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.
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_ParserCreateXML_SetElementHandlerXML_SetCharacterDataHandlerXML_ParseThese 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.
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.
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.
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.
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.
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.
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.
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;
}
}
...
}
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.
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:
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:
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.
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.
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_NEVERXML_PARAM_ENTITY_PARSING_UNLESS_STANDALONEstandalone was set to "yes" in the XML declaration.XML_PARAM_ENTITY_PARSING_ALWAYSIn order to read an external DTD, you also have to set an external entity reference handler as described above.
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;
Construct a new parser using the suite of memory handling functions
specified in ms. If ms is NULL, then use the
standard set of memory management functions. If sep is
non NULL, then namespace processing is enabled in the created parser
and the character pointed at by sep is used as the separator between
the namespace URI and the local part of the name.
XML_Parser
XML_ExternalEntityParserCreate(XML_Parser p,
const XML_Char *context,
const XML_Char *encoding);
XML_Parser object for parsing an external
general entity. Context is the context argument passed in a call to a
ExternalEntityRefHandler. Other state information such as handlers,
user data, namespace processing is inherited from the parser passed as
the 1st argument. So you shouldn't need to call any of the behavior
changing functions on this parser (unless you want it to act
differently than the parent parser).
void XML_ParserFree(XML_Parser p);
XML_Bool XML_ParserReset(XML_Parser p);
parser is
ready to start parsing a new document. This function may not be used
on a parser created using XML_ExternalEntityParserCreate; it will return XML_FALSE in that case. Returns
XML_TRUE on success. Your application is responsible for
dealing with any memory associated with user data.
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
};
s is a buffer
containing part (or perhaps all) of the document. The number of bytes of s
that are part of the document is indicated by len. This means
that s doesn't have to be null terminated. It also means that
if len is larger than the number of bytes in the block of
memory that s points at, then a memory fault is likely. The
isFinal parameter informs the parser that this is the last
piece of the document. Frequently, the last piece is empty (i.e.
len is zero.)
If a parse error occurred, it returns XML_STATUS_ERROR.
Otherwise it returns XML_STATUS_OK value.
XML_Status
XML_ParseBuffer(XML_Parser p,
int len,
int isFinal);
XML_Parse,
except in this case Expat provides the buffer. By obtaining the
buffer from Expat with the XML_GetBuffer function, the application can avoid double
copying of the input.
void *
XML_GetBuffer(XML_Parser p,
int len);
len to read a piece of the document
into. A NULL value is returned if Expat can't allocate enough memory for
this buffer. This has to be called prior to every call to
XML_ParseBuffer. A
typical use would look like this:
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;
}
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);
Set handler for start (and empty) tags. Attributes are passed to the start handler as a pointer to a vector of char pointers. Each attribute seen in a start (or empty) tag occupies 2 consecutive places in this vector: the attribute name followed by the attribute value. These pairs are terminated by a null pointer.
Note that an empty tag generates a call to both start and end handlers (in that order).
XML_SetEndElementHandler(XML_Parser p,
XML_EndElementHandler);
typedef void
(*XML_EndElementHandler)(void *userData,
const XML_Char *name);
Set handler for end (and empty) tags. As noted above, an empty tag generates a call to both start and end handlers.
XML_SetElementHandler(XML_Parser p,
XML_StartElementHandler start,
XML_EndElementHandler end);
Set handlers for start and end tags with one call.
XML_SetCharacterDataHandler(XML_Parser p,
XML_CharacterDataHandler charhndl)
typedef void
(*XML_CharacterDataHandler)(void *userData,
const XML_Char *s,
int len);
Set a text handler. The string your handler receives is NOT nul-terminated. You have to use the length argument to deal with the end of the string. A single block of contiguous text free of markup may still result in a sequence of calls to this handler. In other words, if you're searching for a pattern in the text, it may be split across calls to this handler.
XML_SetProcessingInstructionHandler(XML_Parser p,
XML_ProcessingInstructionHandler proc)
typedef void
(*XML_ProcessingInstructionHandler)(void *userData,
const XML_Char *target,
const XML_Char *data);
Set a handler for processing instructions. The target is the first word in the processing instruction. The data is the rest of the characters in it after skipping all whitespace after the initial word.
XML_SetCommentHandler(XML_Parser p,
XML_CommentHandler cmnt)
typedef void
(*XML_CommentHandler)(void *userData,
const XML_Char *data);
Set a handler for comments. The data is all text inside the comment delimiters.
XML_SetStartCdataSectionHandler(XML_Parser p,
XML_StartCdataSectionHandler start);
typedef void (*XML_StartCdataSectionHandler)(void *userData);
Set a handler that gets called at the beginning of a CDATA section.
XML_SetEndCdataSectionHandler(XML_Parser p,
XML_EndCdataSectionHandler end);
typedef void (*XML_EndCdataSectionHandler)(void *userData);
Set a handler that gets called at the end of a CDATA section.
XML_SetCdataSectionHandler(XML_Parser p,
XML_StartCdataSectionHandler start,
XML_EndCdataSectionHandler end)
Sets both CDATA section handlers with one call.
XML_SetDefaultHandler(XML_Parser p,
XML_DefaultHandler hndl)
typedef void
(*XML_DefaultHandler)(void *userData,
const XML_Char *s,
int len);
Sets a handler for any characters in the document which wouldn't otherwise be handled. This includes both data for which no handlers can be set (like some kinds of DTD declarations) and data which could be reported but which currently has no handler set. The characters are passed exactly as they were present in the XML document except that they will be encoded in UTF-8 or UTF-16. Line boundaries are not normalized. Note that a byte order mark character is not passed to the default handler. There are no guarantees about how characters are divided between calls to the default handler: for example, a comment might be split between multiple calls. Setting the handler with this call has the side effect of turning off expansion of references to internally defined general entities. Instead these references are passed to the default handler.
See also XML_DefaultCurrent.
XML_SetDefaultHandlerExpand(XML_Parser p,
XML_DefaultHandler hndl)
typedef void
(*XML_DefaultHandler)(void *userData,
const XML_Char *s,
int len);
This sets a default handler, but doesn't inhibit the expansion of internal entity references. The entity reference will not be passed to the default handler.
See also XML_DefaultCurrent.
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);
Set an external entity reference handler. This handler is also
called for processing an external DTD subset if parameter entity parsing
is in effect. (See
XML_SetParamEntityParsing.)
The base parameter is the base to use for relative system identifiers. It is set by XML_SetBase and may be null. The public id parameter is the public id given in the entity declaration and may be null. The system id is the system identifier specified in the entity declaration and is never null.
There are a couple of ways in which this handler differs from others.
First, this handler returns an integer. A non-zero value should be returned
for successful handling of the external entity reference. Returning a zero
indicates failure, and causes the calling parser to return
an XML_ERROR_EXTERNAL_ENTITY_HANDLING error.
Second, instead of having userData as its first argument, it receives the parser that encountered the entity reference. This, along with the context parameter, may be used as arguments to a call to XML_ExternalEntityParserCreate. Using the returned parser, the body of the external entity can be recursively parsed.
Since this handler may be called recursively, it should not be saving information into global or static variables.
XML_SetSkippedEntityHandler(XML_Parser p,
XML_SkippedEntityHandler handler)
typedef void
(*XML_SkippedEntityHandler)(void *userData,
const XML_Char *entityName,
int is_parameter_entity);
Set a skipped entity handler. This is called in two situations:
XML_SetDefaultHandler
has been called.The is_parameter_entity argument will be non-zero for
a parameter entity and zero for a general entity.
Note: skipped parameter entities in declarations and skipped general entities in attribute values cannot be reported, because the event would be out of sync with the reporting of the declarations or attribute values
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;
Set a handler to deal with encodings other than the
built in set. This should be done before
XML_Parse or XML_ParseBuffer have been called on the
given parser.
If the handler knows how to deal with an encoding with the given
name, it should fill in the info data structure and return
1. Otherwise it should return 0. The handler will be called at most
once per parsed (external) entity. The optional application data
pointer encodingHandlerData will be passed back to the
handler.
The map array contains information for every possible possible leading
byte in a byte sequence. If the corresponding value is >= 0, then it's
a single byte sequence and the byte encodes that Unicode value. If the
value is -1, then that byte is invalid as the initial byte in a sequence.
If the value is -n, where n is an integer > 1, then n is the number of
bytes in the sequence and the actual conversion is accomplished by a
call to the function pointed at by convert. This function may return -1
if the sequence itself is invalid. The convert pointer may be null if
there are only single byte codes. The data parameter passed to the convert
function is the data pointer from XML_Encoding. The
string s is NOT nul-terminated and points at the sequence of
bytes to be converted.
The function pointed at by release is called by the
parser when it is finished with the encoding. It may be NULL.
XML_SetStartNamespaceDeclHandler(XML_Parser p, XML_StartNamespaceDeclHandler start);
typedef void
(*XML_StartNamespaceDeclHandler)(void *userData,
const XML_Char *prefix,
const XML_Char *uri);
Set a handler to be called when a namespace is declared. Namespace declarations occur inside start tags. But the namespace declaration start handler is called before the start tag handler for each namespace declared in that start tag.
XML_SetEndNamespaceDeclHandler(XML_Parser p, XML_EndNamespaceDeclHandler end);
typedef void
(*XML_EndNamespaceDeclHandler)(void *userData,
const XML_Char *prefix);
Set a handler to be called when leaving the scope of a namespace declaration. This will be called, for each namespace declaration, after the handler for the end tag of the element in which the namespace was declared.
XML_SetNamespaceDeclHandler(XML_Parser p,
XML_StartNamespaceDeclHandler start,
XML_EndNamespaceDeclHandler end)
Sets both namespace declaration handlers with a single call
XML_SetXmlDeclHandler(XML_Parser p, XML_XmlDeclHandler xmldecl);
typedef void
(*XML_XmlDeclHandler) (void *userData,
const XML_Char *version,
const XML_Char *encoding,
int standalone);
Sets a handler that is called for XML declarations and also for
text declarations discovered in external entities. The way to
distinguish is that the version parameter will be NULL
for text declarations. The encoding parameter may be NULL
for an XML declaration. The standalone argument will
contain -1, 0, or 1 indicating respectively that there was no
standalone parameter in the declaration, that it was given as no, or
that it was given as yes.
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);
Set a handler that is called at the start of a DOCTYPE declaration,
before any external or internal subset is parsed. Both sysid
and pubid may be NULL. The has_internal_subset
will be non-zero if the DOCTYPE declaration has an internal subset.
XML_SetEndDoctypeDeclHandler(XML_Parser p, XML_EndDoctypeDeclHandler end);
typedef void (*XML_EndDoctypeDeclHandler)(void *userData);
Set a handler that is called at the end of a DOCTYPE declaration, after parsing any external subset.
XML_SetDoctypeDeclHandler(XML_Parser p, XML_StartDoctypeDeclHandler start, XML_EndDoctypeDeclHandler end);
Set both doctype handlers with one call.
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;
};
Sets a handler for element declarations in a DTD. The handler gets called with the name of the element in the declaration and a pointer to a structure that contains the element model. It is the application's responsibility to free this data structure.
The model argument is the root of a tree of
XML_Content nodes. If type equals
XML_CTYPE_EMPTY or XML_CTYPE_ANY, then
quant will be XML_CQUANT_NONE, and the other
fields will be zero or NULL. If type is
XML_CTYPE_MIXED, then quant will be
XML_CQUANT_NONE or XML_CQUANT_REP and
numchildren will contain the number of elements that are
allowed to be mixed in and children points to an array of
XML_Content structures that will all have type
XML_CTYPE_NAME with no quantification. Only the root node can be type
XML_CTYPE_EMPTY, XML_CTYPE_ANY, or
XML_CTYPE_MIXED.
For type XML_CTYPE_NAME, the name field
points to the name and the numchildren and
children fields will be zero and NULL. The
quant field will indicate any quantifiers placed on the
name.
Types XML_CTYPE_CHOICE and XML_CTYPE_SEQ
indicate a choice or sequence respectively. The
numchildren field indicates how many nodes in the choice
or sequence and children points to the nodes.
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);
Set a handler for attlist declarations in the DTD. This handler is
called for each attribute. So a single attlist declaration
with multiple attributes declared will generate multiple calls to this
handler. The elname parameter returns the name of the
element for which the attribute is being declared. The attribute name
is in the attname parameter. The attribute type is in the
att_type parameter. It is the string representing the
type in the declaration with whitespace removed.
The dflt parameter holds the default value. It will be
NULL in the case of "#IMPLIED" or "#REQUIRED" attributes. You can
distinguish these two cases by checking the isrequired
parameter, which will be true in the case of "#REQUIRED" attributes.
Attributes which are "#FIXED" will have also have a true
isrequired, but they will have the non-NULL fixed value
in the dflt parameter.
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);
Sets a handler that will be called for all entity declarations.
The is_parameter_entity argument will be non-zero in the
case of parameter entities and zero otherwise.
For internal entities (<!ENTITY foo "bar">),
value will be non-NULL and systemId,
publicId, and notationName will all be NULL.
The value string is not NULL terminated; the length is
provided in the value_length parameter. Do not use
value_length to test for internal entities, since it is
legal to have zero-length values. Instead check for whether or not
value is NULL.
The notationName
argument will have a non-NULL value only for unparsed entity
declarations.
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);
Set a handler that receives declarations of unparsed entities. These are entity declarations that have a notation (NDATA) field:
<!ENTITY logo SYSTEM "images/logo.gif" NDATA gif>
This handler is obsolete and is provided for backwards compatibility. Use instead XML_SetEntityDeclHandler.
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);
Set a handler that receives notation declarations.
XML_SetNotStandaloneHandler(XML_Parser p,
XML_NotStandaloneHandler h)
typedef int (*XML_NotStandaloneHandler)(void *userData);
Set a handler that is called if the document is not "standalone".
This happens when there is an external subset or a reference to a
parameter entity, but does not have standalone set to "yes" in an XML
declaration. If this handler returns 0, then the parser will throw an
XML_ERROR_NOT_STANDALONE error.
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);
XML_GetErrorCode.
long XML_GetCurrentByteIndex(XML_Parser p);
int XML_GetCurrentLineNumber(XML_Parser p);
int XML_GetCurrentColumnNumber(XML_Parser p);
int XML_GetCurrentByteCount(XML_Parser p);
0 if the event is inside a reference to an internal
entity and for the end-tag event for empty element tags (the later can
be used to distinguish empty-element tags from empty elements using
separate start and end tags).
const char *
XML_GetInputContext(XML_Parser p,
int *offset,
int *size);
Returns the parser's input buffer, sets the integer pointed at by
offset to the offset within this buffer of the current
parse position, and set the integer pointed at by size to
the size of the returned buffer.
This should only be called from within a handler during an active parse and the returned buffer should only be referred to from within the handler that made the call. This input buffer contains the untranslated bytes of the input.
Only a limited amount of context is kept, so if the event triggering a call spans over a very large amount of input, the actual parse position may be before the beginning of the buffer.
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);
userData when it is finished with the parser. So if you
call this when there's already a pointer there, and you haven't freed
the memory associated with it, then you've probably just leaked
memory.
void * XML_GetUserData(XML_Parser p);
void XML_UseParserAsHandlerArg(XML_Parser p);
XML_GetUserData
function.
int
XML_SetBase(XML_Parser p,
const XML_Char *base);
const XML_Char * XML_GetBase(XML_Parser p);
int XML_GetSpecifiedAttributeCount(XML_Parser p);
atts array passed to the start tag handler of the first
attribute set due to defaults. It supplies information for the last
call to a start handler. If called inside a start handler, then that
means the current call.
int XML_GetIdAttributeIndex(XML_Parser p);
XML_StartElementHandler, or -1 if there is no ID
attribute. If called inside a start handler, then that means the
current call.
int
XML_SetEncoding(XML_Parser p,
const XML_Char *encoding);
XML_Parse or XML_ParseBuffer have been called on the given parser.
int
XML_SetParamEntityParsing(XML_Parser p,
enum XML_ParamEntityParsing code);
code.
The choices for code are:
XML_PARAM_ENTITY_PARSING_NEVERXML_PARAM_ENTITY_PARSING_UNLESS_STANDALONEXML_PARAM_ENTITY_PARSING_ALWAYSenum XML_Error XML_UseForeignDTD(XML_Parser parser, XML_Bool useDTD);
This function allows an application to provide an external subset
for the document type declaration for documents which do not specify
an external subset of their own. For documents which specify an
external subset in their DOCTYPE declaration, the application-provided
subset will be ignored. If the document does not contain a DOCTYPE
declaration at all and useDTD is true, the
application-provided subset will be parsed, but the
startDoctypeDeclHandler and
endDoctypeDeclHandler functions, if set, will not be
called. The setting of parameter entity parsing, controlled using
XML_SetParamEntityParsing, will be honored.
The application-provided external subset is read by calling the
external entity reference handler set via XML_SetExternalEntityRefHandler with both
publicId and systemId set to NULL.
If this function is called after parsing has begun, it returns
XML_ERROR_CANT_CHANGE_FEATURE_ONCE_PARSING and ignores
useDTD. If called when Expat has been compiled without
DTD support, it returns
XML_ERROR_FEATURE_REQUIRES_XML_DTD. Otherwise, it
returns XML_ERROR_NONE.
void
XML_SetReturnNSTriplet(XML_Parser parser,
int do_nst);
This function only has an effect when using a parser created with
XML_ParserCreateNS,
i.e. when namespace processing is in effect. The do_nst
sets whether or not prefixes are returned with names qualified with a
namespace prefix. If this function is called with do_nst
non-zero, then afterwards namespace qualified names (that is qualified
with a prefix as opposed to belonging to a default namespace) are
returned as a triplet with the three parts separated by the namespace
separator specified when the parser was created. The order of
returned parts is URI, local name, and prefix.
If
do_nst is zero, then namespaces are reported in the
default manner, URI then local_name separated by the namespace
separator.
void XML_DefaultCurrent(XML_Parser parser);
XML_SetDefaultHandler or
XML_SetDefaultHandlerExpand. It does nothing if there is
not a default handler.
XML_LChar * XML_ExpatVersion();
"expat_1.95.1").
struct XML_Expat_Version XML_ExpatVersionInfo();
typedef struct {
int major;
int minor;
int micro;
} XML_Expat_Version;
XML_MAJOR_VERSIONXML_MINOR_VERSIONXML_MICRO_VERSIONconst 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;
Returns a list of "feature" records, providing details on how Expat was configured at compile time. Most applications should not need to worry about this, but this information is otherwise not available from Expat. This function allows code that does need to check these features to do so at runtime.
The return value is an array of XML_Feature,
terminated by a record with a feature of
XML_FEATURE_END and name of NULL,
identifying the feature-test macros Expat was compiled with. Since an
application that requires this kind of information needs to determine
the type of character the name points to, records for the
XML_FEATURE_SIZEOF_XML_CHAR and
XML_FEATURE_SIZEOF_XML_LCHAR will be located at the
beginning of the list, followed by XML_FEATURE_UNICODE
and XML_FEATURE_UNICODE_WCHAR_T, if they are present at
all.
Some features have an associated value. If there isn't an
associated value, the value field is set to 0. At this
time, the following features have been defined to have values:
XML_FEATURE_SIZEOF_XML_CHARXML_Char
character.XML_FEATURE_SIZEOF_XML_LCHARXML_LChar
character.XML_FEATURE_CONTEXT_BYTESXML_GetInputContext.