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Daniel Veillard | 28fdf8b | 2011-03-07 08:12:39 +0800 | [diff] [blame] | 10 | </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 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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://opencsw.org/packages/libxml2">Solaris binaries</a></li><li><a href="http://www.explain.com.au/oss/libxml2xslt.html">MacOsX binaries</a></li><li><a href="http://lxml.de/">lxml Python bindings</a></li><li><a href="http://cpan.uwinnipeg.ca/dist/XML-LibXML">Perl bindings</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 bootstrapped |
Daniel Veillard | f781dba | 2006-06-09 13:34:49 +0000 | [diff] [blame] | 11 | using the XML tollkit from the C language. It is not intended to be |
| 12 | extensive. I hope the automatically generated documents will provide the |
| 13 | completeness required, but as a separate set of documents. The interfaces of |
| 14 | the XML parser are by principle low level, Those interested in a higher level |
| 15 | API should <a href="#DOM">look at DOM</a>.</p><p>The <a href="html/libxml-parser.html">parser interfaces for XML</a> are |
| 16 | separated from the <a href="html/libxml-htmlparser.html">HTML parser |
| 17 | interfaces</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 accepts |
| 18 | documents either from in-memory strings or from files. The functions are |
Daniel Veillard | e38217a | 2013-05-10 15:40:13 +0800 | [diff] [blame] | 19 | defined in "parser.h":</p><dl> |
| 20 | <dt><code>xmlDocPtr xmlParseMemory(char *buffer, int size);</code></dt> |
Daniel Veillard | 1177ca4 | 2003-04-26 22:29:54 +0000 | [diff] [blame] | 21 | <dd><p>Parse a null-terminated string containing the document.</p> |
Daniel Veillard | 0b28e88 | 2002-07-24 23:47:05 +0000 | [diff] [blame] | 22 | </dd> |
Daniel Veillard | e38217a | 2013-05-10 15:40:13 +0800 | [diff] [blame] | 23 | </dl><dl> |
| 24 | <dt><code>xmlDocPtr xmlParseFile(const char *filename);</code></dt> |
Daniel Veillard | f781dba | 2006-06-09 13:34:49 +0000 | [diff] [blame] | 25 | <dd><p>Parse an XML document contained in a (possibly compressed) |
| 26 | file.</p> |
Daniel Veillard | 0b28e88 | 2002-07-24 23:47:05 +0000 | [diff] [blame] | 27 | </dd> |
Daniel Veillard | f781dba | 2006-06-09 13:34:49 +0000 | [diff] [blame] | 28 | </dl><p>The parser returns a pointer to the document structure (or NULL in case of |
| 29 | failure).</p><h3 id="Invoking1">Invoking the parser: the push method</h3><p>In order for the application to keep the control when the document is |
| 30 | being fetched (which is common for GUI based programs) libxml2 provides a |
| 31 | push interface, too, as of version 1.8.3. Here are the interface |
| 32 | functions:</p><pre>xmlParserCtxtPtr xmlCreatePushParserCtxt(xmlSAXHandlerPtr sax, |
Daniel Veillard | c948420 | 2001-10-24 12:35:52 +0000 | [diff] [blame] | 33 | void *user_data, |
| 34 | const char *chunk, |
| 35 | int size, |
| 36 | const char *filename); |
| 37 | int xmlParseChunk (xmlParserCtxtPtr ctxt, |
| 38 | const char *chunk, |
| 39 | int size, |
Daniel Veillard | 1177ca4 | 2003-04-26 22:29:54 +0000 | [diff] [blame] | 40 | int terminate);</pre><p>and here is a simple example showing how to use the interface:</p><pre> FILE *f; |
Daniel Veillard | c948420 | 2001-10-24 12:35:52 +0000 | [diff] [blame] | 41 | |
Daniel Veillard | 024f199 | 2003-12-10 16:43:49 +0000 | [diff] [blame] | 42 | f = fopen(filename, "r"); |
Daniel Veillard | c948420 | 2001-10-24 12:35:52 +0000 | [diff] [blame] | 43 | if (f != NULL) { |
| 44 | int res, size = 1024; |
| 45 | char chars[1024]; |
| 46 | xmlParserCtxtPtr ctxt; |
| 47 | |
| 48 | res = fread(chars, 1, 4, f); |
| 49 | if (res > 0) { |
| 50 | ctxt = xmlCreatePushParserCtxt(NULL, NULL, |
| 51 | chars, res, filename); |
| 52 | while ((res = fread(chars, 1, size, f)) > 0) { |
| 53 | xmlParseChunk(ctxt, chars, res, 0); |
| 54 | } |
| 55 | xmlParseChunk(ctxt, chars, 0, 1); |
| 56 | doc = ctxt->myDoc; |
| 57 | xmlFreeParserCtxt(ctxt); |
| 58 | } |
Daniel Veillard | f781dba | 2006-06-09 13:34:49 +0000 | [diff] [blame] | 59 | }</pre><p>The HTML parser embedded into libxml2 also has a push interface; the |
| 60 | functions 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 loading |
| 61 | the document in memory and then building the tree itself. Reading a document |
| 62 | without building the tree is possible using the SAX interfaces (see SAX.h and |
| 63 | <a href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">James |
| 64 | Henstridge's documentation</a>). Note also that the push interface can be |
| 65 | limited to SAX: just use the two first arguments of |
| 66 | <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. Basically |
| 67 | there is a set of functions dedicated to building new elements. (These are |
| 68 | also described in <libxml/tree.h>.) For example, here is a piece of |
| 69 | code that produces the XML document used in the previous examples:</p><pre> #include <libxml/tree.h> |
Daniel Veillard | c948420 | 2001-10-24 12:35:52 +0000 | [diff] [blame] | 70 | xmlDocPtr doc; |
| 71 | xmlNodePtr tree, subtree; |
| 72 | |
Daniel Veillard | 024f199 | 2003-12-10 16:43:49 +0000 | [diff] [blame] | 73 | doc = xmlNewDoc("1.0"); |
| 74 | doc->children = xmlNewDocNode(doc, NULL, "EXAMPLE", NULL); |
| 75 | xmlSetProp(doc->children, "prop1", "gnome is great"); |
| 76 | xmlSetProp(doc->children, "prop2", "& linux too"); |
| 77 | tree = xmlNewChild(doc->children, NULL, "head", NULL); |
| 78 | subtree = xmlNewChild(tree, NULL, "title", "Welcome to Gnome"); |
| 79 | tree = xmlNewChild(doc->children, NULL, "chapter", NULL); |
| 80 | subtree = xmlNewChild(tree, NULL, "title", "The Linux adventure"); |
| 81 | subtree = xmlNewChild(tree, NULL, "p", "bla bla bla ..."); |
| 82 | subtree = xmlNewChild(tree, NULL, "image", NULL); |
Daniel Veillard | f781dba | 2006-06-09 13:34:49 +0000 | [diff] [blame] | 83 | 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> your |
| 84 | code has access to the internal structure of all the elements of the tree. |
| 85 | The names should be somewhat simple like <strong>parent</strong>, |
| 86 | <strong>children</strong>, <strong>next</strong>, <strong>prev</strong>, |
| 87 | <strong>properties</strong>, etc... For example, still with the previous |
| 88 | example:</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 Linux |
| 89 | adventure".</p><p><strong>NOTE</strong>: XML allows <em>PI</em>s and <em>comments</em> to be |
| 90 | present before the document root, so <code>doc->children</code> may point |
| 91 | to an element which is not the document Root Element; a function |
| 92 | <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. Here |
Daniel Veillard | e38217a | 2013-05-10 15:40:13 +0800 | [diff] [blame] | 93 | is an excerpt from the <a href="html/libxml-tree.html">tree API</a>:</p><dl> |
| 94 | <dt><code>xmlAttrPtr xmlSetProp(xmlNodePtr node, const xmlChar *name, const |
Daniel Veillard | f781dba | 2006-06-09 13:34:49 +0000 | [diff] [blame] | 95 | xmlChar *value);</code></dt> |
| 96 | <dd><p>This sets (or changes) an attribute carried by an ELEMENT node. |
| 97 | The value can be NULL.</p> |
Daniel Veillard | 0b28e88 | 2002-07-24 23:47:05 +0000 | [diff] [blame] | 98 | </dd> |
Daniel Veillard | e38217a | 2013-05-10 15:40:13 +0800 | [diff] [blame] | 99 | </dl><dl> |
| 100 | <dt><code>const xmlChar *xmlGetProp(xmlNodePtr node, const xmlChar |
Daniel Veillard | f781dba | 2006-06-09 13:34:49 +0000 | [diff] [blame] | 101 | *name);</code></dt> |
| 102 | <dd><p>This function returns a pointer to new copy of the property |
| 103 | content. Note that the user must deallocate the result.</p> |
Daniel Veillard | 0b28e88 | 2002-07-24 23:47:05 +0000 | [diff] [blame] | 104 | </dd> |
Daniel Veillard | f781dba | 2006-06-09 13:34:49 +0000 | [diff] [blame] | 105 | </dl><p>Two functions are provided for reading and writing the text associated |
Daniel Veillard | e38217a | 2013-05-10 15:40:13 +0800 | [diff] [blame] | 106 | with elements:</p><dl> |
| 107 | <dt><code>xmlNodePtr xmlStringGetNodeList(xmlDocPtr doc, const xmlChar |
Daniel Veillard | f781dba | 2006-06-09 13:34:49 +0000 | [diff] [blame] | 108 | *value);</code></dt> |
| 109 | <dd><p>This function takes an "external" string and converts it to one |
| 110 | text node or possibly to a list of entity and text nodes. All |
| 111 | non-predefined entity references like &Gnome; will be stored |
| 112 | internally as entity nodes, hence the result of the function may not be |
| 113 | a single node.</p> |
Daniel Veillard | 0b28e88 | 2002-07-24 23:47:05 +0000 | [diff] [blame] | 114 | </dd> |
Daniel Veillard | e38217a | 2013-05-10 15:40:13 +0800 | [diff] [blame] | 115 | </dl><dl> |
| 116 | <dt><code>xmlChar *xmlNodeListGetString(xmlDocPtr doc, xmlNodePtr list, int |
Daniel Veillard | f781dba | 2006-06-09 13:34:49 +0000 | [diff] [blame] | 117 | inLine);</code></dt> |
| 118 | <dd><p>This function is the inverse of |
| 119 | <code>xmlStringGetNodeList()</code>. It generates a new string |
| 120 | containing the content of the text and entity nodes. Note the extra |
| 121 | argument inLine. If this argument is set to 1, the function will expand |
| 122 | entity references. For example, instead of returning the &Gnome; |
| 123 | XML encoding in the string, it will substitute it with its value (say, |
| 124 | "GNU Network Object Model Environment").</p> |
Daniel Veillard | 0b28e88 | 2002-07-24 23:47:05 +0000 | [diff] [blame] | 125 | </dd> |
Daniel Veillard | e38217a | 2013-05-10 15:40:13 +0800 | [diff] [blame] | 126 | </dl><h3><a name="Saving" id="Saving">Saving a tree</a></h3><p>Basically 3 options are possible:</p><dl> |
| 127 | <dt><code>void xmlDocDumpMemory(xmlDocPtr cur, xmlChar**mem, int |
Daniel Veillard | f781dba | 2006-06-09 13:34:49 +0000 | [diff] [blame] | 128 | *size);</code></dt> |
Daniel Veillard | 1177ca4 | 2003-04-26 22:29:54 +0000 | [diff] [blame] | 129 | <dd><p>Returns a buffer into which the document has been saved.</p> |
Daniel Veillard | 0b28e88 | 2002-07-24 23:47:05 +0000 | [diff] [blame] | 130 | </dd> |
Daniel Veillard | e38217a | 2013-05-10 15:40:13 +0800 | [diff] [blame] | 131 | </dl><dl> |
| 132 | <dt><code>extern void xmlDocDump(FILE *f, xmlDocPtr doc);</code></dt> |
Daniel Veillard | 1177ca4 | 2003-04-26 22:29:54 +0000 | [diff] [blame] | 133 | <dd><p>Dumps a document to an open file descriptor.</p> |
Daniel Veillard | 0b28e88 | 2002-07-24 23:47:05 +0000 | [diff] [blame] | 134 | </dd> |
Daniel Veillard | e38217a | 2013-05-10 15:40:13 +0800 | [diff] [blame] | 135 | </dl><dl> |
| 136 | <dt><code>int xmlSaveFile(const char *filename, xmlDocPtr cur);</code></dt> |
Daniel Veillard | f781dba | 2006-06-09 13:34:49 +0000 | [diff] [blame] | 137 | <dd><p>Saves the document to a file. In this case, the compression |
| 138 | interface is triggered if it has been turned on.</p> |
Daniel Veillard | 0b28e88 | 2002-07-24 23:47:05 +0000 | [diff] [blame] | 139 | </dd> |
Daniel Veillard | f781dba | 2006-06-09 13:34:49 +0000 | [diff] [blame] | 140 | </dl><h3><a name="Compressio" id="Compressio">Compression</a></h3><p>The library transparently handles compression when doing file-based |
| 141 | accesses. The level of compression on saves can be turned on either globally |
Daniel Veillard | e38217a | 2013-05-10 15:40:13 +0800 | [diff] [blame] | 142 | or individually for one file:</p><dl> |
| 143 | <dt><code>int xmlGetDocCompressMode (xmlDocPtr doc);</code></dt> |
Daniel Veillard | 1177ca4 | 2003-04-26 22:29:54 +0000 | [diff] [blame] | 144 | <dd><p>Gets the document compression ratio (0-9).</p> |
Daniel Veillard | 0b28e88 | 2002-07-24 23:47:05 +0000 | [diff] [blame] | 145 | </dd> |
Daniel Veillard | e38217a | 2013-05-10 15:40:13 +0800 | [diff] [blame] | 146 | </dl><dl> |
| 147 | <dt><code>void xmlSetDocCompressMode (xmlDocPtr doc, int mode);</code></dt> |
Daniel Veillard | 1177ca4 | 2003-04-26 22:29:54 +0000 | [diff] [blame] | 148 | <dd><p>Sets the document compression ratio.</p> |
Daniel Veillard | 0b28e88 | 2002-07-24 23:47:05 +0000 | [diff] [blame] | 149 | </dd> |
Daniel Veillard | e38217a | 2013-05-10 15:40:13 +0800 | [diff] [blame] | 150 | </dl><dl> |
| 151 | <dt><code>int xmlGetCompressMode(void);</code></dt> |
Daniel Veillard | 1177ca4 | 2003-04-26 22:29:54 +0000 | [diff] [blame] | 152 | <dd><p>Gets the default compression ratio.</p> |
Daniel Veillard | 0b28e88 | 2002-07-24 23:47:05 +0000 | [diff] [blame] | 153 | </dd> |
Daniel Veillard | e38217a | 2013-05-10 15:40:13 +0800 | [diff] [blame] | 154 | </dl><dl> |
| 155 | <dt><code>void xmlSetCompressMode(int mode);</code></dt> |
Daniel Veillard | 1177ca4 | 2003-04-26 22:29:54 +0000 | [diff] [blame] | 156 | <dd><p>Sets the default compression ratio.</p> |
Daniel Veillard | 0b28e88 | 2002-07-24 23:47:05 +0000 | [diff] [blame] | 157 | </dd> |
Daniel Veillard | 1177ca4 | 2003-04-26 22:29:54 +0000 | [diff] [blame] | 158 | </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> |