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diff --git a/docs/manual/dom.html b/docs/manual/dom.html new file mode 100644 index 0000000..e4f1579 --- /dev/null +++ b/docs/manual/dom.html @@ -0,0 +1,649 @@ +<html> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> +<title>Document object model</title> +<link rel="stylesheet" href="../pugixml.css" type="text/css"> +<meta name="generator" content="DocBook XSL Stylesheets V1.75.2"> +<link rel="home" href="../manual.html" title="pugixml 0.9"> +<link rel="up" href="../manual.html" title="pugixml 0.9"> +<link rel="prev" href="install.html" title="Installation"> +<link rel="next" href="loading.html" title="Loading document"> +</head> +<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> +<table width="100%"><tr> +<td>pugixml 0.9 manual | + <a href="../manual.html">Overview</a> | + <a href="install.html">Installation</a> | + Document: + <b>Object model</b> · <a href="loading.html">Loading</a> · <a href="access.html">Accessing</a> · <a href="modify.html">Modifying</a> · <a href="saving.html">Saving</a> | + <a href="xpath.html">XPath</a> | + <a href="apiref.html">API Reference</a> | + <a href="toc.html">Table of Contents</a> +</td> +<td width="*" align="right"><div class="spirit-nav"> +<a accesskey="p" href="install.html"><img src="../images/prev.png" alt="Prev"></a><a accesskey="u" href="../manual.html"><img src="../images/up.png" alt="Up"></a><a accesskey="h" href="../manual.html"><img src="../images/home.png" alt="Home"></a><a accesskey="n" href="loading.html"><img src="../images/next.png" alt="Next"></a> +</div></td> +</tr></table> +<hr> +<div class="section"> +<div class="titlepage"><div><div><h2 class="title" style="clear: both"> +<a name="manual.dom"></a><a class="link" href="dom.html" title="Document object model"> Document object model</a> +</h2></div></div></div> +<div class="toc"><dl> +<dt><span class="section"><a href="dom.html#manual.dom.tree"> Tree structure</a></span></dt> +<dt><span class="section"><a href="dom.html#manual.dom.cpp"> C++ interface</a></span></dt> +<dt><span class="section"><a href="dom.html#manual.dom.unicode"> Unicode interface</a></span></dt> +<dt><span class="section"><a href="dom.html#manual.dom.thread"> Thread-safety guarantees</a></span></dt> +<dt><span class="section"><a href="dom.html#manual.dom.exception"> Exception guarantees</a></span></dt> +<dt><span class="section"><a href="dom.html#manual.dom.memory"> Memory management</a></span></dt> +<dd><dl> +<dt><span class="section"><a href="dom.html#manual.dom.memory.custom"> Custom memory allocation/deallocation + functions</a></span></dt> +<dt><span class="section"><a href="dom.html#manual.dom.memory.internals"> Document memory management + internals</a></span></dt> +</dl></dd> +</dl></div> +<p> + pugixml stores XML data in DOM-like way: the entire XML document (both document + structure and element data) is stored in memory as a tree. The tree can be + loaded from character stream (file, string, C++ I/O stream), then traversed + via special API or XPath expressions. The whole tree is mutable: both node + structure and node/attribute data can be changed at any time. Finally, the + result of document transformations can be saved to a character stream (file, + C++ I/O stream or custom transport). + </p> +<div class="section"> +<div class="titlepage"><div><div><h3 class="title"> +<a name="manual.dom.tree"></a><a class="link" href="dom.html#manual.dom.tree" title="Tree structure"> Tree structure</a> +</h3></div></div></div> +<p> + The XML document is represented with a tree data structure. The root of the + tree is the document itself, which corresponds to C++ type <code class="computeroutput"><span class="identifier">xml_document</span></code>. Document has one or more + child nodes, which correspond to C++ type <code class="computeroutput"><span class="identifier">xml_node</span></code>. + Nodes have different types; depending on a type, a node can have a collection + of child nodes, a collection of attributes, which correspond to C++ type + <code class="computeroutput"><span class="identifier">xml_attribute</span></code>, and some additional + data (i.e. name). + </p> +<a name="xml_node_type"></a><p> + The tree nodes can be of one of the following types (which together form + the enumeration <code class="computeroutput"><span class="identifier">xml_node_type</span></code>): + </p> +<div class="itemizedlist"><ul class="itemizedlist" type="disc"> +<li class="listitem"> + Document node ( <a name="node_document"></a><code class="literal">node_document</code>) - this + is the root of the tree, which consists of several child nodes. This + node corresponds to <code class="computeroutput"><span class="identifier">xml_document</span></code> + class; note that <code class="computeroutput"><span class="identifier">xml_document</span></code> + is a sub-class of <code class="computeroutput"><span class="identifier">xml_node</span></code>, + so the entire node interface is also available. However, document node + is special in several ways, which will be covered below. There can be + only one document node in the tree; document node does not have any XML + representation. <br><br> + + </li> +<li class="listitem"> + Element/tag node ( <a name="node_element"></a><code class="literal">node_element</code>) - this + is the most common type of node, which represents XML elements. Element + nodes have a name, a collection of attributes and a collection of child + nodes (both of which may be empty). The attribute is a simple name/value + pair. The example XML representation of element node is as follows: + </li> +</ul></div> +<pre class="programlisting"><span class="special"><</span><span class="identifier">node</span> <span class="identifier">attr</span><span class="special">=</span><span class="string">"value"</span><span class="special">><</span><span class="identifier">child</span><span class="special">/></</span><span class="identifier">node</span><span class="special">></span> +</pre> +<div class="blockquote"><blockquote class="blockquote"><p> + There are two element nodes here; one has name <code class="computeroutput"><span class="string">"node"</span></code>, + single attribute <code class="computeroutput"><span class="string">"attr"</span></code> + and single child <code class="computeroutput"><span class="string">"child"</span></code>, + another has name <code class="computeroutput"><span class="string">"child"</span></code> + and does not have any attributes or child nodes. + </p></blockquote></div> +<div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"> + Plain character data nodes ( <a name="node_pcdata"></a><code class="literal">node_pcdata</code>) + represent plain text in XML. PCDATA nodes have a value, but do not have + name or children/attributes. Note that plain character data is not a + part of the element node but instead has its own node; for example, an + element node can have several child PCDATA nodes. The example XML representation + of text node is as follows: + </li></ul></div> +<pre class="programlisting"><span class="special"><</span><span class="identifier">node</span><span class="special">></span> <span class="identifier">text1</span> <span class="special"><</span><span class="identifier">child</span><span class="special">/></span> <span class="identifier">text2</span> <span class="special"></</span><span class="identifier">node</span><span class="special">></span> +</pre> +<div class="blockquote"><blockquote class="blockquote"><p> + Here <code class="computeroutput"><span class="string">"node"</span></code> element + has three children, two of which are PCDATA nodes with values <code class="computeroutput"><span class="string">"text1"</span></code> and <code class="computeroutput"><span class="string">"text2"</span></code>. + </p></blockquote></div> +<div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"> + Character data nodes ( <a name="node_cdata"></a><code class="literal">node_cdata</code>) represent + text in XML that is quoted in a special way. CDATA nodes do not differ + from PCDATA nodes except in XML representation - the above text example + looks like this with CDATA: + </li></ul></div> +<pre class="programlisting"><span class="special"><</span><span class="identifier">node</span><span class="special">></span> <span class="special"><![</span><span class="identifier">CDATA</span><span class="special">[[</span><span class="identifier">text1</span><span class="special">]]></span> <span class="special"><</span><span class="identifier">child</span><span class="special">/></span> <span class="special"><![</span><span class="identifier">CDATA</span><span class="special">[[</span><span class="identifier">text2</span><span class="special">]]></span> <span class="special"></</span><span class="identifier">node</span><span class="special">></span> +</pre> +<div class="blockquote"><blockquote class="blockquote"><p> + CDATA nodes make it easy to include non-escaped <, & and > characters + in plain text. CDATA value can not contain the character sequence ]]>, + since it is used to determine the end of node contents. + </p></blockquote></div> +<div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"> + Comment nodes ( <a name="node_comment"></a><code class="literal">node_comment</code>) represent + comments in XML. Comment nodes have a value, but do not have name or + children/attributes. The example XML representation of comment node is + as follows: + </li></ul></div> +<pre class="programlisting"><span class="special"><!--</span> <span class="identifier">comment</span> <span class="identifier">text</span> <span class="special">--></span> +</pre> +<div class="blockquote"><blockquote class="blockquote"><p> + Here the comment node has value <code class="computeroutput"><span class="string">"comment + text"</span></code>. By default comment nodes are treated as non-essential + part of XML markup and are not loaded during XML parsing. You can override + this behavior by adding <code class="computeroutput"><span class="identifier">parse_comments</span></code> + flag. + </p></blockquote></div> +<div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"> + Processing instruction node ( <a name="node_pi"></a><code class="literal">node_pi</code>) represent + processing instructions (PI) in XML. PI nodes have a name and an optional + value, but do not have children/attributes. The example XML representation + of PI node is as follows: + </li></ul></div> +<pre class="programlisting"><span class="special"><?</span><span class="identifier">name</span> <span class="identifier">value</span><span class="special">?></span> +</pre> +<div class="blockquote"><blockquote class="blockquote"><p> + Here the name (also called PI target) is <code class="computeroutput"><span class="string">"name"</span></code>, + and the value is <code class="computeroutput"><span class="string">"value"</span></code>. + By default PI nodes are treated as non-essential part of XML markup and + are not loaded during XML parsing. You can override this behavior by adding + <code class="computeroutput"><span class="identifier">parse_pi</span></code> flag. + </p></blockquote></div> +<div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"> + Declaration node ( <a name="node_declaration"></a><code class="literal">node_declaration</code>) + represents document declarations in XML. Declaration nodes have a name + (<code class="computeroutput"><span class="string">"xml"</span></code>) and an + optional collection of attributes, but does not have value or children. + There can be only one declaration node in a document; moreover, it should + be the topmost node (its parent should be the document). The example + XML representation of declaration node is as follows: + </li></ul></div> +<pre class="programlisting"><span class="special"><?</span><span class="identifier">xml</span> <span class="identifier">version</span><span class="special">=</span><span class="string">"1.0"</span><span class="special">?></span> +</pre> +<div class="blockquote"><blockquote class="blockquote"><p> + Here the node has name <code class="computeroutput"><span class="string">"xml"</span></code> + and a single attribute with name <code class="computeroutput"><span class="string">"version"</span></code> + and value <code class="computeroutput"><span class="string">"1.0"</span></code>. + By default declaration nodes are treated as non-essential part of XML markup + and are not loaded during XML parsing. You can override this behavior by + adding <code class="computeroutput"><span class="identifier">parse_declaration</span></code> + flag. Also, by default a dummy declaration is output when XML document + is saved unless there is already a declaration in the document; you can + disable this by adding <code class="computeroutput"><span class="identifier">format_no_declaration</span></code> + flag. + </p></blockquote></div> +<p> + Finally, here is a complete example of XML document and the corresponding + tree representation (<a href="../samples/tree.xml" target="_top">samples/tree.xml</a>): + </p> +<div class="informaltable"><table class="table"> +<colgroup> +<col> +<col> +</colgroup> +<tbody><tr> +<td> + <p> + +</p> +<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="special"><?</span><span class="identifier">xml</span> <span class="identifier">version</span><span class="special">=</span><span class="string">"1.0"</span><span class="special">?></span> +<span class="special"><</span><span class="identifier">mesh</span> <span class="identifier">name</span><span class="special">=</span><span class="string">"mesh_root"</span><span class="special">></span> + <span class="special"><!--</span> <span class="identifier">here</span> <span class="identifier">is</span> <span class="identifier">a</span> <span class="identifier">mesh</span> <span class="identifier">node</span> <span class="special">--></span> + <span class="identifier">some</span> <span class="identifier">text</span> + <span class="special"><![</span><span class="identifier">CDATA</span><span class="special">[</span><span class="identifier">someothertext</span><span class="special">]]></span> + <span class="identifier">some</span> <span class="identifier">more</span> <span class="identifier">text</span> + <span class="special"><</span><span class="identifier">node</span> <span class="identifier">attr1</span><span class="special">=</span><span class="string">"value1"</span> <span class="identifier">attr2</span><span class="special">=</span><span class="string">"value2"</span> <span class="special">/></span> + <span class="special"><</span><span class="identifier">node</span> <span class="identifier">attr1</span><span class="special">=</span><span class="string">"value2"</span><span class="special">></span> + <span class="special"><</span><span class="identifier">innernode</span><span class="special">/></span> + <span class="special"></</span><span class="identifier">node</span><span class="special">></span> +<span class="special"></</span><span class="identifier">mesh</span><span class="special">></span> +<span class="special"><?</span><span class="identifier">include</span> <span class="identifier">somedata</span><span class="special">?></span> +</pre> +<p> + </p> + </td> +<td> + <p> + <a href="../images/dom_tree.png" target="_top"><span class="inlinemediaobject"><img src="../images/dom_tree_thumb.png" alt="dom_tree_thumb"></span></a> + </p> + </td> +</tr></tbody> +</table></div> +</div> +<div class="section"> +<div class="titlepage"><div><div><h3 class="title"> +<a name="manual.dom.cpp"></a><a class="link" href="dom.html#manual.dom.cpp" title="C++ interface"> C++ interface</a> +</h3></div></div></div> +<div class="note"><table border="0" summary="Note"> +<tr> +<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../images/note.png"></td> +<th align="left">Note</th> +</tr> +<tr><td align="left" valign="top"><p> + All pugixml classes and functions are located in <code class="computeroutput"><span class="identifier">pugi</span></code> + namespace; you have to either use explicit name qualification (i.e. <code class="computeroutput"><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span></code>), or to gain access to relevant + symbols via <code class="computeroutput"><span class="keyword">using</span></code> directive + (i.e. <code class="computeroutput"><span class="keyword">using</span> <span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span><span class="special">;</span></code> or <code class="computeroutput"><span class="keyword">using</span> + <span class="keyword">namespace</span> <span class="identifier">pugi</span><span class="special">;</span></code>). The namespace will be omitted from declarations + in this documentation hereafter; all code examples will use fully-qualified + names. + </p></td></tr> +</table></div> +<p> + Despite the fact that there are several node types, there are only three + C++ types representing the tree (<code class="computeroutput"><span class="identifier">xml_document</span></code>, + <code class="computeroutput"><span class="identifier">xml_node</span></code>, <code class="computeroutput"><span class="identifier">xml_attribute</span></code>); + some operations on <code class="computeroutput"><span class="identifier">xml_node</span></code> + are only valid for certain node types. They are described below. + </p> +<a name="xml_document"></a><p> + <code class="computeroutput"><span class="identifier">xml_document</span></code> is the owner + of the entire document structure; it is a non-copyable class. The interface + of <code class="computeroutput"><span class="identifier">xml_document</span></code> consists + of loading functions (see <a class="xref" href="loading.html" title="Loading document"> Loading document</a>), saving functions (see <a class="xref" href="saving.html" title="Saving document"> Saving document</a>) + and the interface of <code class="computeroutput"><span class="identifier">xml_node</span></code>, + which allows for document inspection and/or modification. Note that while + <code class="computeroutput"><span class="identifier">xml_document</span></code> is a sub-class + of <code class="computeroutput"><span class="identifier">xml_node</span></code>, <code class="computeroutput"><span class="identifier">xml_node</span></code> is not a polymorphic type; the + inheritance is only used to simplify usage. + </p> +<a name="xml_document::ctor"></a><a name="xml_document::dtor"></a><p> + Default constructor of <code class="computeroutput"><span class="identifier">xml_document</span></code> + initializes the document to the tree with only a root node (document node). + You can then populate it with data using either tree modification functions + or loading functions; all loading functions destroy the previous tree with + all occupied memory, which puts existing nodes/attributes from this document + to invalid state. Destructor of <code class="computeroutput"><span class="identifier">xml_document</span></code> + also destroys the tree, thus the lifetime of the document object should exceed + the lifetimes of any node/attribute handles that point to the tree. + </p> +<div class="caution"><table border="0" summary="Caution"> +<tr> +<td rowspan="2" align="center" valign="top" width="25"><img alt="[Caution]" src="../images/caution.png"></td> +<th align="left">Caution</th> +</tr> +<tr><td align="left" valign="top"><p> + While technically node/attribute handles can be alive when the tree they're + referring to is destroyed, calling any member function of these handles + results in undefined behavior. Thus it is recommended to make sure that + the document is destroyed only after all references to its nodes/attributes + are destroyed. + </p></td></tr> +</table></div> +<a name="xml_node"></a><a name="xml_node::type"></a><p> + <code class="computeroutput"><span class="identifier">xml_node</span></code> is the handle to + document node; it can point to any node in the document, including document + itself. There is a common interface for nodes of all types; the actual node + type can be queried via <code class="computeroutput"><span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">type</span><span class="special">()</span></code> method. Note that <code class="computeroutput"><span class="identifier">xml_node</span></code> + is only a handle to the actual node, not the node itself - you can have several + <code class="computeroutput"><span class="identifier">xml_node</span></code> handles pointing + to the same underlying object. Destroying <code class="computeroutput"><span class="identifier">xml_node</span></code> + handle does not destroy the node and does not remove it from the tree. The + size of <code class="computeroutput"><span class="identifier">xml_node</span></code> is equal + to that of a pointer, so it is nothing more than a lightweight wrapper around + pointer; you can safely pass or return <code class="computeroutput"><span class="identifier">xml_node</span></code> + objects by value without additional overhead. + </p> +<a name="node_null"></a><p> + There is a special value of <code class="computeroutput"><span class="identifier">xml_node</span></code> + type, known as null node or empty node (such nodes have type <code class="computeroutput"><span class="identifier">node_null</span></code>). It does not correspond to any + node in any document, and thus resembles null pointer. However, all operations + are defined on empty nodes; generally the operations don't do anything and + return empty nodes/attributes or empty strings as their result (see documentation + for specific functions for more detailed information). This is useful for + chaining calls; i.e. you can get the grandparent of a node like so: <code class="computeroutput"><span class="identifier">node</span><span class="special">.</span><span class="identifier">parent</span><span class="special">().</span><span class="identifier">parent</span><span class="special">()</span></code>; if a node is a null node or it does not + have a parent, the first <code class="computeroutput"><span class="identifier">parent</span><span class="special">()</span></code> call returns null node; the second <code class="computeroutput"><span class="identifier">parent</span><span class="special">()</span></code> + call then also returns null node, so you don't have to check for errors twice. + </p> +<a name="xml_attribute"></a><p> + <code class="computeroutput"><span class="identifier">xml_attribute</span></code> is the handle + to an XML attribute; it has the same semantics as <code class="computeroutput"><span class="identifier">xml_node</span></code>, + i.e. there can be several <code class="computeroutput"><span class="identifier">xml_attribute</span></code> + handles pointing to the same underlying object, there is a special null attribute + value, which propagates to function results. + </p> +<a name="xml_attribute::ctor"></a><a name="xml_node::ctor"></a><p> + Both <code class="computeroutput"><span class="identifier">xml_node</span></code> and <code class="computeroutput"><span class="identifier">xml_attribute</span></code> have the default constructor + which initializes them to null objects. + </p> +<a name="xml_attribute::comparison"></a><a name="xml_node::comparison"></a><p> + <code class="computeroutput"><span class="identifier">xml_node</span></code> and <code class="computeroutput"><span class="identifier">xml_attribute</span></code> try to behave like pointers, + that is, they can be compared with other objects of the same type, making + it possible to use them as keys of associative containers. All handles to + the same underlying object are equal, and any two handles to different underlying + objects are not equal. Null handles only compare as equal to themselves. + The result of relational comparison can not be reliably determined from the + order of nodes in file or other ways. Do not use relational comparison operators + except for search optimization (i.e. associative container keys). + </p> +<a name="xml_attribute::unspecified_bool_type"></a><a name="xml_node::unspecified_bool_type"></a><a name="xml_attribute::empty"></a><a name="xml_node::empty"></a><p> + Additionally handles they can be implicitly cast to boolean-like objects, + so that you can test if the node/attribute is empty by just doing <code class="computeroutput"><span class="keyword">if</span> <span class="special">(</span><span class="identifier">node</span><span class="special">)</span> <span class="special">{</span> <span class="special">...</span> + <span class="special">}</span></code> or <code class="computeroutput"><span class="keyword">if</span> + <span class="special">(!</span><span class="identifier">node</span><span class="special">)</span> <span class="special">{</span> <span class="special">...</span> + <span class="special">}</span> <span class="keyword">else</span> <span class="special">{</span> <span class="special">...</span> <span class="special">}</span></code>. + Alternatively you can check if a given <code class="computeroutput"><span class="identifier">xml_node</span></code>/<code class="computeroutput"><span class="identifier">xml_attribute</span></code> handle is null by calling + the following methods: + </p> +<pre class="programlisting"><span class="keyword">bool</span> <span class="identifier">xml_attribute</span><span class="special">::</span><span class="identifier">empty</span><span class="special">()</span> <span class="keyword">const</span><span class="special">;</span> +<span class="keyword">bool</span> <span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">empty</span><span class="special">()</span> <span class="keyword">const</span><span class="special">;</span> +</pre> +<p> + Nodes and attributes do not exist outside of document tree, so you can't + create them without adding them to some document. Once underlying node/attribute + objects are destroyed, the handles to those objects become invalid. While + this means that destruction of the entire tree invalidates all node/attribute + handles, it also means that destroying a subtree (by calling <code class="computeroutput"><span class="identifier">remove_child</span></code>) or removing an attribute + invalidates the corresponding handles. There is no way to check handle validity; + you have to ensure correctness through external mechanisms. + </p> +</div> +<div class="section"> +<div class="titlepage"><div><div><h3 class="title"> +<a name="manual.dom.unicode"></a><a class="link" href="dom.html#manual.dom.unicode" title="Unicode interface"> Unicode interface</a> +</h3></div></div></div> +<p> + There are two choices of interface and internal representation when configuring + pugixml: you can either choose the UTF-8 (also called char) interface or + UTF-16/32 (also called wchar_t) one. The choice is controlled via <code class="computeroutput"><span class="identifier">PUGIXML_WCHAR_MODE</span></code> define; you can set + it via <code class="filename">pugiconfig.hpp</code> or via preprocessor options, as discussed in <a class="xref" href="install.html#manual.install.building.config" title="Additional configuration options"> Additional configuration + options</a>. + If this define is set, the wchar_t interface is used; otherwise (by default) + the char interface is used. The exact wide character encoding is assumed + to be either UTF-16 or UTF-32 and is determined based on size of <code class="computeroutput"><span class="keyword">wchar_t</span></code> type. + </p> +<div class="note"><table border="0" summary="Note"> +<tr> +<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../images/note.png"></td> +<th align="left">Note</th> +</tr> +<tr><td align="left" valign="top"><p> + If size of <code class="computeroutput"><span class="keyword">wchar_t</span></code> is 2, pugixml + assumes UTF-16 encoding instead of UCS-2, which means that some characters + are represented as two code points. + </p></td></tr> +</table></div> +<p> + All tree functions that work with strings work with either C-style null terminated + strings or STL strings of the selected character type. For example, node + name accessors look like this in char mode: + </p> +<pre class="programlisting"><span class="keyword">const</span> <span class="keyword">char</span><span class="special">*</span> <span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">name</span><span class="special">()</span> <span class="keyword">const</span><span class="special">;</span> +<span class="keyword">bool</span> <span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">set_name</span><span class="special">(</span><span class="keyword">const</span> <span class="keyword">char</span><span class="special">*</span> <span class="identifier">value</span><span class="special">);</span> +</pre> +<p> + and like this in wchar_t mode: + </p> +<pre class="programlisting"><span class="keyword">const</span> <span class="keyword">wchar_t</span><span class="special">*</span> <span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">name</span><span class="special">()</span> <span class="keyword">const</span><span class="special">;</span> +<span class="keyword">bool</span> <span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">set_name</span><span class="special">(</span><span class="keyword">const</span> <span class="keyword">wchar_t</span><span class="special">*</span> <span class="identifier">value</span><span class="special">);</span> +</pre> +<a name="char_t"></a><a name="string_t"></a><p> + There is a special type, <code class="computeroutput"><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">char_t</span></code>, + that is defined as the character type and depends on the library configuration; + it will be also used in the documentation hereafter. There is also a type + <code class="computeroutput"><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">string_t</span></code>, which is defined as the STL string + of the character type; it corresponds to <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span></code> + in char mode and to <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">wstring</span></code> in wchar_t mode. + </p> +<p> + In addition to the interface, the internal implementation changes to store + XML data as <code class="computeroutput"><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">char_t</span></code>; this means that these two modes + have different memory usage characteristics. The conversion to <code class="computeroutput"><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">char_t</span></code> upon document loading and from + <code class="computeroutput"><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">char_t</span></code> upon document saving happen automatically, + which also carries minor performance penalty. The general advice however + is to select the character mode based on usage scenario, i.e. if UTF-8 is + inconvenient to process and most of your XML data is localized, wchar_t mode + is probably a better choice. + </p> +<a name="as_utf8"></a><a name="as_wide"></a><p> + There are cases when you'll have to convert string data between UTF-8 and + wchar_t encodings; the following helper functions are provided for such purposes: + </p> +<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">as_utf8</span><span class="special">(</span><span class="keyword">const</span> <span class="keyword">wchar_t</span><span class="special">*</span> <span class="identifier">str</span><span class="special">);</span> +<span class="identifier">std</span><span class="special">::</span><span class="identifier">wstring</span> <span class="identifier">as_wide</span><span class="special">(</span><span class="keyword">const</span> <span class="keyword">char</span><span class="special">*</span> <span class="identifier">str</span><span class="special">);</span> +</pre> +<p> + Both functions accept null-terminated string as an argument <code class="computeroutput"><span class="identifier">str</span></code>, and return the converted string. + <code class="computeroutput"><span class="identifier">as_utf8</span></code> performs conversion + from UTF-16/32 to UTF-8; <code class="computeroutput"><span class="identifier">as_wide</span></code> + performs conversion from UTF-8 to UTF-16/32. Invalid UTF sequences are silently + discarded upon conversion. <code class="computeroutput"><span class="identifier">str</span></code> + has to be a valid string; passing null pointer results in undefined behavior. + </p> +<div class="note"><table border="0" summary="Note"> +<tr> +<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../images/note.png"></td> +<th align="left">Note</th> +</tr> +<tr><td align="left" valign="top"> +<p> + Most examples in this documentation assume char interface and therefore + will not compile with <code class="computeroutput"><span class="identifier">PUGIXML_WCHAR_MODE</span></code>. + This is to simplify the documentation; usually the only changes you'll + have to make is to pass <code class="computeroutput"><span class="keyword">wchar_t</span></code> + string literals, i.e. instead of + </p> +<p> + <code class="computeroutput"><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span> <span class="identifier">node</span> + <span class="special">=</span> <span class="identifier">doc</span><span class="special">.</span><span class="identifier">child</span><span class="special">(</span><span class="string">"bookstore"</span><span class="special">).</span><span class="identifier">find_child_by_attribute</span><span class="special">(</span><span class="string">"book"</span><span class="special">,</span> <span class="string">"id"</span><span class="special">,</span> <span class="string">"12345"</span><span class="special">);</span></code> + </p> +<p> + you'll have to do + </p> +<p> + <code class="computeroutput"><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span> <span class="identifier">node</span> + <span class="special">=</span> <span class="identifier">doc</span><span class="special">.</span><span class="identifier">child</span><span class="special">(</span><span class="identifier">L</span><span class="string">"bookstore"</span><span class="special">).</span><span class="identifier">find_child_by_attribute</span><span class="special">(</span><span class="identifier">L</span><span class="string">"book"</span><span class="special">,</span> <span class="identifier">L</span><span class="string">"id"</span><span class="special">,</span> <span class="identifier">L</span><span class="string">"12345"</span><span class="special">);</span></code> + </p> +</td></tr> +</table></div> +</div> +<div class="section"> +<div class="titlepage"><div><div><h3 class="title"> +<a name="manual.dom.thread"></a><a class="link" href="dom.html#manual.dom.thread" title="Thread-safety guarantees"> Thread-safety guarantees</a> +</h3></div></div></div> +<p> + Almost all functions in pugixml have the following thread-safety guarantees: + </p> +<div class="itemizedlist"><ul class="itemizedlist" type="disc"> +<li class="listitem"> + it is safe to call free functions from multiple threads + </li> +<li class="listitem"> + it is safe to perform concurrent read-only accesses to the same tree + (all constant member functions do not modify the tree) + </li> +<li class="listitem"> + it is safe to perform concurrent read/write accesses, if there is only + one read or write access to the single tree at a time + </li> +</ul></div> +<p> + Concurrent modification and traversing of a single tree requires synchronization, + for example via reader-writer lock. Modification includes altering document + structure and altering individual node/attribute data, i.e. changing names/values. + </p> +<p> + The only exception is <code class="computeroutput"><span class="identifier">set_memory_management_functions</span></code>; + it modifies global variables and as such is not thread-safe. Its usage policy + has more restrictions, see <a class="xref" href="dom.html#manual.dom.memory.custom" title="Custom memory allocation/deallocation functions"> Custom memory allocation/deallocation + functions</a>. + </p> +</div> +<div class="section"> +<div class="titlepage"><div><div><h3 class="title"> +<a name="manual.dom.exception"></a><a class="link" href="dom.html#manual.dom.exception" title="Exception guarantees"> Exception guarantees</a> +</h3></div></div></div> +<p> + With the exception of XPath, pugixml itself does not throw any exceptions. + Additionally, most pugixml functions have a no-throw exception guarantee. + </p> +<p> + This is not applicable to functions that operate on STL strings or IOstreams; + such functions have either strong guarantee (functions that operate on strings) + or basic guarantee (functions that operate on streams). Also functions that + call user-defined callbacks (i.e. <code class="computeroutput"><span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">traverse</span></code> + or <code class="computeroutput"><span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">find_node</span></code>) do not provide any exception + guarantees beyond the ones provided by callback. + </p> +<p> + XPath functions may throw <code class="computeroutput"><span class="identifier">xpath_exception</span></code> + on parsing error; also, XPath implementation uses STL, and thus may throw + i.e. <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">bad_alloc</span></code> in low memory conditions. Still, + XPath functions provide strong exception guarantee. + </p> +</div> +<div class="section"> +<div class="titlepage"><div><div><h3 class="title"> +<a name="manual.dom.memory"></a><a class="link" href="dom.html#manual.dom.memory" title="Memory management"> Memory management</a> +</h3></div></div></div> +<p> + pugixml requests the memory needed for document storage in big chunks, and + allocates document data inside those chunks. This section discusses replacing + functions used for chunk allocation and internal memory management implementation. + </p> +<div class="section"> +<div class="titlepage"><div><div><h4 class="title"> +<a name="manual.dom.memory.custom"></a><a class="link" href="dom.html#manual.dom.memory.custom" title="Custom memory allocation/deallocation functions"> Custom memory allocation/deallocation + functions</a> +</h4></div></div></div> +<a name="allocation_function"></a><a name="deallocation_function"></a><p> + All memory for tree structure/data is allocated via globally specified + functions, which default to malloc/free. You can set your own allocation + functions with set_memory_management functions. The function interfaces + are the same as that of malloc/free: + </p> +<pre class="programlisting"><span class="keyword">typedef</span> <span class="keyword">void</span><span class="special">*</span> <span class="special">(*</span><span class="identifier">allocation_function</span><span class="special">)(</span><span class="identifier">size_t</span> <span class="identifier">size</span><span class="special">);</span> +<span class="keyword">typedef</span> <span class="keyword">void</span> <span class="special">(*</span><span class="identifier">deallocation_function</span><span class="special">)(</span><span class="keyword">void</span><span class="special">*</span> <span class="identifier">ptr</span><span class="special">);</span> +</pre> +<a name="set_memory_management_functions"></a><a name="get_memory_allocation_function"></a><a name="get_memory_deallocation_function"></a><p> + You can use the following accessor functions to change or get current memory + management functions: + </p> +<pre class="programlisting"><span class="keyword">void</span> <span class="identifier">set_memory_management_functions</span><span class="special">(</span><span class="identifier">allocation_function</span> <span class="identifier">allocate</span><span class="special">,</span> <span class="identifier">deallocation_function</span> <span class="identifier">deallocate</span><span class="special">);</span> +<span class="identifier">allocation_function</span> <span class="identifier">get_memory_allocation_function</span><span class="special">();</span> +<span class="identifier">deallocation_function</span> <span class="identifier">get_memory_deallocation_function</span><span class="special">();</span> +</pre> +<p> + Allocation function is called with the size (in bytes) as an argument and + should return a pointer to memory block with alignment that is suitable + for pointer storage and size that is greater or equal to the requested + one. If the allocation fails, the function has to return null pointer (throwing + an exception from allocation function results in undefined behavior). Deallocation + function is called with the pointer that was returned by the previous call + or with a null pointer; null pointer deallocation should be handled as + a no-op. If memory management functions are not thread-safe, library thread + safety is not guaranteed. + </p> +<p> + This is a simple example of custom memory management (<a href="../samples/custom_memory_management.cpp" target="_top">samples/custom_memory_management.cpp</a>): + </p> +<p> + +</p> +<pre class="programlisting"><span class="keyword">void</span><span class="special">*</span> <span class="identifier">custom_allocate</span><span class="special">(</span><span class="identifier">size_t</span> <span class="identifier">size</span><span class="special">)</span> +<span class="special">{</span> + <span class="keyword">return</span> <span class="keyword">new</span> <span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">nothrow</span><span class="special">)</span> <span class="keyword">char</span><span class="special">[</span><span class="identifier">size</span><span class="special">];</span> +<span class="special">}</span> + +<span class="keyword">void</span> <span class="identifier">custom_deallocate</span><span class="special">(</span><span class="keyword">void</span><span class="special">*</span> <span class="identifier">ptr</span><span class="special">)</span> +<span class="special">{</span> + <span class="keyword">delete</span><span class="special">[]</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="keyword">char</span><span class="special">*>(</span><span class="identifier">ptr</span><span class="special">);</span> +<span class="special">}</span> +</pre> +<p> + </p> +<p> + +</p> +<pre class="programlisting"><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">set_memory_management_functions</span><span class="special">(</span><span class="identifier">custom_allocate</span><span class="special">,</span> <span class="identifier">custom_deallocate</span><span class="special">);</span> +</pre> +<p> + </p> +<p> + When setting new memory management functions, care must be taken to make + sure that there are no live pugixml objects. Otherwise when the objects + are destroyed, the new deallocation function will be called with the memory + obtained by the old allocation function, resulting in undefined behavior. + </p> +<div class="note"><table border="0" summary="Note"> +<tr> +<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../images/note.png"></td> +<th align="left">Note</th> +</tr> +<tr><td align="left" valign="top"><p> + Currently memory for XPath objects is allocated using default operators + new/delete; this will change in the next version. + </p></td></tr> +</table></div> +</div> +<div class="section"> +<div class="titlepage"><div><div><h4 class="title"> +<a name="manual.dom.memory.internals"></a><a class="link" href="dom.html#manual.dom.memory.internals" title="Document memory management internals"> Document memory management + internals</a> +</h4></div></div></div> +<p> + Constructing a document object using the default constructor does not result + in any allocations; document node is stored inside the <code class="computeroutput"><span class="identifier">xml_document</span></code> + object. + </p> +<p> + When the document is loaded from file/buffer, unless an inplace loading + function is used (see <a class="xref" href="loading.html#manual.loading.memory" title="Loading document from memory"> Loading document from memory</a>), a complete copy of character + stream is made; all names/values of nodes and attributes are allocated + in this buffer. This buffer is allocated via a single large allocation + and is only freed when document memory is reclaimed (i.e. if the <code class="computeroutput"><span class="identifier">xml_document</span></code> object is destroyed or if + another document is loaded in the same object). Also when loading from + file or stream, an additional large allocation may be performed if encoding + conversion is required; a temporary buffer is allocated, and it is freed + before load function returns. + </p> +<p> + All additional memory, such as memory for document structure (node/attribute + objects) and memory for node/attribute names/values is allocated in pages + on the order of 32 kilobytes; actual objects are allocated inside the pages + using a memory management scheme optimized for fast allocation/deallocation + of many small objects. Because of the scheme specifics, the pages are only + destroyed if all objects inside them are destroyed; also, generally destroying + an object does not mean that subsequent object creation will reuse the + same memory. This means that it is possible to devise a usage scheme which + will lead to higher memory usage than expected; one example is adding a + lot of nodes, and them removing all even numbered ones; not a single page + is reclaimed in the process. However this is an example specifically crafted + to produce unsatisfying behavior; in all practical usage scenarios the + memory consumption is less than that of a general-purpose allocator because + allocation meta-data is very small in size. + </p> +</div> +</div> +</div> +<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> +<td align="left"></td> +<td align="right"><div class="copyright-footer">Copyright © 2010 Arseny Kapoulkine<p> + Distributed under the MIT License + </p> +</div></td> +</tr></table> +<hr> +<table width="100%"><tr> +<td>pugixml 0.9 manual | + <a href="../manual.html">Overview</a> | + <a href="install.html">Installation</a> | + Document: + <b>Object model</b> · <a href="loading.html">Loading</a> · <a href="access.html">Accessing</a> · <a href="modify.html">Modifying</a> · <a href="saving.html">Saving</a> | + <a href="xpath.html">XPath</a> | + <a href="apiref.html">API Reference</a> | + <a href="toc.html">Table of Contents</a> +</td> +<td width="*" align="right"><div class="spirit-nav"> +<a accesskey="p" href="install.html"><img src="../images/prev.png" alt="Prev"></a><a accesskey="u" href="../manual.html"><img src="../images/up.png" alt="Up"></a><a accesskey="h" href="../manual.html"><img src="../images/home.png" alt="Home"></a><a accesskey="n" href="loading.html"><img src="../images/next.png" alt="Next"></a> +</div></td> +</tr></table> +</body> +</html> |