doc/xml.html - third_party/github.com/GNOME/libxml2 - Git at Google

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    "http://www.w3.org/TR/REC-html40/loose.dtd">
 <html>
 <head>
 <title>The XML library for Gnome</title>
 <meta name="GENERATOR" content="amaya V1.3b">
 </head>
 <body bgcolor="#ffffff">

 <h1 align="center">The XML library for Gnome</h1>
 <p>
 This document describes the <a href="http://www.w3.org/XML/">XML</a> library
 provideed in the <a href="http://www.gnome.org/">Gnome</a> framework. XML is a
 standard to build tag based structured documents. The internal document
 repesentation is as close as possible to the <a
 href="http://www.w3.org/DOM/">DOM</a> interfaces.</p>

 <h2>xml</h2>
 <p>
 XML is a standard for markup based structured documents, here is <a
 name="example">an example</a>:</p>
 <pre>&lt;?xml version="1.0"?>
 &lt;EXAMPLE prop1="gnome is great" prop2="&amp;linux; too">
   &lt;head>
    &lt;title>Welcome to Gnome&lt;/title>
   &lt;/head>
   &lt;chapter>
    &lt;title>The Linux adventure&lt;/title>
    &lt;p>bla bla bla ...&lt;/p>
    &lt;image href="linus.gif"/>
    &lt;p>...&lt;/p>
   &lt;/chapter>
 &lt;/EXAMPLE></pre>
 <p>
 The first line specify that it's an XML document and gives useful informations
 about it's encoding. Then the document is a text format whose structure is
 specified by tags between brackets. <strong>Each tag opened have to be
 closed</strong> XML is pedantic about this, not that for example the image
 tage has no content (just an attribute) and is closed by ending up the tag
 with <code>/></code>.</p>

 <h2>The tree output</h2>
 <p>
 The parser returns a tree built during the document analysis. The value
 returned is an <strong>xmlDocPtr</strong> (i.e. a pointer to an
 <strong>xmlDoc</strong> structure). This structure contains informations like
 the file  name, the document type, and a <strong>root</strong> pointer which
 is the root of the document (or more exactly the first child under the root
 which is the document). The tree is made of <strong>xmlNode</strong>s, chained
 in double linked lists of siblings and with childs&lt;->parent relationship.
 An xmlNode can also carry properties (a chain of xmlAttr structures). An
 attribute may have a value which is a list of TEXT or ENTITY_REF nodes.</p>
 <p>
 Here is an example (erroneous w.r.t. the XML spec since there should be only
 one ELEMENT under the root):</p>
 <p>
 <img src="structure.gif" alt=" structure.gif "></p>
 <p>
 In the source package there is a small program (not installed by default)
 called <strong>tester</strong> which parses XML files given as argument and
 prints them back as parsed, this is useful to detect errors both in XML code
 and in the XML parser itself. It has an option <strong>--debug</strong> which
 prints the actual in-memory structure of the document, here is the result with
 the <a href="#example">example</a> given before:</p>
 <pre>DOCUMENT
 version=1.0
 standalone=true
   ELEMENT EXAMPLE
     ATTRIBUTE prop1
       TEXT
       content=gnome is great
     ATTRIBUTE prop2
       ENTITY_REF
       TEXT
       content= too
     ELEMENT head
       ELEMENT title
         TEXT
         content=Welcome to Gnome
     ELEMENT chapter
       ELEMENT title
         TEXT
         content=The Linux adventure
       ELEMENT p
         TEXT
         content=bla bla bla ...
       ELEMENT image
         ATTRIBUTE href
           TEXT
           content=linus.gif
       ELEMENT p
         TEXT
         content=...</pre>
 <p>
 This should be useful to learn the internal representation model.</p>

 <h2>The XML library interfaces</h2>
 <p>
 This section is directly intended to help programmers getting bootstrapped
 using the XML library from the C language. It doesn't intent to be extensive,
 I hope the automatically generated docs will provide the completeness
 required, but as a separated set of documents. The interfaces of the XML
 library are by principle low level, there is nearly zero abstration. Those
 interested in a higher level API should <a href="#DOM">look at DOM</a>
 (unfortunately not completed).</p>

 <h3>Invoking the parser</h3>
 <p>
 Usually, the first thing to do is to read an XML input, the parser accepts to
 parse both memory mapped documents or direct files. The functions are defined
 in "parser.h":</p>
 <dl>
 <dt><code>xmlDocPtr xmlParseMemory(char *buffer, int size);</code></dt>
 <dd><p>
 parse a zero 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 file (possibly compressed)</p>
 </dd>
 </dl>
 <p>
 This returns a pointer to the document structure (or NULL in case of
 failure).</p>
 <p>
 A couple of comments can be made, first this mean that the parser is
 memory-hungry, first to load the document in memory, second to build the tree.
 Reading a document without building the tree will be possible in the future by
 pluggin the code to the SAX interface (see SAX.c).</p>

 <h3>Building a tree from scratch</h3>
 <p>
 The other way to get an XML tree in memory is by building it. Basically there
 is a set of functions dedicated to building new elements, those are also
 described in "tree.h", here is for example the piece of code producing the
 example used before:</p>
 <pre>    xmlDocPtr doc;
     xmlNodePtr tree, subtree;

     doc = xmlNewDoc("1.0");
     doc->root = xmlNewDocNode(doc, NULL, "EXAMPLE", NULL);
     xmlSetProp(doc->root, "prop1", "gnome is great");
     xmlSetProp(doc->root, "prop2", "&amp;linux; too");
     tree = xmlNewChild(doc->root, NULL, "head", NULL);
     subtree = xmlNewChild(tree, NULL, "title", "Welcome to Gnome");
     tree = xmlNewChild(doc->root, 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>Traversing the tree</h3>
 <p>
 Basically by including "tree.h" your code has access to the internal structure
 of all the element of the tree. The names should be somewhat simple like
 <strong>parent</strong>, <strong>childs</strong>, <strong>next</strong>,
 <strong>prev</strong>, <strong>properties</strong>, etc... For example still
 with the previous example:</p>
 <pre><code>doc->root->childs->childs</code></pre>
 <p>
 points to the title element,</p>
 <pre>doc->root->childs->next->child->child</pre>
 <p>
 points to the text node containing the chapter titlle "The Linux adventure"
 and</p>
 <pre>doc->root->properties->next->val</pre>
 <p>
 points to the entity reference containing the value of "&amp;linux" at the
 beginning of the second attribute of the root element "EXAMPLE".</p>

 <h3>Modifying the tree</h3>
 <p>
 functions are provided to read and write the document content:</p>
 <dl>
 <dt><code>xmlAttrPtr xmlSetProp(xmlNodePtr node, const CHAR *name, const CHAR
 *value);</code></dt>
 <dd><p>
 This set (or change) an attribute carried by an ELEMENT node the value can be
 NULL</p>
 </dd>
 </dl>
 <dl>
 <dt><code>const CHAR *xmlGetProp(xmlNodePtr node, const CHAR
 *name);</code></dt>
 <dd><p>
 This function returns a pointer to the property content, note that no extra
 copy is made</p>
 </dd>
 </dl>
 <p>
 Two functions must be used to read an write the text associated to
 elements:</p>
 <dl>
 <dt><code>xmlNodePtr xmlStringGetNodeList(xmlDocPtr doc, const CHAR
 *value);</code></dt>
 <dd><p>
 This function takes an "external" string and convert it to one text node or
 possibly to a list of entity and text nodes. All non-predefined entity
 references like &amp;Gnome; will be stored internally as an entity node, hence
 the result of the function may not be a single node.</p>
 </dd>
 </dl>
 <dl>
 <dt><code>CHAR *xmlNodeListGetString(xmlDocPtr doc, xmlNodePtr list, int
 inLine);</code></dt>
 <dd><p>
 this is the dual function, which generate a new string containing the content
 of the text and entity nodes. Note the extra argument inLine, if set to 1
 instead of returning the &amp;Gnome; XML encoding in the string it will
 substitute it with it's value say "GNU Network Object Model Environment". Set
 it if you want to use the string for non XML usage like User Interface.</p>
 </dd>
 </dl>

 <h3>Saving a tree</h3>
 <p>
 Basically 3 options are possible:</p>
 <dl>
 <dt><code>void xmlDocDumpMemory(xmlDocPtr cur, CHAR**mem, int
 *size);</code></dt>
 <dd><p>
 returns a buffer where the document has been saved</p>
 </dd>
 </dl>
 <dl>
 <dt><code>extern void xmlDocDump(FILE *f, xmlDocPtr doc);</code></dt>
 <dd><p>
 dumps a buffer to an open file descriptor</p>
 </dd>
 </dl>
 <dl>
 <dt><code>int xmlSaveFile(const char *filename, xmlDocPtr cur);</code></dt>
 <dd><p>
 save the document ot a file. In that case the compression interface is
 triggered if turned on</p>
 </dd>
 </dl>

 <h3>Compression</h3>
 <p>
 The library handle transparently compression when doing file based accesses,
 the level of compression on saves can be tuned either globally or individually
 for one file:</p>
 <dl>
 <dt><code>int  xmlGetDocCompressMode (xmlDocPtr doc);</code></dt>
 <dd><p>
 Get the document compression ratio (0-9)</p>
 </dd>
 </dl>
 <dl>
 <dt><code>void xmlSetDocCompressMode (xmlDocPtr doc, int mode);</code></dt>
 <dd><p>
 Set the document compression ratio</p>
 </dd>
 </dl>
 <dl>
 <dt><code>int  xmlGetCompressMode(void);</code></dt>
 <dd><p>
 Get the default compression ratio</p>
 </dd>
 </dl>
 <dl>
 <dt><code>void xmlSetCompressMode(int mode);</code></dt>
 <dd><p>
 set the default compression ratio</p>
 </dd>
 </dl>

 <h2><a name="DOM">DOM Principles</a></h2>
 <p>
 <a href="http://www.w3.org/DOM/">DOM</a> stands for the <em>Document Object
 Model</em> this is an API for accessing XML or HTML structured documents.
 Native support for DOM in Gnome is on the way (module gnome-dom), and it will
 be based on gnome-xml. This will be a far cleaner interface to manipulate XML
 files within Gnome since it won't expose the internal structure. DOM defiles a
 set of IDL (or Java) interfaces allowing to traverse and manipulate a
 document. The DOM library will allow accessing and modifying "live" documents
 presents on other programs like this:</p>
 <p>
 <img src="DOM.gif" alt=" DOM.gif "></p>
 <p>
 This should help greatly doing things like modifying a gnumeric spreadsheet
 embedded in a GWP document for example.</p>
 <p>
 </p>
 </body>
 </html>
	<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"
	"http://www.w3.org/TR/REC-html40/loose.dtd">
	<html>
	<head>
	<title>The XML library for Gnome</title>
	<meta name="GENERATOR" content="amaya V1.3b">
	</head>
	<body bgcolor="#ffffff">

	<h1 align="center">The XML library for Gnome</h1>
	<p>
	This document describes the <a href="http://www.w3.org/XML/">XML</a> library
	provideed in the <a href="http://www.gnome.org/">Gnome</a> framework. XML is a
	standard to build tag based structured documents. The internal document
	repesentation is as close as possible to the <a
	href="http://www.w3.org/DOM/">DOM</a> interfaces.</p>

	<h2>xml</h2>
	<p>
	XML is a standard for markup based structured documents, here is <a
	name="example">an example</a>:</p>
	<pre><?xml version="1.0"?>
	<EXAMPLE prop1="gnome is great" prop2="&linux; too">
	<head>
	<title>Welcome to Gnome</title>
	</head>
	<chapter>
	<title>The Linux adventure</title>
	<p>bla bla bla ...</p>
	<image href="linus.gif"/>
	<p>...</p>
	</chapter>
	</EXAMPLE></pre>
	<p>
	The first line specify that it's an XML document and gives useful informations
	about it's encoding. Then the document is a text format whose structure is
	specified by tags between brackets. <strong>Each tag opened have to be
	closed</strong> XML is pedantic about this, not that for example the image
	tage has no content (just an attribute) and is closed by ending up the tag
	with <code>/></code>.</p>

	<h2>The tree output</h2>
	<p>
	The parser returns a tree built during the document analysis. The value
	returned is an <strong>xmlDocPtr</strong> (i.e. a pointer to an
	<strong>xmlDoc</strong> structure). This structure contains informations like
	the file name, the document type, and a <strong>root</strong> pointer which
	is the root of the document (or more exactly the first child under the root
	which is the document). The tree is made of <strong>xmlNode</strong>s, chained
	in double linked lists of siblings and with childs<->parent relationship.
	An xmlNode can also carry properties (a chain of xmlAttr structures). An
	attribute may have a value which is a list of TEXT or ENTITY_REF nodes.</p>
	<p>
	Here is an example (erroneous w.r.t. the XML spec since there should be only
	one ELEMENT under the root):</p>
	<p>
	<img src="structure.gif" alt=" structure.gif "></p>
	<p>
	In the source package there is a small program (not installed by default)
	called <strong>tester</strong> which parses XML files given as argument and
	prints them back as parsed, this is useful to detect errors both in XML code
	and in the XML parser itself. It has an option <strong>--debug</strong> which
	prints the actual in-memory structure of the document, here is the result with
	the <a href="#example">example</a> given before:</p>
	<pre>DOCUMENT
	version=1.0
	standalone=true
	ELEMENT EXAMPLE
	ATTRIBUTE prop1
	TEXT
	content=gnome is great
	ATTRIBUTE prop2
	ENTITY_REF
	TEXT
	content= too
	ELEMENT head
	ELEMENT title
	TEXT
	content=Welcome to Gnome
	ELEMENT chapter
	ELEMENT title
	TEXT
	content=The Linux adventure
	ELEMENT p
	TEXT
	content=bla bla bla ...
	ELEMENT image
	ATTRIBUTE href
	TEXT
	content=linus.gif
	ELEMENT p
	TEXT
	content=...</pre>
	<p>
	This should be useful to learn the internal representation model.</p>

	<h2>The XML library interfaces</h2>
	<p>
	This section is directly intended to help programmers getting bootstrapped
	using the XML library from the C language. It doesn't intent to be extensive,
	I hope the automatically generated docs will provide the completeness
	required, but as a separated set of documents. The interfaces of the XML
	library are by principle low level, there is nearly zero abstration. Those
	interested in a higher level API should <a href="#DOM">look at DOM</a>
	(unfortunately not completed).</p>

	<h3>Invoking the parser</h3>
	<p>
	Usually, the first thing to do is to read an XML input, the parser accepts to
	parse both memory mapped documents or direct files. The functions are defined
	in "parser.h":</p>
	<dl>
	<dt><code>xmlDocPtr xmlParseMemory(char *buffer, int size);</code></dt>
	<dd><p>
	parse a zero 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 file (possibly compressed)</p>
	</dd>
	</dl>
	<p>
	This returns a pointer to the document structure (or NULL in case of
	failure).</p>
	<p>
	A couple of comments can be made, first this mean that the parser is
	memory-hungry, first to load the document in memory, second to build the tree.
	Reading a document without building the tree will be possible in the future by
	pluggin the code to the SAX interface (see SAX.c).</p>

	<h3>Building a tree from scratch</h3>
	<p>
	The other way to get an XML tree in memory is by building it. Basically there
	is a set of functions dedicated to building new elements, those are also
	described in "tree.h", here is for example the piece of code producing the
	example used before:</p>
	<pre> xmlDocPtr doc;
	xmlNodePtr tree, subtree;

	doc = xmlNewDoc("1.0");
	doc->root = xmlNewDocNode(doc, NULL, "EXAMPLE", NULL);
	xmlSetProp(doc->root, "prop1", "gnome is great");
	xmlSetProp(doc->root, "prop2", "&linux; too");
	tree = xmlNewChild(doc->root, NULL, "head", NULL);
	subtree = xmlNewChild(tree, NULL, "title", "Welcome to Gnome");
	tree = xmlNewChild(doc->root, 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>Traversing the tree</h3>
	<p>
	Basically by including "tree.h" your code has access to the internal structure
	of all the element of the tree. The names should be somewhat simple like
	<strong>parent</strong>, <strong>childs</strong>, <strong>next</strong>,
	<strong>prev</strong>, <strong>properties</strong>, etc... For example still
	with the previous example:</p>
	<pre><code>doc->root->childs->childs</code></pre>
	<p>
	points to the title element,</p>
	<pre>doc->root->childs->next->child->child</pre>
	<p>
	points to the text node containing the chapter titlle "The Linux adventure"
	and</p>
	<pre>doc->root->properties->next->val</pre>
	<p>
	points to the entity reference containing the value of "&linux" at the
	beginning of the second attribute of the root element "EXAMPLE".</p>

	<h3>Modifying the tree</h3>
	<p>
	functions are provided to read and write the document content:</p>
	<dl>
	<dt><code>xmlAttrPtr xmlSetProp(xmlNodePtr node, const CHAR *name, const CHAR
	*value);</code></dt>
	<dd><p>
	This set (or change) an attribute carried by an ELEMENT node the value can be
	NULL</p>
	</dd>
	</dl>
	<dl>
	<dt><code>const CHAR *xmlGetProp(xmlNodePtr node, const CHAR
	*name);</code></dt>
	<dd><p>
	This function returns a pointer to the property content, note that no extra
	copy is made</p>
	</dd>
	</dl>
	<p>
	Two functions must be used to read an write the text associated to
	elements:</p>
	<dl>
	<dt><code>xmlNodePtr xmlStringGetNodeList(xmlDocPtr doc, const CHAR
	*value);</code></dt>
	<dd><p>
	This function takes an "external" string and convert it to one text node or
	possibly to a list of entity and text nodes. All non-predefined entity
	references like &Gnome; will be stored internally as an entity node, hence
	the result of the function may not be a single node.</p>
	</dd>
	</dl>
	<dl>
	<dt><code>CHAR *xmlNodeListGetString(xmlDocPtr doc, xmlNodePtr list, int
	inLine);</code></dt>
	<dd><p>
	this is the dual function, which generate a new string containing the content
	of the text and entity nodes. Note the extra argument inLine, if set to 1
	instead of returning the &Gnome; XML encoding in the string it will
	substitute it with it's value say "GNU Network Object Model Environment". Set
	it if you want to use the string for non XML usage like User Interface.</p>
	</dd>
	</dl>

	<h3>Saving a tree</h3>
	<p>
	Basically 3 options are possible:</p>
	<dl>
	<dt><code>void xmlDocDumpMemory(xmlDocPtr cur, CHAR**mem, int
	*size);</code></dt>
	<dd><p>
	returns a buffer where the document has been saved</p>
	</dd>
	</dl>
	<dl>
	<dt><code>extern void xmlDocDump(FILE *f, xmlDocPtr doc);</code></dt>
	<dd><p>
	dumps a buffer to an open file descriptor</p>
	</dd>
	</dl>
	<dl>
	<dt><code>int xmlSaveFile(const char *filename, xmlDocPtr cur);</code></dt>
	<dd><p>
	save the document ot a file. In that case the compression interface is
	triggered if turned on</p>
	</dd>
	</dl>

	<h3>Compression</h3>
	<p>
	The library handle transparently compression when doing file based accesses,
	the level of compression on saves can be tuned either globally or individually
	for one file:</p>
	<dl>
	<dt><code>int xmlGetDocCompressMode (xmlDocPtr doc);</code></dt>
	<dd><p>
	Get the document compression ratio (0-9)</p>
	</dd>
	</dl>
	<dl>
	<dt><code>void xmlSetDocCompressMode (xmlDocPtr doc, int mode);</code></dt>
	<dd><p>
	Set the document compression ratio</p>
	</dd>
	</dl>
	<dl>
	<dt><code>int xmlGetCompressMode(void);</code></dt>
	<dd><p>
	Get the default compression ratio</p>
	</dd>
	</dl>
	<dl>
	<dt><code>void xmlSetCompressMode(int mode);</code></dt>
	<dd><p>
	set the default compression ratio</p>
	</dd>
	</dl>

	<h2><a name="DOM">DOM Principles</a></h2>
	<p>
	<a href="http://www.w3.org/DOM/">DOM</a> stands for the <em>Document Object
	Model</em> this is an API for accessing XML or HTML structured documents.
	Native support for DOM in Gnome is on the way (module gnome-dom), and it will
	be based on gnome-xml. This will be a far cleaner interface to manipulate XML
	files within Gnome since it won't expose the internal structure. DOM defiles a
	set of IDL (or Java) interfaces allowing to traverse and manipulate a
	document. The DOM library will allow accessing and modifying "live" documents
	presents on other programs like this:</p>
	<p>
	<img src="DOM.gif" alt=" DOM.gif "></p>
	<p>
	This should help greatly doing things like modifying a gnumeric spreadsheet
	embedded in a GWP document for example.</p>
	<p>
	</p>
	</body>
	</html>