mirror of
https://gitlab.gnome.org/GNOME/libxml2.git
synced 2025-01-29 21:46:59 +03:00
144 lines
14 KiB
HTML
144 lines
14 KiB
HTML
<?xml version="1.0" encoding="ISO-8859-1"?>
|
|
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
|
|
<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" /><link rel="SHORTCUT ICON" href="/favicon.ico" /><style type="text/css">
|
|
TD {font-family: Verdana,Arial,Helvetica}
|
|
BODY {font-family: Verdana,Arial,Helvetica; margin-top: 2em; margin-left: 0em; margin-right: 0em}
|
|
H1 {font-family: Verdana,Arial,Helvetica}
|
|
H2 {font-family: Verdana,Arial,Helvetica}
|
|
H3 {font-family: Verdana,Arial,Helvetica}
|
|
A:link, A:visited, A:active { text-decoration: underline }
|
|
</style><title>The parser interfaces</title></head><body bgcolor="#8b7765" text="#000000" link="#a06060" vlink="#000000"><table border="0" width="100%" cellpadding="5" cellspacing="0" align="center"><tr><td width="120"><a href="http://swpat.ffii.org/"><img src="epatents.png" alt="Action against software patents" /></a></td><td width="180"><a href="http://www.gnome.org/"><img src="gnome2.png" alt="Gnome2 Logo" /></a><a href="http://www.w3.org/Status"><img src="w3c.png" alt="W3C Logo" /></a><a href="http://www.redhat.com/"><img src="redhat.gif" alt="Red Hat Logo" /></a><div align="left"><a href="http://xmlsoft.org/"><img src="Libxml2-Logo-180x168.gif" alt="Made with Libxml2 Logo" /></a></div></td><td><table border="0" width="90%" cellpadding="2" cellspacing="0" align="center" bgcolor="#000000"><tr><td><table width="100%" border="0" cellspacing="1" cellpadding="3" bgcolor="#fffacd"><tr><td align="center"><h1>The XML C parser and toolkit of Gnome</h1><h2>The parser interfaces</h2></td></tr></table></td></tr></table></td></tr></table><table border="0" cellpadding="4" cellspacing="0" width="100%" align="center"><tr><td bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td valign="top" width="200" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Developer Menu</b></center></td></tr><tr><td bgcolor="#fffacd"><form action="search.php" enctype="application/x-www-form-urlencoded" method="get"><input name="query" type="text" size="20" value="" /><input name="submit" type="submit" value="Search ..." /></form><ul><li><a href="index.html" style="font-weight:bold">Main Menu</a></li><li><a href="html/index.html" style="font-weight:bold">Reference Manual</a></li><li><a href="examples/index.html" style="font-weight:bold">Code Examples</a></li><li><a href="guidelines.html">XML Guidelines</a></li><li><a href="tutorial/index.html">Tutorial</a></li><li><a href="xmlreader.html">The Reader Interface</a></li><li><a href="ChangeLog.html">ChangeLog</a></li><li><a href="XSLT.html">XSLT</a></li><li><a href="python.html">Python and bindings</a></li><li><a href="architecture.html">libxml2 architecture</a></li><li><a href="tree.html">The tree output</a></li><li><a href="interface.html">The SAX interface</a></li><li><a href="xmlmem.html">Memory Management</a></li><li><a href="xmlio.html">I/O Interfaces</a></li><li><a href="library.html">The parser interfaces</a></li><li><a href="entities.html">Entities or no entities</a></li><li><a href="namespaces.html">Namespaces</a></li><li><a href="upgrade.html">Upgrading 1.x code</a></li><li><a href="threads.html">Thread safety</a></li><li><a href="DOM.html">DOM Principles</a></li><li><a href="example.html">A real example</a></li><li><a href="xml.html">flat page</a>, <a href="site.xsl">stylesheet</a></li></ul></td></tr></table><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>API Indexes</b></center></td></tr><tr><td bgcolor="#fffacd"><ul><li><a href="APIchunk0.html">Alphabetic</a></li><li><a href="APIconstructors.html">Constructors</a></li><li><a href="APIfunctions.html">Functions/Types</a></li><li><a href="APIfiles.html">Modules</a></li><li><a href="APIsymbols.html">Symbols</a></li></ul></td></tr></table><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Related links</b></center></td></tr><tr><td bgcolor="#fffacd"><ul><li><a href="http://mail.gnome.org/archives/xml/">Mail archive</a></li><li><a href="http://xmlsoft.org/XSLT/">XSLT libxslt</a></li><li><a href="http://phd.cs.unibo.it/gdome2/">DOM gdome2</a></li><li><a href="http://www.aleksey.com/xmlsec/">XML-DSig xmlsec</a></li><li><a href="ftp://xmlsoft.org/">FTP</a></li><li><a href="http://www.zlatkovic.com/projects/libxml/">Windows binaries</a></li><li><a href="http://www.blastwave.org/packages.php/libxml2">Solaris binaries</a></li><li><a href="http://www.explain.com.au/oss/libxml2xslt.html">MacOsX binaries</a></li><li><a href="http://libxmlplusplus.sourceforge.net/">C++ bindings</a></li><li><a href="http://www.zend.com/php5/articles/php5-xmlphp.php#Heading4">PHP bindings</a></li><li><a href="http://sourceforge.net/projects/libxml2-pas/">Pascal bindings</a></li><li><a href="http://libxml.rubyforge.org/">Ruby bindings</a></li><li><a href="http://tclxml.sourceforge.net/">Tcl bindings</a></li><li><a href="http://bugzilla.gnome.org/buglist.cgi?product=libxml2">Bug Tracker</a></li></ul></td></tr></table></td></tr></table></td><td valign="top" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%"><tr><td><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td><table border="0" cellpadding="3" cellspacing="1" width="100%"><tr><td bgcolor="#fffacd"><p>This section is directly intended to help programmers getting
|
|
bootstrappedusing the XML tollkit from the C language. It is not intended to
|
|
beextensive. I hope the automatically generated documents will provide
|
|
thecompleteness required, but as a separate set of documents. The interfaces
|
|
ofthe XML parser are by principle low level, Those interested in a higher
|
|
levelAPI should <a href="#DOM">look at DOM</a>.</p><p>The <a href="html/libxml-parser.html">parser interfaces for
|
|
XML</a>areseparated from the <a href="html/libxml-htmlparser.html">HTML
|
|
parserinterfaces</a>. Let's have a look at how the XML parser can be
|
|
called:</p><h3><a name="Invoking" id="Invoking">Invoking the parser : the pull method</a></h3><p>Usually, the first thing to do is to read an XML input. The parser
|
|
acceptsdocuments either from in-memory strings or from files. The functions
|
|
aredefined in "parser.h":</p><dl><dt><code>xmlDocPtr xmlParseMemory(char *buffer, int size);</code></dt>
|
|
<dd><p>Parse a null-terminated string containing the document.</p>
|
|
</dd>
|
|
</dl><dl><dt><code>xmlDocPtr xmlParseFile(const char *filename);</code></dt>
|
|
<dd><p>Parse an XML document contained in a (possibly compressed)file.</p>
|
|
</dd>
|
|
</dl><p>The parser returns a pointer to the document structure (or NULL in case
|
|
offailure).</p><h3 id="Invoking1">Invoking the parser: the push method</h3><p>In order for the application to keep the control when the document isbeing
|
|
fetched (which is common for GUI based programs) libxml2 provides apush
|
|
interface, too, as of version 1.8.3. Here are the interfacefunctions:</p><pre>xmlParserCtxtPtr xmlCreatePushParserCtxt(xmlSAXHandlerPtr sax,
|
|
void *user_data,
|
|
const char *chunk,
|
|
int size,
|
|
const char *filename);
|
|
int xmlParseChunk (xmlParserCtxtPtr ctxt,
|
|
const char *chunk,
|
|
int size,
|
|
int terminate);</pre><p>and here is a simple example showing how to use the interface:</p><pre> FILE *f;
|
|
|
|
f = fopen(filename, "r");
|
|
if (f != NULL) {
|
|
int res, size = 1024;
|
|
char chars[1024];
|
|
xmlParserCtxtPtr ctxt;
|
|
|
|
res = fread(chars, 1, 4, f);
|
|
if (res > 0) {
|
|
ctxt = xmlCreatePushParserCtxt(NULL, NULL,
|
|
chars, res, filename);
|
|
while ((res = fread(chars, 1, size, f)) > 0) {
|
|
xmlParseChunk(ctxt, chars, res, 0);
|
|
}
|
|
xmlParseChunk(ctxt, chars, 0, 1);
|
|
doc = ctxt->myDoc;
|
|
xmlFreeParserCtxt(ctxt);
|
|
}
|
|
}</pre><p>The HTML parser embedded into libxml2 also has a push interface;
|
|
thefunctions are just prefixed by "html" rather than "xml".</p><h3 id="Invoking2">Invoking the parser: the SAX interface</h3><p>The tree-building interface makes the parser memory-hungry, first
|
|
loadingthe document in memory and then building the tree itself. Reading a
|
|
documentwithout building the tree is possible using the SAX interfaces (see
|
|
SAX.h and<a href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">JamesHenstridge's
|
|
documentation</a>). Note also that the push interface can belimited to SAX:
|
|
just use the two first arguments of<code>xmlCreatePushParserCtxt()</code>.</p><h3><a name="Building" id="Building">Building a tree from scratch</a></h3><p>The other way to get an XML tree in memory is by building it.
|
|
Basicallythere is a set of functions dedicated to building new elements.
|
|
(These arealso described in <libxml/tree.h>.) For example, here is a
|
|
piece ofcode that produces the XML document used in the previous examples:</p><pre> #include <libxml/tree.h>
|
|
xmlDocPtr doc;
|
|
xmlNodePtr tree, subtree;
|
|
|
|
doc = xmlNewDoc("1.0");
|
|
doc->children = xmlNewDocNode(doc, NULL, "EXAMPLE", NULL);
|
|
xmlSetProp(doc->children, "prop1", "gnome is great");
|
|
xmlSetProp(doc->children, "prop2", "& linux too");
|
|
tree = xmlNewChild(doc->children, NULL, "head", NULL);
|
|
subtree = xmlNewChild(tree, NULL, "title", "Welcome to Gnome");
|
|
tree = xmlNewChild(doc->children, NULL, "chapter", NULL);
|
|
subtree = xmlNewChild(tree, NULL, "title", "The Linux adventure");
|
|
subtree = xmlNewChild(tree, NULL, "p", "bla bla bla ...");
|
|
subtree = xmlNewChild(tree, NULL, "image", NULL);
|
|
xmlSetProp(subtree, "href", "linus.gif");</pre><p>Not really rocket science ...</p><h3><a name="Traversing" id="Traversing">Traversing the tree</a></h3><p>Basically by <a href="html/libxml-tree.html">including
|
|
"tree.h"</a>yourcode has access to the internal structure of all the elements
|
|
of the tree.The names should be somewhat simple like
|
|
<strong>parent</strong>,<strong>children</strong>, <strong>next</strong>,
|
|
<strong>prev</strong>,<strong>properties</strong>, etc... For example, still
|
|
with the previousexample:</p><pre><code>doc->children->children->children</code></pre><p>points to the title element,</p><pre>doc->children->children->next->children->children</pre><p>points to the text node containing the chapter title "The
|
|
Linuxadventure".</p><p><strong>NOTE</strong>: XML allows <em>PI</em>s and <em>comments</em>to
|
|
bepresent before the document root, so <code>doc->children</code>may
|
|
pointto an element which is not the document Root Element; a
|
|
function<code>xmlDocGetRootElement()</code>was added for this purpose.</p><h3><a name="Modifying" id="Modifying">Modifying the tree</a></h3><p>Functions are provided for reading and writing the document content.
|
|
Hereis an excerpt from the <a href="html/libxml-tree.html">tree API</a>:</p><dl><dt><code>xmlAttrPtr xmlSetProp(xmlNodePtr node, const xmlChar *name,
|
|
constxmlChar *value);</code></dt>
|
|
<dd><p>This sets (or changes) an attribute carried by an ELEMENT node.The
|
|
value can be NULL.</p>
|
|
</dd>
|
|
</dl><dl><dt><code>const xmlChar *xmlGetProp(xmlNodePtr node, const
|
|
xmlChar*name);</code></dt>
|
|
<dd><p>This function returns a pointer to new copy of the
|
|
propertycontent. Note that the user must deallocate the result.</p>
|
|
</dd>
|
|
</dl><p>Two functions are provided for reading and writing the text associatedwith
|
|
elements:</p><dl><dt><code>xmlNodePtr xmlStringGetNodeList(xmlDocPtr doc, const
|
|
xmlChar*value);</code></dt>
|
|
<dd><p>This function takes an "external" string and converts it to
|
|
onetext node or possibly to a list of entity and text nodes.
|
|
Allnon-predefined entity references like &Gnome; will be
|
|
storedinternally as entity nodes, hence the result of the function may
|
|
not bea single node.</p>
|
|
</dd>
|
|
</dl><dl><dt><code>xmlChar *xmlNodeListGetString(xmlDocPtr doc, xmlNodePtr list,
|
|
intinLine);</code></dt>
|
|
<dd><p>This function is the inverse
|
|
of<code>xmlStringGetNodeList()</code>. It generates a new
|
|
stringcontaining the content of the text and entity nodes. Note the
|
|
extraargument inLine. If this argument is set to 1, the function will
|
|
expandentity references. For example, instead of returning the
|
|
&Gnome;XML encoding in the string, it will substitute it with its
|
|
value (say,"GNU Network Object Model Environment").</p>
|
|
</dd>
|
|
</dl><h3><a name="Saving" id="Saving">Saving a tree</a></h3><p>Basically 3 options are possible:</p><dl><dt><code>void xmlDocDumpMemory(xmlDocPtr cur, xmlChar**mem,
|
|
int*size);</code></dt>
|
|
<dd><p>Returns a buffer into which the document has been saved.</p>
|
|
</dd>
|
|
</dl><dl><dt><code>extern void xmlDocDump(FILE *f, xmlDocPtr doc);</code></dt>
|
|
<dd><p>Dumps a document to an open file descriptor.</p>
|
|
</dd>
|
|
</dl><dl><dt><code>int xmlSaveFile(const char *filename, xmlDocPtr cur);</code></dt>
|
|
<dd><p>Saves the document to a file. In this case, the
|
|
compressioninterface is triggered if it has been turned on.</p>
|
|
</dd>
|
|
</dl><h3><a name="Compressio" id="Compressio">Compression</a></h3><p>The library transparently handles compression when doing
|
|
file-basedaccesses. The level of compression on saves can be turned on either
|
|
globallyor individually for one file:</p><dl><dt><code>int xmlGetDocCompressMode (xmlDocPtr doc);</code></dt>
|
|
<dd><p>Gets the document compression ratio (0-9).</p>
|
|
</dd>
|
|
</dl><dl><dt><code>void xmlSetDocCompressMode (xmlDocPtr doc, int mode);</code></dt>
|
|
<dd><p>Sets the document compression ratio.</p>
|
|
</dd>
|
|
</dl><dl><dt><code>int xmlGetCompressMode(void);</code></dt>
|
|
<dd><p>Gets the default compression ratio.</p>
|
|
</dd>
|
|
</dl><dl><dt><code>void xmlSetCompressMode(int mode);</code></dt>
|
|
<dd><p>Sets the default compression ratio.</p>
|
|
</dd>
|
|
</dl><p><a href="bugs.html">Daniel Veillard</a></p></td></tr></table></td></tr></table></td></tr></table></td></tr></table></td></tr></table></body></html>
|