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| author | Arseny Kapoulkine <arseny.kapoulkine@gmail.com> | 2015-04-10 22:26:57 -0700 |
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| committer | Arseny Kapoulkine <arseny.kapoulkine@gmail.com> | 2015-04-10 22:26:57 -0700 |
| commit | e90d2ac8ba44fbcf4d5702643f708f2c86bde42e (patch) | |
| tree | a52fe8e4efee8176da169998c203c1a93f6a6ff1 /docs/manual/dom.html | |
| parent | 6457f0941204a79ec5ba359a12aa00bf06f0e621 (diff) | |
| parent | 405fefc8777c55900a4e44561b545a9abb5276ba (diff) | |
Merge branch 'master' into compact
Diffstat (limited to 'docs/manual/dom.html')
| -rw-r--r-- | docs/manual/dom.html | 732 |
1 files changed, 0 insertions, 732 deletions
diff --git a/docs/manual/dom.html b/docs/manual/dom.html deleted file mode 100644 index 3d7cd29..0000000 --- a/docs/manual/dom.html +++ /dev/null @@ -1,732 +0,0 @@ -<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 V1.78.1"> -<link rel="home" href="../manual.html" title="pugixml 1.5"> -<link rel="up" href="../manual.html" title="pugixml 1.5"> -<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> -<a href="http://pugixml.org/">pugixml 1.5</a> 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 class="toc"> -<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.tuning"> Memory consumption tuning</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 a character stream (file, string, C++ I/O stream), then traversed - with the 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 <a class="link" href="dom.html#xml_document">xml_document</a>. - Document has one or more child nodes, which correspond to C++ type <a class="link" href="dom.html#xml_node">xml_node</a>. 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 <a class="link" href="dom.html#xml_attribute">xml_attribute</a>, - 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" style="list-style-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 <a class="link" href="dom.html#xml_document">xml_document</a> - class; note that <a class="link" href="dom.html#xml_document">xml_document</a> is - a sub-class of <a class="link" href="dom.html#xml_node">xml_node</a>, so the entire - node interface is also available. However, document node is special in - several ways, which are 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 nodes 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" style="list-style-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 - a name or children/attributes. Note that <span class="bold"><strong>plain - character data is not a part of the element node but instead has its - own node</strong></span>; an element node can have several child PCDATA nodes. - The example XML representation of text nodes 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" style="list-style-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" style="list-style-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 a name or - children/attributes. The example XML representation of a 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 with <a class="link" href="loading.html#parse_comments">parse_comments</a> - flag. - </p></blockquote></div> -<div class="itemizedlist"><ul class="itemizedlist" style="list-style-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 a 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 with - <a class="link" href="loading.html#parse_pi">parse_pi</a> flag. - </p></blockquote></div> -<div class="itemizedlist"><ul class="itemizedlist" style="list-style-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 do 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 a 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 with - <a class="link" href="loading.html#parse_declaration">parse_declaration</a> 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 with - <a class="link" href="saving.html#format_no_declaration">format_no_declaration</a> flag. - </p></blockquote></div> -<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> - Document type declaration node (<a name="node_doctype"></a><code class="literal">node_doctype</code>) - represents document type declarations in XML. Document type declaration - nodes have a value, which corresponds to the entire document type contents; - no additional nodes are created for inner elements like <code class="computeroutput"><span class="special"><!</span><span class="identifier">ENTITY</span><span class="special">></span></code>. There can be only one document type - declaration node in a document; moreover, it should be the topmost node - (its parent should be the document). The example XML representation of - a document type declaration node is as follows: - </li></ul></div> -<pre class="programlisting"><span class="special"><!</span><span class="identifier">DOCTYPE</span> <span class="identifier">greeting</span> <span class="special">[</span> <span class="special"><!</span><span class="identifier">ELEMENT</span> <span class="identifier">greeting</span> <span class="special">(</span><span class="preprocessor">#PCDATA</span><span class="special">)></span> <span class="special">]></span> -</pre> -<div class="blockquote"><blockquote class="blockquote"><p> - Here the node has value <code class="computeroutput"><span class="string">"greeting [ <!ELEMENT - greeting (#PCDATA)> ]"</span></code>. By default document type - declaration nodes are treated as non-essential part of XML markup and are - not loaded during XML parsing. You can override this behavior with <a class="link" href="loading.html#parse_doctype">parse_doctype</a> 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 the <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 all - 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++ classes 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. The classes are described below. - </p> -<a name="xml_document"></a><a name="xml_document::document_element"></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 entire 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 present only to simplify usage. Alternatively you can use - the <code class="computeroutput"><span class="identifier">document_element</span></code> function - to get the element node that's the immediate child of the document. - </p> -<a name="xml_document::ctor"></a><a name="xml_document::dtor"></a><a name="xml_document::reset"></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 node/attribute handles for this - document to invalid state. If you want to destroy the previous tree, you - can use the <code class="computeroutput"><span class="identifier">xml_document</span><span class="special">::</span><span class="identifier">reset</span></code> - function; it destroys the tree and replaces it with either an empty one or - a copy of the specified document. 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 for 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 the document - node itself. There is a common interface for nodes of all types; the actual - <a class="link" href="dom.html#xml_node_type">node type</a> can be queried via the <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 - a 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, which makes error handling easier. - </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 and 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 in 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 in any other way. Do not use relational comparison - operators except for search optimization (i.e. associative container keys). - </p> -<a name="xml_attribute::hash_value"></a><a name="xml_node::hash_value"></a><p> - If you want to use <code class="computeroutput"><span class="identifier">xml_node</span></code> - or <code class="computeroutput"><span class="identifier">xml_attribute</span></code> objects - as keys in hash-based associative containers, you can use the <code class="computeroutput"><span class="identifier">hash_value</span></code> member functions. They return - the hash values that are guaranteed to be the same for all handles to the - same underlying object. The hash value for null handles is 0. - </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> - Finally handles can be implicitly cast to boolean-like objects, so that you - can test if the node/attribute is empty with the following code: <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 without a 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 <a class="link" href="modify.html#xml_node::remove_child">xml_node::remove_child</a>) - 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 <a class="link" href="install.html#PUGIXML_WCHAR_MODE">PUGIXML_WCHAR_MODE</a> - 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 the 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 the 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 non-ASCII, 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 a 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. - There are also two overloads with the same semantics which accept a string - as an argument: - </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="identifier">std</span><span class="special">::</span><span class="identifier">wstring</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="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&</span> <span class="identifier">str</span><span class="special">);</span> -</pre> -<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 <a class="link" href="install.html#PUGIXML_WCHAR_MODE">PUGIXML_WCHAR_MODE</a>. - This is done 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" style="list-style-type: disc; "> -<li class="listitem"> - it is safe to call free (non-member) 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 <a class="link" href="dom.html#set_memory_management_functions">set_memory_management_functions</a>; - 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. <a class="link" href="access.html#xml_node::traverse">xml_node::traverse</a> - or <a class="link" href="access.html#xml_node::find_node">xml_node::find_node</a>) do not - provide any exception guarantees beyond the ones provided by the callback. - </p> -<p> - If exception handling is not disabled with <a class="link" href="install.html#PUGIXML_NO_EXCEPTIONS">PUGIXML_NO_EXCEPTIONS</a> - define, XPath functions may throw <a class="link" href="xpath.html#xpath_exception">xpath_exception</a> - on parsing errors; also, XPath functions may throw <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, tree data and XPath objects is allocated - via globally specified functions, which default to malloc/free. You can - set your own allocation functions with set_memory_management function. - 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 a memory block with alignment that is suitable - for storage of primitive types (usually a maximum of <code class="computeroutput"><span class="keyword">void</span><span class="special">*</span></code> and <code class="computeroutput"><span class="keyword">double</span></code> - types alignment is sufficient) and size that is greater than 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). - </p> -<p> - Deallocation function is called with the pointer that was returned by some - call to allocation function; it is never called with a null pointer. 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> -<div class="section"> -<div class="titlepage"><div><div><h4 class="title"> -<a name="manual.dom.memory.tuning"></a><a class="link" href="dom.html#manual.dom.memory.tuning" title="Memory consumption tuning"> Memory consumption tuning</a> -</h4></div></div></div> -<p> - There are several important buffering optimizations in pugixml that rely - on predefined constants. These constants have default values that were - tuned for common usage patterns; for some applications, changing these - constants might improve memory consumption or increase performance. Changing - these constants is not recommended unless their default values result in - visible problems. - </p> -<p> - These constants can be tuned via configuration defines, as discussed in - <a class="xref" href="install.html#manual.install.building.config" title="Additional configuration options"> Additional configuration - options</a>; it is recommended to set them in <code class="filename">pugiconfig.hpp</code>. - </p> -<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> -<li class="listitem"> - <code class="computeroutput"><span class="identifier">PUGIXML_MEMORY_PAGE_SIZE</span></code> - controls the page size for document memory allocation. Memory for node/attribute - objects is allocated in pages of the specified size. The default size - is 32 Kb; for some applications the size is too large (i.e. embedded - systems with little heap space or applications that keep lots of XML - documents in memory). A minimum size of 1 Kb is recommended. <br><br> - - </li> -<li class="listitem"> - <code class="computeroutput"><span class="identifier">PUGIXML_MEMORY_OUTPUT_STACK</span></code> - controls the cumulative stack space required to output the node. Any - output operation (i.e. saving a subtree to file) uses an internal buffering - scheme for performance reasons. The default size is 10 Kb; if you're - using node output from threads with little stack space, decreasing - this value can prevent stack overflows. A minimum size of 1 Kb is recommended. - <br><br> - - </li> -<li class="listitem"> - <code class="computeroutput"><span class="identifier">PUGIXML_MEMORY_XPATH_PAGE_SIZE</span></code> - controls the page size for XPath memory allocation. Memory for XPath - query objects as well as internal memory for XPath evaluation is allocated - in pages of the specified size. The default size is 4 Kb; if you have - a lot of resident XPath query objects, you might need to decrease the - size to improve memory consumption. A minimum size of 256 bytes is - recommended. - </li> -</ul></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 <a class="link" href="dom.html#xml_document">xml_document</a> - 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 <a class="link" href="dom.html#xml_document">xml_document</a> 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 © 2014 Arseny Kapoulkine<p> - Distributed under the MIT License - </p> -</div></td> -</tr></table> -<hr> -<table width="100%"><tr> -<td> -<a href="http://pugixml.org/">pugixml 1.5</a> 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> |