more compilers(Igor),better thread support on Windows
- cleanup of Unix Makefiles and spec file
- Improvements to the documentation (John Fleck)

### 2.4.26: Oct 18 2002

- Patches for Windows CE port, improvements on Windows paths handling
- Fixes to the validation code (DTD and Schemas), xmlNodeGetPath() ,HTMLserialization, Namespace compliance, and a number of smallproblems

### 2.4.25: Sep 26 2002

- A number of bug fixes: XPath, validation, Python bindings, DOM andtree,xmlI/O, Html
- Serious rewrite of XInclude
- Made XML Schemas regexp part of the default build and APIs, smallfixand improvement of the regexp core
- Changed the validation code to reuse XML Schemas regexp APIs
- Better handling of Windows file paths, improvement of Makefiles(Igor,Daniel Gehriger, Mark Vakoc)
- Improved the python I/O bindings, the tests, added resolver andregexpAPIs
- New logos from Marc Liyanage
- Tutorial improvements: John Fleck, Christopher Harris
- Makefile: Fixes for AMD x86_64 (Mandrake), DESTDIR(ChristopheMerlet)
- removal of all stderr/perror use for error reporting
- Better error reporting: XPath and DTD validation
- update of the trio portability layer (Bjorn Reese)

2.4.24: Aug 22 2002

- XPath fixes (William), xf:escape-uri() (Wesley Terpstra)
- Python binding fixes: makefiles (William), generator, rpm build,x86-64(fcrozat)
- HTML <style> and boolean attributes serializer fixes
- C14N improvements by Aleksey
- doc cleanups: Rick Jones
- Windows compiler makefile updates: Igor and Elizabeth Barham
- XInclude: implementation of fallback and xml:base fixup added

### 2.4.23: July 6 2002

- performances patches: Peter Jacobi
- c14n fixes, testsuite and performances: Aleksey Sanin
- added xmlDocFormatDump: Chema Celorio
- new tutorial: John Fleck
- new hash functions and performances: Sander Vesik, portability fixfromPeter Jacobi
- a number of bug fixes: XPath (William Brack, Richard Jinks), XMLandHTML parsers, ID lookup function
- removal of all remaining sprintf: Aleksey Sanin

### 2.4.22: May 27 2002

- a number of bug fixes: configure scripts, base handling, parser,memoryusage, HTML parser, XPath, documentation (ChristianCornelssen),indentation, URI parsing
- Optimizations for XMLSec, fixing and making public some of thenetworkprotocol handlers (Aleksey)
- performance patch from Gary Pennington
- Charles Bozeman provided date and time support for XMLSchemasdatatypes

### 2.4.21: Apr 29 2002

This release is both a bug fix release and also contains the earlyXMLSchemas structuresand datatypescode, beware,allinterfaces are likely to change, there is huge holes, it is clearly a workinprogress and don't even think of putting this code in a productionsystem,it's actually not compiled in by default. The real fixes are:

- a couple of bugs or limitations introduced in 2.4.20
- patches for Borland C++ and MSC by Igor
- some fixes on XPath strings and conformance patches by RichardJinks
- patch from Aleksey for the ExcC14N specification
- OSF/1 bug fix by Bjorn

### 2.4.20: Apr 15 2002

- bug fixes: file descriptor leak, XPath, HTML output, DTD validation
- XPath conformance testing by Richard Jinks
- Portability fixes: Solaris, MPE/iX, Windows, OSF/1, pythonbindings,libxml.m4

### 2.4.19: Mar 25 2002

- bug fixes: half a dozen XPath bugs, Validation, ISO-Latin toUTF8encoder
- portability fixes in the HTTP code
- memory allocation checks using valgrind, and profiling tests
- revamp of the Windows build and Makefiles

### 2.4.18: Mar 18 2002

- bug fixes: tree, SAX, canonicalization, validation,portability,XPath
- removed the --with-buffer option it was becoming unmaintainable
- serious cleanup of the Python makefiles
- speedup patch to XPath very effective for DocBook stylesheets
- Fixes for Windows build, cleanup of the documentation

### 2.4.17: Mar 8 2002

- a lot of bug fixes, including "namespace nodes have no parentsinXPath"
- fixed/improved the Python wrappers, added more examples andmoreregression tests, XPath extension functions can now returnnode-sets
- added the XML Canonicalization support from Aleksey Sanin

### 2.4.16: Feb 20 2002

- a lot of bug fixes, most of them were triggered by the XMLTestsuitefrom OASIS and W3C. Compliance has been significantlyimproved.
- a couple of portability fixes too.

### 2.4.15: Feb 11 2002

- Fixed the Makefiles, especially the python module ones
- A few bug fixes and cleanup
- Includes cleanup

### 2.4.14: Feb 8 2002

- Change of License to the MITLicensebasicallyfor integration in XFree86 codebase, and removingconfusion around theprevious dual-licensing
- added Python bindings, beta software but should already bequitecomplete
- a large number of fixes and cleanups, especially for alltreemanipulations
- cleanup of the headers, generation of a reference API definitioninXML

### 2.4.13: Jan 14 2002

- update of the documentation: John Fleck and Charlie Bozeman
- cleanup of timing code from Justin Fletcher
- fixes for Windows and initial thread support on Win32: Igor andSergueiNarojnyi
- Cygwin patch from Robert Collins
- added xmlSetEntityReferenceFunc() for Keith Isdale work on xsldbg

### 2.4.12: Dec 7 2001

- a few bug fixes: thread (Gary Pennington), xmllint (GeertKloosterman),XML parser (Robin Berjon), XPointer (Danny Jamshy), I/Ocleanups(robert)
- Eric Lavigne contributed project files for MacOS
- some makefiles cleanups

### 2.4.11: Nov 26 2001

- fixed a couple of errors in the includes, fixed a few bugs, somecodecleanups
- xmllint man pages improvement by Heiko Rupp
- updated VMS build instructions from John A Fotheringham
- Windows Makefiles updates from Igor

### 2.4.10: Nov 10 2001

- URI escaping fix (Joel Young)
- added xmlGetNodePath() (for paths or XPointers generation)
- Fixes namespace handling problems when using DTD and validation
- improvements on xmllint: Morus Walter patches for --format and--encode,Stefan Kost and Heiko Rupp improvements on the --shell
- fixes for xmlcatalog linking pointed by Weiqi Gao
- fixes to the HTML parser

### 2.4.9: Nov 6 2001

- fixes more catalog bugs
- avoid a compilation problem, improve xmlGetLineNo()

### 2.4.8: Nov 4 2001

- fixed SGML catalogs broken in previous release, updatedxmlcatalogtool
- fixed a compile errors and some includes troubles.

### 2.4.7: Oct 30 2001

- exported some debugging interfaces
- serious rewrite of the catalog code
- integrated Gary Pennington thread safety patch, added configureoptionand regression tests
- removed an HTML parser bug
- fixed a couple of potentially serious validation bugs
- integrated the SGML DocBook support in xmllint
- changed the nanoftp anonymous login passwd
- some I/O cleanup and a couple of interfaces for Perl wrapper
- general bug fixes
- updated xmllint man page by John Fleck
- some VMS and Windows updates

### 2.4.6: Oct 10 2001

- added an updated man pages by John Fleck
- portability and configure fixes
- an infinite loop on the HTML parser was removed (William)
- Windows makefile patches from Igor
- fixed half a dozen bugs reported for libxml or libxslt
- updated xmlcatalog to be able to modify SGML super catalogs

### 2.4.5: Sep 14 2001

- Remove a few annoying bugs in 2.4.4
- forces the HTML serializer to output decimal charrefs since someversionof Netscape can't handle hexadecimal ones

### 1.8.16: Sep 14 2001

- maintenance release of the old libxml1 branch, couple of bugandportability fixes

### 2.4.4: Sep 12 2001

- added --convert to xmlcatalog, bug fixes and cleanups of XMLCatalog
- a few bug fixes and some portability changes
- some documentation cleanups

### 2.4.3: Aug 23 2001

- XML Catalog support see the doc
- New NaN/Infinity floating point code
- A few bug fixes

### 2.4.2: Aug 15 2001

- adds xmlLineNumbersDefault() to control line number generation
- lot of bug fixes
- the Microsoft MSC projects files should now be up to date
- inheritance of namespaces from DTD defaulted attributes
- fixes a serious potential security bug
- added a --format option to xmllint

### 2.4.1: July 24 2001

- possibility to keep line numbers in the tree
- some computation NaN fixes
- extension of the XPath API
- cleanup for alpha and ia64 targets
- patch to allow saving through HTTP PUT or POST

### 2.4.0: July 10 2001

- Fixed a few bugs in XPath, validation, and tree handling.
- Fixed XML Base implementation, added a couple of examples totheregression tests
- A bit of cleanup

### 2.3.14: July 5 2001

- fixed some entities problems and reduce memory requirementwhensubstituting them
- lots of improvements in the XPath queries interpreter canbesubstantially faster
- Makefiles and configure cleanups
- Fixes to XPath variable eval, and compare on empty node set
- HTML tag closing bug fixed
- Fixed an URI reference computation problem when validating

### 2.3.13: June 28 2001

- 2.3.12 configure.in was broken as well as the push mode XML parser
- a few more fixes for compilation on Windows MSC by Yon Derek

### 1.8.14: June 28 2001

- Zbigniew Chyla gave a patch to use the old XML parser in push mode
- Small Makefile fix

### 2.3.12: June 26 2001

- lots of cleanup
- a couple of validation fix
- fixed line number counting
- fixed serious problems in the XInclude processing
- added support for UTF8 BOM at beginning of entities
- fixed a strange gcc optimizer bugs in xpath handling of float,gcc-3.0miscompile uri.c (William), Thomas Leitner provided a fix fortheoptimizer on Tru64
- incorporated Yon Derek and Igor Zlatkovic fixes and improvementsforcompilation on Windows MSC
- update of libxml-doc.el (Felix Natter)
- fixed 2 bugs in URI normalization code

### 2.3.11: June 17 2001

- updates to trio, Makefiles and configure should fix someportabilityproblems (alpha)
- fixed some HTML serialization problems (pre, script, andblock/inlinehandling), added encoding aware APIs, cleanup of thiscode
- added xmlHasNsProp()
- implemented a specific PI for encoding support in the DocBookSGMLparser
- some XPath fixes (-Infinity, / as a function parameter andnamespacesnode selection)
- fixed a performance problem and an error in the validation code
- fixed XInclude routine to implement the recursive behaviour
- fixed xmlFreeNode problem when libxml is included statically twice
- added --version to xmllint for bug reports

### 2.3.10: June 1 2001

- fixed the SGML catalog support
- a number of reported bugs got fixed, in XPath, iconv detection,XIncludeprocessing
- XPath string function should now handle unicode correctly

### 2.3.9: May 19 2001

Lots of bugfixes, and added a basic SGML catalog support:

- HTML push bugfix #54891 and another patch from Jonas Borgström
- some serious speed optimization again
- some documentation cleanups
- trying to get better linking on Solaris (-R)
- XPath API cleanup from Thomas Broyer
- Validation bug fixed #54631, added a patch from Gary Pennington,fixedxmlValidGetValidElements()
- Added an INSTALL file
- Attribute removal added to API: #54433
- added a basic support for SGML catalogs
- fixed xmlKeepBlanksDefault(0) API
- bugfix in xmlNodeGetLang()
- fixed a small configure portability problem
- fixed an inversion of SYSTEM and PUBLIC identifier in HTML document

### 1.8.13: May 14 2001

- bugfixes release of the old libxml1 branch used by Gnome

### 2.3.8: May 3 2001

- Integrated an SGML DocBook parser for the Gnome project
- Fixed a few things in the HTML parser
- Fixed some XPath bugs raised by XSLT use, tried to fix thefloatingpoint portability issue
- Speed improvement (8M/s for SAX, 3M/s for DOM, 1.5M/s forDOM+validationusing the XML REC as input and a 700MHz celeron).
- incorporated more Windows cleanup
- added xmlSaveFormatFile()
- fixed problems in copying nodes with entities references (gdome)
- removed some troubles surrounding the new validation module

### 2.3.7: April 22 2001

- lots of small bug fixes, corrected XPointer
- Non deterministic content model validation support
- added xmlDocCopyNode for gdome2
- revamped the way the HTML parser handles end of tags
- XPath: corrections of namespaces support and number formatting
- Windows: Igor Zlatkovic patches for MSC compilation
- HTML output fixes from P C Chow and William M. Brack
- Improved validation speed sensible for DocBook
- fixed a big bug with ID declared in external parsed entities
- portability fixes, update of Trio from Bjorn Reese

### 2.3.6: April 8 2001

- Code cleanup using extreme gcc compiler warning options, foundandcleared half a dozen potential problem
- the Eazel team found an XML parser bug
- cleaned up the user of some of the string formatting function. usedthetrio library code to provide the one needed when the platform ismissingthem
- xpath: removed a memory leak and fixed the predicate evaluationproblem,extended the testsuite and cleaned up the result. XPointer seemsbroken...

### 2.3.5: Mar 23 2001

- Biggest change is separate parsing and evaluation of XPathexpressions,there is some new APIs for this too
- included a number of bug fixes(XML push parser, 51876,notations,52299)
- Fixed some portability issues

### 2.3.4: Mar 10 2001

- Fixed bugs #51860 and #51861
- Added a global variable xmlDefaultBufferSize to allow defaultbuffersize to be application tunable.
- Some cleanup in the validation code, still a bug left and thispartshould probably be rewritten to support ambiguous content model:-\
- Fix a couple of serious bugs introduced or raised by changes in2.3.3parser
- Fixed another bug in xmlNodeGetContent()
- Bjorn fixed XPath node collection and Number formatting
- Fixed a loop reported in the HTML parsing
- blank space are reported even if the Dtd content model proves thattheyare formatting spaces, this is for XML conformance

### 2.3.3: Mar 1 2001

- small change in XPath for XSLT
- documentation cleanups
- fix in validation by Gary Pennington
- serious parsing performances improvements

### 2.3.2: Feb 24 2001

- chasing XPath bugs, found a bunch, completed some TODO
- fixed a Dtd parsing bug
- fixed a bug in xmlNodeGetContent
- ID/IDREF support partly rewritten by Gary Pennington

### 2.3.1: Feb 15 2001

- some XPath and HTML bug fixes for XSLT
- small extension of the hash table interfaces for DOMgdome2implementation
- A few bug fixes

### 2.3.0: Feb 8 2001 (2.2.12 was on 25 Jan but I didn't kept track)

- Lots of XPath bug fixes
- Add a mode with Dtd lookup but without validation error reportingforXSLT
- Add support for text node without escaping (XSLT)
- bug fixes for xmlCheckFilename
- validation code bug fixes from Gary Pennington
- Patch from Paul D. Smith correcting URI path normalization
- Patch to allow simultaneous install of libxml-develandlibxml2-devel
- the example Makefile is now fixed
- added HTML to the RPM packages
- tree copying bugfixes
- updates to Windows makefiles
- optimization patch from Bjorn Reese

### 2.2.11: Jan 4 2001

- bunch of bug fixes (memory I/O, xpath, ftp/http, ...)
- added htmlHandleOmittedElem()
- Applied Bjorn Reese's IPV6 first patch
- Applied Paul D. Smith patches for validation of XInclude results
- added XPointer xmlns() new scheme support

### 2.2.10: Nov 25 2000

- Fix the Windows problems of 2.2.8
- integrate OpenVMS patches
- better handling of some nasty HTML input
- Improved the XPointer implementation
- integrate a number of provided patches

### 2.2.9: Nov 25 2000

- erroneous release :-(

### 2.2.8: Nov 13 2000

- First version of XIncludesupport
- Patch in conditional section handling
- updated MS compiler project
- fixed some XPath problems
- added an URI escaping function
- some other bug fixes

### 2.2.7: Oct 31 2000

- added message redirection
- XPath improvements (thanks TOM !)
- xmlIOParseDTD() added
- various small fixes in the HTML, URI, HTTP and XPointer support
- some cleanup of the Makefile, autoconf and the distribution content

### 2.2.6: Oct 25 2000:

- Added an hash table module, migrated a number of internal structuretothose
- Fixed a posteriori validation problems
- HTTP module cleanups
- HTML parser improvements (tag errors, script/style handling,attributenormalization)
- coalescing of adjacent text nodes
- couple of XPath bug fixes, exported the internal API

### 2.2.5: Oct 15 2000:

- XPointer implementation and testsuite
- Lot of XPath fixes, added variable and functions registration,moretests
- Portability fixes, lots of enhancements toward an easy Windows buildandrelease
- Late validation fixes
- Integrated a lot of contributed patches
- added memory management docs
- a performance problem when using large buffer seems fixed

### 2.2.4: Oct 1 2000:

- main XPath problem fixed
- Integrated portability patches for Windows
- Serious bug fixes on the URI and HTML code

### 2.2.3: Sep 17 2000

- bug fixes
- cleanup of entity handling code
- overall review of all loops in the parsers, all sprintf usage hasbeenchecked too
- Far better handling of larges Dtd. Validating against DocBook XMLDtdworks smoothly now.

### 1.8.10: Sep 6 2000

- bug fix release for some Gnome projects

### 2.2.2: August 12 2000

- mostly bug fixes
- started adding routines to access xml parser context options

### 2.2.1: July 21 2000

- a purely bug fixes release
- fixed an encoding support problem when parsing from a memory block
- fixed a DOCTYPE parsing problem
- removed a bug in the function allowing to override the memoryallocationroutines

### 2.2.0: July 14 2000

- applied a lot of portability fixes
- better encoding support/cleanup and saving (content is nowalwaysencoded in UTF-8)
- the HTML parser now correctly handles encodings
- added xmlHasProp()
- fixed a serious problem with &#38;
- propagated the fix to FTP client
- cleanup, bugfixes, etc ...
- Added a page about libxmlInternationalizationsupport

### 1.8.9: July 9 2000

- fixed the spec the RPMs should be better
- fixed a serious bug in the FTP implementation, released 1.8.9 tosolverpmfind users problem

### 2.1.1: July 1 2000

- fixes a couple of bugs in the 2.1.0 packaging
- improvements on the HTML parser

### 2.1.0 and 1.8.8: June 29 2000

- 1.8.8 is mostly a commodity package for upgrading to libxml2accordingto new instructions. It fixes a nastyproblemabout &#38; charref parsing
- 2.1.0 also ease the upgrade from libxml v1 to the recent version.italso contains numerous fixes and enhancements:
  - added xmlStopParser() to stop parsing
  - improved a lot parsing speed when there is large CDATA blocs
  - includes XPath patches provided by Picdar Technology
  - tried to fix as much as possible DTD validation andnamespacerelated problems
  - output to a given encoding has been added/tested
  - lot of various fixes

### 2.0.0: Apr 12 2000

- First public release of libxml2. If you are using libxml, it's agoodidea to check the 1.x to 2.x upgrade instructions. NOTE: whileinitiallyscheduled for Apr 3 the release occurred only on Apr 12 due tomassiveworkload.
- The include are now located under $prefix/include/libxml (insteadof$prefix/include/gnome-xml), they also are referenced by

      #include <libxml/xxx.h>

  instead of

      #include "xxx.h"

- a new URI module for parsing URIs and following strictly RFC 2396
- the memory allocation routines used by libxml can now beoverloadeddynamically by using xmlMemSetup()
- The previously CVS only tool tester has beenrenamedxmllintand is now installed as part of thelibxml2package
- The I/O interface has been revamped. There is now ways to pluginspecific I/O modules, either at the URI scheme detection levelusingxmlRegisterInputCallbacks() or by passing I/O functions whencreating aparser context using xmlCreateIOParserCtxt()
- there is a C preprocessor macro LIBXML_VERSION providing theversionnumber of the libxml module in use
- a number of optional features of libxml can now be excluded atconfiguretime (FTP/HTTP/HTML/XPath/Debug)

### 2.0.0beta: Mar 14 2000

- This is a first Beta release of libxml version 2
- It's available only fromxmlsoft.orgFTP, it's packaged aslibxml2-2.0.0beta and available as tar andRPMs
- This version is now the head in the Gnome CVS base, the old oneisavailable under the tag LIB_XML_1_X
- This includes a very large set of changes. From a programmatic pointofview applications should not have to be modified too much, check theupgrade page
- Some interfaces may changes (especially a bit about encoding).
- the updates includes:
  - fix I18N support. ISO-Latin-x/UTF-8/UTF-16 (nearly) seemscorrectlyhandled now
  - Better handling of entities, especially well-formedness checkingandproper PEref extensions in external subsets
  - DTD conditional sections
  - Validation now correctly handle entities content
  - changestructuresto accommodate DOM
- Serious progress were made toward compliance, here are the result of the testagainsttheOASIS testsuite (except the Japanese tests since I don't supportthatencoding yet). This URL is rebuilt every couple of hours using theCVShead version.

### 1.8.7: Mar 6 2000

- This is a bug fix release:
- It is possible to disable the ignorable blanks heuristic usedbylibxml-1.x, a new function xmlKeepBlanksDefault(0) will allow this.Notethat for adherence to XML spec, this behaviour will be disabledbydefault in 2.x . The same function will allow to keep compatibilityforold code.
- Blanks in <a> </a> constructs are not ignoredanymore,avoiding heuristic is really the Right Way :-\
- The unchecked use of snprintf which was breakinglibxml-1.8.6compilation on some platforms has been fixed
- nanoftp.c nanohttp.c: Fixed '#' and '?' stripping whenprocessingURIs

### 1.8.6: Jan 31 2000

- added a nanoFTP transport module, debugged until the new version of rpmfindcanuseit without troubles

### 1.8.5: Jan 21 2000

- adding APIs to parse a well balanced chunk of XML (production [43] contentof theXMLspec)
- fixed a hideous bug in xmlGetProp pointed by Rune.Djurhuus@fast.no
- Jody Goldberg <jgoldberg@home.com> provided another patchtryingto solve the zlib checks problems
- The current state in gnome CVS base is expected to ship as 1.8.5withgnumeric soon

### 1.8.4: Jan 13 2000

- bug fixes, reintroduced xmlNewGlobalNs(), fixed xmlNewNs()
- all exit() call should have been removed from libxml
- fixed a problem with INCLUDE_WINSOCK on WIN32 platform
- added newDocFragment()

### 1.8.3: Jan 5 2000

- a Push interface for the XML and HTML parsers
- a shell-like interface to the document tree (try tester --shell :-)
- lots of bug fixes and improvement added over XMas holidays
- fixed the DTD parsing code to work with the xhtml DTD
- added xmlRemoveProp(), xmlRemoveID() and xmlRemoveRef()
- Fixed bugs in xmlNewNs()
- External entity loading code has been revamped, now itusesxmlLoadExternalEntity(), some fix on entities processing wereadded
- cleaned up WIN32 includes of socket stuff

### 1.8.2: Dec 21 1999

- I got another problem with includes and C++, I hope this issue isfixedfor good this time
- Added a few tree modification functions:xmlReplaceNode,xmlAddPrevSibling, xmlAddNextSibling, xmlNodeSetNameandxmlDocSetRootElement
- Tried to improve the HTML output with help from Chris Lahey

### 1.8.1: Dec 18 1999

- various patches to avoid troubles when using libxml with C++compilersthe "namespace" keyword and C escaping in include files
- a problem in one of the core macros IS_CHAR was corrected
- fixed a bug introduced in 1.8.0 breaking default namespaceprocessing,and more specifically the Dia application
- fixed a posteriori validation (validation after parsing, or by usingaDtd not specified in the original document)
- fixed a bug in

### 1.8.0: Dec 12 1999

- cleanup, especially memory wise
- the parser should be more reliable, especially the HTML one, itshouldnot crash, whatever the input !
- Integrated various patches, especially a speedup improvement forlargedataset from CarlNygard,configure with --with-buffers to enable them.
- attribute normalization, oops should have been added long ago !
- attributes defaulted from DTDs should be available, xmlSetProp()nowdoes entities escaping by default.

### 1.7.4: Oct 25 1999

- Lots of HTML improvement
- Fixed some errors when saving both XML and HTML
- More examples, the regression tests should now look clean
- Fixed a bug with contiguous charref

### 1.7.3: Sep 29 1999

- portability problems fixed
- snprintf was used unconditionally, leading to link problems onsystemwere it's not available, fixed

### 1.7.1: Sep 24 1999

- The basic type for strings manipulated by libxml has been renamedin1.7.1 from CHARto xmlChar. Thereasonis that CHAR was conflicting with a predefined type on Windows.Howeveron non WIN32 environment, compatibility is provided by the way ofa#define .
- Changed another error : the use of a structure field called errno,andleading to troubles on platforms where it's a macro

### 1.7.0: Sep 23 1999

- Added the ability to fetch remote DTD or parsed entities, see the nanohttpmodule.
- Added an errno to report errors by another mean than a simpleprintflike callback
- Finished ID/IDREF support and checking when validation
- Serious memory leaks fixed (there is now a memory wrappermodule)
- Improvement of XPathimplementation
- Added an HTML parser front-end

## XML

XML is astandardformarkup-based structured documents. Here is an example XMLdocument:

    <?xml version="1.0"?>
    <EXAMPLE prop1="gnome is great" prop2="&amp; linux too">
      <head>
       <title>Welcome to Gnome</title>
      </head>
      <chapter>
       <title>The Linux adventure</title>
       <p>bla bla bla ...</p>
       <image href="linus.gif"/>
       <p>...</p>
      </chapter>
    </EXAMPLE>

The first line specifies that it is an XML document and givesusefulinformation about its encoding. Then the rest of the document is atextformat whose structure is specified by tags between brackets.Eachtag opened has to be closed. XML is pedantic about this.However, ifa tag is empty (no content), a single tag can serve as both theopening andclosing tag if it ends with `/>`rather thanwith`>`. Note that, for example, the image tag has no content(justan attribute) and is closed by ending the tag with`/>`.

XML can be applied successfully to a wide range of tasks, ranging fromlongterm structured document maintenance (where it follows the steps ofSGML) tosimple data encoding mechanisms like configuration file formatting(glade),spreadsheets (gnumeric), or even shorter lived documents such asWebDAV whereit is used to encode remote calls between a client and aserver.

## XSLT

Check the separate libxslt page

XSL Transformations, is alanguagefor transforming XML documents into other XML documents (orHTML/textualoutput).

A separate library called libxslt is available implementing XSLT-1.0forlibxml2. This module "libxslt" too can be found in the Gnome CVS base.

You can check the progresses on the libxslt Changelog.

## Python and bindings

There are a number of language bindings and wrappers available forlibxml2,the list below is not exhaustive. Please contact the xml-bindings@gnome.org(archives) inorder toget updates to this list or to discuss the specific topic of libxml2orlibxslt wrappers or bindings:

- Libxml++seemsthemost up-to-date C++ bindings for libxml2, check the documentationandthe examples.
- There is another C++wrapperbased on the gdome2 bindingsmaintained by Tobias Peters.
- and a third C++ wrapper by Peter Jones <pjones@pmade.org>

  Website: http://pmade.org/pjones/software/xmlwrapp/

- MattSergeantdevelopedXML::LibXSLT, a Perl wrapperforlibxml2/libxslt as part of the AxKitXMLapplication server.
- If you're interested into scripting XML processing, have a look at XSHan XML editing shell basedonLibxml2 Perl bindings.
- Dave Kuhlmanprovidesanearlier version of the libxml/libxslt wrappers for Python.
- Gopal.V and Peter Minten develop libxml#, a setofC# libxml2 bindings.
- Petr Kozelka provides Pascal units togluelibxml2with Kylix, Delphi and other Pascal compilers.
- Uwe Fechner also provides idom2, aDOM2implementation for Kylix2/D5/D6 from Borland.
- There is bindings forRubyand libxml2 bindings are also available in Ruby through the libgdome-rubymodulemaintainedby Tobias Peters.
- Steve Ball and contributors maintains libxml2 and libxslt bindingsforTcl.
- libxml2 and libxslt is the default XML library for PHP5.
- LibxmlJisaneffort to create a 100% JAXP-compatible Java wrapper for libxml2andlibxslt as part of GNU ClasspathX project.
- Patrick McPhee provides Rexx bindings fof libxml2 and libxslt, lookforRexxXML.
- SatimageprovidesXMLLibosax.This is an osax for Mac OS X with a set of commands toimplement inAppleScript the XML DOM, XPATH and XSLT. Also includescommands forProperty-lists (Apple's fast lookup table XML format.)
- Francesco Montorsi developped wxXml2wrappersthat interface libxml2, allowing wxWidgets applications toload/save/editXML instances.

The distribution includes a set of Python bindings, which are guaranteedtobe maintained as part of the library in the future, though thePythoninterface have not yet reached the completeness of the C API.

Note that some of the Python purist dislike the default set ofPythonbindings, rather than complaining I suggest they have a look at lxml the more pythonic bindings forlibxml2and libxsltand helpMartijnFaassencomplete those.

StéphaneBidoulmaintains aWindows portof the Python bindings.

Note to people interested in building bindings, the API is formalized asan XML API description filewhich allows toautomatea large part of the Python bindings, this includes functiondescriptions,enums, structures, typedefs, etc... The Python script used tobuild thebindings is python/generator.py in the source distribution.

To install the Python bindings there are 2 options:

- If you use an RPM based distribution, simply install the libxml2-pythonRPM(andif needed the libxslt-pythonRPM).
- Otherwise use the libxml2-pythonmoduledistributioncorresponding to your installed version oflibxml2 andlibxslt. Note that to install it you will need both libxml2and libxsltinstalled and run "python setup.py build install" in themodule tree.

The distribution includes a set of examples and regression tests forthepython bindings in the `python/tests`directory. Here aresomeexcerpts from those tests:

### tst.py:

This is a basic test of the file interface and DOM navigation:

    import libxml2, sys

    doc = libxml2.parseFile("tst.xml")
    if doc.name != "tst.xml":
        print "doc.name failed"
        sys.exit(1)
    root = doc.children
    if root.name != "doc":
        print "root.name failed"
        sys.exit(1)
    child = root.children
    if child.name != "foo":
        print "child.name failed"
        sys.exit(1)
    doc.freeDoc()

The Python module is called libxml2; parseFile is the equivalentofxmlParseFile (most of the bindings are automatically generated, and thexmlprefix is removed and the casing convention are kept). All node seen atthebinding level share the same subset of accessors:

- `name`: returns the node name
- `type`: returns a string indicating the node type
- `content`: returns the content of the node, it is basedonxmlNodeGetContent() and hence is recursive.
- `parent`, `children`,`last`,`next`, `prev`,`doc`,`properties`: pointing to the associatedelement in the tree,those may return None in case no such linkexists.

Also note the need to explicitly deallocate documents with freeDoc().Reference counting for libxml2 trees would need quite a lot of worktofunction properly, and rather than risk memory leaks if notimplementedcorrectly it sounds safer to have an explicit function to free atree. Thewrapper python objects like doc, root or child are themautomatically garbagecollected.

### validate.py:

This test check the validation interfaces and redirection oferrormessages:

    import libxml2

    #deactivate error messages from the validation
    def noerr(ctx, str):
        pass

    libxml2.registerErrorHandler(noerr, None)

    ctxt = libxml2.createFileParserCtxt("invalid.xml")
    ctxt.validate(1)
    ctxt.parseDocument()
    doc = ctxt.doc()
    valid = ctxt.isValid()
    doc.freeDoc()
    if valid != 0:
        print "validity check failed"

The first thing to notice is the call to registerErrorHandler(), itdefinesa new error handler global to the library. It is used to avoid seeingtheerror messages when trying to validate the invalid document.

The main interest of that test is the creation of a parser contextwithcreateFileParserCtxt() and how the behaviour can be changed beforecallingparseDocument() . Similarly the informations resulting from theparsing phaseare also available using context methods.

Contexts like nodes are defined as class and the libxml2 wrappers mapstheC function interfaces in terms of objects method as much as possible.Thebest to get a complete view of what methods are supported is to look atthelibxml2.py module containing all the wrappers.

### push.py:

This test show how to activate the push parser interface:

    import libxml2

    ctxt = libxml2.createPushParser(None, "<foo", 4, "test.xml")
    ctxt.parseChunk("/>", 2, 1)
    doc = ctxt.doc()

    doc.freeDoc()

The context is created with a special call based onthexmlCreatePushParser() from the C library. The first argument is anoptionalSAX callback object, then the initial set of data, the length and thename ofthe resource in case URI-References need to be computed by theparser.

Then the data are pushed using the parseChunk() method, the lastcallsetting the third argument terminate to 1.

### pushSAX.py:

this test show the use of the event based parsing interfaces. In thiscasethe parser does not build a document, but provides callback informationasthe parser makes progresses analyzing the data being provided:

    import libxml2
    log = ""

    class callback:
        def startDocument(self):
            global log
            log = log + "startDocument:"

        def endDocument(self):
            global log
            log = log + "endDocument:"

        def startElement(self, tag, attrs):
            global log
            log = log + "startElement %s %s:" % (tag, attrs)

        def endElement(self, tag):
            global log
            log = log + "endElement %s:" % (tag)

        def characters(self, data):
            global log
            log = log + "characters: %s:" % (data)

        def warning(self, msg):
            global log
            log = log + "warning: %s:" % (msg)

        def error(self, msg):
            global log
            log = log + "error: %s:" % (msg)

        def fatalError(self, msg):
            global log
            log = log + "fatalError: %s:" % (msg)

    handler = callback()

    ctxt = libxml2.createPushParser(handler, "<foo", 4, "test.xml")
    chunk = " url='tst'>b"
    ctxt.parseChunk(chunk, len(chunk), 0)
    chunk = "ar</foo>"
    ctxt.parseChunk(chunk, len(chunk), 1)

    reference = "startDocument:startElement foo {'url': 'tst'}:" + \
                "characters: bar:endElement foo:endDocument:"
    if log != reference:
        print "Error got: %s" % log
        print "Expected: %s" % reference

The key object in that test is the handler, it provides a number ofentrypoints which can be called by the parser as it makes progresses toindicatethe information set obtained. The full set of callback is larger thanwhatthe callback class in that specific example implements (see theSAXdefinition for a complete list). The wrapper will only call those suppliedbythe object when activated. The startElement receives the names of theelementand a dictionary containing the attributes carried by this element.

Also note that the reference string generated from the callback showsasingle character call even though the string "bar" is passed to theparserfrom 2 different call to parseChunk()

### xpath.py:

This is a basic test of XPath wrappers support

    import libxml2

    doc = libxml2.parseFile("tst.xml")
    ctxt = doc.xpathNewContext()
    res = ctxt.xpathEval("//*")
    if len(res) != 2:
        print "xpath query: wrong node set size"
        sys.exit(1)
    if res[0].name != "doc" or res[1].name != "foo":
        print "xpath query: wrong node set value"
        sys.exit(1)
    doc.freeDoc()
    ctxt.xpathFreeContext()

This test parses a file, then create an XPath context to evaluateXPathexpression on it. The xpathEval() method execute an XPath query andreturnsthe result mapped in a Python way. String and numbers are nativelyconverted,and node sets are returned as a tuple of libxml2 Python nodeswrappers. Likethe document, the XPath context need to be freed explicitly,also not thatthe result of the XPath query may point back to the documenttree and hencethe document must be freed after the result of the query isused.

### xpathext.py:

This test shows how to extend the XPath engine with functions writteninpython:

    import libxml2

    def foo(ctx, x):
        return x + 1

    doc = libxml2.parseFile("tst.xml")
    ctxt = doc.xpathNewContext()
    libxml2.registerXPathFunction(ctxt._o, "foo", None, foo)
    res = ctxt.xpathEval("foo(1)")
    if res != 2:
        print "xpath extension failure"
    doc.freeDoc()
    ctxt.xpathFreeContext()

Note how the extension function is registered with the context (butthatpart is not yet finalized, this may change slightly in the future).

### tstxpath.py:

This test is similar to the previous one but shows how theextensionfunction can access the XPath evaluation context:

    def foo(ctx, x):
        global called

        #
        # test that access to the XPath evaluation contexts
        #
        pctxt = libxml2.xpathParserContext(_obj=ctx)
        ctxt = pctxt.context()
        called = ctxt.function()
        return x + 1

All the interfaces around the XPath parser(or rather evaluation)contextare not finalized, but it should be sufficient to do contextual workat theevaluation point.

### Memory debugging:

last but not least, all tests starts with the following prologue:

    #memory debug specific
    libxml2.debugMemory(1)

and ends with the following epilogue:

    #memory debug specific
    libxml2.cleanupParser()
    if libxml2.debugMemory(1) == 0:
        print "OK"
    else:
        print "Memory leak %d bytes" % (libxml2.debugMemory(1))
        libxml2.dumpMemory()

Those activate the memory debugging interface of libxml2 whereallallocated block in the library are tracked. The prologue then cleans upthelibrary state and checks that all allocated memory has been freed. If notitcalls dumpMemory() which saves that list in a `.memdump`file.

## libxml2 architecture

Libxml2 is made of multiple components; some of them are optional, andmostof the block interfaces are public. The main components are:

- an Input/Output layer
- FTP and HTTP client layers (optional)
- an Internationalization layer managing the encodings support
- a URI module
- the XML parser and its basic SAX interface
- an HTML parser using the same SAX interface (optional)
- a SAX tree module to build an in-memory DOM representation
- a tree module to manipulate the DOM representation
- a validation module using the DOM representation (optional)
- an XPath module for global lookup in a DOM representation(optional)
- a debug module (optional)

Graphically this gives the following:

## The tree output

The parser returns a tree built during the document analysis. Thevaluereturned is an xmlDocPtr(i.e., a pointer toanxmlDocstructure). This structure contains informationsuchas the file name, the document type, and achildrenpointerwhich is the root of the document (or moreexactly the first child under theroot which is the document). The tree ismade of xmlNodes,chained in double-linked lists of siblingsand with a children<->parentrelationship. An xmlNode can also carryproperties (a chain of xmlAttrstructures). An attribute may have a valuewhich is a list of TEXT orENTITY_REF nodes.

Here is an example (erroneous with respect to the XML spec sincethereshould be only one ELEMENT under the root):

In the source package there is a small program (not installed bydefault)called xmllintwhich parses XML files given asargument andprints them back as parsed. This is useful for detecting errorsboth in XMLcode and in the XML parser itself. It has an option--debugwhich prints the actual in-memory structure of thedocument; here is theresult with the examplegivenbefore:

    DOCUMENT
    version=1.0
    standalone=true
      ELEMENT EXAMPLE
        ATTRIBUTE prop1
          TEXT
          content=gnome is great
        ATTRIBUTE prop2
          ENTITY_REF
          TEXT
          content= linux too
        ELEMENT head
          ELEMENT title
            TEXT
            content=Welcome to Gnome
        ELEMENT chapter
          ELEMENT title
            TEXT
            content=The Linux adventure
          ELEMENT p
            TEXT
            content=bla bla bla ...
          ELEMENT image
            ATTRIBUTE href
              TEXT
              content=linus.gif
          ELEMENT p
            TEXT
            content=...

This should be useful for learning the internal representation model.

## The SAX interface

Sometimes the DOM tree output is just too large to fit reasonablyintomemory. In that case (and if you don't expect to save back the XMLdocumentloaded using libxml), it's better to use the SAX interface of libxml.SAX isa callback-based interfaceto the parser. Beforeparsing,the application layer registers a customized set of callbacks whicharecalled by the library as it progresses through the XML input.

To get more detailed step-by-step guidance on using the SAX interfaceoflibxml, see the nicedocumentation.writtenby JamesHenstridge.

You can debug the SAX behaviour by using thetestSAXprogram located in the gnome-xml module (it's usuallynot shipped in thebinary packages of libxml, but you can find it in the tarsourcedistribution). Here is the sequence of callbacks that would be reportedbytestSAX when parsing the example XML document shown earlier:

    SAX.setDocumentLocator()
    SAX.startDocument()
    SAX.getEntity(amp)
    SAX.startElement(EXAMPLE, prop1='gnome is great', prop2='&amp; linux too')
    SAX.characters(   , 3)
    SAX.startElement(head)
    SAX.characters(    , 4)
    SAX.startElement(title)
    SAX.characters(Welcome to Gnome, 16)
    SAX.endElement(title)
    SAX.characters(   , 3)
    SAX.endElement(head)
    SAX.characters(   , 3)
    SAX.startElement(chapter)
    SAX.characters(    , 4)
    SAX.startElement(title)
    SAX.characters(The Linux adventure, 19)
    SAX.endElement(title)
    SAX.characters(    , 4)
    SAX.startElement(p)
    SAX.characters(bla bla bla ..., 15)
    SAX.endElement(p)
    SAX.characters(    , 4)
    SAX.startElement(image, href='linus.gif')
    SAX.endElement(image)
    SAX.characters(    , 4)
    SAX.startElement(p)
    SAX.characters(..., 3)
    SAX.endElement(p)
    SAX.characters(   , 3)
    SAX.endElement(chapter)
    SAX.characters( , 1)
    SAX.endElement(EXAMPLE)
    SAX.endDocument()

Most of the other interfaces of libxml2 are based on the DOMtree-buildingfacility, so nearly everything up to the end of this documentpresupposes theuse of the standard DOM tree build. Note that the DOM treeitself is built bya set of registered default callbacks, without internalspecificinterface.

## Validation & DTDs

Table of Content:

1. General overview
2. The definition
3. Simple rules
   1. How to reference a DTD from a document
   2. Declaring elements
   3. Declaring attributes
4. Some examples
5. How to validate
6. Other resources

### General overview

Well what is validation and what is a DTD ?

DTD is the acronym for Document Type Definition. This is a descriptionofthe content for a family of XML files. This is part of the XML1.0specification, and allows one to describe and verify that a givendocumentinstance conforms to the set of rules detailing its structure andcontent.

Validation is the process of checking a document against a DTD(moregenerally against a set of construction rules).

The validation process and building DTDs are the two most difficultpartsof the XML life cycle. Briefly a DTD defines all the possible elementsto befound within your document, what is the formal shape of your documenttree(by defining the allowed content of an element; either text, aregularexpression for the allowed list of children, or mixed content i.e.both textand children). The DTD also defines the valid attributes for allelements andthe types of those attributes.

### The definition

The W3C XML Recommendation(Tim Bray's annotated versionofRev1):

- Declaringelements
- Declaringattributes

(unfortunately) all this is inherited from the SGML world, the syntaxisancient...

### Simple rules

Writing DTDs can be done in many ways. The rules to build them if youneedsomething permanent or something which can evolve over time can beradicallydifferent. Really complex DTDs like DocBook ones are flexible butquiteharder to design. I will just focus on DTDs for a formats with a fixedsimplestructure. It is just a set of basic rules, and definitely notexhaustive norusable for complex DTD design.

#### How to reference a DTD from a document:

Assuming the top element of the document is `spec`and the dtdisplaced in the file `mydtd`in the subdirectory`dtds`ofthe directory from where the document were loaded:

`<!DOCTYPE spec SYSTEM "dtds/mydtd">`

Notes:

- The system string is actually an URI-Reference (as defined in RFC 2396) so you can useafull URL string indicating the location of your DTD on the Web. This isareally good thing to do if you want others to validate yourdocument.
- It is also possible to associate a `PUBLIC`identifier(amagic string) so that the DTD is looked up in catalogs on the clientsidewithout having to locate it on the web.
- A DTD contains a set of element and attribute declarations, buttheydon't define what the root of the document should be. This isexplicitlytold to the parser/validator as the first element ofthe`DOCTYPE`declaration.

#### Declaring elements:

The following declares an element `spec`:

`<!ELEMENT spec (front, body, back?)>`

It also expresses that the spec element contains one`front`,one `body`and one optional`back`children elements inthis order. The declaration of oneelement of the structure and its contentare done in a single declaration.Similarly the following declares`div1`elements:

`<!ELEMENT div1 (head, (p | list | note)*, div2?)>`

which means div1 contains one `head`then a series ofoptional`p`, `list`s and `note`s and thenanoptional `div2`. And last but not least an element cancontaintext:

`<!ELEMENT b (#PCDATA)>`

`b`contains text or being of mixed content (text and elementsinno particular order):

`<!ELEMENT p (#PCDATA|a|ul|b|i|em)*>`

`p` can contain text or `a`,`ul`,`b`, `i` or `em`elements inno particularorder.

#### Declaring attributes:

Again the attributes declaration includes their content definition:

`<!ATTLIST termdef name CDATA #IMPLIED>`

means that the element `termdef`can have a`name`attribute containing text (`CDATA`) and which isoptional(`#IMPLIED`). The attribute value can also be definedwithin aset:

`<!ATTLIST list type(bullets|ordered|glossary)"ordered">`

means `list`element have a `type`attribute with3allowed values "bullets", "ordered" or "glossary" and which defaultto"ordered" if the attribute is not explicitly specified.

The content type of an attribute can be text(`CDATA`),anchor/reference/references(`ID`/`IDREF`/`IDREFS`),entity(ies)(`ENTITY`/`ENTITIES`) orname(s)(`NMTOKEN`/`NMTOKENS`). The following definesthat a`chapter`element can have an optional`id`attributeof type `ID`, usable for reference fromattribute of typeIDREF:

`<!ATTLIST chapter id ID #IMPLIED>`

The last value of an attribute definition can be`#REQUIRED`meaning that the attribute has to be given,`#IMPLIED`meaning that it is optional, or the default value(possibly prefixed by`#FIXED`if it is the only allowed).

Notes:

- Usually the attributes pertaining to a given element are declared inasingle expression, but it is just a convention adopted by a lot ofDTDwriters:

      <!ATTLIST termdef
                id      ID      #REQUIRED
                name    CDATA   #IMPLIED>

  The previous construct defines both`id`and`name`attributes for the element`termdef`.

### Some examples

The directory `test/valid/dtds/`in the libxml2distributioncontains some complex DTD examples. The example in thefile`test/valid/dia.xml`shows an XML file where the simple DTDisdirectly included within the document.

### How to validate

The simplest way is to use the xmllint program included with libxml.The`--valid`option turns-on validation of the files given asinput.For example the following validates a copy of the first revision of theXML1.0 specification:

`xmllint --valid --noout test/valid/REC-xml-19980210.xml`

the -- noout is used to disable output of the resulting tree.

The `--dtdvalid dtd`allows validation of the document(s)againsta given DTD.

Libxml2 exports an API to handle DTDs and validation, check the associateddescription.

### Other resources

DTDs are as old as SGML. So there may be a number of examples on-line,Iwill just list one for now, others pointers welcome:

- XML-101 DTD

I suggest looking at the examples found under test/valid/dtd and any ofthelarge number of books available on XML. The dia example in test/validshouldbe both simple and complete enough to allow you to build your own.

## Memory Management

Table of Content:

1. General overview
2. Setting libxml2 set of memory routines
3. Cleaning up after parsing
4. Debugging routines
5. General memory requirements

### General overview

The module `xmlmemory.h`providesthe interfaces to the libxml2 memory system:

- libxml2 does not use the libc memory allocator directly butxmlFree(),xmlMalloc() and xmlRealloc()
- those routines can be reallocated to a specific set of routine,bydefault the libc ones i.e. free(), malloc() and realloc()
- the xmlmemory.c module includes a set of debugging routine

### Setting libxml2 set of memory routines

It is sometimes useful to not use the default memory allocator, eitherfordebugging, analysis or to implement a specific behaviour on memorymanagement(like on embedded systems). Two function calls are available to doso:

- xmlMemGet()whichreturn the current set of functions in use by the parser
- xmlMemSetup()whichallow to set up a new set of memory allocation functions

Of course a call to xmlMemSetup() should probably be done beforecallingany other libxml2 routines (unless you are sure your allocationsroutines arecompatibles).

### Cleaning up after parsing

Libxml2 is not stateless, there is a few set of memory structuresneedingallocation before the parser is fully functional (some encodingstructuresfor example). This also mean that once parsing is finished there isa tinyamount of memory (a few hundred bytes) which can be recollected if youdon'treuse the parser immediately:

- xmlCleanupParser()isa centralized routine to free the parsing states. Note that itwon'tdeallocate any produced tree if any (use the xmlFreeDoc() andrelatedroutines for this).
- xmlInitParser()isthe dual routine allowing to preallocate the parsing statewhich can beuseful for example to avoid initialization reentrancyproblems when usinglibxml2 in multithreaded applications

Generally xmlCleanupParser() is safe, if needed the state will berebuildat the next invocation of parser routines, but be careful of theconsequencesin multithreaded applications.

### Debugging routines

When configured using --with-mem-debug flag (off by default), libxml2usesa set of memory allocation debugging routines keeping track of allallocatedblocks and the location in the code where the routine was called. Acouple ofother debugging routines allow to dump the memory allocated infos toa fileor call a specific routine when a given block number is allocated:

- xmlMallocLoc()xmlReallocLoc()andxmlMemStrdupLoc()arethe memory debugging replacement allocation routines
- xmlMemoryDump()dumpsall the informations about the allocated memory block leftsin the`.memdump`file

When developing libxml2 memory debug is enabled, the tests programscallxmlMemoryDump () and the "make test" regression tests will check foranymemory leak during the full regression test sequence, this helps alotensuring that libxml2 does not leak memory and bullet proofmemoryallocations use (some libc implementations are known to be far toopermissiveresulting in major portability problems!).

If the .memdump reports a leak, it displays the allocation functionandalso tries to give some informations about the content and structure oftheallocated blocks left. This is sufficient in most cases to find theculprit,but not always. Assuming the allocation problem is reproducible, itispossible to find more easily:

1. write down the block number xxxx not allocated
2. export the environment variable XML_MEM_BREAKPOINT=xxxx , theeasiestwhen using GDB is to simply give the command

   `set environment XML_MEM_BREAKPOINT xxxx`

   before running the program.

3. run the program under a debugger and set a breakpointonxmlMallocBreakpoint() a specific function called when this preciseblockis allocated
4. when the breakpoint is reached you can then do a fine analysis oftheallocation an step to see the condition resulting in themissingdeallocation.

I used to use a commercial tool to debug libxml2 memory problems butafternoticing that it was not detecting memory leaks that simple mechanismwasused and proved extremely efficient until now. Lately I have also used valgrindwith quite somesuccess,it is tied to the i386 architecture since it works by emulating theprocessorand instruction set, it is slow but extremely efficient, i.e. itspot memoryusage errors in a very precise way.

### General memory requirements

How much libxml2 memory require ? It's hard to tell in average itdependsof a number of things:

- the parser itself should work in a fixed amount of memory, exceptforinformation maintained about the stacks of names and entitieslocations.The I/O and encoding handlers will probably account for a fewKBytes.This is true for both the XML and HTML parser (though the HTMLparserneed more state).
- If you are generating the DOM tree then memory requirements willgrownearly linear with the size of the data. In general for abalancedtextual document the internal memory requirement is about 4 timesthesize of the UTF8 serialization of this document (example theXML-1.0recommendation is a bit more of 150KBytes and takes 650KBytes ofmainmemory when parsed). Validation will add a amount of memory requiredformaintaining the external Dtd state which should be linear withthecomplexity of the content model defined by the Dtd
- If you need to work with fixed memory requirements or don't needthefull DOM tree then using the xmlReaderinterfaceis probably the best way toproceed, it still allows tovalidate or operate on subset of the tree ifneeded.
- If you don't care about the advanced features of libxml2likevalidation, DOM, XPath or XPointer, don't use entities, need to workwithfixed memory requirements, and try to get the fastest parsingpossiblethen the SAX interface should be used, but it has knownrestrictions.

## Encodings support

If you are not really familiar with Internationalization (usual shortcutisI18N) , Unicode, characters and glyphs, I suggest you read a presentationbyTim Bray on Unicode and why you should care about it.

If you don't understand why it does not make sense to have astringwithout knowing what encoding it uses, then as Joel Spolsky said please do notwriteanother line of code until you finish reading that article.. It isaprerequisite to understand this page, and avoid a lot of problemswithlibxml2, XML or text processing in general.

Table of Content:

1. What does internationalization supportmean?
2. The internal encoding, howandwhy
3. How is it implemented ?
4. Default supported encodings
5. How to extend theexistingsupport

### What does internationalization support mean ?

XML was designed from the start to allow the support of any charactersetby using Unicode. Any conformant XML parser has to support the UTF-8andUTF-16 default encodings which can both express the full unicode ranges.UTF8is a variable length encoding whose greatest points are to reuse thesameencoding for ASCII and to save space for Western encodings, but it is abitmore complex to handle in practice. UTF-16 use 2 bytes per character(andsometimes combines two pairs), it makes implementation easier, but looksabit overkill for Western languages encoding. Moreover the XMLspecificationallows the document to be encoded in other encodings at thecondition thatthey are clearly labeled as such. For example the following isa wellformedXML document encoded in ISO-8859-1 and using accentuated lettersthat weFrench like for both markup and content:

    <?xml version="1.0" encoding="ISO-8859-1"?>
    <très>là</très>

Having internationalization support in libxml2 means the following:

- the document is properly parsed
- informations about it's encoding are saved
- it can be modified
- it can be saved in its original encoding
- it can also be saved in another encoding supported by libxml2(forexample straight UTF8 or even an ASCII form)

Another very important point is that the whole libxml2 API, withtheexception of a few routines to read with a specific encoding or save toaspecific encoding, is completely agnostic about the original encoding ofthedocument.

It should be noted too that the HTML parser embedded in libxml2 nowobeythe same rules too, the following document will be (as of 2.2.2) handledinan internationalized fashion by libxml2 too:

    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"
                          "http://www.w3.org/TR/REC-html40/loose.dtd">
    <html lang="fr">
    <head>
      <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=ISO-8859-1">
    </head>
    <body>
    <p>W3C crée des standards pour le Web.</body>
    </html>

### The internal encoding, how and why

One of the core decisions was to force all documents to be converted toadefault internal encoding, and that encoding to be UTF-8, here aretherationales for those choices:

- keeping the native encoding in the internal form would force thelibxmlusers (or the code associated) to be fully aware of the encoding oftheoriginal document, for examples when adding a text node to adocument,the content would have to be provided in the document encoding,i.e. theclient code would have to check it before hand, make sure it'sconformantto the encoding, etc ... Very hard in practice, though in somespecificcases this may make sense.
- the second decision was which encoding. From the XML spec only UTF8andUTF16 really makes sense as being the two only encodings for whichthereis mandatory support. UCS-4 (32 bits fixed size encoding) couldbeconsidered an intelligent choice too since it's a direct Unicodemappingsupport. I selected UTF-8 on the basis of efficiency andcompatibilitywith surrounding software:
  - UTF-8 while a bit more complex to convert from/to (i.e.slightlymore costly to import and export CPU wise) is also far morecompactthan UTF-16 (and UCS-4) for a majority of the documents I seeit usedfor right now (RPM RDF catalogs, advogato data, variousconfigurationfile formats, etc.) and the key point for today'scomputerarchitecture is efficient uses of caches. If one nearlydouble thememory requirement to store the same amount of data, thiswill trashcaches (main memory/external caches/internal caches) and mytake isthat this harms the system far more than the CPU requirementsneededfor the conversion to UTF-8
  - Most of libxml2 version 1 users were using it with straightASCIImost of the time, doing the conversion with an internalencodingrequiring all their code to be rewritten was a seriousshow-stopperfor using UTF-16 or UCS-4.
  - UTF-8 is being used as the de-facto internal encoding standardforrelated code like the pangoupcoming Gnome text widget, anda lot of Unix code (yet another placewhere Unix programmer base takesa different approach from Microsoft- they are using UTF-16)

What does this mean in practice for the libxml2 user:

- xmlChar, the libxml2 data type is a byte, those bytes must beassembledas UTF-8 valid strings. The proper way to terminate an xmlChar *stringis simply to append 0 byte, as usual.
- One just need to make sure that when using chars outside the ASCIIset,the values has been properly converted to UTF-8

### How is it implemented ?

Let's describe how all this works within libxml, basically theI18N(internationalization) support get triggered only during I/O operation,i.e.when reading a document or saving one. Let's look first at thereadingsequence:

1. when a document is processed, we usually don't know the encoding,asimple heuristic allows to detect UTF-16 and UCS-4 from encodingswherethe ASCII range (0-0x7F) maps with ASCII
2. the xml declaration if available is parsed, including theencodingdeclaration. At that point, if the autodetected encoding isdifferentfrom the one declared a call to xmlSwitchEncoding() isissued.
3. If there is no encoding declaration, then the input has to be ineitherUTF-8 or UTF-16, if it is not then at some point when processingtheinput, the converter/checker of UTF-8 form will raise an encodingerror.You may end-up with a garbled document, or no document at all !Example:

       ~/XML -> ./xmllint err.xml
       err.xml:1: error: Input is not proper UTF-8, indicate encoding !
       <très>là</très>
          ^
       err.xml:1: error: Bytes: 0xE8 0x73 0x3E 0x6C
       <très>là</très>
          ^

4. xmlSwitchEncoding() does an encoding name lookup, canonicalize it,andthen search the default registered encoding converters for thatencoding.If it's not within the default set and iconv() support has beencompiledit, it will ask iconv for such an encoder. If this fails then theparserwill report an error and stops processing:

       ~/XML -> ./xmllint err2.xml
       err2.xml:1: error: Unsupported encoding UnsupportedEnc
       <?xml version="1.0" encoding="UnsupportedEnc"?>
                                                    ^

5. From that point the encoder processes progressively the input (itisplugged as a front-end to the I/O module) for that entity. Itcapturesand converts on-the-fly the document to be parsed to UTF-8. Theparseritself just does UTF-8 checking of this input and processittransparently. The only difference is that the encoding informationhasbeen added to the parsing context (more precisely to theinputcorresponding to this entity).
6. The result (when using DOM) is an internal form completely in UTF-8withjust an encoding information on the document node.

Ok then what happens when saving the document (assuming youcollected/builtan xmlDoc DOM like structure) ? It depends on the functioncalled,xmlSaveFile() will just try to save in the original encoding,whilexmlSaveFileTo() and xmlSaveFileEnc() can optionally save to agivenencoding:

1. if no encoding is given, libxml2 will look for an encodingvalueassociated to the document and if it exists will try to save tothatencoding,

   otherwise everything is written in the internal form, i.e. UTF-8

2. so if an encoding was specified, either at the API level or onthedocument, libxml2 will again canonicalize the encoding name, lookupfor aconverter in the registered set or through iconv. If not foundthefunction will return an error code
3. the converter is placed before the I/O buffer layer, as another kindofbuffer, then libxml2 will simply push the UTF-8 serialization tothroughthat buffer, which will then progressively be converted and pushedontothe I/O layer.
4. It is possible that the converter code fails on some input, forexampletrying to push an UTF-8 encoded Chinese character through theUTF-8 toISO-8859-1 converter won't work. Since the encoders areprogressive theywill just report the error and the number of bytesconverted, at thatpoint libxml2 will decode the offending character,remove it from thebuffer and replace it with the associated charRefencoding &#123; andresume the conversion. This guarantees that anydocument will be savedwithout losses (except for markup names where thisis not legal, this isa problem in the current version, in practice avoidusing non-asciicharacters for tag or attribute names). A special "ascii"encoding nameis used to save documents to a pure ascii form can be usedwhenportability is really crucial

Here are a few examples based on the same test document:

    ~/XML -> ./xmllint isolat1
    <?xml version="1.0" encoding="ISO-8859-1"?>
    <très>là</très>
    ~/XML -> ./xmllint --encode UTF-8 isolat1
    <?xml version="1.0" encoding="UTF-8"?>
    <trÃ¨s>lÃ  </trÃ¨s>
    ~/XML ->

The same processing is applied (and reuse most of the code) for HTMLI18Nprocessing. Looking up and modifying the content encoding is a bitmoredifficult since it is located in a <meta> tag under the<head>,so a couple of functions htmlGetMetaEncoding() andhtmlSetMetaEncoding() havebeen provided. The parser also attempts to switchencoding on the fly whendetecting such a tag on input. Except for that theprocessing is the same(and again reuses the same code).

### Default supported encodings

libxml2 has a set of default converters for the followingencodings(located in encoding.c):

1. UTF-8 is supported by default (null handlers)
2. UTF-16, both little and big endian
3. ISO-Latin-1 (ISO-8859-1) covering most western languages
4. ASCII, useful mostly for saving
5. HTML, a specific handler for the conversion of UTF-8 to ASCII withHTMLpredefined entities like &copy; for the Copyright sign.

More over when compiled on an Unix platform with iconv support the fullsetof encodings supported by iconv can be instantly be used by libxml. On alinuxmachine with glibc-2.1 the list of supported encodings and aliases fill3 fullpages, and include UCS-4, the full set of ISO-Latin encodings, and thevariousJapanese ones.

To convert from the UTF-8 values returned from the API to anotherencodingthen it is possible to use the function provided from the encoding modulelike UTF8Toisolat1, or usethePOSIX iconv()APIdirectly.

#### Encoding aliases

From 2.2.3, libxml2 has support to register encoding names aliases.Thegoal is to be able to parse document whose encoding is supported butwherethe name differs (for example from the default set of names acceptedbyiconv). The following functions allow to register and handle new aliasesforexisting encodings. Once registered libxml2 will automatically lookupthealiases when handling a document:

- int xmlAddEncodingAlias(const char *name, const char *alias);
- int xmlDelEncodingAlias(const char *alias);
- const char * xmlGetEncodingAlias(const char *alias);
- void xmlCleanupEncodingAliases(void);

### How to extend the existing support

Well adding support for new encoding, or overriding one of theencoders(assuming it is buggy) should not be hard, just write input andoutputconversion routines to/from UTF-8, and register themusingxmlNewCharEncodingHandler(name, xxxToUTF8, UTF8Toxxx), and they willbecalled automatically if the parser(s) encounter such an encodingname(register it uppercase, this will help). The description of theencoders,their arguments and expected return values are described in theencoding.hheader.

## I/O Interfaces

Table of Content:

1. General overview
2. The basic buffer type
3. Input I/O handlers
4. Output I/O handlers
5. The entities loader
6. Example of customized I/O

### General overview

The module `xmlIO.h`providestheinterfaces to the libxml2 I/O system. This consists of 4 main parts:

- Entities loader, this is a routine which tries to fetch theentities(files) based on their PUBLIC and SYSTEM identifiers. The defaultloaderdon't look at the public identifier since libxml2 do not maintainacatalog. You can redefine you own entity loader byusing`xmlGetExternalEntityLoader()`and`xmlSetExternalEntityLoader()`.Check theexample.
- Input I/O buffers which are a commodity structure used by theparser(s)input layer to handle fetching the informations to feed theparser. Thisprovides buffering and is also a placeholder where theencodingconverters to UTF8 are piggy-backed.
- Output I/O buffers are similar to the Input ones and fulfillsimilartask but when generating a serialization from a tree.
- A mechanism to register sets of I/O callbacks and associate themwithspecific naming schemes like the protocol part of the URIs.

  This affect the default I/O operations and allows to use specificI/Ohandlers for certain names.

The general mechanism used when loading http://rpmfind.net/xml.htmlforexample in the HTML parser is the following:

1. The default entity loader calls`xmlNewInputFromFile()`withthe parsing context and the URIstring.
2. the URI string is checked against the existing registered handlersusingtheir match() callback function, if the HTTP module was compiledin, it isregistered and its match() function will succeeds
3. the open() function of the handler is called and if successfulwillreturn an I/O Input buffer
4. the parser will the start reading from this buffer andprogressivelyfetch information from the resource, calling the read()function of thehandler until the resource is exhausted
5. if an encoding change is detected it will be installed on theinputbuffer, providing buffering and efficient use of theconversionroutines
6. once the parser has finished, the close() function of the handleriscalled once and the Input buffer and associated resourcesaredeallocated.

The user defined callbacks are checked first to allow overriding ofthedefault libxml2 I/O routines.

### The basic buffer type

All the buffer manipulation handling is done usingthe`xmlBuffer`type define in `tree.h`which isaresizable memory buffer. The buffer allocation strategy can be selected tobeeither best-fit or use an exponential doubling one (CPU vs. memoryusetrade-off). The values are`XML_BUFFER_ALLOC_EXACT`and`XML_BUFFER_ALLOC_DOUBLEIT`,and can be set individually or on asystem wide basis using`xmlBufferSetAllocationScheme()`. A numberof functions allows tomanipulate buffers with names starting withthe`xmlBuffer...`prefix.

### Input I/O handlers

An Input I/O handler is a simplestructure`xmlParserInputBuffer`containing a context associated totheresource (file descriptor, or pointer to a protocol handler), the read()andclose() callbacks to use and an xmlBuffer. And extra xmlBuffer and acharsetencoding handler are also present to support charset conversionwhenneeded.

### Output I/O handlers

An Output handler `xmlOutputBuffer`is completely similar toanInput one except the callbacks are write() and close().

### The entities loader

The entity loader resolves requests for new entities and create inputsforthe parser. Creating an input from a filename or an URI string isdonethrough the xmlNewInputFromFile() routine. The default entity loader donothandle the PUBLIC identifier associated with an entity (if any). So itjustcalls xmlNewInputFromFile() with the SYSTEM identifier (which ismandatory inXML).

If you want to hook up a catalog mechanism then you simply need tooverridethe default entity loader, here is an example:

    #include <libxml/xmlIO.h>

    xmlExternalEntityLoader defaultLoader = NULL;

    xmlParserInputPtr
    xmlMyExternalEntityLoader(const char *URL, const char *ID,
                                   xmlParserCtxtPtr ctxt) {
        xmlParserInputPtr ret;
        const char *fileID = NULL;
        /* lookup for the fileID depending on ID */

        ret = xmlNewInputFromFile(ctxt, fileID);
        if (ret != NULL)
            return(ret);
        if (defaultLoader != NULL)
            ret = defaultLoader(URL, ID, ctxt);
        return(ret);
    }

    int main(..) {
        ...

        /*
         * Install our own entity loader
         */
        defaultLoader = xmlGetExternalEntityLoader();
        xmlSetExternalEntityLoader(xmlMyExternalEntityLoader);

        ...
    }

### Example of customized I/O

This example come from areal use case,xmlDocDump() closes the FILE * passed by the applicationand this was aproblem. The solutionwasto redefine anew output handler with the closing call deactivated:

1. First define a new I/O output allocator where the output don't closethefile:

       xmlOutputBufferPtr
       xmlOutputBufferCreateOwn(FILE *file, xmlCharEncodingHandlerPtr encoder) {
           xmlOutputBufferPtr ret;

           if (xmlOutputCallbackInitialized == 0)
               xmlRegisterDefaultOutputCallbacks();

           if (file == NULL) return(NULL);
           ret = xmlAllocOutputBuffer(encoder);
           if (ret != NULL) {
               ret->context = file;
               ret->writecallback = xmlFileWrite;
               ret->closecallback = NULL;  /* No close callback */
           }
           return(ret);
       }

2. And then use it to save the document:

       FILE *f;
       xmlOutputBufferPtr output;
       xmlDocPtr doc;
       int res;

       f = ...
       doc = ....

       output = xmlOutputBufferCreateOwn(f, NULL);
       res = xmlSaveFileTo(output, doc, NULL);

## Catalog support

Table of Content:

1. General overview
2. The definition
3. Using catalogs
4. Some examples
5. How to tune catalog usage
6. How to debug catalog processing
7. How to create and maintain catalogs
8. The implementor corner quick review oftheAPI
9. Other resources

### General overview

What is a catalog? Basically it's a lookup mechanism used when an entity(afile or a remote resource) references another entity. The catalog lookupisinserted between the moment the reference is recognized by the software(XMLparser, stylesheet processing, or even images referenced for inclusionin arendering) and the time where loading that resource is actuallystarted.

It is basically used for 3 things:

- mapping from "logical" names, the public identifiers and a moreconcretename usable for download (and URI). For example it can associatethelogical name

  "-//OASIS//DTD DocBook XML V4.1.2//EN"

  of the DocBook 4.1.2 XML DTD with the actual URL where it canbedownloaded

  http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd

- remapping from a given URL to another one, like an HTTPindirectionsaying that

  "http://www.oasis-open.org/committes/tr.xsl"

  should really be looked at

  "http://www.oasis-open.org/committes/entity/stylesheets/base/tr.xsl"

- providing a local cache mechanism allowing to load theentitiesassociated to public identifiers or remote resources, this is areallyimportant feature for any significant deployment of XML or SGMLsince itallows to avoid the aleas and delays associated to fetchingremoteresources.

### The definitions

Libxml, as of 2.4.3 implements 2 kind of catalogs:

- the older SGML catalogs, the official spec is SGML OpenTechnicalResolution TR9401:1997, but is better understood by reading the SP CatalogpagefromJames Clark. This is relatively old and not the preferredmode ofoperation of libxml.
- XMLCatalogsisfar more flexible, more recent, uses an XML syntax andshould scale quitebetter. This is the default option of libxml.

### Using catalog

In a normal environment libxml2 will by default check the presence ofacatalog in /etc/xml/catalog, and assuming it has been correctlypopulated,the processing is completely transparent to the document user. Totake aconcrete example, suppose you are authoring a DocBook document, thisonestarts with the following DOCTYPE definition:

    <?xml version='1.0'?>
    <!DOCTYPE book PUBLIC "-//Norman Walsh//DTD DocBk XML V3.1.4//EN"
              "http://nwalsh.com/docbook/xml/3.1.4/db3xml.dtd">

When validating the document with libxml, the catalog will beautomaticallyconsulted to lookup the public identifier "-//Norman Walsh//DTDDocBk XMLV3.1.4//EN" and the systemidentifier"http://nwalsh.com/docbook/xml/3.1.4/db3xml.dtd", and if theseentities havebeen installed on your system and the catalogs actually point tothem, libxmlwill fetch them from the local disk.

Note: Really don't usethisDOCTYPE example it's a really old version, but is fine as an example.

Libxml2 will check the catalog each time that it is requested to loadanentity, this includes DTD, external parsed entities, stylesheets, etc ...Ifyour system is correctly configured all the authoring phase andprocessingshould use only local files, even if your document stays portablebecause ituses the canonical public and system ID, referencing the remotedocument.

### Some examples:

Here is a couple of fragments from XML Catalogs used in libxml2earlyregression tests in `test/catalogs`:

    <?xml version="1.0"?>
    <!DOCTYPE catalog PUBLIC
       "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN"
       "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd">
    <catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog">
      <public publicId="-//OASIS//DTD DocBook XML V4.1.2//EN"
       uri="http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"/>
    ...

This is the beginning of a catalog for DocBook 4.1.2, XML Catalogsarewritten in XML, there is a specific namespace for catalogelements"urn:oasis:names:tc:entity:xmlns:xml:catalog". The first entry inthiscatalog is a `public`mapping it allows to associate aPublicIdentifier with an URI.

    ...
        <rewriteSystem systemIdStartString="http://www.oasis-open.org/docbook/"
                       rewritePrefix="file:///usr/share/xml/docbook/"/>
    ...

A `rewriteSystem`is a very powerful instruction, it saysthatany URI starting with a given prefix should be looked at anotherURIconstructed by replacing the prefix with an new one. In effect this actslikea cache system for a full area of the Web. In practice it is extremelyusefulwith a file prefix if you have installed a copy of those resources onyourlocal system.

    ...
    <delegatePublic publicIdStartString="-//OASIS//DTD XML Catalog //"
                    catalog="file:///usr/share/xml/docbook.xml"/>
    <delegatePublic publicIdStartString="-//OASIS//ENTITIES DocBook XML"
                    catalog="file:///usr/share/xml/docbook.xml"/>
    <delegatePublic publicIdStartString="-//OASIS//DTD DocBook XML"
                    catalog="file:///usr/share/xml/docbook.xml"/>
    <delegateSystem systemIdStartString="http://www.oasis-open.org/docbook/"
                    catalog="file:///usr/share/xml/docbook.xml"/>
    <delegateURI uriStartString="http://www.oasis-open.org/docbook/"
                    catalog="file:///usr/share/xml/docbook.xml"/>
    ...

Delegation is the core features which allows to build a tree ofcatalogs,easier to maintain than a single catalog, based on PublicIdentifier, SystemIdentifier or URI prefixes it instructs the catalogsoftware to look upentries in another resource. This feature allow to buildhierarchies ofcatalogs, the set of entries presented should be sufficient toredirect theresolution of all DocBook references to the specific catalogin`/usr/share/xml/docbook.xml`this one in turn could delegateallreferences for DocBook 4.2.1 to a specific catalog installed at the sametimeas the DocBook resources on the local machine.

### How to tune catalog usage:

The user can change the default catalog behaviour by redirecting queriestoits own set of catalogs, this can be done by settingthe`XML_CATALOG_FILES`environment variable to a list of catalogs,anempty one should deactivate loading the default`/etc/xml/catalog`default catalog

### How to debug catalog processing:

Setting up the `XML_DEBUG_CATALOG`environment variable willmakelibxml2 output debugging informations for each catalog operations,forexample:

    orchis:~/XML -> xmllint --memory --noout test/ent2
    warning: failed to load external entity "title.xml"
    orchis:~/XML -> export XML_DEBUG_CATALOG=
    orchis:~/XML -> xmllint --memory --noout test/ent2
    Failed to parse catalog /etc/xml/catalog
    Failed to parse catalog /etc/xml/catalog
    warning: failed to load external entity "title.xml"
    Catalogs cleanup
    orchis:~/XML ->

The test/ent2 references an entity, running the parser from memorymakesthe base URI unavailable and the the "title.xml" entity cannot beloaded.Setting up the debug environment variable allows to detect that anattempt ismade to load the `/etc/xml/catalog`but since it's notpresent theresolution fails.

But the most advanced way to debug XML catalog processing is to usethexmlcatalogcommand shipped with libxml2, it allows toloadcatalogs and make resolution queries to see what is going on. This isalsoused for the regression tests:

    orchis:~/XML -> ./xmlcatalog test/catalogs/docbook.xml \
                       "-//OASIS//DTD DocBook XML V4.1.2//EN"
    http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd
    orchis:~/XML ->

For debugging what is going on, adding one -v flags increase theverbositylevel to indicate the processing done (adding a second flag alsoindicatewhat elements are recognized at parsing):

    orchis:~/XML -> ./xmlcatalog -v test/catalogs/docbook.xml \
                       "-//OASIS//DTD DocBook XML V4.1.2//EN"
    Parsing catalog test/catalogs/docbook.xml's content
    Found public match -//OASIS//DTD DocBook XML V4.1.2//EN
    http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd
    Catalogs cleanup
    orchis:~/XML ->

A shell interface is also available to debug and process multiplequeries(and for regression tests):

    orchis:~/XML -> ./xmlcatalog -shell test/catalogs/docbook.xml \
                       "-//OASIS//DTD DocBook XML V4.1.2//EN"
    > help
    Commands available:
    public PublicID: make a PUBLIC identifier lookup
    system SystemID: make a SYSTEM identifier lookup
    resolve PublicID SystemID: do a full resolver lookup
    add 'type' 'orig' 'replace' : add an entry
    del 'values' : remove values
    dump: print the current catalog state
    debug: increase the verbosity level
    quiet: decrease the verbosity level
    exit:  quit the shell
    > public "-//OASIS//DTD DocBook XML V4.1.2//EN"
    http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd
    > quit
    orchis:~/XML ->

This should be sufficient for most debugging purpose, this wasactuallyused heavily to debug the XML Catalog implementation itself.

### How to create and maintaincatalogs:

Basically XML Catalogs are XML files, you can either use XML toolstomanage them or use xmlcatalogfor this. The basic stepisto create a catalog the -create option provide this facility:

    orchis:~/XML -> ./xmlcatalog --create tst.xml
    <?xml version="1.0"?>
    <!DOCTYPE catalog PUBLIC "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN"
             "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd">
    <catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"/>
    orchis:~/XML ->

By default xmlcatalog does not overwrite the original catalog and savetheresult on the standard output, this can be overridden using the-nooutoption. The `-add`command allows to add entries inthecatalog:

    orchis:~/XML -> ./xmlcatalog --noout --create --add "public" \
      "-//OASIS//DTD DocBook XML V4.1.2//EN" \
      http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd tst.xml
    orchis:~/XML -> cat tst.xml
    <?xml version="1.0"?>
    <!DOCTYPE catalog PUBLIC "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" \
      "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd">
    <catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog">
    <public publicId="-//OASIS//DTD DocBook XML V4.1.2//EN"
            uri="http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"/>
    </catalog>
    orchis:~/XML ->

The `-add`option will always take 3 parameters even if someofthe XML Catalog constructs (like nextCatalog) will have only asingleargument, just pass a third empty string, it will be ignored.

Similarly the `-del`option remove matching entries fromthecatalog:

    orchis:~/XML -> ./xmlcatalog --del \
      "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" tst.xml
    <?xml version="1.0"?>
    <!DOCTYPE catalog PUBLIC "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN"
        "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd">
    <catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"/>
    orchis:~/XML ->

The catalog is now empty. Note that the matching of`-del`isexact and would have worked in a similar fashion with thePublic IDstring.

This is rudimentary but should be sufficient to manage a not toocomplexcatalog tree of resources.

### The implementor corner quick review oftheAPI:

First, and like for every other module of libxml, there is anautomaticallygenerated API page forcatalogsupport.

The header for the catalog interfaces should be included as:

    #include <libxml/catalog.h>

The API is voluntarily kept very simple. First it is not obviousthatapplications really need access to it since it is the default behaviouroflibxml2 (Note: it is possible to completely override libxml2 defaultcatalogby using xmlSetExternalEntityLoadertoplug anapplication specific resolver).

Basically libxml2 support 2 catalog lists:

- the default one, global shared by all the application
- a per-document catalog, this one is built if the document usesthe`oasis-xml-catalog`PIs to specify its own catalog list, itisassociated to the parser context and destroyed when the parsingcontextis destroyed.

the document one will be used first if it exists.

#### Initialization routines:

xmlInitializeCatalog(), xmlLoadCatalog() and xmlLoadCatalogs() shouldbeused at startup to initialize the catalog, if the catalog shouldbeinitialized with specific values xmlLoadCatalog() orxmlLoadCatalogs()should be called before xmlInitializeCatalog() which wouldotherwise do adefault initialization first.

The xmlCatalogAddLocal() call is used by the parser to grow thedocumentown catalog list if needed.

#### Preferences setup:

The XML Catalog spec requires the possibility to select defaultpreferencesbetween public and system delegation,xmlCatalogSetDefaultPrefer() allowsthis, xmlCatalogSetDefaults() andxmlCatalogGetDefaults() allow to control ifXML Catalogs resolution shouldbe forbidden, allowed for global catalog, fordocument catalog or both, thedefault is to allow both.

And of course xmlCatalogSetDebug() allows to generate debugmessages(through the xmlGenericError() mechanism).

#### Querying routines:

xmlCatalogResolve(), xmlCatalogResolveSystem(),xmlCatalogResolvePublic()and xmlCatalogResolveURI() are relatively explicitif you read the XMLCatalog specification they correspond to section 7algorithms, they shouldalso work if you have loaded an SGML catalog with asimplified semantic.

xmlCatalogLocalResolve() and xmlCatalogLocalResolveURI() are the samebutoperate on the document catalog list

#### Cleanup and Miscellaneous:

xmlCatalogCleanup() free-up the global catalog, xmlCatalogFreeLocal()isthe per-document equivalent.

xmlCatalogAdd() and xmlCatalogRemove() are used to dynamically modifythefirst catalog in the global list, and xmlCatalogDump() allows to dumpacatalog state, those routines are primarily designed for xmlcatalog, I'mnotsure that exposing more complex interfaces (like navigation ones) wouldbereally useful.

The xmlParseCatalogFile() is a function used to load XML Catalogfiles,it's similar as xmlParseFile() except it bypass all catalog lookups,it'sprovided because this functionality may be useful for client tools.

#### threaded environments:

Since the catalog tree is built progressively, some care has been takentotry to avoid troubles in multithreaded environments. The code is nowthreadsafe assuming that the libxml2 library has been compiled withthreadssupport.

### Other resources

The XML Catalog specification is relatively recent so there isn'tmuchliterature to point at:

- You can find a good rant from Norm Walsh about theneedfor catalogs, it provides a lot of context informations even ifIdon't agree with everything presented. Norm also wrote a morerecentarticle XMLentitiesand URI resolversdescribing them.
- An oldXMLcatalog proposalfrom John Cowan
- The Resource DirectoryDescriptionLanguage(RDDL) another catalog system but more orientedtowardproviding metadata for XML namespaces.
- the page from the OASIS Technical Committee onEntityResolutionwho maintains XML Catalog, you will find pointers tothespecification update, some background and pointers to otherstoolsproviding XML Catalog support
- There is a shell scriptto generateXMLCatalogs for DocBook 4.1.2 . If it can write to the /etc/xml/directory,it will set-up /etc/xml/catalog and /etc/xml/docbook based ontheresources found on the system. Otherwise it will just create~/xmlcatalogand ~/dbkxmlcatalog and doing:

  `export XML_CATALOG_FILES=$HOME/xmlcatalog`

  should allow to process DocBook documentations withoutrequiringnetwork accesses for the DTD or stylesheets

- I have uploaded asmalltarballcontaining XML Catalogs for DocBook 4.1.2 which seemsto workfine for me too
- The xmlcatalogmanualpage

If you have suggestions for corrections or additions, simply contactme:

## The parser interfaces

This section is directly intended to help programmers gettingbootstrappedusing the XML tollkit from the C language. It is not intended tobeextensive. I hope the automatically generated documents will providethecompleteness required, but as a separate set of documents. The interfacesofthe XML parser are by principle low level, Those interested in a higherlevelAPI should look at DOM.

The parser interfaces forXMLareseparated from the HTMLparserinterfaces. Let's have a look at how the XML parser can becalled:

### Invoking the parser : the pull method

Usually, the first thing to do is to read an XML input. The parseracceptsdocuments either from in-memory strings or from files. The functionsaredefined in "parser.h":

`xmlDocPtr xmlParseMemory(char *buffer, int size);`

  Parse a null-terminated string containing the document.

`xmlDocPtr xmlParseFile(const char *filename);`

  Parse an XML document contained in a (possibly compressed)file.

The parser returns a pointer to the document structure (or NULL in caseoffailure).

### Invoking the parser: the push method

In order for the application to keep the control when the document isbeingfetched (which is common for GUI based programs) libxml2 provides apushinterface, too, as of version 1.8.3. Here are the interfacefunctions:

    xmlParserCtxtPtr xmlCreatePushParserCtxt(xmlSAXHandlerPtr sax,
                                             void *user_data,
                                             const char *chunk,
                                             int size,
                                             const char *filename);
    int              xmlParseChunk          (xmlParserCtxtPtr ctxt,
                                             const char *chunk,
                                             int size,
                                             int terminate);

and here is a simple example showing how to use the interface:

                FILE *f;

                f = fopen(filename, "r");
                if (f != NULL) {
                    int res, size = 1024;
                    char chars[1024];
                    xmlParserCtxtPtr ctxt;

                    res = fread(chars, 1, 4, f);
                    if (res > 0) {
                        ctxt = xmlCreatePushParserCtxt(NULL, NULL,
                                    chars, res, filename);
                        while ((res = fread(chars, 1, size, f)) > 0) {
                            xmlParseChunk(ctxt, chars, res, 0);
                        }
                        xmlParseChunk(ctxt, chars, 0, 1);
                        doc = ctxt->myDoc;
                        xmlFreeParserCtxt(ctxt);
                    }
                }

The HTML parser embedded into libxml2 also has a push interface;thefunctions are just prefixed by "html" rather than "xml".

### Invoking the parser: the SAX interface

The tree-building interface makes the parser memory-hungry, firstloadingthe document in memory and then building the tree itself. Reading adocumentwithout building the tree is possible using the SAX interfaces (seeSAX.h andJamesHenstridge'sdocumentation). Note also that the push interface can belimited to SAX:just use the two first arguments of`xmlCreatePushParserCtxt()`.

### Building a tree from scratch

The other way to get an XML tree in memory is by building it.Basicallythere is a set of functions dedicated to building new elements.(These arealso described in <libxml/tree.h>.) For example, here is apiece ofcode that produces the XML document used in the previous examples:

        #include <libxml/tree.h>
        xmlDocPtr doc;
        xmlNodePtr tree, subtree;

        doc = xmlNewDoc("1.0");
        doc->children = xmlNewDocNode(doc, NULL, "EXAMPLE", NULL);
        xmlSetProp(doc->children, "prop1", "gnome is great");
        xmlSetProp(doc->children, "prop2", "& linux too");
        tree = xmlNewChild(doc->children, NULL, "head", NULL);
        subtree = xmlNewChild(tree, NULL, "title", "Welcome to Gnome");
        tree = xmlNewChild(doc->children, NULL, "chapter", NULL);
        subtree = xmlNewChild(tree, NULL, "title", "The Linux adventure");
        subtree = xmlNewChild(tree, NULL, "p", "bla bla bla ...");
        subtree = xmlNewChild(tree, NULL, "image", NULL);
        xmlSetProp(subtree, "href", "linus.gif");

Not really rocket science ...

### Traversing the tree

Basically by including"tree.h"yourcode has access to the internal structure of all the elementsof the tree.The names should be somewhat simple likeparent,children, next,prev,properties, etc... For example, stillwith the previousexample:

    doc->children->children->children

points to the title element,

    doc->children->children->next->children->children

points to the text node containing the chapter title "TheLinuxadventure".

NOTE: XML allows PIs and commentstobepresent before the document root, so `doc->children`maypointto an element which is not the document Root Element; afunction`xmlDocGetRootElement()`was added for this purpose.

### Modifying the tree

Functions are provided for reading and writing the document content.Hereis an excerpt from the tree API:

`xmlAttrPtr xmlSetProp(xmlNodePtr node, const xmlChar *name,constxmlChar *value);`

  This sets (or changes) an attribute carried by an ELEMENT node.Thevalue can be NULL.

`const xmlChar *xmlGetProp(xmlNodePtr node, constxmlChar*name);`

  This function returns a pointer to new copy of thepropertycontent. Note that the user must deallocate the result.

Two functions are provided for reading and writing the text associatedwithelements:

`xmlNodePtr xmlStringGetNodeList(xmlDocPtr doc, constxmlChar*value);`

  This function takes an "external" string and converts it toonetext node or possibly to a list of entity and text nodes.Allnon-predefined entity references like &Gnome; will bestoredinternally as entity nodes, hence the result of the function maynot bea single node.

`xmlChar *xmlNodeListGetString(xmlDocPtr doc, xmlNodePtr list,intinLine);`

  This function is the inverseof`xmlStringGetNodeList()`. It generates a newstringcontaining the content of the text and entity nodes. Note theextraargument inLine. If this argument is set to 1, the function willexpandentity references. For example, instead of returning the&Gnome;XML encoding in the string, it will substitute it with itsvalue (say,"GNU Network Object Model Environment").

### Saving a tree

Basically 3 options are possible:

`void xmlDocDumpMemory(xmlDocPtr cur, xmlChar**mem,int*size);`

  Returns a buffer into which the document has been saved.

`extern void xmlDocDump(FILE *f, xmlDocPtr doc);`

  Dumps a document to an open file descriptor.

`int xmlSaveFile(const char *filename, xmlDocPtr cur);`

  Saves the document to a file. In this case, thecompressioninterface is triggered if it has been turned on.

### Compression

The library transparently handles compression when doingfile-basedaccesses. The level of compression on saves can be turned on eithergloballyor individually for one file:

`int xmlGetDocCompressMode (xmlDocPtr doc);`

  Gets the document compression ratio (0-9).

`void xmlSetDocCompressMode (xmlDocPtr doc, int mode);`

  Sets the document compression ratio.

`int xmlGetCompressMode(void);`

  Gets the default compression ratio.

`void xmlSetCompressMode(int mode);`

  Sets the default compression ratio.

## Entities or no entities

Entities in principle are similar to simple C macros. An entity definesanabbreviation for a given string that you can reuse many times throughoutthecontent of your document. Entities are especially useful when a givenstringmay occur frequently within a document, or to confine the change neededto adocument to a restricted area in the internal subset of the document (atthebeginning). Example:

    1 <?xml version="1.0"?>
    2 <!DOCTYPE EXAMPLE SYSTEM "example.dtd" [
    3 <!ENTITY xml "Extensible Markup Language">
    4 ]>
    5 <EXAMPLE>
    6    &xml;
    7 </EXAMPLE>

Line 3 declares the xml entity. Line 6 uses the xml entity, byprefixingits name with '&' and following it by ';' without any spacesadded. Thereare 5 predefined entities in libxml2 allowing you to escapecharacters withpredefined meaning in some parts of the xml documentcontent:&lt;for the character '<',&gt;for the character '>',&apos;for the character''',&quot;for the character '"',and&amp;for the character '&'.

One of the problems related to entities is that you may want the parsertosubstitute an entity's content so that you can see the replacement textinyour application. Or you may prefer to keep entity references as such inthecontent to be able to save the document back without losing thisusuallyprecious information (if the user went through the pain ofexplicitlydefining entities, he may have a a rather negative attitude if youblindlysubstitute them as saving time). The xmlSubstituteEntitiesDefault()functionallows you to check and change the behaviour, which is to notsubstituteentities by default.

Here is the DOM tree built by libxml2 for the previous document inthedefault case:

    /gnome/src/gnome-xml -> ./xmllint --debug test/ent1
    DOCUMENT
    version=1.0
       ELEMENT EXAMPLE
         TEXT
         content=
         ENTITY_REF
           INTERNAL_GENERAL_ENTITY xml
           content=Extensible Markup Language
         TEXT
         content=

And here is the result when substituting entities:

    /gnome/src/gnome-xml -> ./tester --debug --noent test/ent1
    DOCUMENT
    version=1.0
       ELEMENT EXAMPLE
         TEXT
         content=     Extensible Markup Language

So, entities or no entities? Basically, it depends on your use case.Isuggest that you keep the non-substituting default behaviour and avoidusingentities in your XML document or data if you are not willing to handletheentity references elements in the DOM tree.

Note that at save time libxml2 enforces the conversion of thepredefinedentities where necessary to prevent well-formedness problems, andwill alsotransparently replace those with chars (i.e. it will not generateentityreference elements in the DOM tree or call the reference() SAX callbackwhenfinding them in the input).

WARNING: handlingentitieson top of the libxml2 SAX interface is difficult!!! If you plan tousenon-predefined entities in your documents, then the learning curve tohandlethen using the SAX API may be long. If you plan to use complexdocuments, Istrongly suggest you consider using the DOM interface instead andlet libxmldeal with the complexity rather than trying to do it yourself.

## Namespaces

The libxml2 library implements XML namespacessupportbyrecognizing namespace constructs in the input, and does namespacelookupautomatically when building the DOM tree. A namespace declarationisassociated with an in-memory structure and all elements or attributeswithinthat namespace point to it. Hence testing the namespace is a simple andfastequality operation at the user level.

I suggest that people using libxml2 use a namespace, and declare it intheroot element of their document as the default namespace. Then they don'tneedto use the prefix in the content but we will have a basis for futuresemanticrefinement and merging of data from different sources. This doesn'tincreasethe size of the XML output significantly, but significantly increasesitsvalue in the long-term. Example:

    <mydoc xmlns="http://mydoc.example.org/schemas/">
       <elem1>...</elem1>
       <elem2>...</elem2>
    </mydoc>

The namespace value has to be an absolute URL, but the URL doesn't havetopoint to any existing resource on the Web. It will bind all the elementandattributes with that URL. I suggest to use an URL within a domainyoucontrol, and that the URL should contain some kind of version informationifpossible. For example, `"http://www.gnome.org/gnumeric/1.0/"`isagood namespace scheme.

Then when you load a file, make sure that a namespace carryingtheversion-independent prefix is installed on the root element of yourdocument,and if the version information don't match something you know, warnthe userand be liberal in what you accept as the input. Also do *not* try tobasenamespace checking on the prefix value. <foo:text> may be exactlythesame as <bar:text> in another document. What really matters is theURIassociated with the element or the attribute, not the prefix string (whichisjust a shortcut for the full URI). In libxml, element and attributes havean`ns`field pointing to an xmlNs structure detailing thenamespaceprefix and its URI.

@@Interfaces@@

    xmlNodePtr node;
    if(!strncmp(node->name,"mytag",5)
      && node->ns
      && !strcmp(node->ns->href,"http://www.mysite.com/myns/1.0")) {
      ...
    }

Usually people object to using namespaces together with validitychecking.I will try to make sure that using namespaces won't break validitychecking,so even if you plan to use or currently are using validation Istronglysuggest adding namespaces to your document. A default namespacescheme`xmlns="http://...."`should not break validity even onlessflexible parsers. Using namespaces to mix and differentiate contentcomingfrom multiple DTDs will certainly break current validation schemes. Tochecksuch documents one needs to use schema-validation, which is supportedinlibxml2 as well. See relagx-ngand w3c-schema.

## Upgrading 1.x code

Incompatible changes:

Version 2 of libxml2 is the first version introducing seriousbackwardincompatible changes. The main goals were:

- a general cleanup. A number of mistakes inherited from the veryearlyversions couldn't be changed due to compatibility constraints.Examplethe "childs" element in the nodes.
- Uniformization of the various nodes, at least for their header andlinkparts (doc, parent, children, prev, next), the goal is asimplerprogramming model and simplifying the task of the DOMimplementors.
- better conformances to the XML specification, for example version1.xhad an heuristic to try to detect ignorable white spaces. As a resulttheSAX event generated were ignorableWhitespace() while the specrequirescharacter() in that case. This also mean that a number of DOMnodecontaining blank text may populate the DOM tree which were notpresentbefore.

### How to fix libxml-1.x code:

So client code of libxml designed to run with version 1.x may have tobechanged to compile against version 2.x of libxml. Here is a list ofchangesthat I have collected, they may not be sufficient, so in case you findotherchange which are required, dropme amail:

1. The package name have changed from libxml to libxml2, the librarynameis now -lxml2 . There is a new xml2-config script which should beused toselect the right parameters libxml2
2. Node childsfield has beenrenamedchildrenso s/childs/children/g should beapplied(probability of having "childs" anywhere else is close to 0+
3. The document don't have anymore a rootelement ithasbeen replaced by childrenand usually you will getalist of element here. For example a Dtd element for the internalsubsetand it's declaration may be found in that list, as well asprocessinginstructions or comments found before or after the documentroot element.Use xmlDocGetRootElement(doc)to get theroot element ofa document. Alternatively if you are sure to not referenceDTDs nor havePIs or comments before or after the rootelements/->root/->children/g will probably do it.
4. The white space issue, this one is more complex, unless special caseofvalidating parsing, the line breaks and spaces usually used forindentingand formatting the document content becomes significant. So theyarereported by SAX and if your using the DOM tree, corresponding nodesaregenerated. Too approach can be taken:
   1. lazy one, use the compatibilitycallxmlKeepBlanksDefault(0)but be aware that youarerelying on a special (and possibly broken) set of heuristicsoflibxml to detect ignorable blanks. Don't complain if it breaksormake your application not 100% clean w.r.t. to it's input.
   2. the Right Way: change you code to accept possiblyinsignificantblanks characters, or have your tree populated withweird blank textnodes. You can spot them using the commodityfunctionxmlIsBlankNode(node)returning 1 for suchblanknodes.

   Note also that with the new default the output functions don't addanyextra indentation when saving a tree in order to be able to roundtrip(read and save) without inflating the document with extraformattingchars.

5. The include path has changed to $prefix/libxml/ and theincludesthemselves uses this new prefix in includes instructions... Ifyou areusing (as expected) the

       xml2-config --cflags

   output to generate you compile commands this will probably work outofthe box

6. xmlDetectCharEncoding takes an extra argument indicating the lengthinbyte of the head of the document available for character detection.

### Ensuring both libxml-1.x and libxml-2.x compatibility

Two new version of libxml (1.8.11) and libxml2 (2.3.4) have beenreleasedto allow smooth upgrade of existing libxml v1code whileretainingcompatibility. They offers the following:

1. similar include naming, one shoulduse#include<libxml/...>in both cases.
2. similar identifiers defined via macros for the child and rootfields:respectivelyxmlChildrenNodeandxmlRootNode
3. a new macro LIBXML_TEST_VERSIONwhich should beinsertedonce in the client code

So the roadmap to upgrade your existing libxml applications isthefollowing:

1. install the libxml-1.8.8 (and libxml-devel-1.8.8) packages
2. find all occurrences where the xmlDoc rootfield isusedand change it to xmlRootNode
3. similarly find all occurrences where thexmlNodechildsfield is used and change ittoxmlChildrenNode
4. add a LIBXML_TEST_VERSIONmacro somewhere inyourmain()or in the library init entry point
5. Recompile, check compatibility, it should still work
6. Change your configure script to look first for xml2-config and fallbackusing xml-config . Use the --cflags and --libs output of the commandasthe Include and Linking parameters needed to use libxml.
7. install libxml2-2.3.x and libxml2-devel-2.3.x (libxml-1.8.yandlibxml-devel-1.8.y can be kept simultaneously)
8. remove your config.cache, relaunch your configuration mechanism,andrecompile, if steps 2 and 3 were done right it should compileas-is
9. Test that your application is still running correctly, if not thismaybe due to extra empty nodes due to formating spaces being kept inlibxml2contrary to libxml1, in that case insert xmlKeepBlanksDefault(1)in yourcode before calling the parser (nexttoLIBXML_TEST_VERSIONis a fine place).

Following those steps should work. It worked for some of my own code.

Let me put some emphasis on the fact that there is far more changesfromlibxml 1.x to 2.x than the ones you may have to patch for. The overallcodehas been considerably cleaned up and the conformance to the XMLspecificationhas been drastically improved too. Don't take those changes asan excuse tonot upgrade, it may cost a lot on the long term ...

## Thread safety

Starting with 2.4.7, libxml2 makes provisions to ensure thatconcurrentthreads can safely work in parallel parsing different documents.There ishowever a couple of things to do to ensure it:

- configure the library accordingly using the --with-threads options
- call xmlInitParser() in the "main" thread before using any ofthelibxml2 API (except possibly selecting a different memoryallocator)

Note that the thread safety cannot be ensured for multiple threadssharingthe same document, the locking must be done at the application level,libxmlexports a basic mutex and reentrant mutexes API in<libxml/threads.h>.The parts of the library checked for thread safetyare:

- concurrent loading
- file access resolution
- catalog access
- catalog building
- entities lookup/accesses
- validation
- global variables per-thread override
- memory handling

XPath is supposed to be thread safe now, but this wasn'ttestedseriously.

## DOM Principles

DOMstands for the DocumentObjectModel; this is an API for accessing XML or HTML structureddocuments.Native support for DOM in Gnome is on the way (module gnome-dom),and will bebased on gnome-xml. This will be a far cleaner interface tomanipulate XMLfiles within Gnome since it won't expose the internalstructure.

The current DOM implementation on top of libxml2 is the gdome2 Gnome module,thisis a full DOM interface, thanks to Paolo Casarini, check the Gdome2 homepageformoreinformations.

## A real example

Here is a real size example, where the actual content of theapplicationdata is not kept in the DOM tree but uses internal structures. Itis based ona proposal to keep a database of jobs related to Gnome, with anXML basedstorage structure. Here is an XML encodedjobsbase:

    <?xml version="1.0"?>
    <gjob:Helping xmlns:gjob="http://www.gnome.org/some-location">
      <gjob:Jobs>

        <gjob:Job>
          <gjob:Project ID="3"/>
          <gjob:Application>GBackup</gjob:Application>
          <gjob:Category>Development</gjob:Category>

          <gjob:Update>
            <gjob:Status>Open</gjob:Status>
            <gjob:Modified>Mon, 07 Jun 1999 20:27:45 -0400 MET DST</gjob:Modified>
            <gjob:Salary>USD 0.00</gjob:Salary>
          </gjob:Update>

          <gjob:Developers>
            <gjob:Developer>
            </gjob:Developer>
          </gjob:Developers>

          <gjob:Contact>
            <gjob:Person>Nathan Clemons</gjob:Person>
            <gjob:Email>nathan@windsofstorm.net</gjob:Email>
            <gjob:Company>
            </gjob:Company>
            <gjob:Organisation>
            </gjob:Organisation>
            <gjob:Webpage>
            </gjob:Webpage>
            <gjob:Snailmail>
            </gjob:Snailmail>
            <gjob:Phone>
            </gjob:Phone>
          </gjob:Contact>

          <gjob:Requirements>
          The program should be released as free software, under the GPL.
          </gjob:Requirements>

          <gjob:Skills>
          </gjob:Skills>

          <gjob:Details>
          A GNOME based system that will allow a superuser to configure
          compressed and uncompressed files and/or file systems to be backed
          up with a supported media in the system.  This should be able to
          perform via find commands generating a list of files that are passed
          to tar, dd, cpio, cp, gzip, etc., to be directed to the tape machine
          or via operations performed on the filesystem itself. Email
          notification and GUI status display very important.
          </gjob:Details>

        </gjob:Job>

      </gjob:Jobs>
    </gjob:Helping>

While loading the XML file into an internal DOM tree is a matter ofcallingonly a couple of functions, browsing the tree to gather the data andgeneratethe internal structures is harder, and more error prone.

The suggested principle is to be tolerant with respect to theinputstructure. For example, the ordering of the attributes is notsignificant,the XML specification is clear about it. It's also usually a goodidea not todepend on the order of the children of a given node, unless itreally makesthings harder. Here is some code to parse the information for aperson:

    /*
     * A person record
     */
    typedef struct person {
        char *name;
        char *email;
        char *company;
        char *organisation;
        char *smail;
        char *webPage;
        char *phone;
    } person, *personPtr;

    /*
     * And the code needed to parse it
     */
    personPtr parsePerson(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
        personPtr ret = NULL;

    DEBUG("parsePerson\n");
        /*
         * allocate the struct
         */
        ret = (personPtr) malloc(sizeof(person));
        if (ret == NULL) {
            fprintf(stderr,"out of memory\n");
            return(NULL);
        }
        memset(ret, 0, sizeof(person));

        /* We don't care what the top level element name is */
        cur = cur->xmlChildrenNode;
        while (cur != NULL) {
            if ((!strcmp(cur->name, "Person")) && (cur->ns == ns))
                ret->name = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
            if ((!strcmp(cur->name, "Email")) && (cur->ns == ns))
                ret->email = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
            cur = cur->next;
        }

        return(ret);
    }

Here are a couple of things to notice:

- Usually a recursive parsing style is the more convenient one: XMLdatais by nature subject to repetitive constructs and usually exhibitshighlystructured patterns.
- The two arguments of type xmlDocPtrand xmlNsPtr,i.e.the pointer to the global XML document and the namespace reserved totheapplication. Document wide information are needed for example todecodeentities and it's a good coding practice to define a namespace foryourapplication set of data and test that the element and attributesyou'reanalyzing actually pertains to your application space. This isdone by asimple equality test (cur->ns == ns).
- To retrieve text and attributes value, you can use thefunctionxmlNodeListGetStringto gather all the text and entityreferencenodes generated by the DOM output and produce an single textstring.

Here is another piece of code used to parse another level ofthestructure:

    #include <libxml/tree.h>
    /*
     * a Description for a Job
     */
    typedef struct job {
        char *projectID;
        char *application;
        char *category;
        personPtr contact;
        int nbDevelopers;
        personPtr developers[100]; /* using dynamic alloc is left as an exercise */
    } job, *jobPtr;

    /*
     * And the code needed to parse it
     */
    jobPtr parseJob(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
        jobPtr ret = NULL;

    DEBUG("parseJob\n");
        /*
         * allocate the struct
         */
        ret = (jobPtr) malloc(sizeof(job));
        if (ret == NULL) {
            fprintf(stderr,"out of memory\n");
            return(NULL);
        }
        memset(ret, 0, sizeof(job));

        /* We don't care what the top level element name is */
        cur = cur->xmlChildrenNode;
        while (cur != NULL) {

            if ((!strcmp(cur->name, "Project")) && (cur->ns == ns)) {
                ret->projectID = xmlGetProp(cur, "ID");
                if (ret->projectID == NULL) {
                    fprintf(stderr, "Project has no ID\n");
                }
            }
            if ((!strcmp(cur->name, "Application")) && (cur->ns == ns))
                ret->application = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
            if ((!strcmp(cur->name, "Category")) && (cur->ns == ns))
                ret->category = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
            if ((!strcmp(cur->name, "Contact")) && (cur->ns == ns))
                ret->contact = parsePerson(doc, ns, cur);
            cur = cur->next;
        }

        return(ret);
    }

Once you are used to it, writing this kind of code is quite simple,butboring. Ultimately, it could be possible to write stubbers taking eitherCdata structure definitions, a set of XML examples or an XML DTD andproducethe code needed to import and export the content between C data andXMLstorage. This is left as an exercise to the reader :-)

Feel free to use the code for the fullCparsing exampleas a template, it is also available with Makefile intheGnome CVS base under gnome-xml/example

## Contributions

- Bjorn Reese, William Brack and Thomas Broyer have provided a numberofpatches, Gary Pennington worked on the validation API, threadingsupportand Solaris port.
- John Fleck helps maintaining the documentation and man pages.
- Igor Zlatkovicis nowthemaintainer of the Windows port, heprovidesbinaries
- Gary PenningtonprovidesSolaris binaries
- MattSergeantdevelopedXML::LibXSLT, a Perl wrapperforlibxml2/libxslt as part of the AxKitXMLapplication server
- Felix Natterand Geert Kloostermanprovide an emacs moduleto lookup libxml(2)functionsdocumentation
- Ziying Sherwinprovided man pages
- there is a module for libxml/libxsltsupportin OpenNSD/AOLServer
- Dave Kuhlmanprovidedthefirst version of libxml/libxslt wrappers for Python
- Petr Kozelka provides Pascal units togluelibxml2with Kylix and Delphi and other Pascal compilers
- Aleksey Saninimplemented theXML Canonicalization and XMLDigitalSignature implementations forlibxml2
- SteveBallandcontributors maintain tclbindings for libxml2 andlibxslt, as well as tkxmllinta GUI forxmllintand tkxsltproca GUIfor xsltproc.