Expat XML Parser

Expat is a library, written in C, for parsing XML documents. It's the underlying XML parser for the open source Mozilla project, Perl's XML::Parser, Python's xml.parsers.expat, and other open-source XML parsers.

This library is the creation of James Clark, who's also given us groff (an nroff look-alike), Jade (an implemention of ISO's DSSSL stylesheet language for SGML), XP (a Java XML parser package), XT (a Java XSL engine). James was also the technical lead on the XML Working Group at W3C that produced the XML specification.

This is free software, licensed under the MIT/X Consortium license. You may download it from the Expat home page.

The bulk of this document was originally commissioned as an article by XML.com. They graciously allowed Clark Cooper to retain copyright and to distribute it with Expat.

Table of Contents

• Overview
• Building and Installing
• Using Expat
• Reference
  • Parser Creation Functions
    • XML_ParserCreate
    • XML_ParserCreateNS
    • XML_ParserCreate_MM
    • XML_ExternalEntityParserCreate
    • XML_ParserFree
    • XML_ParserReset
  • Parsing Functions
    • XML_Parse
    • XML_ParseBuffer
    • XML_GetBuffer
  • Handler Setting Functions
    • XML_SetStartElementHandler
    • XML_SetEndElementHandler
    • XML_SetElementHandler
    • XML_SetCharacterDataHandler
    • XML_SetProcessingInstructionHandler
    • XML_SetCommentHandler
    • XML_SetStartCdataSectionHandler
    • XML_SetEndCdataSectionHandler
    • XML_SetCdataSectionHandler
    • XML_SetDefaultHandler
    • XML_SetDefaultHandlerExpand
    • XML_SetExternalEntityRefHandler
    • XML_SetSkippedEntityHandler
    • XML_SetUnknownEncodingHandler
    • XML_SetStartNamespaceDeclHandler
    • XML_SetEndNamespaceDeclHandler
    • XML_SetNamespaceDeclHandler
    • XML_SetXmlDeclHandler
    • XML_SetStartDoctypeDeclHandler
    • XML_SetEndDoctypeDeclHandler
    • XML_SetDoctypeDeclHandler
    • XML_SetElementDeclHandler
    • XML_SetAttlistDeclHandler
    • XML_SetEntityDeclHandler
    • XML_SetUnparsedEntityDeclHandler
    • XML_SetNotationDeclHandler
    • XML_SetNotStandaloneHandler
  • Parse Position and Error Reporting Functions
    • XML_GetErrorCode
    • XML_ErrorString
    • XML_GetCurrentByteIndex
    • XML_GetCurrentLineNumber
    • XML_GetCurrentColumnNumber
    • XML_GetCurrentByteCount
    • XML_GetInputContext
  • Miscellaneous Functions
    • XML_SetUserData
    • XML_GetUserData
    • XML_UseParserAsHandlerArg
    • XML_SetBase
    • XML_GetBase
    • XML_GetSpecifiedAttributeCount
    • XML_GetIdAttributeIndex
    • XML_SetEncoding
    • XML_SetParamEntityParsing
    • XML_UseForeignDTD
    • XML_SetReturnNSTriplet
    • XML_DefaultCurrent
    • XML_ExpatVersion
    • XML_ExpatVersionInfo
    • XML_GetFeatureList

Overview

Expat is a stream-oriented parser. You register callback (or handler) functions with the parser and then start feeding it the document. As the parser recognizes parts of the document, it will call the appropriate handler for that part (if you've registered one.) The document is fed to the parser in pieces, so you can start parsing before you have all the document. This also allows you to parse really huge documents that won't fit into memory.

Expat can be intimidating due to the many kinds of handlers and options you can set. But you only need to learn four functions in order to do 90% of what you'll want to do with it:

XML_ParserCreate

Create a new parser object.

XML_SetElementHandler

Set handlers for start and end tags.

XML_SetCharacterDataHandler

Set handler for text.

XML_Parse

Pass a buffer full of document to the parser

These functions and others are described in the reference part of this document. The reference section also describes in detail the parameters passed to the different types of handlers.

Let's look at a very simple example program that only uses 3 of the above functions (it doesn't need to set a character handler.) The program outline.c prints an element outline, indenting child elements to distinguish them from the parent element that contains them. The start handler does all the work. It prints two indenting spaces for every level of ancestor elements, then it prints the element and attribute information. Finally it increments the global Depth variable.

int Depth;

void
start(void *data, const char *el, const char **attr) {
  int i;

  for (i = 0; i < Depth; i++)
    printf("  ");

  printf("%s", el);

  for (i = 0; attr[i]; i += 2) {
    printf(" %s='%s'", attr[i], attr[i + 1]);
  }

  printf("\n");
  Depth++;
}  /* End of start handler */

The end tag simply does the bookkeeping work of decrementing Depth.

void
end(void *data, const char *el) {
  Depth--;
}  /* End of end handler */

After creating the parser, the main program just has the job of shoveling the document to the parser so that it can do its work.

Building and Installing Expat

The Expat distribution comes as a compressed (with GNU gzip) tar file. You may download the latest version from Source Forge. After unpacking this, cd into the directory. Then follow either the Win32 directions or Unix directions below.

Building under Win32

If you're using the GNU compiler under cygwin, follow the Unix directions in the next section. Otherwise if you have Microsoft's Developer Studio installed, then from Windows Explorer double-click on "expat.dsp" in the lib directory and build and install in the usual manner.

Alternatively, you may download the Win32 binary package that contains the "expat.h" include file and a pre-built DLL.

Building under Unix (or GNU)

First you'll need to run the configure shell script in order to configure the Makefiles and headers for your system.

If you're happy with all the defaults that configure picks for you, and you have permission on your system to install into /usr/local, you can install Expat with this sequence of commands:

   ./configure
   make
   make install

There are some options that you can provide to this script, but the only one we'll mention here is the --prefix option. You can find out all the options available by running configure with just the --help option.

By default, the configure script sets things up so that the library gets installed in /usr/local/lib and the associated header file in /usr/local/include. But if you were to give the option, --prefix=/home/me/mystuff, then the library and header would get installed in /home/me/mystuff/lib and /home/me/mystuff/include respectively.

Using Expat

Compiling and Linking Against Expat

Unless you installed Expat in a location not expected by your compiler and linker, all you have to do to use Expat in your programs is to include the Expat header (#include <expat.h>) in your files that make calls to it and to tell the linker that it needs to link against the Expat library. On Unix systems, this would usually be done with the -lexpat argument. Otherwise, you'll need to tell the compiler where to look for the Expat header and the linker where to find the Expat library. You may also need to take steps to tell the operating system where to find this libary at run time.

On a Unix-based system, here's what a Makefile might look like when Expat is installed in a standard location:

CC=cc
LDFLAGS=
LIBS= -lexpat
xmlapp: xmlapp.o
        $(CC) $(LDFLAGS) -o xmlapp xmlapp.o $(LIBS)

If you installed Expat in, say, /home/me/mystuff, then the Makefile would look like this:

CC=cc
CFLAGS= -I/home/me/mystuff/include
LDFLAGS=
LIBS= -L/home/me/mystuff/lib -lexpat
xmlapp: xmlapp.o
        $(CC) $(LDFLAGS) -o xmlapp xmlapp.o $(LIBS)

You'd also have to set the environment variable LD_LIBRARY_PATH to /home/me/mystuff/lib (or to ${LD_LIBRARY_PATH}:/home/me/mystuff/lib if LD_LIBRARY_PATH already has some directories in it) in order to run your application.

Expat Basics

As we saw in the example in the overview, the first step in parsing an XML document with Expat is to create a parser object. There are three functions in the Expat API for creating a parser object. However, only two of these (XML_ParserCreate and XML_ParserCreateNS) can be used for constructing a parser for a top-level document. The object returned by these functions is an opaque pointer (i.e. "expat.h" declares it as void *) to data with further internal structure. In order to free the memory associated with this object you must call XML_ParserFree. Note that if you have provided any user data that gets stored in the parser, then your application is responsible for freeing it prior to calling XML_ParserFree.

The objects returned by the parser creation functions are good for parsing only one XML document or external parsed entity. If your application needs to parse many XML documents, then it needs to create a parser object for each one. The best way to deal with this is to create a higher level object that contains all the default initialization you want for your parser objects.

Walking through a document hierarchy with a stream oriented parser will require a good stack mechanism in order to keep track of current context. For instance, to answer the simple question, "What element does this text belong to?" requires a stack, since the parser may have descended into other elements that are children of the current one and has encountered this text on the way out.

The things you're likely to want to keep on a stack are the currently opened element and it's attributes. You push this information onto the stack in the start handler and you pop it off in the end handler.

For some tasks, it is sufficient to just keep information on what the depth of the stack is (or would be if you had one.) The outline program shown above presents one example. Another such task would be skipping over a complete element. When you see the start tag for the element you want to skip, you set a skip flag and record the depth at which the element started. When the end tag handler encounters the same depth, the skipped element has ended and the flag may be cleared. If you follow the convention that the root element starts at 1, then you can use the same variable for skip flag and skip depth.

void
init_info(Parseinfo *info) {
  info->skip = 0;
  info->depth = 1;
  /* Other initializations here */
}  /* End of init_info */

void
rawstart(void *data, const char *el, const char **attr) {
  Parseinfo *inf = (Parseinfo *) data;

  if (! inf->skip) {
    if (should_skip(inf, el, attr)) {
      inf->skip = inf->depth;
    }
    else
      start(inf, el, attr);     /* This does rest of start handling */
  }

  inf->depth++;
}  /* End of rawstart */

void
rawend(void *data, const char *el) {
  Parseinfo *inf = (Parseinfo *) data;

  inf->depth--;

  if (! inf->skip)
    end(inf, el);              /* This does rest of end handling */

  if (inf->skip == inf->depth)
    inf->skip = 0;
}  /* End rawend */

Notice in the above example the difference in how depth is manipulated in the start and end handlers. The end tag handler should be the mirror image of the start tag handler. This is necessary to properly model containment. Since, in the start tag handler, we incremented depth after the main body of start tag code, then in the end handler, we need to manipulate it before the main body. If we'd decided to increment it first thing in the start handler, then we'd have had to decrement it last thing in the end handler.

Communicating between handlers

In order to be able to pass information between different handlers without using globals, you'll need to define a data structure to hold the shared variables. You can then tell Expat (with the XML_SetUserData function) to pass a pointer to this structure to the handlers. This is typically the first argument received by most handlers.

XML Version

Expat is an XML 1.0 parser, and as such never complains based on the value of the version pseudo-attribute in the XML declaration, if present.

If an application needs to check the version number (to support alternate processing), it should use the XML_SetXmlDeclHandler function to set a handler that uses the information in the XML declaration to determine what to do. This example shows how to check that only a version number of "1.0" is accepted:

static int wrong_version;
static XML_Parser parser;

static void
xmldecl_handler(void            *userData,
                const XML_Char  *version,
                const XML_Char  *encoding,
                int              standalone)
{
  static const XML_Char Version_1_0[] = {'1', '.', '0', 0};

  int i;

  for (i = 0; i < (sizeof(Version_1_0) / sizeof(Version_1_0[0])); ++i) {
    if (version[i] != Version_1_0[i]) {
      wrong_version = 1;
      /* also clear all other handlers: */
      XML_SetCharacterDataHandler(parser, NULL);
      ...
      return;
    }
  }
  ...
}

Namespace Processing

When the parser is created using the XML_ParserCreateNS, function, Expat performs namespace processing. Under namespace processing, Expat consumes xmlns and xmlns:... attributes, which declare namespaces for the scope of the element in which they occur. This means that your start handler will not see these attributes. Your application can still be informed of these declarations by setting namespace declaration handlers with XML_SetNamespaceDeclHandler.

Element type and attribute names that belong to a given namespace are passed to the appropriate handler in expanded form. By default this expanded form is a concatenation of the namespace URI, the separator character (which is the 2nd argument to XML_ParserCreateNS), and the local name (i.e. the part after the colon). Names with undeclared prefixes are passed through to the handlers unchanged, with the prefix and colon still attached. Unprefixed attribute names are never expanded, and unprefixed element names are only expanded when they are in the scope of a default namespace.

However if XML_SetReturnNSTriplet has been called with a non-zero do_nst parameter, then the expanded form for names with an explicit prefix is a concatenation of: URI, separator, local name, separator, prefix.

You can set handlers for the start of a namespace declaration and for the end of a scope of a declaration with the XML_SetNamespaceDeclHandler function. The StartNamespaceDeclHandler is called prior to the start tag handler and the EndNamespaceDeclHandler is called before the corresponding end tag that ends the namespace's scope. The namespace start handler gets passed the prefix and URI for the namespace. For a default namespace declaration (xmlns='...'), the prefix will be null. The URI will be null for the case where the default namespace is being unset. The namespace end handler just gets the prefix for the closing scope.

These handlers are called for each declaration. So if, for instance, a start tag had three namespace declarations, then the StartNamespaceDeclHandler would be called three times before the start tag handler is called, once for each declaration.

Character Encodings

While XML is based on Unicode, and every XML processor is required to recognized UTF-8 and UTF-16 (1 and 2 byte encodings of Unicode), other encodings may be declared in XML documents or entities. For the main document, an XML declaration may contain an encoding declaration:

<?xml version="1.0" encoding="ISO-8859-2"?>

External parsed entities may begin with a text declaration, which looks like an XML declaration with just an encoding declaration:

<?xml encoding="Big5"?>

With Expat, you may also specify an encoding at the time of creating a parser. This is useful when the encoding information may come from a source outside the document itself (like a higher level protocol.)

There are four built-in encodings in Expat:

• UTF-8
• UTF-16
• ISO-8859-1
• US-ASCII

Anything else discovered in an encoding declaration or in the protocol encoding specified in the parser constructor, triggers a call to the UnknownEncodingHandler. This handler gets passed the encoding name and a pointer to an XML_Encoding data structure. Your handler must fill in this structure and return 1 if it knows how to deal with the encoding. Otherwise the handler should return 0. The handler also gets passed a pointer to an optional application data structure that you may indicate when you set the handler.

Expat places restrictions on character encodings that it can support by filling in the XML_Encoding structure. include file:

1. Every ASCII character that can appear in a well-formed XML document must be represented by a single byte, and that byte must correspond to it's ASCII encoding (except for the characters $@\^'{}~)
2. Characters must be encoded in 4 bytes or less.
3. All characters encoded must have Unicode scalar values less than or equal to 65535 (0xFFFF)This does not apply to the built-in support for UTF-16 and UTF-8
4. No character may be encoded by more that one distinct sequence of bytes

XML_Encoding contains an array of integers that correspond to the 1st byte of an encoding sequence. If the value in the array for a byte is zero or positive, then the byte is a single byte encoding that encodes the Unicode scalar value contained in the array. A -1 in this array indicates a malformed byte. If the value is -2, -3, or -4, then the byte is the beginning of a 2, 3, or 4 byte sequence respectively. Multi-byte sequences are sent to the convert function pointed at in the XML_Encoding structure. This function should return the Unicode scalar value for the sequence or -1 if the sequence is malformed.

One pitfall that novice Expat users are likely to fall into is that although Expat may accept input in various encodings, the strings that it passes to the handlers are always encoded in UTF-8 or UTF-16 (depending on how Expat was compiled). Your application is responsible for any translation of these strings into other encodings.

Handling External Entity References

Expat does not read or parse external entities directly. Note that any external DTD is a special case of an external entity. If you've set no ExternalEntityRefHandler, then external entity references are silently ignored. Otherwise, it calls your handler with the information needed to read and parse the external entity.

Your handler isn't actually responsible for parsing the entity, but it is responsible for creating a subsidiary parser with XML_ExternalEntityParserCreate that will do the job. This returns an instance of XML_Parser that has handlers and other data structures initialized from the parent parser. You may then use XML_Parse or XML_ParseBuffer calls against this parser. Since external entities my refer to other external entities, your handler should be prepared to be called recursively.

Parsing DTDs

In order to parse parameter entities, before starting the parse, you must call XML_SetParamEntityParsing with one of the following arguments:

XML_PARAM_ENTITY_PARSING_NEVER

Don't parse parameter entities or the external subset

XML_PARAM_ENTITY_PARSING_UNLESS_STANDALONE

Parse parameter entites and the external subset unless standalone was set to "yes" in the XML declaration.

XML_PARAM_ENTITY_PARSING_ALWAYS

Always parse parameter entities and the external subset

In order to read an external DTD, you also have to set an external entity reference handler as described above.

Expat Reference

Parser Creation

XML_Parser
XML_ParserCreate(const XML_Char *encoding);

XML_Parser
XML_ParserCreateNS(const XML_Char *encoding,
                   XML_Char sep);

XML_Parser
XML_ParserCreate_MM(const XML_Char *encoding,
                    const XML_Memory_Handling_Suite *ms,
		    const XML_Char *sep);

typedef struct {
  void *(*malloc_fcn)(size_t size);
  void *(*realloc_fcn)(void *ptr, size_t size);
  void (*free_fcn)(void *ptr);
} XML_Memory_Handling_Suite;

XML_Parser
XML_ExternalEntityParserCreate(XML_Parser p,
                               const XML_Char *context,
                               const XML_Char *encoding);

void
XML_ParserFree(XML_Parser p);

XML_Bool
XML_ParserReset(XML_Parser p);

Parsing

To state the obvious: the three parsing functions XML_Parse, XML_ParseBuffer and >XML_GetBuffer must not be called from within a handler unless they operate on a separate parser instance, that is, one that did not call the handler. For example, it is OK to call the parsing functions from within an XML_ExternalEntityRefHandler, if they apply to the parser created by XML_ExternalEntityParserCreate.

XML_Status
XML_Parse(XML_Parser p,
          const char *s,
          int len,
          int isFinal);

enum XML_Status {
  XML_STATUS_ERROR = 0,
  XML_STATUS_OK = 1
};

XML_Status
XML_ParseBuffer(XML_Parser p,
                int len,
                int isFinal);

void *
XML_GetBuffer(XML_Parser p,
              int len);

for (;;) {
  int bytes_read;
  void *buff = XML_GetBuffer(p, BUFF_SIZE);
  if (buff == NULL) {
    /* handle error */
  }

  bytes_read = read(docfd, buff, BUFF_SIZE);
  if (bytes_read < 0) {
    /* handle error */
  }

  if (! XML_ParseBuffer(p, bytes_read, bytes_read == 0)) {
    /* handle parse error */
  }

  if (bytes_read == 0)
    break;
}

Handler Setting

Although handlers are typically set prior to parsing and left alone, an application may choose to set or change the handler for a parsing event while the parse is in progress. For instance, your application may choose to ignore all text not descended from a para element. One way it could do this is to set the character handler when a para start tag is seen, and unset it for the corresponding end tag.

A handler may be unset by providing a NULL pointer to the appropriate handler setter. None of the handler setting functions have a return value.

Your handlers will be receiving strings in arrays of type XML_Char. This type is defined in expat.h as char * and contains bytes encoding UTF-8. Note that you'll receive them in this form independent of the original encoding of the document.

XML_SetStartElementHandler(XML_Parser p,
                           XML_StartElementHandler start);

typedef void
(*XML_StartElementHandler)(void *userData,
                           const XML_Char *name,
                           const XML_Char **atts);

XML_SetEndElementHandler(XML_Parser p,
                         XML_EndElementHandler);

typedef void
(*XML_EndElementHandler)(void *userData,
                         const XML_Char *name);

XML_SetElementHandler(XML_Parser p,
                      XML_StartElementHandler start,
                      XML_EndElementHandler end);

XML_SetCharacterDataHandler(XML_Parser p,
                            XML_CharacterDataHandler charhndl)

typedef void
(*XML_CharacterDataHandler)(void *userData,
                            const XML_Char *s,
                            int len);

XML_SetProcessingInstructionHandler(XML_Parser p,
                                    XML_ProcessingInstructionHandler proc)

typedef void
(*XML_ProcessingInstructionHandler)(void *userData,
                                    const XML_Char *target,
                                    const XML_Char *data);

XML_SetCommentHandler(XML_Parser p,
                      XML_CommentHandler cmnt)

typedef void
(*XML_CommentHandler)(void *userData,
                      const XML_Char *data);

XML_SetStartCdataSectionHandler(XML_Parser p,
                                XML_StartCdataSectionHandler start);

typedef void
(*XML_StartCdataSectionHandler)(void *userData);

XML_SetEndCdataSectionHandler(XML_Parser p,
                              XML_EndCdataSectionHandler end);

typedef void
(*XML_EndCdataSectionHandler)(void *userData);

XML_SetCdataSectionHandler(XML_Parser p,
                           XML_StartCdataSectionHandler start,
                           XML_EndCdataSectionHandler end)

XML_SetDefaultHandler(XML_Parser p,
                      XML_DefaultHandler hndl)

typedef void
(*XML_DefaultHandler)(void *userData,
                      const XML_Char *s,
                      int len);

XML_SetDefaultHandlerExpand(XML_Parser p,
                            XML_DefaultHandler hndl)

typedef void
(*XML_DefaultHandler)(void *userData,
                      const XML_Char *s,
                      int len);

XML_SetExternalEntityRefHandler(XML_Parser p,
                                XML_ExternalEntityRefHandler hndl)

typedef int
(*XML_ExternalEntityRefHandler)(XML_Parser p,
                                const XML_Char *context,
                                const XML_Char *base,
                                const XML_Char *systemId,
                                const XML_Char *publicId);

XML_SetSkippedEntityHandler(XML_Parser p,
                            XML_SkippedEntityHandler handler)

typedef void
(*XML_SkippedEntityHandler)(void *userData,
                            const XML_Char *entityName,
                            int is_parameter_entity);

XML_SetUnknownEncodingHandler(XML_Parser p,
                              XML_UnknownEncodingHandler enchandler,
			      void *encodingHandlerData)

typedef int
(*XML_UnknownEncodingHandler)(void *encodingHandlerData,
                              const XML_Char *name,
                              XML_Encoding *info);

typedef struct {
  int map[256];
  void *data;
  int (*convert)(void *data, const char *s);
  void (*release)(void *data);
} XML_Encoding;

XML_SetStartNamespaceDeclHandler(XML_Parser p,
			         XML_StartNamespaceDeclHandler start);

typedef void
(*XML_StartNamespaceDeclHandler)(void *userData,
                                 const XML_Char *prefix,
                                 const XML_Char *uri);

XML_SetEndNamespaceDeclHandler(XML_Parser p,
			       XML_EndNamespaceDeclHandler end);

typedef void
(*XML_EndNamespaceDeclHandler)(void *userData,
                               const XML_Char *prefix);

XML_SetNamespaceDeclHandler(XML_Parser p,
                            XML_StartNamespaceDeclHandler start,
                            XML_EndNamespaceDeclHandler end)

XML_SetXmlDeclHandler(XML_Parser p,
		      XML_XmlDeclHandler xmldecl);

typedef void
(*XML_XmlDeclHandler) (void            *userData,
                       const XML_Char  *version,
                       const XML_Char  *encoding,
                       int             standalone);

XML_SetStartDoctypeDeclHandler(XML_Parser p,
			       XML_StartDoctypeDeclHandler start);

typedef void
(*XML_StartDoctypeDeclHandler)(void           *userData,
                               const XML_Char *doctypeName,
                               const XML_Char *sysid,
                               const XML_Char *pubid,
                               int            has_internal_subset);

XML_SetEndDoctypeDeclHandler(XML_Parser p,
			     XML_EndDoctypeDeclHandler end);

typedef void
(*XML_EndDoctypeDeclHandler)(void *userData);

XML_SetDoctypeDeclHandler(XML_Parser p,
			  XML_StartDoctypeDeclHandler start,
			  XML_EndDoctypeDeclHandler end);

XML_SetElementDeclHandler(XML_Parser p,
			  XML_ElementDeclHandler eldecl);

typedef void
(*XML_ElementDeclHandler)(void *userData,
                          const XML_Char *name,
                          XML_Content *model);

enum XML_Content_Type {
  XML_CTYPE_EMPTY = 1,
  XML_CTYPE_ANY,
  XML_CTYPE_MIXED,
  XML_CTYPE_NAME,
  XML_CTYPE_CHOICE,
  XML_CTYPE_SEQ
};

enum XML_Content_Quant {
  XML_CQUANT_NONE,
  XML_CQUANT_OPT,
  XML_CQUANT_REP,
  XML_CQUANT_PLUS
};

typedef struct XML_cp XML_Content;

struct XML_cp {
  enum XML_Content_Type		type;
  enum XML_Content_Quant	quant;
  const XML_Char *		name;
  unsigned int			numchildren;
  XML_Content *			children;
};

XML_SetAttlistDeclHandler(XML_Parser p,
                          XML_AttlistDeclHandler attdecl);

typedef void
(*XML_AttlistDeclHandler) (void           *userData,
                           const XML_Char *elname,
                           const XML_Char *attname,
                           const XML_Char *att_type,
                           const XML_Char *dflt,
                           int            isrequired);

XML_SetEntityDeclHandler(XML_Parser p,
			 XML_EntityDeclHandler handler);

typedef void
(*XML_EntityDeclHandler) (void           *userData,
                          const XML_Char *entityName,
                          int            is_parameter_entity,
                          const XML_Char *value,
                          int            value_length,
                          const XML_Char *base,
                          const XML_Char *systemId,
                          const XML_Char *publicId,
                          const XML_Char *notationName);

XML_SetUnparsedEntityDeclHandler(XML_Parser p,
                                 XML_UnparsedEntityDeclHandler h)

typedef void
(*XML_UnparsedEntityDeclHandler)(void *userData,
                                 const XML_Char *entityName,
                                 const XML_Char *base,
                                 const XML_Char *systemId,
                                 const XML_Char *publicId,
                                 const XML_Char *notationName);

<!ENTITY logo SYSTEM "images/logo.gif" NDATA gif>

XML_SetNotationDeclHandler(XML_Parser p,
                           XML_NotationDeclHandler h)

typedef void
(*XML_NotationDeclHandler)(void *userData,
                           const XML_Char *notationName,
                           const XML_Char *base,
                           const XML_Char *systemId,
                           const XML_Char *publicId);

XML_SetNotStandaloneHandler(XML_Parser p,
                            XML_NotStandaloneHandler h)

typedef int 
(*XML_NotStandaloneHandler)(void *userData);

Parse position and error reporting functions

These are the functions you'll want to call when the parse functions return 0 (i.e. a parse error has ocurred), although the position reporting functions are useful outside of errors. The position reported is the byte position (in the original document or entity encoding) of the first of the sequence of characters that generated the current event (or the error that caused the parse functions to return 0.)

The position reporting functions are accurate only outside of the DTD. In other words, they usually return bogus information when called from within a DTD declaration handler.

enum XML_Error
XML_GetErrorCode(XML_Parser p);

const XML_LChar *
XML_ErrorString(int code);

long
XML_GetCurrentByteIndex(XML_Parser p);

int
XML_GetCurrentLineNumber(XML_Parser p);

int
XML_GetCurrentColumnNumber(XML_Parser p);

int
XML_GetCurrentByteCount(XML_Parser p);

const char *
XML_GetInputContext(XML_Parser p,
                    int *offset,
                    int *size);

Miscellaneous functions

The functions in this section either obtain state information from the parser or can be used to dynamicly set parser options.

void
XML_SetUserData(XML_Parser p,
                void *userData);

void *
XML_GetUserData(XML_Parser p);

void
XML_UseParserAsHandlerArg(XML_Parser p);

int
XML_SetBase(XML_Parser p,
            const XML_Char *base);

const XML_Char *
XML_GetBase(XML_Parser p);

int
XML_GetSpecifiedAttributeCount(XML_Parser p);

int
XML_GetIdAttributeIndex(XML_Parser p);

int
XML_SetEncoding(XML_Parser p,
                const XML_Char *encoding);

int
XML_SetParamEntityParsing(XML_Parser p,
                          enum XML_ParamEntityParsing code);

enum XML_Error
XML_UseForeignDTD(XML_Parser parser, XML_Bool useDTD);

void
XML_SetReturnNSTriplet(XML_Parser parser,
                       int        do_nst);

void
XML_DefaultCurrent(XML_Parser parser);

XML_LChar *
XML_ExpatVersion();

struct XML_Expat_Version
XML_ExpatVersionInfo();

typedef struct {
  int major;
  int minor;
  int micro;
} XML_Expat_Version;

const XML_Feature *
XML_GetFeatureList();

enum XML_FeatureEnum {
  XML_FEATURE_END = 0,
  XML_FEATURE_UNICODE,
  XML_FEATURE_UNICODE_WCHAR_T,
  XML_FEATURE_DTD,
  XML_FEATURE_CONTEXT_BYTES,
  XML_FEATURE_MIN_SIZE,
  XML_FEATURE_SIZEOF_XML_CHAR,
  XML_FEATURE_SIZEOF_XML_LCHAR
};

typedef struct {
  enum XML_FeatureEnum  feature;
  XML_LChar            *name;
  long int              value;
} XML_Feature;