1<?xml version="1.0" encoding="iso-8859-1"?> 2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" 3 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 4<html> 5<head> 6<!-- 7 __ __ _ 8 ___\ \/ /_ __ __ _| |_ 9 / _ \\ /| '_ \ / _` | __| 10 | __// \| |_) | (_| | |_ 11 \___/_/\_\ .__/ \__,_|\__| 12 |_| XML parser 13 14 Copyright (c) 2000 Clark Cooper <coopercc@users.sourceforge.net> 15 Copyright (c) 2000-2004 Fred L. Drake, Jr. <fdrake@users.sourceforge.net> 16 Copyright (c) 2002-2012 Karl Waclawek <karl@waclawek.net> 17 Copyright (c) 2017-2025 Sebastian Pipping <sebastian@pipping.org> 18 Copyright (c) 2017 Jakub Wilk <jwilk@jwilk.net> 19 Copyright (c) 2021 Tomas Korbar <tkorbar@redhat.com> 20 Copyright (c) 2021 Nicolas Cavallari <nicolas.cavallari@green-communications.fr> 21 Copyright (c) 2022 Thijs Schreijer <thijs@thijsschreijer.nl> 22 Copyright (c) 2023 Hanno Böck <hanno@gentoo.org> 23 Copyright (c) 2023 Sony Corporation / Snild Dolkow <snild@sony.com> 24 Licensed under the MIT license: 25 26 Permission is hereby granted, free of charge, to any person obtaining 27 a copy of this software and associated documentation files (the 28 "Software"), to deal in the Software without restriction, including 29 without limitation the rights to use, copy, modify, merge, publish, 30 distribute, sublicense, and/or sell copies of the Software, and to permit 31 persons to whom the Software is furnished to do so, subject to the 32 following conditions: 33 34 The above copyright notice and this permission notice shall be included 35 in all copies or substantial portions of the Software. 36 37 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 38 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 39 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN 40 NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 41 DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR 42 OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE 43 USE OR OTHER DEALINGS IN THE SOFTWARE. 44--> 45 <title>Expat XML Parser</title> 46 <meta name="author" content="Clark Cooper, coopercc@netheaven.com" /> 47 <meta http-equiv="Content-Style-Type" content="text/css" /> 48 <link href="ok.min.css" rel="stylesheet" type="text/css" /> 49 <link href="style.css" rel="stylesheet" type="text/css" /> 50</head> 51<body> 52 <div> 53 <h1> 54 The Expat XML Parser 55 <small>Release 2.7.1</small> 56 </h1> 57 </div> 58<div class="content"> 59 60<p>Expat is a library, written in C, for parsing XML documents. It's 61the underlying XML parser for the open source Mozilla project, Perl's 62<code>XML::Parser</code>, Python's <code>xml.parsers.expat</code>, and 63other open-source XML parsers.</p> 64 65<p>This library is the creation of James Clark, who's also given us 66groff (an nroff look-alike), Jade (an implementation of ISO's DSSSL 67stylesheet language for SGML), XP (a Java XML parser package), XT (a 68Java XSL engine). James was also the technical lead on the XML 69Working Group at W3C that produced the XML specification.</p> 70 71<p>This is free software, licensed under the <a 72href="../COPYING">MIT/X Consortium license</a>. You may download it 73from <a href="https://libexpat.github.io/">the Expat home page</a>. 74</p> 75 76<p>The bulk of this document was originally commissioned as an article 77by <a href="https://www.xml.com/">XML.com</a>. They graciously allowed 78Clark Cooper to retain copyright and to distribute it with Expat. 79This version has been substantially extended to include documentation 80on features which have been added since the original article was 81published, and additional information on using the original 82interface.</p> 83 84<hr /> 85<h2>Table of Contents</h2> 86<ul> 87 <li><a href="#overview">Overview</a></li> 88 <li><a href="#building">Building and Installing</a></li> 89 <li><a href="#using">Using Expat</a></li> 90 <li><a href="#reference">Reference</a> 91 <ul> 92 <li><a href="#creation">Parser Creation Functions</a> 93 <ul> 94 <li><a href="#XML_ParserCreate">XML_ParserCreate</a></li> 95 <li><a href="#XML_ParserCreateNS">XML_ParserCreateNS</a></li> 96 <li><a href="#XML_ParserCreate_MM">XML_ParserCreate_MM</a></li> 97 <li><a href="#XML_ExternalEntityParserCreate">XML_ExternalEntityParserCreate</a></li> 98 <li><a href="#XML_ParserFree">XML_ParserFree</a></li> 99 <li><a href="#XML_ParserReset">XML_ParserReset</a></li> 100 </ul> 101 </li> 102 <li><a href="#parsing">Parsing Functions</a> 103 <ul> 104 <li><a href="#XML_Parse">XML_Parse</a></li> 105 <li><a href="#XML_ParseBuffer">XML_ParseBuffer</a></li> 106 <li><a href="#XML_GetBuffer">XML_GetBuffer</a></li> 107 <li><a href="#XML_StopParser">XML_StopParser</a></li> 108 <li><a href="#XML_ResumeParser">XML_ResumeParser</a></li> 109 <li><a href="#XML_GetParsingStatus">XML_GetParsingStatus</a></li> 110 </ul> 111 </li> 112 <li><a href="#setting">Handler Setting Functions</a> 113 <ul> 114 <li><a href="#XML_SetStartElementHandler">XML_SetStartElementHandler</a></li> 115 <li><a href="#XML_SetEndElementHandler">XML_SetEndElementHandler</a></li> 116 <li><a href="#XML_SetElementHandler">XML_SetElementHandler</a></li> 117 <li><a href="#XML_SetCharacterDataHandler">XML_SetCharacterDataHandler</a></li> 118 <li><a href="#XML_SetProcessingInstructionHandler">XML_SetProcessingInstructionHandler</a></li> 119 <li><a href="#XML_SetCommentHandler">XML_SetCommentHandler</a></li> 120 <li><a href="#XML_SetStartCdataSectionHandler">XML_SetStartCdataSectionHandler</a></li> 121 <li><a href="#XML_SetEndCdataSectionHandler">XML_SetEndCdataSectionHandler</a></li> 122 <li><a href="#XML_SetCdataSectionHandler">XML_SetCdataSectionHandler</a></li> 123 <li><a href="#XML_SetDefaultHandler">XML_SetDefaultHandler</a></li> 124 <li><a href="#XML_SetDefaultHandlerExpand">XML_SetDefaultHandlerExpand</a></li> 125 <li><a href="#XML_SetExternalEntityRefHandler">XML_SetExternalEntityRefHandler</a></li> 126 <li><a href="#XML_SetExternalEntityRefHandlerArg">XML_SetExternalEntityRefHandlerArg</a></li> 127 <li><a href="#XML_SetSkippedEntityHandler">XML_SetSkippedEntityHandler</a></li> 128 <li><a href="#XML_SetUnknownEncodingHandler">XML_SetUnknownEncodingHandler</a></li> 129 <li><a href="#XML_SetStartNamespaceDeclHandler">XML_SetStartNamespaceDeclHandler</a></li> 130 <li><a href="#XML_SetEndNamespaceDeclHandler">XML_SetEndNamespaceDeclHandler</a></li> 131 <li><a href="#XML_SetNamespaceDeclHandler">XML_SetNamespaceDeclHandler</a></li> 132 <li><a href="#XML_SetXmlDeclHandler">XML_SetXmlDeclHandler</a></li> 133 <li><a href="#XML_SetStartDoctypeDeclHandler">XML_SetStartDoctypeDeclHandler</a></li> 134 <li><a href="#XML_SetEndDoctypeDeclHandler">XML_SetEndDoctypeDeclHandler</a></li> 135 <li><a href="#XML_SetDoctypeDeclHandler">XML_SetDoctypeDeclHandler</a></li> 136 <li><a href="#XML_SetElementDeclHandler">XML_SetElementDeclHandler</a></li> 137 <li><a href="#XML_SetAttlistDeclHandler">XML_SetAttlistDeclHandler</a></li> 138 <li><a href="#XML_SetEntityDeclHandler">XML_SetEntityDeclHandler</a></li> 139 <li><a href="#XML_SetUnparsedEntityDeclHandler">XML_SetUnparsedEntityDeclHandler</a></li> 140 <li><a href="#XML_SetNotationDeclHandler">XML_SetNotationDeclHandler</a></li> 141 <li><a href="#XML_SetNotStandaloneHandler">XML_SetNotStandaloneHandler</a></li> 142 </ul> 143 </li> 144 <li><a href="#position">Parse Position and Error Reporting Functions</a> 145 <ul> 146 <li><a href="#XML_GetErrorCode">XML_GetErrorCode</a></li> 147 <li><a href="#XML_ErrorString">XML_ErrorString</a></li> 148 <li><a href="#XML_GetCurrentByteIndex">XML_GetCurrentByteIndex</a></li> 149 <li><a href="#XML_GetCurrentLineNumber">XML_GetCurrentLineNumber</a></li> 150 <li><a href="#XML_GetCurrentColumnNumber">XML_GetCurrentColumnNumber</a></li> 151 <li><a href="#XML_GetCurrentByteCount">XML_GetCurrentByteCount</a></li> 152 <li><a href="#XML_GetInputContext">XML_GetInputContext</a></li> 153 </ul> 154 </li> 155 <li> 156 <a href="#attack-protection">Attack Protection</a> 157 <ul> 158 <li><a href="#XML_SetBillionLaughsAttackProtectionMaximumAmplification">XML_SetBillionLaughsAttackProtectionMaximumAmplification</a></li> 159 <li><a href="#XML_SetBillionLaughsAttackProtectionActivationThreshold">XML_SetBillionLaughsAttackProtectionActivationThreshold</a></li> 160 <li><a href="#XML_SetReparseDeferralEnabled">XML_SetReparseDeferralEnabled</a></li> 161 </ul> 162 </li> 163 <li><a href="#miscellaneous">Miscellaneous Functions</a> 164 <ul> 165 <li><a href="#XML_SetUserData">XML_SetUserData</a></li> 166 <li><a href="#XML_GetUserData">XML_GetUserData</a></li> 167 <li><a href="#XML_UseParserAsHandlerArg">XML_UseParserAsHandlerArg</a></li> 168 <li><a href="#XML_SetBase">XML_SetBase</a></li> 169 <li><a href="#XML_GetBase">XML_GetBase</a></li> 170 <li><a href="#XML_GetSpecifiedAttributeCount">XML_GetSpecifiedAttributeCount</a></li> 171 <li><a href="#XML_GetIdAttributeIndex">XML_GetIdAttributeIndex</a></li> 172 <li><a href="#XML_GetAttributeInfo">XML_GetAttributeInfo</a></li> 173 <li><a href="#XML_SetEncoding">XML_SetEncoding</a></li> 174 <li><a href="#XML_SetParamEntityParsing">XML_SetParamEntityParsing</a></li> 175 <li><a href="#XML_SetHashSalt">XML_SetHashSalt</a></li> 176 <li><a href="#XML_UseForeignDTD">XML_UseForeignDTD</a></li> 177 <li><a href="#XML_SetReturnNSTriplet">XML_SetReturnNSTriplet</a></li> 178 <li><a href="#XML_DefaultCurrent">XML_DefaultCurrent</a></li> 179 <li><a href="#XML_ExpatVersion">XML_ExpatVersion</a></li> 180 <li><a href="#XML_ExpatVersionInfo">XML_ExpatVersionInfo</a></li> 181 <li><a href="#XML_GetFeatureList">XML_GetFeatureList</a></li> 182 <li><a href="#XML_FreeContentModel">XML_FreeContentModel</a></li> 183 <li><a href="#XML_MemMalloc">XML_MemMalloc</a></li> 184 <li><a href="#XML_MemRealloc">XML_MemRealloc</a></li> 185 <li><a href="#XML_MemFree">XML_MemFree</a></li> 186 </ul> 187 </li> 188 </ul> 189 </li> 190</ul> 191 192<hr /> 193<h2><a name="overview">Overview</a></h2> 194 195<p>Expat is a stream-oriented parser. You register callback (or 196handler) functions with the parser and then start feeding it the 197document. As the parser recognizes parts of the document, it will 198call the appropriate handler for that part (if you've registered one.) 199The document is fed to the parser in pieces, so you can start parsing 200before you have all the document. This also allows you to parse really 201huge documents that won't fit into memory.</p> 202 203<p>Expat can be intimidating due to the many kinds of handlers and 204options you can set. But you only need to learn four functions in 205order to do 90% of what you'll want to do with it:</p> 206 207<dl> 208 209<dt><code><a href= "#XML_ParserCreate" 210 >XML_ParserCreate</a></code></dt> 211 <dd>Create a new parser object.</dd> 212 213<dt><code><a href= "#XML_SetElementHandler" 214 >XML_SetElementHandler</a></code></dt> 215 <dd>Set handlers for start and end tags.</dd> 216 217<dt><code><a href= "#XML_SetCharacterDataHandler" 218 >XML_SetCharacterDataHandler</a></code></dt> 219 <dd>Set handler for text.</dd> 220 221<dt><code><a href= "#XML_Parse" 222 >XML_Parse</a></code></dt> 223 <dd>Pass a buffer full of document to the parser</dd> 224</dl> 225 226<p>These functions and others are described in the <a 227href="#reference">reference</a> part of this document. The reference 228section also describes in detail the parameters passed to the 229different types of handlers.</p> 230 231<p>Let's look at a very simple example program that only uses 3 of the 232above functions (it doesn't need to set a character handler.) The 233program <a href="../examples/outline.c">outline.c</a> prints an 234element outline, indenting child elements to distinguish them from the 235parent element that contains them. The start handler does all the 236work. It prints two indenting spaces for every level of ancestor 237elements, then it prints the element and attribute 238information. Finally it increments the global <code>Depth</code> 239variable.</p> 240 241<pre class="eg"> 242int Depth; 243 244void XMLCALL 245start(void *data, const char *el, const char **attr) { 246 int i; 247 248 for (i = 0; i < Depth; i++) 249 printf(" "); 250 251 printf("%s", el); 252 253 for (i = 0; attr[i]; i += 2) { 254 printf(" %s='%s'", attr[i], attr[i + 1]); 255 } 256 257 printf("\n"); 258 Depth++; 259} /* End of start handler */ 260</pre> 261 262<p>The end tag simply does the bookkeeping work of decrementing 263<code>Depth</code>.</p> 264<pre class="eg"> 265void XMLCALL 266end(void *data, const char *el) { 267 Depth--; 268} /* End of end handler */ 269</pre> 270 271<p>Note the <code>XMLCALL</code> annotation used for the callbacks. 272This is used to ensure that the Expat and the callbacks are using the 273same calling convention in case the compiler options used for Expat 274itself and the client code are different. Expat tries not to care 275what the default calling convention is, though it may require that it 276be compiled with a default convention of "cdecl" on some platforms. 277For code which uses Expat, however, the calling convention is 278specified by the <code>XMLCALL</code> annotation on most platforms; 279callbacks should be defined using this annotation.</p> 280 281<p>The <code>XMLCALL</code> annotation was added in Expat 1.95.7, but 282existing working Expat applications don't need to add it (since they 283are already using the "cdecl" calling convention, or they wouldn't be 284working). The annotation is only needed if the default calling 285convention may be something other than "cdecl". To use the annotation 286safely with older versions of Expat, you can conditionally define it 287<em>after</em> including Expat's header file:</p> 288 289<pre class="eg"> 290#include <expat.h> 291 292#ifndef XMLCALL 293#if defined(_MSC_EXTENSIONS) && !defined(__BEOS__) && !defined(__CYGWIN__) 294#define XMLCALL __cdecl 295#elif defined(__GNUC__) 296#define XMLCALL __attribute__((cdecl)) 297#else 298#define XMLCALL 299#endif 300#endif 301</pre> 302 303<p>After creating the parser, the main program just has the job of 304shoveling the document to the parser so that it can do its work.</p> 305 306<hr /> 307<h2><a name="building">Building and Installing Expat</a></h2> 308 309<p>The Expat distribution comes as a compressed (with GNU gzip) tar 310file. You may download the latest version from <a href= 311"https://sourceforge.net/projects/expat/" >Source Forge</a>. After 312unpacking this, cd into the directory. Then follow either the Win32 313directions or Unix directions below.</p> 314 315<h3>Building under Win32</h3> 316 317<p>If you're using the GNU compiler under cygwin, follow the Unix 318directions in the next section. Otherwise if you have Microsoft's 319Developer Studio installed, 320you can use CMake to generate a <code>.sln</code> file, e.g. 321<code> 322cmake -G"Visual Studio 16 2019" -DCMAKE_BUILD_TYPE=RelWithDebInfo . 323</code>, and build Expat using <code>msbuild /m expat.sln</code> after.</p> 324 325<p>Alternatively, you may download the Win32 binary package that 326contains the "expat.h" include file and a pre-built DLL.</p> 327 328<h3>Building under Unix (or GNU)</h3> 329 330<p>First you'll need to run the configure shell script in order to 331configure the Makefiles and headers for your system.</p> 332 333<p>If you're happy with all the defaults that configure picks for you, 334and you have permission on your system to install into /usr/local, you 335can install Expat with this sequence of commands:</p> 336 337<pre class="eg"> 338./configure 339make 340make install 341</pre> 342 343<p>There are some options that you can provide to this script, but the 344only one we'll mention here is the <code>--prefix</code> option. You 345can find out all the options available by running configure with just 346the <code>--help</code> option.</p> 347 348<p>By default, the configure script sets things up so that the library 349gets installed in <code>/usr/local/lib</code> and the associated 350header file in <code>/usr/local/include</code>. But if you were to 351give the option, <code>--prefix=/home/me/mystuff</code>, then the 352library and header would get installed in 353<code>/home/me/mystuff/lib</code> and 354<code>/home/me/mystuff/include</code> respectively.</p> 355 356<h3>Configuring Expat Using the Pre-Processor</h3> 357 358<p>Expat's feature set can be configured using a small number of 359pre-processor definitions. The symbols are:</p> 360 361<dl class="cpp-symbols"> 362<dt><a name="XML_GE">XML_GE</a></dt> 363<dd> 364Added in Expat 2.6.0. 365Include support for 366<a href="https://www.w3.org/TR/2006/REC-xml-20060816/#sec-physical-struct">general entities</a> 367(syntax <code>&e1;</code> to reference and 368syntax <code><!ENTITY e1 'value1'></code> (an internal general entity) or 369<code><!ENTITY e2 SYSTEM 'file2'></code> (an external general entity) to declare). 370With <code>XML_GE</code> enabled, general entities will be replaced by their declared replacement text; 371for this to work for <em>external</em> general entities, in addition an 372<code><a href="#XML_SetExternalEntityRefHandler">XML_ExternalEntityRefHandler</a></code> must be set using 373<code><a href="#XML_SetExternalEntityRefHandler">XML_SetExternalEntityRefHandler</a></code>. 374Also, enabling <code>XML_GE</code> makes 375the functions <code><a href="#XML_SetBillionLaughsAttackProtectionMaximumAmplification"> 376XML_SetBillionLaughsAttackProtectionMaximumAmplification</a></code> and <code> 377<a href="#XML_SetBillionLaughsAttackProtectionActivationThreshold"> 378XML_SetBillionLaughsAttackProtectionActivationThreshold</a></code> available. 379<br/> 380With <code>XML_GE</code> disabled, Expat has a smaller memory footprint and can be faster, but will 381not load external general entities and will replace all general entities 382(except the <a href="https://www.w3.org/TR/2006/REC-xml-20060816/#sec-predefined-ent">predefined five</a>: 383<code>amp</code>, <code>apos</code>, <code>gt</code>, <code>lt</code>, <code>quot</code>) 384with a self-reference: 385for example, referencing an entity <code>e1</code> via <code>&e1;</code> will be replaced 386by text <code>&e1;</code>. 387</dd> 388 389<dt><a name="XML_DTD">XML_DTD</a></dt> 390<dd>Include support for using and reporting DTD-based content. If 391this is defined, default attribute values from an external DTD subset 392are reported and attribute value normalization occurs based on the 393type of attributes defined in the external subset. Without 394this, Expat has a smaller memory footprint and can be faster, but will 395not load external parameter entities or process conditional sections. If defined, makes 396the functions <code><a 397href="#XML_SetBillionLaughsAttackProtectionMaximumAmplification"> 398XML_SetBillionLaughsAttackProtectionMaximumAmplification</a></code> and <code> 399<a href="#XML_SetBillionLaughsAttackProtectionActivationThreshold"> 400XML_SetBillionLaughsAttackProtectionActivationThreshold</a></code> available.</dd> 401 402<dt><a name="XML_NS">XML_NS</a></dt> 403<dd>When defined, support for the <cite><a href= 404"https://www.w3.org/TR/REC-xml-names/" >Namespaces in XML</a></cite> 405specification is included.</dd> 406 407<dt><a name="XML_UNICODE">XML_UNICODE</a></dt> 408<dd>When defined, character data reported to the application is 409encoded in UTF-16 using wide characters of the type 410<code>XML_Char</code>. This is implied if 411<code>XML_UNICODE_WCHAR_T</code> is defined.</dd> 412 413<dt><a name="XML_UNICODE_WCHAR_T">XML_UNICODE_WCHAR_T</a></dt> 414<dd>If defined, causes the <code>XML_Char</code> character type to be 415defined using the <code>wchar_t</code> type; otherwise, <code>unsigned 416short</code> is used. Defining this implies 417<code>XML_UNICODE</code>.</dd> 418 419<dt><a name="XML_LARGE_SIZE">XML_LARGE_SIZE</a></dt> 420<dd>If defined, causes the <code>XML_Size</code> and <code>XML_Index</code> 421integer types to be at least 64 bits in size. This is intended to support 422processing of very large input streams, where the return values of 423<code><a href="#XML_GetCurrentByteIndex" >XML_GetCurrentByteIndex</a></code>, 424<code><a href="#XML_GetCurrentLineNumber" >XML_GetCurrentLineNumber</a></code> and 425<code><a href="#XML_GetCurrentColumnNumber" >XML_GetCurrentColumnNumber</a></code> 426could overflow. It may not be supported by all compilers, and is turned 427off by default.</dd> 428 429<dt><a name="XML_CONTEXT_BYTES">XML_CONTEXT_BYTES</a></dt> 430<dd>The number of input bytes of markup context which the parser will 431ensure are available for reporting via <code><a href= 432"#XML_GetInputContext" >XML_GetInputContext</a></code>. This is 433normally set to 1024, and must be set to a positive integer to enable. 434If this is set to zero, the input context will not be available and <code><a 435href= "#XML_GetInputContext" >XML_GetInputContext</a></code> will 436always report <code>NULL</code>. Without this, Expat has a smaller memory 437footprint and can be faster.</dd> 438 439<dt><a name="XML_STATIC">XML_STATIC</a></dt> 440<dd>On Windows, this should be set if Expat is going to be linked 441statically with the code that calls it; this is required to get all 442the right MSVC magic annotations correct. This is ignored on other 443platforms.</dd> 444 445<dt><a name="XML_ATTR_INFO">XML_ATTR_INFO</a></dt> 446<dd>If defined, makes the additional function <code><a href= 447"#XML_GetAttributeInfo" >XML_GetAttributeInfo</a></code> available 448for reporting attribute byte offsets.</dd> 449</dl> 450 451<hr /> 452<h2><a name="using">Using Expat</a></h2> 453 454<h3>Compiling and Linking Against Expat</h3> 455 456<p>Unless you installed Expat in a location not expected by your 457compiler and linker, all you have to do to use Expat in your programs 458is to include the Expat header (<code>#include <expat.h></code>) 459in your files that make calls to it and to tell the linker that it 460needs to link against the Expat library. On Unix systems, this would 461usually be done with the <code>-lexpat</code> argument. Otherwise, 462you'll need to tell the compiler where to look for the Expat header 463and the linker where to find the Expat library. You may also need to 464take steps to tell the operating system where to find this library at 465run time.</p> 466 467<p>On a Unix-based system, here's what a Makefile might look like when 468Expat is installed in a standard location:</p> 469 470<pre class="eg"> 471CC=cc 472LDFLAGS= 473LIBS= -lexpat 474xmlapp: xmlapp.o 475 $(CC) $(LDFLAGS) -o xmlapp xmlapp.o $(LIBS) 476</pre> 477 478<p>If you installed Expat in, say, <code>/home/me/mystuff</code>, then 479the Makefile would look like this:</p> 480 481<pre class="eg"> 482CC=cc 483CFLAGS= -I/home/me/mystuff/include 484LDFLAGS= 485LIBS= -L/home/me/mystuff/lib -lexpat 486xmlapp: xmlapp.o 487 $(CC) $(LDFLAGS) -o xmlapp xmlapp.o $(LIBS) 488</pre> 489 490<p>You'd also have to set the environment variable 491<code>LD_LIBRARY_PATH</code> to <code>/home/me/mystuff/lib</code> (or 492to <code>${LD_LIBRARY_PATH}:/home/me/mystuff/lib</code> if 493LD_LIBRARY_PATH already has some directories in it) in order to run 494your application.</p> 495 496<h3>Expat Basics</h3> 497 498<p>As we saw in the example in the overview, the first step in parsing 499an XML document with Expat is to create a parser object. There are <a 500href="#creation">three functions</a> in the Expat API for creating a 501parser object. However, only two of these (<code><a href= 502"#XML_ParserCreate" >XML_ParserCreate</a></code> and <code><a href= 503"#XML_ParserCreateNS" >XML_ParserCreateNS</a></code>) can be used for 504constructing a parser for a top-level document. The object returned 505by these functions is an opaque pointer (i.e. "expat.h" declares it as 506void *) to data with further internal structure. In order to free the 507memory associated with this object you must call <code><a href= 508"#XML_ParserFree" >XML_ParserFree</a></code>. Note that if you have 509provided any <a href="#userdata">user data</a> that gets stored in the 510parser, then your application is responsible for freeing it prior to 511calling <code>XML_ParserFree</code>.</p> 512 513<p>The objects returned by the parser creation functions are good for 514parsing only one XML document or external parsed entity. If your 515application needs to parse many XML documents, then it needs to create 516a parser object for each one. The best way to deal with this is to 517create a higher level object that contains all the default 518initialization you want for your parser objects.</p> 519 520<p>Walking through a document hierarchy with a stream oriented parser 521will require a good stack mechanism in order to keep track of current 522context. For instance, to answer the simple question, "What element 523does this text belong to?" requires a stack, since the parser may have 524descended into other elements that are children of the current one and 525has encountered this text on the way out.</p> 526 527<p>The things you're likely to want to keep on a stack are the 528currently opened element and it's attributes. You push this 529information onto the stack in the start handler and you pop it off in 530the end handler.</p> 531 532<p>For some tasks, it is sufficient to just keep information on what 533the depth of the stack is (or would be if you had one.) The outline 534program shown above presents one example. Another such task would be 535skipping over a complete element. When you see the start tag for the 536element you want to skip, you set a skip flag and record the depth at 537which the element started. When the end tag handler encounters the 538same depth, the skipped element has ended and the flag may be 539cleared. If you follow the convention that the root element starts at 5401, then you can use the same variable for skip flag and skip 541depth.</p> 542 543<pre class="eg"> 544void 545init_info(Parseinfo *info) { 546 info->skip = 0; 547 info->depth = 1; 548 /* Other initializations here */ 549} /* End of init_info */ 550 551void XMLCALL 552rawstart(void *data, const char *el, const char **attr) { 553 Parseinfo *inf = (Parseinfo *) data; 554 555 if (! inf->skip) { 556 if (should_skip(inf, el, attr)) { 557 inf->skip = inf->depth; 558 } 559 else 560 start(inf, el, attr); /* This does rest of start handling */ 561 } 562 563 inf->depth++; 564} /* End of rawstart */ 565 566void XMLCALL 567rawend(void *data, const char *el) { 568 Parseinfo *inf = (Parseinfo *) data; 569 570 inf->depth--; 571 572 if (! inf->skip) 573 end(inf, el); /* This does rest of end handling */ 574 575 if (inf->skip == inf->depth) 576 inf->skip = 0; 577} /* End rawend */ 578</pre> 579 580<p>Notice in the above example the difference in how depth is 581manipulated in the start and end handlers. The end tag handler should 582be the mirror image of the start tag handler. This is necessary to 583properly model containment. Since, in the start tag handler, we 584incremented depth <em>after</em> the main body of start tag code, then 585in the end handler, we need to manipulate it <em>before</em> the main 586body. If we'd decided to increment it first thing in the start 587handler, then we'd have had to decrement it last thing in the end 588handler.</p> 589 590<h3 id="userdata">Communicating between handlers</h3> 591 592<p>In order to be able to pass information between different handlers 593without using globals, you'll need to define a data structure to hold 594the shared variables. You can then tell Expat (with the <code><a href= 595"#XML_SetUserData" >XML_SetUserData</a></code> function) to pass a 596pointer to this structure to the handlers. This is the first 597argument received by most handlers. In the <a href="#reference" 598>reference section</a>, an argument to a callback function is named 599<code>userData</code> and have type <code>void *</code> if the user 600data is passed; it will have the type <code>XML_Parser</code> if the 601parser itself is passed. When the parser is passed, the user data may 602be retrieved using <code><a href="#XML_GetUserData" 603>XML_GetUserData</a></code>.</p> 604 605<p>One common case where multiple calls to a single handler may need 606to communicate using an application data structure is the case when 607content passed to the character data handler (set by <code><a href= 608"#XML_SetCharacterDataHandler" 609>XML_SetCharacterDataHandler</a></code>) needs to be accumulated. A 610common first-time mistake with any of the event-oriented interfaces to 611an XML parser is to expect all the text contained in an element to be 612reported by a single call to the character data handler. Expat, like 613many other XML parsers, reports such data as a sequence of calls; 614there's no way to know when the end of the sequence is reached until a 615different callback is made. A buffer referenced by the user data 616structure proves both an effective and convenient place to accumulate 617character data.</p> 618 619<!-- XXX example needed here --> 620 621 622<h3>XML Version</h3> 623 624<p>Expat is an XML 1.0 parser, and as such never complains based on 625the value of the <code>version</code> pseudo-attribute in the XML 626declaration, if present.</p> 627 628<p>If an application needs to check the version number (to support 629alternate processing), it should use the <code><a href= 630"#XML_SetXmlDeclHandler" >XML_SetXmlDeclHandler</a></code> function to 631set a handler that uses the information in the XML declaration to 632determine what to do. This example shows how to check that only a 633version number of <code>"1.0"</code> is accepted:</p> 634 635<pre class="eg"> 636static int wrong_version; 637static XML_Parser parser; 638 639static void XMLCALL 640xmldecl_handler(void *userData, 641 const XML_Char *version, 642 const XML_Char *encoding, 643 int standalone) 644{ 645 static const XML_Char Version_1_0[] = {'1', '.', '0', 0}; 646 647 int i; 648 649 for (i = 0; i < (sizeof(Version_1_0) / sizeof(Version_1_0[0])); ++i) { 650 if (version[i] != Version_1_0[i]) { 651 wrong_version = 1; 652 /* also clear all other handlers: */ 653 XML_SetCharacterDataHandler(parser, NULL); 654 ... 655 return; 656 } 657 } 658 ... 659} 660</pre> 661 662<h3>Namespace Processing</h3> 663 664<p>When the parser is created using the <code><a href= 665"#XML_ParserCreateNS" >XML_ParserCreateNS</a></code>, function, Expat 666performs namespace processing. Under namespace processing, Expat 667consumes <code>xmlns</code> and <code>xmlns:...</code> attributes, 668which declare namespaces for the scope of the element in which they 669occur. This means that your start handler will not see these 670attributes. Your application can still be informed of these 671declarations by setting namespace declaration handlers with <a href= 672"#XML_SetNamespaceDeclHandler" 673><code>XML_SetNamespaceDeclHandler</code></a>.</p> 674 675<p>Element type and attribute names that belong to a given namespace 676are passed to the appropriate handler in expanded form. By default 677this expanded form is a concatenation of the namespace URI, the 678separator character (which is the 2nd argument to <code><a href= 679"#XML_ParserCreateNS" >XML_ParserCreateNS</a></code>), and the local 680name (i.e. the part after the colon). Names with undeclared prefixes 681are not well-formed when namespace processing is enabled, and will 682trigger an error. Unprefixed attribute names are never expanded, 683and unprefixed element names are only expanded when they are in the 684scope of a default namespace.</p> 685 686<p>However if <code><a href= "#XML_SetReturnNSTriplet" 687>XML_SetReturnNSTriplet</a></code> has been called with a non-zero 688<code>do_nst</code> parameter, then the expanded form for names with 689an explicit prefix is a concatenation of: URI, separator, local name, 690separator, prefix.</p> 691 692<p>You can set handlers for the start of a namespace declaration and 693for the end of a scope of a declaration with the <code><a href= 694"#XML_SetNamespaceDeclHandler" >XML_SetNamespaceDeclHandler</a></code> 695function. The StartNamespaceDeclHandler is called prior to the start 696tag handler and the EndNamespaceDeclHandler is called after the 697corresponding end tag that ends the namespace's scope. The namespace 698start handler gets passed the prefix and URI for the namespace. For a 699default namespace declaration (xmlns='...'), the prefix will be 700<code>NULL</code>. 701The URI will be <code>NULL</code> for the case where the default namespace is being 702unset. The namespace end handler just gets the prefix for the closing 703scope.</p> 704 705<p>These handlers are called for each declaration. So if, for 706instance, a start tag had three namespace declarations, then the 707StartNamespaceDeclHandler would be called three times before the start 708tag handler is called, once for each declaration.</p> 709 710<h3>Character Encodings</h3> 711 712<p>While XML is based on Unicode, and every XML processor is required 713to recognized UTF-8 and UTF-16 (1 and 2 byte encodings of Unicode), 714other encodings may be declared in XML documents or entities. For the 715main document, an XML declaration may contain an encoding 716declaration:</p> 717<pre> 718<?xml version="1.0" encoding="ISO-8859-2"?> 719</pre> 720 721<p>External parsed entities may begin with a text declaration, which 722looks like an XML declaration with just an encoding declaration:</p> 723<pre> 724<?xml encoding="Big5"?> 725</pre> 726 727<p>With Expat, you may also specify an encoding at the time of 728creating a parser. This is useful when the encoding information may 729come from a source outside the document itself (like a higher level 730protocol.)</p> 731 732<p><a name="builtin_encodings"></a>There are four built-in encodings 733in Expat:</p> 734<ul> 735<li>UTF-8</li> 736<li>UTF-16</li> 737<li>ISO-8859-1</li> 738<li>US-ASCII</li> 739</ul> 740 741<p>Anything else discovered in an encoding declaration or in the 742protocol encoding specified in the parser constructor, triggers a call 743to the <code>UnknownEncodingHandler</code>. This handler gets passed 744the encoding name and a pointer to an <code>XML_Encoding</code> data 745structure. Your handler must fill in this structure and return 746<code>XML_STATUS_OK</code> if it knows how to deal with the 747encoding. Otherwise the handler should return 748<code>XML_STATUS_ERROR</code>. The handler also gets passed a pointer 749to an optional application data structure that you may indicate when 750you set the handler.</p> 751 752<p>Expat places restrictions on character encodings that it can 753support by filling in the <code>XML_Encoding</code> structure. 754include file:</p> 755<ol> 756<li>Every ASCII character that can appear in a well-formed XML document 757must be represented by a single byte, and that byte must correspond to 758it's ASCII encoding (except for the characters $@\^'{}~)</li> 759<li>Characters must be encoded in 4 bytes or less.</li> 760<li>All characters encoded must have Unicode scalar values less than or 761equal to 65535 (0xFFFF)<em>This does not apply to the built-in support 762for UTF-16 and UTF-8</em></li> 763<li>No character may be encoded by more that one distinct sequence of 764bytes</li> 765</ol> 766 767<p><code>XML_Encoding</code> contains an array of integers that 768correspond to the 1st byte of an encoding sequence. If the value in 769the array for a byte is zero or positive, then the byte is a single 770byte encoding that encodes the Unicode scalar value contained in the 771array. A -1 in this array indicates a malformed byte. If the value is 772-2, -3, or -4, then the byte is the beginning of a 2, 3, or 4 byte 773sequence respectively. Multi-byte sequences are sent to the convert 774function pointed at in the <code>XML_Encoding</code> structure. This 775function should return the Unicode scalar value for the sequence or -1 776if the sequence is malformed.</p> 777 778<p>One pitfall that novice Expat users are likely to fall into is that 779although Expat may accept input in various encodings, the strings that 780it passes to the handlers are always encoded in UTF-8 or UTF-16 781(depending on how Expat was compiled). Your application is responsible 782for any translation of these strings into other encodings.</p> 783 784<h3>Handling External Entity References</h3> 785 786<p>Expat does not read or parse external entities directly. Note that 787any external DTD is a special case of an external entity. If you've 788set no <code>ExternalEntityRefHandler</code>, then external entity 789references are silently ignored. Otherwise, it calls your handler with 790the information needed to read and parse the external entity.</p> 791 792<p>Your handler isn't actually responsible for parsing the entity, but 793it is responsible for creating a subsidiary parser with <code><a href= 794"#XML_ExternalEntityParserCreate" 795>XML_ExternalEntityParserCreate</a></code> that will do the job. This 796returns an instance of <code>XML_Parser</code> that has handlers and 797other data structures initialized from the parent parser. You may then 798use <code><a href= "#XML_Parse" >XML_Parse</a></code> or <code><a 799href= "#XML_ParseBuffer">XML_ParseBuffer</a></code> calls against this 800parser. Since external entities my refer to other external entities, 801your handler should be prepared to be called recursively.</p> 802 803<h3>Parsing DTDs</h3> 804 805<p>In order to parse parameter entities, before starting the parse, 806you must call <code><a href= "#XML_SetParamEntityParsing" 807>XML_SetParamEntityParsing</a></code> with one of the following 808arguments:</p> 809<dl> 810<dt><code>XML_PARAM_ENTITY_PARSING_NEVER</code></dt> 811<dd>Don't parse parameter entities or the external subset</dd> 812<dt><code>XML_PARAM_ENTITY_PARSING_UNLESS_STANDALONE</code></dt> 813<dd>Parse parameter entities and the external subset unless 814<code>standalone</code> was set to "yes" in the XML declaration.</dd> 815<dt><code>XML_PARAM_ENTITY_PARSING_ALWAYS</code></dt> 816<dd>Always parse parameter entities and the external subset</dd> 817</dl> 818 819<p>In order to read an external DTD, you also have to set an external 820entity reference handler as described above.</p> 821 822<h3 id="stop-resume">Temporarily Stopping Parsing</h3> 823 824<p>Expat 1.95.8 introduces a new feature: its now possible to stop 825parsing temporarily from within a handler function, even if more data 826has already been passed into the parser. Applications for this 827include</p> 828 829<ul> 830 <li>Supporting the <a href= "https://www.w3.org/TR/xinclude/" 831 >XInclude</a> specification.</li> 832 833 <li>Delaying further processing until additional information is 834 available from some other source.</li> 835 836 <li>Adjusting processor load as task priorities shift within an 837 application.</li> 838 839 <li>Stopping parsing completely (simply free or reset the parser 840 instead of resuming in the outer parsing loop). This can be useful 841 if an application-domain error is found in the XML being parsed or if 842 the result of the parse is determined not to be useful after 843 all.</li> 844</ul> 845 846<p>To take advantage of this feature, the main parsing loop of an 847application needs to support this specifically. It cannot be 848supported with a parsing loop compatible with Expat 1.95.7 or 849earlier (though existing loops will continue to work without 850supporting the stop/resume feature).</p> 851 852<p>An application that uses this feature for a single parser will have 853the rough structure (in pseudo-code):</p> 854 855<pre class="pseudocode"> 856fd = open_input() 857p = create_parser() 858 859if parse_xml(p, fd) { 860 /* suspended */ 861 862 int suspended = 1; 863 864 while (suspended) { 865 do_something_else() 866 if ready_to_resume() { 867 suspended = continue_parsing(p, fd); 868 } 869 } 870} 871</pre> 872 873<p>An application that may resume any of several parsers based on 874input (either from the XML being parsed or some other source) will 875certainly have more interesting control structures.</p> 876 877<p>This C function could be used for the <code>parse_xml</code> 878function mentioned in the pseudo-code above:</p> 879 880<pre class="eg"> 881#define BUFF_SIZE 10240 882 883/* Parse a document from the open file descriptor 'fd' until the parse 884 is complete (the document has been completely parsed, or there's 885 been an error), or the parse is stopped. Return non-zero when 886 the parse is merely suspended. 887*/ 888int 889parse_xml(XML_Parser p, int fd) 890{ 891 for (;;) { 892 int last_chunk; 893 int bytes_read; 894 enum XML_Status status; 895 896 void *buff = XML_GetBuffer(p, BUFF_SIZE); 897 if (buff == NULL) { 898 /* handle error... */ 899 return 0; 900 } 901 bytes_read = read(fd, buff, BUFF_SIZE); 902 if (bytes_read < 0) { 903 /* handle error... */ 904 return 0; 905 } 906 status = XML_ParseBuffer(p, bytes_read, bytes_read == 0); 907 switch (status) { 908 case XML_STATUS_ERROR: 909 /* handle error... */ 910 return 0; 911 case XML_STATUS_SUSPENDED: 912 return 1; 913 } 914 if (bytes_read == 0) 915 return 0; 916 } 917} 918</pre> 919 920<p>The corresponding <code>continue_parsing</code> function is 921somewhat simpler, since it only need deal with the return code from 922<code><a href= "#XML_ResumeParser">XML_ResumeParser</a></code>; it can 923delegate the input handling to the <code>parse_xml</code> 924function:</p> 925 926<pre class="eg"> 927/* Continue parsing a document which had been suspended. The 'p' and 928 'fd' arguments are the same as passed to parse_xml(). Return 929 non-zero when the parse is suspended. 930*/ 931int 932continue_parsing(XML_Parser p, int fd) 933{ 934 enum XML_Status status = XML_ResumeParser(p); 935 switch (status) { 936 case XML_STATUS_ERROR: 937 /* handle error... */ 938 return 0; 939 case XML_ERROR_NOT_SUSPENDED: 940 /* handle error... */ 941 return 0;. 942 case XML_STATUS_SUSPENDED: 943 return 1; 944 } 945 return parse_xml(p, fd); 946} 947</pre> 948 949<p>Now that we've seen what a mess the top-level parsing loop can 950become, what have we gained? Very simply, we can now use the <code><a 951href= "#XML_StopParser" >XML_StopParser</a></code> function to stop 952parsing, without having to go to great lengths to avoid additional 953processing that we're expecting to ignore. As a bonus, we get to stop 954parsing <em>temporarily</em>, and come back to it when we're 955ready.</p> 956 957<p>To stop parsing from a handler function, use the <code><a href= 958"#XML_StopParser" >XML_StopParser</a></code> function. This function 959takes two arguments; the parser being stopped and a flag indicating 960whether the parse can be resumed in the future.</p> 961 962<!-- XXX really need more here --> 963 964 965<hr /> 966<!-- ================================================================ --> 967 968<h2><a name="reference">Expat Reference</a></h2> 969 970<h3><a name="creation">Parser Creation</a></h3> 971 972<h4 id="XML_ParserCreate">XML_ParserCreate</h4> 973<pre class="fcndec"> 974XML_Parser XMLCALL 975XML_ParserCreate(const XML_Char *encoding); 976</pre> 977<div class="fcndef"> 978<p> 979Construct a new parser. If encoding is non-<code>NULL</code>, it specifies a 980character encoding to use for the document. This overrides the document 981encoding declaration. There are four built-in encodings: 982</p> 983<ul> 984<li>US-ASCII</li> 985<li>UTF-8</li> 986<li>UTF-16</li> 987<li>ISO-8859-1</li> 988</ul> 989<p> 990Any other value will invoke a call to the UnknownEncodingHandler. 991</p> 992</div> 993 994<h4 id="XML_ParserCreateNS">XML_ParserCreateNS</h4> 995<pre class="fcndec"> 996XML_Parser XMLCALL 997XML_ParserCreateNS(const XML_Char *encoding, 998 XML_Char sep); 999</pre> 1000<div class="fcndef"> 1001Constructs a new parser that has namespace processing in effect. Namespace 1002expanded element names and attribute names are returned as a concatenation 1003of the namespace URI, <em>sep</em>, and the local part of the name. This 1004means that you should pick a character for <em>sep</em> that can't be part 1005of an URI. Since Expat does not check namespace URIs for conformance, the 1006only safe choice for a namespace separator is a character that is illegal 1007in XML. For instance, <code>'\xFF'</code> is not legal in UTF-8, and 1008<code>'\xFFFF'</code> is not legal in UTF-16. There is a special case when 1009<em>sep</em> is the null character <code>'\0'</code>: the namespace URI and 1010the local part will be concatenated without any separator - this is intended 1011to support RDF processors. It is a programming error to use the null separator 1012with <a href= "#XML_SetReturnNSTriplet">namespace triplets</a>.</div> 1013 1014<p><strong>Note:</strong> 1015Expat does not validate namespace URIs (beyond encoding) 1016against RFC 3986 today (and is not required to do so with regard to 1017the XML 1.0 namespaces specification) but it may start doing that 1018in future releases. Before that, an application using Expat must 1019be ready to receive namespace URIs containing non-URI characters. 1020</p> 1021 1022<h4 id="XML_ParserCreate_MM">XML_ParserCreate_MM</h4> 1023<pre class="fcndec"> 1024XML_Parser XMLCALL 1025XML_ParserCreate_MM(const XML_Char *encoding, 1026 const XML_Memory_Handling_Suite *ms, 1027 const XML_Char *sep); 1028</pre> 1029<pre class="signature"> 1030typedef struct { 1031 void *(XMLCALL *malloc_fcn)(size_t size); 1032 void *(XMLCALL *realloc_fcn)(void *ptr, size_t size); 1033 void (XMLCALL *free_fcn)(void *ptr); 1034} XML_Memory_Handling_Suite; 1035</pre> 1036<div class="fcndef"> 1037<p>Construct a new parser using the suite of memory handling functions 1038specified in <code>ms</code>. If <code>ms</code> is <code>NULL</code>, then use the 1039standard set of memory management functions. If <code>sep</code> is 1040non-<code>NULL</code>, then namespace processing is enabled in the created parser 1041and the character pointed at by sep is used as the separator between 1042the namespace URI and the local part of the name.</p> 1043</div> 1044 1045<h4 id="XML_ExternalEntityParserCreate">XML_ExternalEntityParserCreate</h4> 1046<pre class="fcndec"> 1047XML_Parser XMLCALL 1048XML_ExternalEntityParserCreate(XML_Parser p, 1049 const XML_Char *context, 1050 const XML_Char *encoding); 1051</pre> 1052<div class="fcndef"> 1053Construct a new <code>XML_Parser</code> object for parsing an external 1054general entity. Context is the context argument passed in a call to a 1055ExternalEntityRefHandler. Other state information such as handlers, 1056user data, namespace processing is inherited from the parser passed as 1057the 1st argument. So you shouldn't need to call any of the behavior 1058changing functions on this parser (unless you want it to act 1059differently than the parent parser). 1060</div> 1061 1062<h4 id="XML_ParserFree">XML_ParserFree</h4> 1063<pre class="fcndec"> 1064void XMLCALL 1065XML_ParserFree(XML_Parser p); 1066</pre> 1067<div class="fcndef"> 1068Free memory used by the parser. Your application is responsible for 1069freeing any memory associated with <a href="#userdata">user data</a>. 1070</div> 1071 1072<h4 id="XML_ParserReset">XML_ParserReset</h4> 1073<pre class="fcndec"> 1074XML_Bool XMLCALL 1075XML_ParserReset(XML_Parser p, 1076 const XML_Char *encoding); 1077</pre> 1078<div class="fcndef"> 1079Clean up the memory structures maintained by the parser so that it may 1080be used again. After this has been called, <code>parser</code> is 1081ready to start parsing a new document. All handlers are cleared from 1082the parser, except for the unknownEncodingHandler. The parser's external 1083state is re-initialized except for the values of ns and ns_triplets. 1084This function may not be used on a parser created using <code><a href= 1085"#XML_ExternalEntityParserCreate" >XML_ExternalEntityParserCreate</a 1086></code>; it will return <code>XML_FALSE</code> in that case. Returns 1087<code>XML_TRUE</code> on success. Your application is responsible for 1088dealing with any memory associated with <a href="#userdata">user data</a>. 1089</div> 1090 1091<h3><a name="parsing">Parsing</a></h3> 1092 1093<p>To state the obvious: the three parsing functions <code><a href= 1094"#XML_Parse" >XML_Parse</a></code>, <code><a href= "#XML_ParseBuffer"> 1095XML_ParseBuffer</a></code> and <code><a href= "#XML_GetBuffer"> 1096XML_GetBuffer</a></code> must not be called from within a handler 1097unless they operate on a separate parser instance, that is, one that 1098did not call the handler. For example, it is OK to call the parsing 1099functions from within an <code>XML_ExternalEntityRefHandler</code>, 1100if they apply to the parser created by 1101<code><a href= "#XML_ExternalEntityParserCreate" 1102>XML_ExternalEntityParserCreate</a></code>.</p> 1103 1104<p>Note: The <code>len</code> argument passed to these functions 1105should be considerably less than the maximum value for an integer, 1106as it could create an integer overflow situation if the added 1107lengths of a buffer and the unprocessed portion of the previous buffer 1108exceed the maximum integer value. Input data at the end of a buffer 1109will remain unprocessed if it is part of an XML token for which the 1110end is not part of that buffer.</p> 1111 1112<p><a name="isFinal"></a>The application <em>must</em> make a concluding 1113<code><a href="#XML_Parse">XML_Parse</a></code> or 1114<code><a href="#XML_ParseBuffer">XML_ParseBuffer</a></code> call 1115with <code>isFinal</code> set to <code>XML_TRUE</code>.</p> 1116 1117<h4 id="XML_Parse">XML_Parse</h4> 1118<pre class="fcndec"> 1119enum XML_Status XMLCALL 1120XML_Parse(XML_Parser p, 1121 const char *s, 1122 int len, 1123 int isFinal); 1124</pre> 1125<pre class="signature"> 1126enum XML_Status { 1127 XML_STATUS_ERROR = 0, 1128 XML_STATUS_OK = 1 1129}; 1130</pre> 1131<div class="fcndef"> 1132<p> 1133Parse some more of the document. The string <code>s</code> is a buffer 1134containing part (or perhaps all) of the document. The number of bytes of s 1135that are part of the document is indicated by <code>len</code>. This means 1136that <code>s</code> doesn't have to be null-terminated. It also means that 1137if <code>len</code> is larger than the number of bytes in the block of 1138memory that <code>s</code> points at, then a memory fault is likely. 1139Negative values for <code>len</code> are rejected since Expat 2.2.1. 1140The 1141<code>isFinal</code> parameter informs the parser that this is the last 1142piece of the document. Frequently, the last piece is empty (i.e. 1143<code>len</code> is zero.) 1144</p> 1145 1146<p> 1147If a parse error occurred, it returns <code>XML_STATUS_ERROR</code>. 1148Otherwise it returns <code>XML_STATUS_OK</code> value. 1149Note that regardless of the return value, there is no guarantee that all 1150provided input has been parsed; only after <a href="#isFinal">the 1151concluding call</a> will all handler callbacks and parsing errors have 1152happened. 1153</p> 1154 1155<p> 1156Simplified, <code>XML_Parse</code> can be considered a convenience wrapper 1157that is pairing calls 1158to <code><a href="#XML_GetBuffer">XML_GetBuffer</a></code> 1159and <code><a href="#XML_ParseBuffer">XML_ParseBuffer</a></code> 1160(when Expat is built with macro <code>XML_CONTEXT_BYTES</code> 1161defined to a positive value, which is both common and default). 1162<code>XML_Parse</code> is then functionally equivalent to calling 1163<code><a href="#XML_GetBuffer">XML_GetBuffer</a></code>, 1164<code>memcpy</code>, and 1165<code><a href="#XML_ParseBuffer">XML_ParseBuffer</a></code>. 1166</p> 1167 1168<p> 1169To avoid double copying of the input, direct use of functions 1170<code><a href="#XML_GetBuffer">XML_GetBuffer</a></code> and 1171<code><a href="#XML_ParseBuffer">XML_ParseBuffer</a></code> is advised 1172for most production use, e.g. 1173if you're using <code>read</code> or similar functionality to fill your 1174buffers, fill directly into the buffer from 1175<code><a href="#XML_GetBuffer">XML_GetBuffer</a></code>, 1176then parse with <code><a href="#XML_ParseBuffer">XML_ParseBuffer</a></code>. 1177</p> 1178</div> 1179 1180<h4 id="XML_ParseBuffer">XML_ParseBuffer</h4> 1181<pre class="fcndec"> 1182enum XML_Status XMLCALL 1183XML_ParseBuffer(XML_Parser p, 1184 int len, 1185 int isFinal); 1186</pre> 1187<div class="fcndef"> 1188<p> 1189This is just like <code><a href= "#XML_Parse" >XML_Parse</a></code>, 1190except in this case Expat provides the buffer. By obtaining the 1191buffer from Expat with the <code><a href= "#XML_GetBuffer" 1192>XML_GetBuffer</a></code> function, the application can avoid double 1193copying of the input. 1194</p> 1195 1196<p> 1197Negative values for <code>len</code> are rejected since Expat 2.6.3. 1198</p> 1199</div> 1200 1201<h4 id="XML_GetBuffer">XML_GetBuffer</h4> 1202<pre class="fcndec"> 1203void * XMLCALL 1204XML_GetBuffer(XML_Parser p, 1205 int len); 1206</pre> 1207<div class="fcndef"> 1208Obtain a buffer of size <code>len</code> to read a piece of the document 1209into. A <code>NULL</code> value is returned if Expat can't allocate enough memory for 1210this buffer. A <code>NULL</code> value may also be returned if <code>len</code> is zero. 1211This has to be called prior to every call to 1212<code><a href= "#XML_ParseBuffer" >XML_ParseBuffer</a></code>. A 1213typical use would look like this: 1214 1215<pre class="eg"> 1216for (;;) { 1217 int bytes_read; 1218 void *buff = XML_GetBuffer(p, BUFF_SIZE); 1219 if (buff == NULL) { 1220 /* handle error */ 1221 } 1222 1223 bytes_read = read(docfd, buff, BUFF_SIZE); 1224 if (bytes_read < 0) { 1225 /* handle error */ 1226 } 1227 1228 if (! XML_ParseBuffer(p, bytes_read, bytes_read == 0)) { 1229 /* handle parse error */ 1230 } 1231 1232 if (bytes_read == 0) 1233 break; 1234} 1235</pre> 1236</div> 1237 1238<h4 id="XML_StopParser">XML_StopParser</h4> 1239<pre class="fcndec"> 1240enum XML_Status XMLCALL 1241XML_StopParser(XML_Parser p, 1242 XML_Bool resumable); 1243</pre> 1244<div class="fcndef"> 1245 1246<p>Stops parsing, causing <code><a href= "#XML_Parse" 1247>XML_Parse</a></code> or <code><a href= "#XML_ParseBuffer" 1248>XML_ParseBuffer</a></code> to return. Must be called from within a 1249call-back handler, except when aborting (when <code>resumable</code> 1250is <code>XML_FALSE</code>) an already suspended parser. Some 1251call-backs may still follow because they would otherwise get 1252lost, including</p> 1253<ul> 1254 <li> the end element handler for empty elements when stopped in the 1255 start element handler,</li> 1256 <li> the end namespace declaration handler when stopped in the end 1257 element handler,</li> 1258 <li> the character data handler when stopped in the character data handler 1259 while making multiple call-backs on a contiguous chunk of characters,</li> 1260</ul> 1261<p>and possibly others.</p> 1262 1263<p>This can be called from most handlers, including DTD related 1264call-backs, except when parsing an external parameter entity and 1265<code>resumable</code> is <code>XML_TRUE</code>. Returns 1266<code>XML_STATUS_OK</code> when successful, 1267<code>XML_STATUS_ERROR</code> otherwise. The possible error codes 1268are:</p> 1269<dl> 1270 <dt><code>XML_ERROR_NOT_STARTED</code></dt> 1271 <dd> 1272 when stopping or suspending a parser before it has started, 1273 added in Expat 2.6.4. 1274 </dd> 1275 <dt><code>XML_ERROR_SUSPENDED</code></dt> 1276 <dd>when suspending an already suspended parser.</dd> 1277 <dt><code>XML_ERROR_FINISHED</code></dt> 1278 <dd>when the parser has already finished.</dd> 1279 <dt><code>XML_ERROR_SUSPEND_PE</code></dt> 1280 <dd>when suspending while parsing an external PE.</dd> 1281</dl> 1282 1283<p>Since the stop/resume feature requires application support in the 1284outer parsing loop, it is an error to call this function for a parser 1285not being handled appropriately; see <a href= "#stop-resume" 1286>Temporarily Stopping Parsing</a> for more information.</p> 1287 1288<p>When <code>resumable</code> is <code>XML_TRUE</code> then parsing 1289is <em>suspended</em>, that is, <code><a href= "#XML_Parse" 1290>XML_Parse</a></code> and <code><a href= "#XML_ParseBuffer" 1291>XML_ParseBuffer</a></code> return <code>XML_STATUS_SUSPENDED</code>. 1292Otherwise, parsing is <em>aborted</em>, that is, <code><a href= 1293"#XML_Parse" >XML_Parse</a></code> and <code><a href= 1294"#XML_ParseBuffer" >XML_ParseBuffer</a></code> return 1295<code>XML_STATUS_ERROR</code> with error code 1296<code>XML_ERROR_ABORTED</code>.</p> 1297 1298<p><strong>Note:</strong> 1299This will be applied to the current parser instance only, that is, if 1300there is a parent parser then it will continue parsing when the 1301external entity reference handler returns. It is up to the 1302implementation of that handler to call <code><a href= 1303"#XML_StopParser" >XML_StopParser</a></code> on the parent parser 1304(recursively), if one wants to stop parsing altogether.</p> 1305 1306<p>When suspended, parsing can be resumed by calling <code><a href= 1307"#XML_ResumeParser" >XML_ResumeParser</a></code>.</p> 1308 1309<p>New in Expat 1.95.8.</p> 1310</div> 1311 1312<h4 id="XML_ResumeParser">XML_ResumeParser</h4> 1313<pre class="fcndec"> 1314enum XML_Status XMLCALL 1315XML_ResumeParser(XML_Parser p); 1316</pre> 1317<div class="fcndef"> 1318<p>Resumes parsing after it has been suspended with <code><a href= 1319"#XML_StopParser" >XML_StopParser</a></code>. Must not be called from 1320within a handler call-back. Returns same status codes as <code><a 1321href= "#XML_Parse">XML_Parse</a></code> or <code><a href= 1322"#XML_ParseBuffer" >XML_ParseBuffer</a></code>. An additional error 1323code, <code>XML_ERROR_NOT_SUSPENDED</code>, will be returned if the 1324parser was not currently suspended.</p> 1325 1326<p><strong>Note:</strong> 1327This must be called on the most deeply nested child parser instance 1328first, and on its parent parser only after the child parser has 1329finished, to be applied recursively until the document entity's parser 1330is restarted. That is, the parent parser will not resume by itself 1331and it is up to the application to call <code><a href= 1332"#XML_ResumeParser" >XML_ResumeParser</a></code> on it at the 1333appropriate moment.</p> 1334 1335<p>New in Expat 1.95.8.</p> 1336</div> 1337 1338<h4 id="XML_GetParsingStatus">XML_GetParsingStatus</h4> 1339<pre class="fcndec"> 1340void XMLCALL 1341XML_GetParsingStatus(XML_Parser p, 1342 XML_ParsingStatus *status); 1343</pre> 1344<pre class="signature"> 1345enum XML_Parsing { 1346 XML_INITIALIZED, 1347 XML_PARSING, 1348 XML_FINISHED, 1349 XML_SUSPENDED 1350}; 1351 1352typedef struct { 1353 enum XML_Parsing parsing; 1354 XML_Bool finalBuffer; 1355} XML_ParsingStatus; 1356</pre> 1357<div class="fcndef"> 1358<p>Returns status of parser with respect to being initialized, 1359parsing, finished, or suspended, and whether the final buffer is being 1360processed. The <code>status</code> parameter <em>must not</em> be 1361<code>NULL</code>.</p> 1362 1363<p>New in Expat 1.95.8.</p> 1364</div> 1365 1366 1367<h3><a name="setting">Handler Setting</a></h3> 1368 1369<p>Although handlers are typically set prior to parsing and left alone, an 1370application may choose to set or change the handler for a parsing event 1371while the parse is in progress. For instance, your application may choose 1372to ignore all text not descended from a <code>para</code> element. One 1373way it could do this is to set the character handler when a para start tag 1374is seen, and unset it for the corresponding end tag.</p> 1375 1376<p>A handler may be <em>unset</em> by providing a <code>NULL</code> pointer to the 1377appropriate handler setter. None of the handler setting functions have 1378a return value.</p> 1379 1380<p>Your handlers will be receiving strings in arrays of type 1381<code>XML_Char</code>. This type is conditionally defined in expat.h as 1382either <code>char</code>, <code>wchar_t</code> or <code>unsigned short</code>. 1383The former implies UTF-8 encoding, the latter two imply UTF-16 encoding. 1384Note that you'll receive them in this form independent of the original 1385encoding of the document.</p> 1386 1387<div class="handler"> 1388<h4 id="XML_SetStartElementHandler">XML_SetStartElementHandler</h4> 1389<pre class="setter"> 1390void XMLCALL 1391XML_SetStartElementHandler(XML_Parser p, 1392 XML_StartElementHandler start); 1393</pre> 1394<pre class="signature"> 1395typedef void 1396(XMLCALL *XML_StartElementHandler)(void *userData, 1397 const XML_Char *name, 1398 const XML_Char **atts); 1399</pre> 1400<p>Set handler for start (and empty) tags. Attributes are passed to the start 1401handler as a pointer to a vector of char pointers. Each attribute seen in 1402a start (or empty) tag occupies 2 consecutive places in this vector: the 1403attribute name followed by the attribute value. These pairs are terminated 1404by a <code>NULL</code> pointer.</p> 1405<p>Note that an empty tag generates a call to both start and end handlers 1406(in that order).</p> 1407</div> 1408 1409<div class="handler"> 1410<h4 id="XML_SetEndElementHandler">XML_SetEndElementHandler</h4> 1411<pre class="setter"> 1412void XMLCALL 1413XML_SetEndElementHandler(XML_Parser p, 1414 XML_EndElementHandler); 1415</pre> 1416<pre class="signature"> 1417typedef void 1418(XMLCALL *XML_EndElementHandler)(void *userData, 1419 const XML_Char *name); 1420</pre> 1421<p>Set handler for end (and empty) tags. As noted above, an empty tag 1422generates a call to both start and end handlers.</p> 1423</div> 1424 1425<div class="handler"> 1426<h4 id="XML_SetElementHandler">XML_SetElementHandler</h4> 1427<pre class="setter"> 1428void XMLCALL 1429XML_SetElementHandler(XML_Parser p, 1430 XML_StartElementHandler start, 1431 XML_EndElementHandler end); 1432</pre> 1433<p>Set handlers for start and end tags with one call.</p> 1434</div> 1435 1436<div class="handler"> 1437<h4 id="XML_SetCharacterDataHandler">XML_SetCharacterDataHandler</h4> 1438<pre class="setter"> 1439void XMLCALL 1440XML_SetCharacterDataHandler(XML_Parser p, 1441 XML_CharacterDataHandler charhndl) 1442</pre> 1443<pre class="signature"> 1444typedef void 1445(XMLCALL *XML_CharacterDataHandler)(void *userData, 1446 const XML_Char *s, 1447 int len); 1448</pre> 1449<p>Set a text handler. The string your handler receives 1450is <em>NOT null-terminated</em>. You have to use the length argument 1451to deal with the end of the string. A single block of contiguous text 1452free of markup may still result in a sequence of calls to this handler. 1453In other words, if you're searching for a pattern in the text, it may 1454be split across calls to this handler. Note: Setting this handler to <code>NULL</code> 1455may <em>NOT immediately</em> terminate call-backs if the parser is currently 1456processing such a single block of contiguous markup-free text, as the parser 1457will continue calling back until the end of the block is reached.</p> 1458</div> 1459 1460<div class="handler"> 1461<h4 id="XML_SetProcessingInstructionHandler">XML_SetProcessingInstructionHandler</h4> 1462<pre class="setter"> 1463void XMLCALL 1464XML_SetProcessingInstructionHandler(XML_Parser p, 1465 XML_ProcessingInstructionHandler proc) 1466</pre> 1467<pre class="signature"> 1468typedef void 1469(XMLCALL *XML_ProcessingInstructionHandler)(void *userData, 1470 const XML_Char *target, 1471 const XML_Char *data); 1472 1473</pre> 1474<p>Set a handler for processing instructions. The target is the first word 1475in the processing instruction. The data is the rest of the characters in 1476it after skipping all whitespace after the initial word.</p> 1477</div> 1478 1479<div class="handler"> 1480<h4 id="XML_SetCommentHandler">XML_SetCommentHandler</h4> 1481<pre class="setter"> 1482void XMLCALL 1483XML_SetCommentHandler(XML_Parser p, 1484 XML_CommentHandler cmnt) 1485</pre> 1486<pre class="signature"> 1487typedef void 1488(XMLCALL *XML_CommentHandler)(void *userData, 1489 const XML_Char *data); 1490</pre> 1491<p>Set a handler for comments. The data is all text inside the comment 1492delimiters.</p> 1493</div> 1494 1495<div class="handler"> 1496<h4 id="XML_SetStartCdataSectionHandler">XML_SetStartCdataSectionHandler</h4> 1497<pre class="setter"> 1498void XMLCALL 1499XML_SetStartCdataSectionHandler(XML_Parser p, 1500 XML_StartCdataSectionHandler start); 1501</pre> 1502<pre class="signature"> 1503typedef void 1504(XMLCALL *XML_StartCdataSectionHandler)(void *userData); 1505</pre> 1506<p>Set a handler that gets called at the beginning of a CDATA section.</p> 1507</div> 1508 1509<div class="handler"> 1510<h4 id="XML_SetEndCdataSectionHandler">XML_SetEndCdataSectionHandler</h4> 1511<pre class="setter"> 1512void XMLCALL 1513XML_SetEndCdataSectionHandler(XML_Parser p, 1514 XML_EndCdataSectionHandler end); 1515</pre> 1516<pre class="signature"> 1517typedef void 1518(XMLCALL *XML_EndCdataSectionHandler)(void *userData); 1519</pre> 1520<p>Set a handler that gets called at the end of a CDATA section.</p> 1521</div> 1522 1523<div class="handler"> 1524<h4 id="XML_SetCdataSectionHandler">XML_SetCdataSectionHandler</h4> 1525<pre class="setter"> 1526void XMLCALL 1527XML_SetCdataSectionHandler(XML_Parser p, 1528 XML_StartCdataSectionHandler start, 1529 XML_EndCdataSectionHandler end) 1530</pre> 1531<p>Sets both CDATA section handlers with one call.</p> 1532</div> 1533 1534<div class="handler"> 1535<h4 id="XML_SetDefaultHandler">XML_SetDefaultHandler</h4> 1536<pre class="setter"> 1537void XMLCALL 1538XML_SetDefaultHandler(XML_Parser p, 1539 XML_DefaultHandler hndl) 1540</pre> 1541<pre class="signature"> 1542typedef void 1543(XMLCALL *XML_DefaultHandler)(void *userData, 1544 const XML_Char *s, 1545 int len); 1546</pre> 1547 1548<p>Sets a handler for any characters in the document which wouldn't 1549otherwise be handled. This includes both data for which no handlers 1550can be set (like some kinds of DTD declarations) and data which could 1551be reported but which currently has no handler set. The characters 1552are passed exactly as they were present in the XML document except 1553that they will be encoded in UTF-8 or UTF-16. Line boundaries are not 1554normalized. Note that a byte order mark character is not passed to the 1555default handler. There are no guarantees about how characters are 1556divided between calls to the default handler: for example, a comment 1557might be split between multiple calls. Setting the handler with 1558this call has the side effect of turning off expansion of references 1559to internally defined general entities. Instead these references are 1560passed to the default handler.</p> 1561 1562<p>See also <code><a 1563href="#XML_DefaultCurrent">XML_DefaultCurrent</a></code>.</p> 1564</div> 1565 1566<div class="handler"> 1567<h4 id="XML_SetDefaultHandlerExpand">XML_SetDefaultHandlerExpand</h4> 1568<pre class="setter"> 1569void XMLCALL 1570XML_SetDefaultHandlerExpand(XML_Parser p, 1571 XML_DefaultHandler hndl) 1572</pre> 1573<pre class="signature"> 1574typedef void 1575(XMLCALL *XML_DefaultHandler)(void *userData, 1576 const XML_Char *s, 1577 int len); 1578</pre> 1579<p>This sets a default handler, but doesn't inhibit the expansion of 1580internal entity references. The entity reference will not be passed 1581to the default handler.</p> 1582 1583<p>See also <code><a 1584href="#XML_DefaultCurrent">XML_DefaultCurrent</a></code>.</p> 1585</div> 1586 1587<div class="handler"> 1588<h4 id="XML_SetExternalEntityRefHandler">XML_SetExternalEntityRefHandler</h4> 1589<pre class="setter"> 1590void XMLCALL 1591XML_SetExternalEntityRefHandler(XML_Parser p, 1592 XML_ExternalEntityRefHandler hndl) 1593</pre> 1594<pre class="signature"> 1595typedef int 1596(XMLCALL *XML_ExternalEntityRefHandler)(XML_Parser p, 1597 const XML_Char *context, 1598 const XML_Char *base, 1599 const XML_Char *systemId, 1600 const XML_Char *publicId); 1601</pre> 1602<p>Set an external entity reference handler. This handler is also 1603called for processing an external DTD subset if parameter entity parsing 1604is in effect. (See <a href="#XML_SetParamEntityParsing"> 1605<code>XML_SetParamEntityParsing</code></a>.)</p> 1606 1607<p>The <code>context</code> parameter specifies the parsing context in 1608the format expected by the <code>context</code> argument to <code><a 1609href="#XML_ExternalEntityParserCreate" 1610>XML_ExternalEntityParserCreate</a></code>. <code>code</code> is 1611valid only until the handler returns, so if the referenced entity is 1612to be parsed later, it must be copied. <code>context</code> is <code>NULL</code> 1613only when the entity is a parameter entity, which is how one can 1614differentiate between general and parameter entities.</p> 1615 1616<p>The <code>base</code> parameter is the base to use for relative 1617system identifiers. It is set by <code><a 1618href="#XML_SetBase">XML_SetBase</a></code> and may be <code>NULL</code>. The 1619<code>publicId</code> parameter is the public id given in the entity 1620declaration and may be <code>NULL</code>. <code>systemId</code> is the system 1621identifier specified in the entity declaration and is never <code>NULL</code>.</p> 1622 1623<p>There are a couple of ways in which this handler differs from 1624others. First, this handler returns a status indicator (an 1625integer). <code>XML_STATUS_OK</code> should be returned for successful 1626handling of the external entity reference. Returning 1627<code>XML_STATUS_ERROR</code> indicates failure, and causes the 1628calling parser to return an 1629<code>XML_ERROR_EXTERNAL_ENTITY_HANDLING</code> error.</p> 1630 1631<p>Second, instead of having the user data as its first argument, it 1632receives the parser that encountered the entity reference. This, along 1633with the context parameter, may be used as arguments to a call to 1634<code><a href= "#XML_ExternalEntityParserCreate" 1635>XML_ExternalEntityParserCreate</a></code>. Using the returned 1636parser, the body of the external entity can be recursively parsed.</p> 1637 1638<p>Since this handler may be called recursively, it should not be saving 1639information into global or static variables.</p> 1640</div> 1641 1642<h4 id="XML_SetExternalEntityRefHandlerArg">XML_SetExternalEntityRefHandlerArg</h4> 1643<pre class="fcndec"> 1644void XMLCALL 1645XML_SetExternalEntityRefHandlerArg(XML_Parser p, 1646 void *arg) 1647</pre> 1648<div class="fcndef"> 1649<p>Set the argument passed to the ExternalEntityRefHandler. If 1650<code>arg</code> is not <code>NULL</code>, it is the new value passed to the 1651handler set using <code><a href="#XML_SetExternalEntityRefHandler" 1652>XML_SetExternalEntityRefHandler</a></code>; if <code>arg</code> is 1653<code>NULL</code>, the argument passed to the handler function will be the parser 1654object itself.</p> 1655 1656<p><strong>Note:</strong> 1657The type of <code>arg</code> and the type of the first argument to the 1658ExternalEntityRefHandler do not match. This function takes a 1659<code>void *</code> to be passed to the handler, while the handler 1660accepts an <code>XML_Parser</code>. This is a historical accident, 1661but will not be corrected before Expat 2.0 (at the earliest) to avoid 1662causing compiler warnings for code that's known to work with this 1663API. It is the responsibility of the application code to know the 1664actual type of the argument passed to the handler and to manage it 1665properly.</p> 1666</div> 1667 1668<div class="handler"> 1669<h4 id="XML_SetSkippedEntityHandler">XML_SetSkippedEntityHandler</h4> 1670<pre class="setter"> 1671void XMLCALL 1672XML_SetSkippedEntityHandler(XML_Parser p, 1673 XML_SkippedEntityHandler handler) 1674</pre> 1675<pre class="signature"> 1676typedef void 1677(XMLCALL *XML_SkippedEntityHandler)(void *userData, 1678 const XML_Char *entityName, 1679 int is_parameter_entity); 1680</pre> 1681<p>Set a skipped entity handler. This is called in two situations:</p> 1682<ol> 1683 <li>An entity reference is encountered for which no declaration 1684 has been read <em>and</em> this is not an error.</li> 1685 <li>An internal entity reference is read, but not expanded, because 1686 <a href="#XML_SetDefaultHandler"><code>XML_SetDefaultHandler</code></a> 1687 has been called.</li> 1688</ol> 1689<p>The <code>is_parameter_entity</code> argument will be non-zero for 1690a parameter entity and zero for a general entity.</p> <p>Note: Skipped 1691parameter entities in declarations and skipped general entities in 1692attribute values cannot be reported, because the event would be out of 1693sync with the reporting of the declarations or attribute values</p> 1694</div> 1695 1696<div class="handler"> 1697<h4 id="XML_SetUnknownEncodingHandler">XML_SetUnknownEncodingHandler</h4> 1698<pre class="setter"> 1699void XMLCALL 1700XML_SetUnknownEncodingHandler(XML_Parser p, 1701 XML_UnknownEncodingHandler enchandler, 1702 void *encodingHandlerData) 1703</pre> 1704<pre class="signature"> 1705typedef int 1706(XMLCALL *XML_UnknownEncodingHandler)(void *encodingHandlerData, 1707 const XML_Char *name, 1708 XML_Encoding *info); 1709 1710typedef struct { 1711 int map[256]; 1712 void *data; 1713 int (XMLCALL *convert)(void *data, const char *s); 1714 void (XMLCALL *release)(void *data); 1715} XML_Encoding; 1716</pre> 1717<p>Set a handler to deal with encodings other than the <a 1718href="#builtin_encodings">built in set</a>. This should be done before 1719<code><a href= "#XML_Parse" >XML_Parse</a></code> or <code><a href= 1720"#XML_ParseBuffer" >XML_ParseBuffer</a></code> have been called on the 1721given parser.</p> <p>If the handler knows how to deal with an encoding 1722with the given name, it should fill in the <code>info</code> data 1723structure and return <code>XML_STATUS_OK</code>. Otherwise it 1724should return <code>XML_STATUS_ERROR</code>. The handler will be called 1725at most once per parsed (external) entity. The optional application 1726data pointer <code>encodingHandlerData</code> will be passed back to 1727the handler.</p> 1728 1729<p>The map array contains information for every possible leading 1730byte in a byte sequence. If the corresponding value is >= 0, then it's 1731a single byte sequence and the byte encodes that Unicode value. If the 1732value is -1, then that byte is invalid as the initial byte in a sequence. 1733If the value is -n, where n is an integer > 1, then n is the number of 1734bytes in the sequence and the actual conversion is accomplished by a 1735call to the function pointed at by convert. This function may return -1 1736if the sequence itself is invalid. The convert pointer may be <code>NULL</code> if 1737there are only single byte codes. The data parameter passed to the convert 1738function is the data pointer from <code>XML_Encoding</code>. The 1739string s is <em>NOT</em> null-terminated and points at the sequence of 1740bytes to be converted.</p> 1741 1742<p>The function pointed at by <code>release</code> is called by the 1743parser when it is finished with the encoding. It may be <code>NULL</code>.</p> 1744</div> 1745 1746<div class="handler"> 1747<h4 id="XML_SetStartNamespaceDeclHandler">XML_SetStartNamespaceDeclHandler</h4> 1748<pre class="setter"> 1749void XMLCALL 1750XML_SetStartNamespaceDeclHandler(XML_Parser p, 1751 XML_StartNamespaceDeclHandler start); 1752</pre> 1753<pre class="signature"> 1754typedef void 1755(XMLCALL *XML_StartNamespaceDeclHandler)(void *userData, 1756 const XML_Char *prefix, 1757 const XML_Char *uri); 1758</pre> 1759<p>Set a handler to be called when a namespace is declared. Namespace 1760declarations occur inside start tags. But the namespace declaration start 1761handler is called before the start tag handler for each namespace declared 1762in that start tag.</p> 1763</div> 1764 1765<div class="handler"> 1766<h4 id="XML_SetEndNamespaceDeclHandler">XML_SetEndNamespaceDeclHandler</h4> 1767<pre class="setter"> 1768void XMLCALL 1769XML_SetEndNamespaceDeclHandler(XML_Parser p, 1770 XML_EndNamespaceDeclHandler end); 1771</pre> 1772<pre class="signature"> 1773typedef void 1774(XMLCALL *XML_EndNamespaceDeclHandler)(void *userData, 1775 const XML_Char *prefix); 1776</pre> 1777<p>Set a handler to be called when leaving the scope of a namespace 1778declaration. This will be called, for each namespace declaration, 1779after the handler for the end tag of the element in which the 1780namespace was declared.</p> 1781</div> 1782 1783<div class="handler"> 1784<h4 id="XML_SetNamespaceDeclHandler">XML_SetNamespaceDeclHandler</h4> 1785<pre class="setter"> 1786void XMLCALL 1787XML_SetNamespaceDeclHandler(XML_Parser p, 1788 XML_StartNamespaceDeclHandler start, 1789 XML_EndNamespaceDeclHandler end) 1790</pre> 1791<p>Sets both namespace declaration handlers with a single call.</p> 1792</div> 1793 1794<div class="handler"> 1795<h4 id="XML_SetXmlDeclHandler">XML_SetXmlDeclHandler</h4> 1796<pre class="setter"> 1797void XMLCALL 1798XML_SetXmlDeclHandler(XML_Parser p, 1799 XML_XmlDeclHandler xmldecl); 1800</pre> 1801<pre class="signature"> 1802typedef void 1803(XMLCALL *XML_XmlDeclHandler)(void *userData, 1804 const XML_Char *version, 1805 const XML_Char *encoding, 1806 int standalone); 1807</pre> 1808<p>Sets a handler that is called for XML declarations and also for 1809text declarations discovered in external entities. The way to 1810distinguish is that the <code>version</code> parameter will be <code>NULL</code> 1811for text declarations. The <code>encoding</code> parameter may be <code>NULL</code> 1812for an XML declaration. The <code>standalone</code> argument will 1813contain -1, 0, or 1 indicating respectively that there was no 1814standalone parameter in the declaration, that it was given as no, or 1815that it was given as yes.</p> 1816</div> 1817 1818<div class="handler"> 1819<h4 id="XML_SetStartDoctypeDeclHandler">XML_SetStartDoctypeDeclHandler</h4> 1820<pre class="setter"> 1821void XMLCALL 1822XML_SetStartDoctypeDeclHandler(XML_Parser p, 1823 XML_StartDoctypeDeclHandler start); 1824</pre> 1825<pre class="signature"> 1826typedef void 1827(XMLCALL *XML_StartDoctypeDeclHandler)(void *userData, 1828 const XML_Char *doctypeName, 1829 const XML_Char *sysid, 1830 const XML_Char *pubid, 1831 int has_internal_subset); 1832</pre> 1833<p>Set a handler that is called at the start of a DOCTYPE declaration, 1834before any external or internal subset is parsed. Both <code>sysid</code> 1835and <code>pubid</code> may be <code>NULL</code>. The <code>has_internal_subset</code> 1836will be non-zero if the DOCTYPE declaration has an internal subset.</p> 1837</div> 1838 1839<div class="handler"> 1840<h4 id="XML_SetEndDoctypeDeclHandler">XML_SetEndDoctypeDeclHandler</h4> 1841<pre class="setter"> 1842void XMLCALL 1843XML_SetEndDoctypeDeclHandler(XML_Parser p, 1844 XML_EndDoctypeDeclHandler end); 1845</pre> 1846<pre class="signature"> 1847typedef void 1848(XMLCALL *XML_EndDoctypeDeclHandler)(void *userData); 1849</pre> 1850<p>Set a handler that is called at the end of a DOCTYPE declaration, 1851after parsing any external subset.</p> 1852</div> 1853 1854<div class="handler"> 1855<h4 id="XML_SetDoctypeDeclHandler">XML_SetDoctypeDeclHandler</h4> 1856<pre class="setter"> 1857void XMLCALL 1858XML_SetDoctypeDeclHandler(XML_Parser p, 1859 XML_StartDoctypeDeclHandler start, 1860 XML_EndDoctypeDeclHandler end); 1861</pre> 1862<p>Set both doctype handlers with one call.</p> 1863</div> 1864 1865<div class="handler"> 1866<h4 id="XML_SetElementDeclHandler">XML_SetElementDeclHandler</h4> 1867<pre class="setter"> 1868void XMLCALL 1869XML_SetElementDeclHandler(XML_Parser p, 1870 XML_ElementDeclHandler eldecl); 1871</pre> 1872<pre class="signature"> 1873typedef void 1874(XMLCALL *XML_ElementDeclHandler)(void *userData, 1875 const XML_Char *name, 1876 XML_Content *model); 1877</pre> 1878<pre class="signature"> 1879enum XML_Content_Type { 1880 XML_CTYPE_EMPTY = 1, 1881 XML_CTYPE_ANY, 1882 XML_CTYPE_MIXED, 1883 XML_CTYPE_NAME, 1884 XML_CTYPE_CHOICE, 1885 XML_CTYPE_SEQ 1886}; 1887 1888enum XML_Content_Quant { 1889 XML_CQUANT_NONE, 1890 XML_CQUANT_OPT, 1891 XML_CQUANT_REP, 1892 XML_CQUANT_PLUS 1893}; 1894 1895typedef struct XML_cp XML_Content; 1896 1897struct XML_cp { 1898 enum XML_Content_Type type; 1899 enum XML_Content_Quant quant; 1900 const XML_Char * name; 1901 unsigned int numchildren; 1902 XML_Content * children; 1903}; 1904</pre> 1905<p>Sets a handler for element declarations in a DTD. The handler gets 1906called with the name of the element in the declaration and a pointer 1907to a structure that contains the element model. It's the user code's 1908responsibility to free model when finished with it. See <code> 1909<a href="#XML_FreeContentModel">XML_FreeContentModel</a></code>. 1910There is no need to free the model from the handler, it can be kept 1911around and freed at a later stage.</p> 1912 1913<p>The <code>model</code> argument is the root of a tree of 1914<code>XML_Content</code> nodes. If <code>type</code> equals 1915<code>XML_CTYPE_EMPTY</code> or <code>XML_CTYPE_ANY</code>, then 1916<code>quant</code> will be <code>XML_CQUANT_NONE</code>, and the other 1917fields will be zero or <code>NULL</code>. If <code>type</code> is 1918<code>XML_CTYPE_MIXED</code>, then <code>quant</code> will be 1919<code>XML_CQUANT_NONE</code> or <code>XML_CQUANT_REP</code> and 1920<code>numchildren</code> will contain the number of elements that are 1921allowed to be mixed in and <code>children</code> points to an array of 1922<code>XML_Content</code> structures that will all have type 1923XML_CTYPE_NAME with no quantification. Only the root node can be type 1924<code>XML_CTYPE_EMPTY</code>, <code>XML_CTYPE_ANY</code>, or 1925<code>XML_CTYPE_MIXED</code>.</p> 1926 1927<p>For type <code>XML_CTYPE_NAME</code>, the <code>name</code> field 1928points to the name and the <code>numchildren</code> and 1929<code>children</code> fields will be zero and <code>NULL</code>. The 1930<code>quant</code> field will indicate any quantifiers placed on the 1931name.</p> 1932 1933<p>Types <code>XML_CTYPE_CHOICE</code> and <code>XML_CTYPE_SEQ</code> 1934indicate a choice or sequence respectively. The 1935<code>numchildren</code> field indicates how many nodes in the choice 1936or sequence and <code>children</code> points to the nodes.</p> 1937</div> 1938 1939<div class="handler"> 1940<h4 id="XML_SetAttlistDeclHandler">XML_SetAttlistDeclHandler</h4> 1941<pre class="setter"> 1942void XMLCALL 1943XML_SetAttlistDeclHandler(XML_Parser p, 1944 XML_AttlistDeclHandler attdecl); 1945</pre> 1946<pre class="signature"> 1947typedef void 1948(XMLCALL *XML_AttlistDeclHandler)(void *userData, 1949 const XML_Char *elname, 1950 const XML_Char *attname, 1951 const XML_Char *att_type, 1952 const XML_Char *dflt, 1953 int isrequired); 1954</pre> 1955<p>Set a handler for attlist declarations in the DTD. This handler is 1956called for <em>each</em> attribute. So a single attlist declaration 1957with multiple attributes declared will generate multiple calls to this 1958handler. The <code>elname</code> parameter returns the name of the 1959element for which the attribute is being declared. The attribute name 1960is in the <code>attname</code> parameter. The attribute type is in the 1961<code>att_type</code> parameter. It is the string representing the 1962type in the declaration with whitespace removed.</p> 1963 1964<p>The <code>dflt</code> parameter holds the default value. It will be 1965<code>NULL</code> in the case of "#IMPLIED" or "#REQUIRED" attributes. You can 1966distinguish these two cases by checking the <code>isrequired</code> 1967parameter, which will be true in the case of "#REQUIRED" attributes. 1968Attributes which are "#FIXED" will have also have a true 1969<code>isrequired</code>, but they will have the non-<code>NULL</code> fixed value 1970in the <code>dflt</code> parameter.</p> 1971</div> 1972 1973<div class="handler"> 1974<h4 id="XML_SetEntityDeclHandler">XML_SetEntityDeclHandler</h4> 1975<pre class="setter"> 1976void XMLCALL 1977XML_SetEntityDeclHandler(XML_Parser p, 1978 XML_EntityDeclHandler handler); 1979</pre> 1980<pre class="signature"> 1981typedef void 1982(XMLCALL *XML_EntityDeclHandler)(void *userData, 1983 const XML_Char *entityName, 1984 int is_parameter_entity, 1985 const XML_Char *value, 1986 int value_length, 1987 const XML_Char *base, 1988 const XML_Char *systemId, 1989 const XML_Char *publicId, 1990 const XML_Char *notationName); 1991</pre> 1992<p>Sets a handler that will be called for all entity declarations. 1993The <code>is_parameter_entity</code> argument will be non-zero in the 1994case of parameter entities and zero otherwise.</p> 1995 1996<p>For internal entities (<code><!ENTITY foo "bar"></code>), 1997<code>value</code> will be non-<code>NULL</code> and <code>systemId</code>, 1998<code>publicId</code>, and <code>notationName</code> will all be <code>NULL</code>. 1999The value string is <em>not</em> null-terminated; the length is 2000provided in the <code>value_length</code> parameter. Do not use 2001<code>value_length</code> to test for internal entities, since it is 2002legal to have zero-length values. Instead check for whether or not 2003<code>value</code> is <code>NULL</code>.</p> <p>The <code>notationName</code> 2004argument will have a non-<code>NULL</code> value only for unparsed entity 2005declarations.</p> 2006</div> 2007 2008<div class="handler"> 2009<h4 id="XML_SetUnparsedEntityDeclHandler">XML_SetUnparsedEntityDeclHandler</h4> 2010<pre class="setter"> 2011void XMLCALL 2012XML_SetUnparsedEntityDeclHandler(XML_Parser p, 2013 XML_UnparsedEntityDeclHandler h) 2014</pre> 2015<pre class="signature"> 2016typedef void 2017(XMLCALL *XML_UnparsedEntityDeclHandler)(void *userData, 2018 const XML_Char *entityName, 2019 const XML_Char *base, 2020 const XML_Char *systemId, 2021 const XML_Char *publicId, 2022 const XML_Char *notationName); 2023</pre> 2024<p>Set a handler that receives declarations of unparsed entities. These 2025are entity declarations that have a notation (NDATA) field:</p> 2026 2027<div id="eg"><pre> 2028<!ENTITY logo SYSTEM "images/logo.gif" NDATA gif> 2029</pre></div> 2030<p>This handler is obsolete and is provided for backwards 2031compatibility. Use instead <a href= "#XML_SetEntityDeclHandler" 2032>XML_SetEntityDeclHandler</a>.</p> 2033</div> 2034 2035<div class="handler"> 2036<h4 id="XML_SetNotationDeclHandler">XML_SetNotationDeclHandler</h4> 2037<pre class="setter"> 2038void XMLCALL 2039XML_SetNotationDeclHandler(XML_Parser p, 2040 XML_NotationDeclHandler h) 2041</pre> 2042<pre class="signature"> 2043typedef void 2044(XMLCALL *XML_NotationDeclHandler)(void *userData, 2045 const XML_Char *notationName, 2046 const XML_Char *base, 2047 const XML_Char *systemId, 2048 const XML_Char *publicId); 2049</pre> 2050<p>Set a handler that receives notation declarations.</p> 2051</div> 2052 2053<div class="handler"> 2054<h4 id="XML_SetNotStandaloneHandler">XML_SetNotStandaloneHandler</h4> 2055<pre class="setter"> 2056void XMLCALL 2057XML_SetNotStandaloneHandler(XML_Parser p, 2058 XML_NotStandaloneHandler h) 2059</pre> 2060<pre class="signature"> 2061typedef int 2062(XMLCALL *XML_NotStandaloneHandler)(void *userData); 2063</pre> 2064<p>Set a handler that is called if the document is not "standalone". 2065This happens when there is an external subset or a reference to a 2066parameter entity, but does not have standalone set to "yes" in an XML 2067declaration. If this handler returns <code>XML_STATUS_ERROR</code>, 2068then the parser will throw an <code>XML_ERROR_NOT_STANDALONE</code> 2069error.</p> 2070</div> 2071 2072<h3><a name="position">Parse position and error reporting functions</a></h3> 2073 2074<p>These are the functions you'll want to call when the parse 2075functions return <code>XML_STATUS_ERROR</code> (a parse error has 2076occurred), although the position reporting functions are useful outside 2077of errors. The position reported is the byte position (in the original 2078document or entity encoding) of the first of the sequence of 2079characters that generated the current event (or the error that caused 2080the parse functions to return <code>XML_STATUS_ERROR</code>.) The 2081exceptions are callbacks triggered by declarations in the document 2082prologue, in which case they exact position reported is somewhere in the 2083relevant markup, but not necessarily as meaningful as for other 2084events.</p> 2085 2086<p>The position reporting functions are accurate only outside of the 2087DTD. In other words, they usually return bogus information when 2088called from within a DTD declaration handler.</p> 2089 2090<h4 id="XML_GetErrorCode">XML_GetErrorCode</h4> 2091<pre class="fcndec"> 2092enum XML_Error XMLCALL 2093XML_GetErrorCode(XML_Parser p); 2094</pre> 2095<div class="fcndef"> 2096Return what type of error has occurred. 2097</div> 2098 2099<h4 id="XML_ErrorString">XML_ErrorString</h4> 2100<pre class="fcndec"> 2101const XML_LChar * XMLCALL 2102XML_ErrorString(enum XML_Error code); 2103</pre> 2104<div class="fcndef"> 2105Return a string describing the error corresponding to code. 2106The code should be one of the enums that can be returned from 2107<code><a href= "#XML_GetErrorCode" >XML_GetErrorCode</a></code>. 2108</div> 2109 2110<h4 id="XML_GetCurrentByteIndex">XML_GetCurrentByteIndex</h4> 2111<pre class="fcndec"> 2112XML_Index XMLCALL 2113XML_GetCurrentByteIndex(XML_Parser p); 2114</pre> 2115<div class="fcndef"> 2116Return the byte offset of the position. This always corresponds to 2117the values returned by <code><a href= "#XML_GetCurrentLineNumber" 2118>XML_GetCurrentLineNumber</a></code> and <code><a href= 2119"#XML_GetCurrentColumnNumber" >XML_GetCurrentColumnNumber</a></code>. 2120</div> 2121 2122<h4 id="XML_GetCurrentLineNumber">XML_GetCurrentLineNumber</h4> 2123<pre class="fcndec"> 2124XML_Size XMLCALL 2125XML_GetCurrentLineNumber(XML_Parser p); 2126</pre> 2127<div class="fcndef"> 2128Return the line number of the position. The first line is reported as 2129<code>1</code>. 2130</div> 2131 2132<h4 id="XML_GetCurrentColumnNumber">XML_GetCurrentColumnNumber</h4> 2133<pre class="fcndec"> 2134XML_Size XMLCALL 2135XML_GetCurrentColumnNumber(XML_Parser p); 2136</pre> 2137<div class="fcndef"> 2138Return the offset, from the beginning of the current line, of 2139the position. 2140</div> 2141 2142<h4 id="XML_GetCurrentByteCount">XML_GetCurrentByteCount</h4> 2143<pre class="fcndec"> 2144int XMLCALL 2145XML_GetCurrentByteCount(XML_Parser p); 2146</pre> 2147<div class="fcndef"> 2148Return the number of bytes in the current event. Returns 2149<code>0</code> if the event is inside a reference to an internal 2150entity and for the end-tag event for empty element tags (the later can 2151be used to distinguish empty-element tags from empty elements using 2152separate start and end tags). 2153</div> 2154 2155<h4 id="XML_GetInputContext">XML_GetInputContext</h4> 2156<pre class="fcndec"> 2157const char * XMLCALL 2158XML_GetInputContext(XML_Parser p, 2159 int *offset, 2160 int *size); 2161</pre> 2162<div class="fcndef"> 2163 2164<p>Returns the parser's input buffer, sets the integer pointed at by 2165<code>offset</code> to the offset within this buffer of the current 2166parse position, and set the integer pointed at by <code>size</code> to 2167the size of the returned buffer.</p> 2168 2169<p>This should only be called from within a handler during an active 2170parse and the returned buffer should only be referred to from within 2171the handler that made the call. This input buffer contains the 2172untranslated bytes of the input.</p> 2173 2174<p>Only a limited amount of context is kept, so if the event 2175triggering a call spans over a very large amount of input, the actual 2176parse position may be before the beginning of the buffer.</p> 2177 2178<p>If <code>XML_CONTEXT_BYTES</code> is zero, this will always 2179return <code>NULL</code>.</p> 2180</div> 2181 2182<h3><a name="attack-protection">Attack Protection</a><a name="billion-laughs"></a></h3> 2183 2184<h4 id="XML_SetBillionLaughsAttackProtectionMaximumAmplification">XML_SetBillionLaughsAttackProtectionMaximumAmplification</h4> 2185<pre class="fcndec"> 2186/* Added in Expat 2.4.0. */ 2187XML_Bool XMLCALL 2188XML_SetBillionLaughsAttackProtectionMaximumAmplification(XML_Parser p, 2189 float maximumAmplificationFactor); 2190</pre> 2191<div class="fcndef"> 2192 <p> 2193 Sets the maximum tolerated amplification factor 2194 for protection against 2195 <a href="https://en.wikipedia.org/wiki/Billion_laughs_attack">billion laughs attacks</a> 2196 (default: <code>100.0</code>) 2197 of parser <code>p</code> to <code>maximumAmplificationFactor</code>, and 2198 returns <code>XML_TRUE</code> upon success and <code>XML_FALSE</code> upon error. 2199 </p> 2200 2201 The amplification factor is calculated as .. 2202 <pre> 2203 amplification := (direct + indirect) / direct 2204 </pre> 2205 .. while parsing, whereas 2206 <code>direct</code> is the number of bytes read from the primary document in parsing and 2207 <code>indirect</code> is the number of bytes added by expanding entities and reading of external DTD files, combined. 2208 2209 <p>For a call to <code>XML_SetBillionLaughsAttackProtectionMaximumAmplification</code> to succeed:</p> 2210 <ul> 2211 <li>parser <code>p</code> must be a non-<code>NULL</code> root parser (without any parent parsers) and</li> 2212 <li><code>maximumAmplificationFactor</code> must be non-<code>NaN</code> and greater than or equal to <code>1.0</code>.</li> 2213 </ul> 2214 2215 <p> 2216 <strong>Note:</strong> 2217 If you ever need to increase this value for non-attack payload, 2218 please <a href="https://github.com/libexpat/libexpat/issues">file a bug report</a>. 2219 </p> 2220 2221 <p> 2222 <strong>Note:</strong> 2223 Peak amplifications 2224 of factor 15,000 for the entire payload and 2225 of factor 30,000 in the middle of parsing 2226 have been observed with small benign files in practice. 2227 2228 So if you do reduce the maximum allowed amplification, 2229 please make sure that the activation threshold is still big enough 2230 to not end up with undesired false positives (i.e. benign files being rejected). 2231 </p> 2232</div> 2233 2234<h4 id="XML_SetBillionLaughsAttackProtectionActivationThreshold">XML_SetBillionLaughsAttackProtectionActivationThreshold</h4> 2235<pre class="fcndec"> 2236/* Added in Expat 2.4.0. */ 2237XML_Bool XMLCALL 2238XML_SetBillionLaughsAttackProtectionActivationThreshold(XML_Parser p, 2239 unsigned long long activationThresholdBytes); 2240</pre> 2241<div class="fcndef"> 2242 <p> 2243 Sets number of output bytes (including amplification from entity expansion and reading DTD files) 2244 needed to activate protection against 2245 <a href="https://en.wikipedia.org/wiki/Billion_laughs_attack">billion laughs attacks</a> 2246 (default: <code>8 MiB</code>) 2247 of parser <code>p</code> to <code>activationThresholdBytes</code>, and 2248 returns <code>XML_TRUE</code> upon success and <code>XML_FALSE</code> upon error. 2249 </p> 2250 2251 <p>For a call to <code>XML_SetBillionLaughsAttackProtectionActivationThreshold</code> to succeed:</p> 2252 <ul> 2253 <li>parser <code>p</code> must be a non-<code>NULL</code> root parser (without any parent parsers).</li> 2254 </ul> 2255 2256 <p> 2257 <strong>Note:</strong> 2258 If you ever need to increase this value for non-attack payload, 2259 please <a href="https://github.com/libexpat/libexpat/issues">file a bug report</a>. 2260 </p> 2261 2262 <p> 2263 <strong>Note:</strong> 2264 Activation thresholds below 4 MiB are known to break support for 2265 <a href="https://en.wikipedia.org/wiki/Darwin_Information_Typing_Architecture">DITA</a> 1.3 payload 2266 and are hence not recommended. 2267 </p> 2268</div> 2269 2270<h4 id="XML_SetReparseDeferralEnabled">XML_SetReparseDeferralEnabled</h4> 2271<pre class="fcndec"> 2272/* Added in Expat 2.6.0. */ 2273XML_Bool XMLCALL 2274XML_SetReparseDeferralEnabled(XML_Parser parser, XML_Bool enabled); 2275</pre> 2276<div class="fcndef"> 2277 <p> 2278 Large tokens may require many parse calls before enough data is available for Expat to parse it in full. 2279 If Expat retried parsing the token on every parse call, parsing could take quadratic time. 2280 To avoid this, Expat only retries once a significant amount of new data is available. 2281 This function allows disabling this behavior. 2282 </p> 2283 <p> 2284 The <code>enabled</code> argument should be <code>XML_TRUE</code> or <code>XML_FALSE</code>. 2285 </p> 2286 <p> 2287 Returns <code>XML_TRUE</code> on success, and <code>XML_FALSE</code> on error. 2288 </p> 2289</div> 2290 2291<h3><a name="miscellaneous">Miscellaneous functions</a></h3> 2292 2293<p>The functions in this section either obtain state information from 2294the parser or can be used to dynamically set parser options.</p> 2295 2296<h4 id="XML_SetUserData">XML_SetUserData</h4> 2297<pre class="fcndec"> 2298void XMLCALL 2299XML_SetUserData(XML_Parser p, 2300 void *userData); 2301</pre> 2302<div class="fcndef"> 2303This sets the user data pointer that gets passed to handlers. It 2304overwrites any previous value for this pointer. Note that the 2305application is responsible for freeing the memory associated with 2306<code>userData</code> when it is finished with the parser. So if you 2307call this when there's already a pointer there, and you haven't freed 2308the memory associated with it, then you've probably just leaked 2309memory. 2310</div> 2311 2312<h4 id="XML_GetUserData">XML_GetUserData</h4> 2313<pre class="fcndec"> 2314void * XMLCALL 2315XML_GetUserData(XML_Parser p); 2316</pre> 2317<div class="fcndef"> 2318This returns the user data pointer that gets passed to handlers. 2319It is actually implemented as a macro. 2320</div> 2321 2322<h4 id="XML_UseParserAsHandlerArg">XML_UseParserAsHandlerArg</h4> 2323<pre class="fcndec"> 2324void XMLCALL 2325XML_UseParserAsHandlerArg(XML_Parser p); 2326</pre> 2327<div class="fcndef"> 2328After this is called, handlers receive the parser in their 2329<code>userData</code> arguments. The user data can still be obtained 2330using the <code><a href= "#XML_GetUserData" 2331>XML_GetUserData</a></code> function. 2332</div> 2333 2334<h4 id="XML_SetBase">XML_SetBase</h4> 2335<pre class="fcndec"> 2336enum XML_Status XMLCALL 2337XML_SetBase(XML_Parser p, 2338 const XML_Char *base); 2339</pre> 2340<div class="fcndef"> 2341Set the base to be used for resolving relative URIs in system 2342identifiers. The return value is <code>XML_STATUS_ERROR</code> if 2343there's no memory to store base, otherwise it's 2344<code>XML_STATUS_OK</code>. 2345</div> 2346 2347<h4 id="XML_GetBase">XML_GetBase</h4> 2348<pre class="fcndec"> 2349const XML_Char * XMLCALL 2350XML_GetBase(XML_Parser p); 2351</pre> 2352<div class="fcndef"> 2353Return the base for resolving relative URIs. 2354</div> 2355 2356<h4 id="XML_GetSpecifiedAttributeCount">XML_GetSpecifiedAttributeCount</h4> 2357<pre class="fcndec"> 2358int XMLCALL 2359XML_GetSpecifiedAttributeCount(XML_Parser p); 2360</pre> 2361<div class="fcndef"> 2362When attributes are reported to the start handler in the atts vector, 2363attributes that were explicitly set in the element occur before any 2364attributes that receive their value from default information in an 2365ATTLIST declaration. This function returns the number of attributes 2366that were explicitly set times two, thus giving the offset in the 2367<code>atts</code> array passed to the start tag handler of the first 2368attribute set due to defaults. It supplies information for the last 2369call to a start handler. If called inside a start handler, then that 2370means the current call. 2371</div> 2372 2373<h4 id="XML_GetIdAttributeIndex">XML_GetIdAttributeIndex</h4> 2374<pre class="fcndec"> 2375int XMLCALL 2376XML_GetIdAttributeIndex(XML_Parser p); 2377</pre> 2378<div class="fcndef"> 2379Returns the index of the ID attribute passed in the atts array in the 2380last call to <code><a href= "#XML_StartElementHandler" 2381>XML_StartElementHandler</a></code>, or -1 if there is no ID 2382attribute. If called inside a start handler, then that means the 2383current call. 2384</div> 2385 2386<h4 id="XML_GetAttributeInfo">XML_GetAttributeInfo</h4> 2387<pre class="fcndec"> 2388const XML_AttrInfo * XMLCALL 2389XML_GetAttributeInfo(XML_Parser parser); 2390</pre> 2391<pre class="signature"> 2392typedef struct { 2393 XML_Index nameStart; /* Offset to beginning of the attribute name. */ 2394 XML_Index nameEnd; /* Offset after the attribute name's last byte. */ 2395 XML_Index valueStart; /* Offset to beginning of the attribute value. */ 2396 XML_Index valueEnd; /* Offset after the attribute value's last byte. */ 2397} XML_AttrInfo; 2398</pre> 2399<div class="fcndef"> 2400Returns an array of <code>XML_AttrInfo</code> structures for the 2401attribute/value pairs passed in the last call to the 2402<code>XML_StartElementHandler</code> that were specified 2403in the start-tag rather than defaulted. Each attribute/value pair counts 2404as 1; thus the number of entries in the array is 2405<code>XML_GetSpecifiedAttributeCount(parser) / 2</code>. 2406</div> 2407 2408<h4 id="XML_SetEncoding">XML_SetEncoding</h4> 2409<pre class="fcndec"> 2410enum XML_Status XMLCALL 2411XML_SetEncoding(XML_Parser p, 2412 const XML_Char *encoding); 2413</pre> 2414<div class="fcndef"> 2415Set the encoding to be used by the parser. It is equivalent to 2416passing a non-<code>NULL</code> encoding argument to the parser creation functions. 2417It must not be called after <code><a href= "#XML_Parse" 2418>XML_Parse</a></code> or <code><a href= "#XML_ParseBuffer" 2419>XML_ParseBuffer</a></code> have been called on the given parser. 2420Returns <code>XML_STATUS_OK</code> on success or 2421<code>XML_STATUS_ERROR</code> on error. 2422</div> 2423 2424<h4 id="XML_SetParamEntityParsing">XML_SetParamEntityParsing</h4> 2425<pre class="fcndec"> 2426int XMLCALL 2427XML_SetParamEntityParsing(XML_Parser p, 2428 enum XML_ParamEntityParsing code); 2429</pre> 2430<div class="fcndef"> 2431This enables parsing of parameter entities, including the external 2432parameter entity that is the external DTD subset, according to 2433<code>code</code>. 2434The choices for <code>code</code> are: 2435<ul> 2436<li><code>XML_PARAM_ENTITY_PARSING_NEVER</code></li> 2437<li><code>XML_PARAM_ENTITY_PARSING_UNLESS_STANDALONE</code></li> 2438<li><code>XML_PARAM_ENTITY_PARSING_ALWAYS</code></li> 2439</ul> 2440<b>Note:</b> If <code>XML_SetParamEntityParsing</code> is called after 2441<code>XML_Parse</code> or <code>XML_ParseBuffer</code>, then it has 2442no effect and will always return 0. 2443</div> 2444 2445<h4 id="XML_SetHashSalt">XML_SetHashSalt</h4> 2446<pre class="fcndec"> 2447int XMLCALL 2448XML_SetHashSalt(XML_Parser p, 2449 unsigned long hash_salt); 2450</pre> 2451<div class="fcndef"> 2452Sets the hash salt to use for internal hash calculations. 2453Helps in preventing DoS attacks based on predicting hash 2454function behavior. In order to have an effect this must be called 2455before parsing has started. Returns 1 if successful, 0 when called 2456after <code>XML_Parse</code> or <code>XML_ParseBuffer</code>. 2457<p><b>Note:</b> This call is optional, as the parser will auto-generate 2458a new random salt value if no value has been set at the start of parsing.</p> 2459<p><b>Note:</b> One should not call <code>XML_SetHashSalt</code> with a 2460hash salt value of 0, as this value is used as sentinel value to indicate 2461that <code>XML_SetHashSalt</code> has <b>not</b> been called. Consequently 2462such a call will have no effect, even if it returns 1.</p> 2463</div> 2464 2465<h4 id="XML_UseForeignDTD">XML_UseForeignDTD</h4> 2466<pre class="fcndec"> 2467enum XML_Error XMLCALL 2468XML_UseForeignDTD(XML_Parser parser, XML_Bool useDTD); 2469</pre> 2470<div class="fcndef"> 2471<p>This function allows an application to provide an external subset 2472for the document type declaration for documents which do not specify 2473an external subset of their own. For documents which specify an 2474external subset in their DOCTYPE declaration, the application-provided 2475subset will be ignored. If the document does not contain a DOCTYPE 2476declaration at all and <code>useDTD</code> is true, the 2477application-provided subset will be parsed, but the 2478<code>startDoctypeDeclHandler</code> and 2479<code>endDoctypeDeclHandler</code> functions, if set, will not be 2480called. The setting of parameter entity parsing, controlled using 2481<code><a href= "#XML_SetParamEntityParsing" 2482>XML_SetParamEntityParsing</a></code>, will be honored.</p> 2483 2484<p>The application-provided external subset is read by calling the 2485external entity reference handler set via <code><a href= 2486"#XML_SetExternalEntityRefHandler" 2487>XML_SetExternalEntityRefHandler</a></code> with both 2488<code>publicId</code> and <code>systemId</code> set to <code>NULL</code>.</p> 2489 2490<p>If this function is called after parsing has begun, it returns 2491<code>XML_ERROR_CANT_CHANGE_FEATURE_ONCE_PARSING</code> and ignores 2492<code>useDTD</code>. If called when Expat has been compiled without 2493DTD support, it returns 2494<code>XML_ERROR_FEATURE_REQUIRES_XML_DTD</code>. Otherwise, it 2495returns <code>XML_ERROR_NONE</code>.</p> 2496 2497<p><b>Note:</b> For the purpose of checking WFC: Entity Declared, passing 2498<code>useDTD == XML_TRUE</code> will make the parser behave as if 2499the document had a DTD with an external subset. This holds true even if 2500the external entity reference handler returns without action.</p> 2501</div> 2502 2503<h4 id="XML_SetReturnNSTriplet">XML_SetReturnNSTriplet</h4> 2504<pre class="fcndec"> 2505void XMLCALL 2506XML_SetReturnNSTriplet(XML_Parser parser, 2507 int do_nst); 2508</pre> 2509<div class="fcndef"> 2510<p> 2511This function only has an effect when using a parser created with 2512<code><a href= "#XML_ParserCreateNS" >XML_ParserCreateNS</a></code>, 2513i.e. when namespace processing is in effect. The <code>do_nst</code> 2514sets whether or not prefixes are returned with names qualified with a 2515namespace prefix. If this function is called with <code>do_nst</code> 2516non-zero, then afterwards namespace qualified names (that is qualified 2517with a prefix as opposed to belonging to a default namespace) are 2518returned as a triplet with the three parts separated by the namespace 2519separator specified when the parser was created. The order of 2520returned parts is URI, local name, and prefix.</p> <p>If 2521<code>do_nst</code> is zero, then namespaces are reported in the 2522default manner, URI then local_name separated by the namespace 2523separator.</p> 2524</div> 2525 2526<h4 id="XML_DefaultCurrent">XML_DefaultCurrent</h4> 2527<pre class="fcndec"> 2528void XMLCALL 2529XML_DefaultCurrent(XML_Parser parser); 2530</pre> 2531<div class="fcndef"> 2532This can be called within a handler for a start element, end element, 2533processing instruction or character data. It causes the corresponding 2534markup to be passed to the default handler set by <code><a 2535href="#XML_SetDefaultHandler" >XML_SetDefaultHandler</a></code> or 2536<code><a href="#XML_SetDefaultHandlerExpand" 2537>XML_SetDefaultHandlerExpand</a></code>. It does nothing if there is 2538not a default handler. 2539</div> 2540 2541<h4 id="XML_ExpatVersion">XML_ExpatVersion</h4> 2542<pre class="fcndec"> 2543XML_LChar * XMLCALL 2544XML_ExpatVersion(); 2545</pre> 2546<div class="fcndef"> 2547Return the library version as a string (e.g. <code>"expat_1.95.1"</code>). 2548</div> 2549 2550<h4 id="XML_ExpatVersionInfo">XML_ExpatVersionInfo</h4> 2551<pre class="fcndec"> 2552struct XML_Expat_Version XMLCALL 2553XML_ExpatVersionInfo(); 2554</pre> 2555<pre class="signature"> 2556typedef struct { 2557 int major; 2558 int minor; 2559 int micro; 2560} XML_Expat_Version; 2561</pre> 2562<div class="fcndef"> 2563Return the library version information as a structure. 2564Some macros are also defined that support compile-time tests of the 2565library version: 2566<ul> 2567<li><code>XML_MAJOR_VERSION</code></li> 2568<li><code>XML_MINOR_VERSION</code></li> 2569<li><code>XML_MICRO_VERSION</code></li> 2570</ul> 2571Testing these constants is currently the best way to determine if 2572particular parts of the Expat API are available. 2573</div> 2574 2575<h4 id="XML_GetFeatureList">XML_GetFeatureList</h4> 2576<pre class="fcndec"> 2577const XML_Feature * XMLCALL 2578XML_GetFeatureList(); 2579</pre> 2580<pre class="signature"> 2581enum XML_FeatureEnum { 2582 XML_FEATURE_END = 0, 2583 XML_FEATURE_UNICODE, 2584 XML_FEATURE_UNICODE_WCHAR_T, 2585 XML_FEATURE_DTD, 2586 XML_FEATURE_CONTEXT_BYTES, 2587 XML_FEATURE_MIN_SIZE, 2588 XML_FEATURE_SIZEOF_XML_CHAR, 2589 XML_FEATURE_SIZEOF_XML_LCHAR, 2590 XML_FEATURE_NS, 2591 XML_FEATURE_LARGE_SIZE 2592}; 2593 2594typedef struct { 2595 enum XML_FeatureEnum feature; 2596 XML_LChar *name; 2597 long int value; 2598} XML_Feature; 2599</pre> 2600<div class="fcndef"> 2601<p>Returns a list of "feature" records, providing details on how 2602Expat was configured at compile time. Most applications should not 2603need to worry about this, but this information is otherwise not 2604available from Expat. This function allows code that does need to 2605check these features to do so at runtime.</p> 2606 2607<p>The return value is an array of <code>XML_Feature</code>, 2608terminated by a record with a <code>feature</code> of 2609<code>XML_FEATURE_END</code> and <code>name</code> of <code>NULL</code>, 2610identifying the feature-test macros Expat was compiled with. Since an 2611application that requires this kind of information needs to determine 2612the type of character the <code>name</code> points to, records for the 2613<code>XML_FEATURE_SIZEOF_XML_CHAR</code> and 2614<code>XML_FEATURE_SIZEOF_XML_LCHAR</code> will be located at the 2615beginning of the list, followed by <code>XML_FEATURE_UNICODE</code> 2616and <code>XML_FEATURE_UNICODE_WCHAR_T</code>, if they are present at 2617all.</p> 2618 2619<p>Some features have an associated value. If there isn't an 2620associated value, the <code>value</code> field is set to 0. At this 2621time, the following features have been defined to have values:</p> 2622 2623<dl> 2624 <dt><code>XML_FEATURE_SIZEOF_XML_CHAR</code></dt> 2625 <dd>The number of bytes occupied by one <code>XML_Char</code> 2626 character.</dd> 2627 <dt><code>XML_FEATURE_SIZEOF_XML_LCHAR</code></dt> 2628 <dd>The number of bytes occupied by one <code>XML_LChar</code> 2629 character.</dd> 2630 <dt><code>XML_FEATURE_CONTEXT_BYTES</code></dt> 2631 <dd>The maximum number of characters of context which can be 2632 reported by <code><a href= "#XML_GetInputContext" 2633 >XML_GetInputContext</a></code>.</dd> 2634</dl> 2635</div> 2636 2637<h4 id="XML_FreeContentModel">XML_FreeContentModel</h4> 2638<pre class="fcndec"> 2639void XMLCALL 2640XML_FreeContentModel(XML_Parser parser, XML_Content *model); 2641</pre> 2642<div class="fcndef"> 2643Function to deallocate the <code>model</code> argument passed to the 2644<code>XML_ElementDeclHandler</code> callback set using <code><a 2645href="#XML_SetElementDeclHandler" >XML_ElementDeclHandler</a></code>. 2646This function should not be used for any other purpose. 2647</div> 2648 2649<p>The following functions allow external code to share the memory 2650allocator an <code>XML_Parser</code> has been configured to use. This 2651is especially useful for third-party libraries that interact with a 2652parser object created by application code, or heavily layered 2653applications. This can be essential when using dynamically loaded 2654libraries which use different C standard libraries (this can happen on 2655Windows, at least).</p> 2656 2657<h4 id="XML_MemMalloc">XML_MemMalloc</h4> 2658<pre class="fcndec"> 2659void * XMLCALL 2660XML_MemMalloc(XML_Parser parser, size_t size); 2661</pre> 2662<div class="fcndef"> 2663Allocate <code>size</code> bytes of memory using the allocator the 2664<code>parser</code> object has been configured to use. Returns a 2665pointer to the memory or <code>NULL</code> on failure. Memory allocated in this 2666way must be freed using <code><a href="#XML_MemFree" 2667>XML_MemFree</a></code>. 2668</div> 2669 2670<h4 id="XML_MemRealloc">XML_MemRealloc</h4> 2671<pre class="fcndec"> 2672void * XMLCALL 2673XML_MemRealloc(XML_Parser parser, void *ptr, size_t size); 2674</pre> 2675<div class="fcndef"> 2676Allocate <code>size</code> bytes of memory using the allocator the 2677<code>parser</code> object has been configured to use. 2678<code>ptr</code> must point to a block of memory allocated by <code><a 2679href="#XML_MemMalloc" >XML_MemMalloc</a></code> or 2680<code>XML_MemRealloc</code>, or be <code>NULL</code>. This function tries to 2681expand the block pointed to by <code>ptr</code> if possible. Returns 2682a pointer to the memory or <code>NULL</code> on failure. On success, the original 2683block has either been expanded or freed. On failure, the original 2684block has not been freed; the caller is responsible for freeing the 2685original block. Memory allocated in this way must be freed using 2686<code><a href="#XML_MemFree" 2687>XML_MemFree</a></code>. 2688</div> 2689 2690<h4 id="XML_MemFree">XML_MemFree</h4> 2691<pre class="fcndec"> 2692void XMLCALL 2693XML_MemFree(XML_Parser parser, void *ptr); 2694</pre> 2695<div class="fcndef"> 2696Free a block of memory pointed to by <code>ptr</code>. The block must 2697have been allocated by <code><a href="#XML_MemMalloc" 2698>XML_MemMalloc</a></code> or <code>XML_MemRealloc</code>, or be <code>NULL</code>. 2699</div> 2700 2701<hr /> 2702 2703 <div class="footer"> 2704 Found a bug in the documentation? 2705 <a href="https://github.com/libexpat/libexpat/issues">Please file a bug report.</a> 2706 </div> 2707 2708</div> 2709</body> 2710</html> 2711
