manual.html

<p><a id="PUGIXML_API"></a><code>PUGIXML_API</code>, <a id="PUGIXML_CLASS"></a><code>PUGIXML_CLASS</code> and <a id="PUGIXML_FUNCTION"></a><code>PUGIXML_FUNCTION</code> defines let you specify custom attributes (i.e. declspec or calling conventions) for pugixml classes and non-member functions. In absence of <code>PUGIXML_CLASS</code> or <code>PUGIXML_FUNCTION</code> definitions, <code>PUGIXML_API</code> definition is used instead. For example, to specify fixed calling convention, you can define <code>PUGIXML_FUNCTION</code> to i.e. <code>__fastcall</code>. Another example is DLL import/export attributes in MSVC (see <a href="#install.building.shared">Building pugixml as a standalone shared library</a>).</p>
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<div class="admonitionblock note">
<table>
<tr>
<td class="icon">
<div class="title">Note</div>
</td>
<td class="content">
In that example <code>PUGIXML_API</code> is inconsistent between several source files; this is an exception to the consistency rule.
</td>
</tr>
</table>
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<div class="paragraph">
<p><a id="PUGIXML_MEMORY_PAGE_SIZE"></a><code>PUGIXML_MEMORY_PAGE_SIZE</code>, <a id="PUGIXML_MEMORY_OUTPUT_STACK"></a><code>PUGIXML_MEMORY_OUTPUT_STACK</code> and <a id="PUGIXML_MEMORY_XPATH_PAGE_SIZE"></a><code>PUGIXML_MEMORY_XPATH_PAGE_SIZE</code> can be used to customize certain important sizes to optimize memory usage for the application-specific patterns. For details see <a href="#dom.memory.tuning">Memory consumption tuning</a>.</p>
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<div class="paragraph">
<p><a id="PUGIXML_HAS_LONG_LONG"></a><code>PUGIXML_HAS_LONG_LONG</code> define enables support for <code>long long</code> type in pugixml. This define is automatically enabled if your platform is known to have <code>long long</code> support (i.e. has C&#43;&#43;11 support or uses a reasonably modern version of a known compiler); if pugixml does not recognize that your platform supports <code>long long</code> but in fact it does, you can enable the define manually.</p>
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<div class="sect2">
<h3 id="install.portability"><a class="anchor" href="#install.portability"></a><a class="link" href="#install.portability">2.3. Portability</a></h3>
<div class="paragraph">
<p>pugixml is written in standard-compliant C&#43;&#43; with some compiler-specific workarounds where appropriate. pugixml is compatible with the C&#43;&#43;11 standard, but does not require C&#43;&#43;11 support. Each version is tested with a unit test suite with code coverage exceeding 99%.</p>
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<div class="paragraph">
<p>pugixml runs on a variety of desktop platforms (including Microsoft Windows, Linux, FreeBSD, Apple MacOSX and Sun Solaris), game consoles (inclusing Microsoft Xbox 360, Microsoft Xbox One, Nintendo Wii, Sony Playstation Portable and Sony Playstation 3) and mobile platforms (including Android, iOS, BlackBerry, Samsung bada and Microsoft Windows CE).</p>
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<div class="paragraph">
<p>pugixml supports various architectures, such as x86/x86-64, PowerPC, ARM, MIPS and SPARC. In general it should run on any architecture since it does not use architecture-specific code and does not rely on features such as unaligned memory access.</p>
</div>
<div class="paragraph">
<p>pugixml can be compiled using any C++ compiler; it was tested with all versions of Microsoft Visual C&#43;&#43; from 6.0 up to 2015, GCC from 3.4 up to 5.2, Clang from 3.2 up to 3.7, as well as a variety of other compilers (e.g. Borland C&#43;&#43;, Digital Mars C&#43;&#43;, Intel C&#43;&#43;, Metrowerks CodeWarrior and PathScale). The code is written to avoid compilation warnings even on reasonably high warning levels.</p>
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<div class="paragraph">
<p>Note that some platforms may have very bare-bones support of C++; in some cases you&#8217;ll have to use <code>PUGIXML_NO_STL</code> and/or <code>PUGIXML_NO_EXCEPTIONS</code> to compile without issues. This mostly applies to old game consoles and embedded systems.</p>
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<div class="sect1">
<h2 id="dom"><a class="anchor" href="#dom"></a><a class="link" href="#dom">3. Document object model</a></h2>
<div class="sectionbody">
<div class="paragraph">
<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&#43;&#43; 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&#43;&#43; I/O stream or custom transport).</p>
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<div class="sect2">
<h3 id="dom.tree"><a class="anchor" href="#dom.tree"></a><a class="link" href="#dom.tree">3.1. Tree structure</a></h3>
<div class="paragraph">
<p>The XML document is represented with a tree data structure. The root of the tree is the document itself, which corresponds to C&#43;&#43; type <a href="#xml_document">xml_document</a>. Document has one or more child nodes, which correspond to C&#43;&#43; type <a href="#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&#43;&#43; type <a href="#xml_attribute">xml_attribute</a>, and some additional data (i.e. name).</p>
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<div id="xml_node_type" class="paragraph">
<p>The tree nodes can be of one of the following types (which together form the enumeration <code>xml_node_type</code>):</p>
</div>
<div class="ulist">
<ul>
<li>
<p>Document node (<a id="node_document"></a><code>node_document</code>) - this is the root of the tree, which consists of several child nodes. This node corresponds to <a href="#xml_document">xml_document</a> class; note that <a href="#xml_document">xml_document</a> is a sub-class of <a href="#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.</p>
</li>
<li>
<p>Element/tag node (<a id="node_element"></a><code>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:</p>
<div class="listingblock">
<div class="content">
<pre>&lt;node attr="value"&gt;&lt;child/&gt;&lt;/node&gt;</pre>
</div>
</div>
<div class="paragraph">
<p>There are two element nodes here: one has name <code>"node"</code>, single attribute <code>"attr"</code> and single child <code>"child"</code>, another has name <code>"child"</code> and does not have any attributes or child nodes.</p>
</div>
</li>
<li>
<p>Plain character data nodes (<a id="node_pcdata"></a><code>node_pcdata</code>) represent plain text in XML. PCDATA nodes have a value, but do not have a name or children/attributes. Note that <strong>plain character data is not a part of the element node but instead has its own node</strong>; an element node can have several child PCDATA nodes. The example XML representation of text nodes is as follows:</p>
<div class="listingblock">
<div class="content">
<pre>&lt;node&gt; text1 &lt;child/&gt; text2 &lt;/node&gt;</pre>
</div>
</div>
<div class="paragraph">
<p>Here <code>"node"</code> element has three children, two of which are PCDATA nodes with values <code>" text1 "</code> and <code>" text2 "</code>.</p>
</div>
</li>
<li>
<p>Character data nodes (<a id="node_cdata"></a><code>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:</p>
<div class="listingblock">
<div class="content">
<pre>&lt;node&gt; &lt;![CDATA[text1]]&gt; &lt;child/&gt; &lt;![CDATA[text2]]&gt; &lt;/node&gt;</pre>
</div>
</div>
<div class="paragraph">
<p>CDATA nodes make it easy to include non-escaped <code>&lt;</code>, <code>&amp;</code> and <code>&gt;</code> characters in plain text. CDATA value can not contain the character sequence <code>]]&gt;</code>, since it is used to determine the end of node contents.</p>
</div>
</li>
<li>
<p>Comment nodes (<a id="node_comment"></a><code>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:</p>
<div class="listingblock">
<div class="content">
<pre>&lt;!-- comment text --&gt;</pre>
</div>
</div>
<div class="paragraph">
<p>Here the comment node has value <code>"comment text"</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 href="#parse_comments">parse_comments</a> flag.</p>
</div>
</li>
<li>
<p>Processing instruction node (<a id="node_pi"></a><code>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:</p>
<div class="listingblock">
<div class="content">
<pre>&lt;?name value?&gt;</pre>
</div>
</div>
<div class="paragraph">
<p>Here the name (also called PI target) is <code>"name"</code>, and the value is <code>"value"</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 href="#parse_pi">parse_pi</a> flag.</p>
</div>
</li>
<li>
<p>Declaration node (<a id="node_declaration"></a><code>node_declaration</code>) represents document declarations in XML. Declaration nodes have a name (<code>"xml"</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:</p>
<div class="listingblock">
<div class="content">
<pre>&lt;?xml version="1.0"?&gt;</pre>
</div>
</div>
<div class="paragraph">
<p>Here the node has name <code>"xml"</code> and a single attribute with name <code>"version"</code> and value <code>"1.0"</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 href="#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 href="#format_no_declaration">format_no_declaration</a> flag.</p>
</div>
</li>
<li>
<p>Document type declaration node (<a id="node_doctype"></a><code>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>&lt;!ENTITY&gt;</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:</p>
<div class="listingblock">
<div class="content">
<pre>&lt;!DOCTYPE greeting [ &lt;!ELEMENT greeting (#PCDATA)&gt; ]&gt;</pre>
</div>
</div>
<div class="paragraph">
<p>Here the node has value <code>"greeting [ &lt;!ELEMENT greeting (#PCDATA)&gt; ]"</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 href="#parse_doctype">parse_doctype</a> flag.</p>
</div>
</li>
</ul>
</div>
<div class="paragraph">
<p>Finally, here is a complete example of XML document and the corresponding tree representation (<a href="samples/tree.xml" class="bare">samples/tree.xml</a>):</p>
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<table class="tableblock frame-none grid-all stretch">
<colgroup>
<col style="width: 50%;">
<col style="width: 50%;">
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<td class="tableblock halign-left valign-top"><div class="content"><div class="listingblock">
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<pre class="pygments highlight"><code data-lang="xml"><span></span><span class="tok-cp">&lt;?xml version=&quot;1.0&quot;?&gt;</span>
<span class="tok-nt">&lt;mesh</span> <span class="tok-na">name=</span><span class="tok-s">&quot;mesh_root&quot;</span><span class="tok-nt">&gt;</span>
    <span class="tok-c">&lt;!-- here is a mesh node --&gt;</span>
    some text
    <span class="tok-cp">&lt;![CDATA[someothertext]]&gt;</span>
    some more text
    <span class="tok-nt">&lt;node</span> <span class="tok-na">attr1=</span><span class="tok-s">&quot;value1&quot;</span> <span class="tok-na">attr2=</span><span class="tok-s">&quot;value2&quot;</span> <span class="tok-nt">/&gt;</span>
    <span class="tok-nt">&lt;node</span> <span class="tok-na">attr1=</span><span class="tok-s">&quot;value2&quot;</span><span class="tok-nt">&gt;</span>
        <span class="tok-nt">&lt;innernode/&gt;</span>
    <span class="tok-nt">&lt;/node&gt;</span>
<span class="tok-nt">&lt;/mesh&gt;</span>
<span class="tok-cp">&lt;?include somedata?&gt;</span></code></pre>
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</div></div></td>
<td class="tableblock halign-left valign-top"><div class="content"><div class="imageblock">
<div class="content">
<a class="image" href="images/dom_tree.png"><img src="images/dom_tree.png" alt="dom tree"></a>
</div>
</div></div></td>
</tr>
</tbody>
</table>
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<div class="sect2">
<h3 id="dom.cpp"><a class="anchor" href="#dom.cpp"></a><a class="link" href="#dom.cpp">3.2. C&#43;&#43; interface</a></h3>
<div class="admonitionblock note">
<table>
<tr>
<td class="icon">
<div class="title">Note</div>
</td>
<td class="content">
All pugixml classes and functions are located in the <code>pugi</code> namespace; you have to either use explicit name qualification (i.e. <code>pugi::xml_node</code>), or to gain access to relevant symbols via <code>using</code> directive (i.e. <code>using pugi::xml_node;</code> or <code>using namespace pugi;</code>). The namespace will be omitted from all declarations in this documentation hereafter; all code examples will use fully qualified names.
</td>
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<div class="paragraph">
<p>Despite the fact that there are several node types, there are only three C&#43;&#43; classes representing the tree (<code>xml_document</code>, <code>xml_node</code>, <code>xml_attribute</code>); some operations on <code>xml_node</code> are only valid for certain node types. The classes are described below.</p>
</div>
<div class="paragraph">
<p><a id="xml_document"></a><a id="xml_document::document_element"></a>
<code>xml_document</code> is the owner of the entire document structure; it is a non-copyable class. The interface of <code>xml_document</code> consists of loading functions (see <a href="#loading">Loading document</a>), saving functions (see <a href="#saving">Saving document</a>) and the entire interface of <code>xml_node</code>, which allows for document inspection and/or modification. Note that while <code>xml_document</code> is a sub-class of <code>xml_node</code>, <code>xml_node</code> is not a polymorphic type; the inheritance is present only to simplify usage. Alternatively you can use the <code>document_element</code> function to get the element node that&#8217;s the immediate child of the document.</p>
</div>
<div class="paragraph">
<p><a id="xml_document::ctor"></a><a id="xml_document::dtor"></a><a id="xml_document::reset"></a>
Default constructor of <code>xml_document</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>xml_document::reset</code> function; it destroys the tree and replaces it with either an empty one or a copy of the specified document. Destructor of <code>xml_document</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>
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<div class="admonitionblock caution">
<table>
<tr>
<td class="icon">
<div class="title">Caution</div>
</td>
<td class="content">
While technically node/attribute handles can be alive when the tree they&#8217;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.
</td>
</tr>
</table>
</div>
<div class="paragraph">
<p><a id="xml_node"></a><a id="xml_node::type"></a>
<code>xml_node</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 href="#xml_node_type">node type</a> can be queried via the <code>xml_node::type()</code> method. Note that <code>xml_node</code> is only a handle to the actual node, not the node itself - you can have several <code>xml_node</code> handles pointing to the same underlying object. Destroying <code>xml_node</code> handle does not destroy the node and does not remove it from the tree. The size of <code>xml_node</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>xml_node</code> objects by value without additional overhead.</p>
</div>
<div id="node_null" class="paragraph">
<p>There is a special value of <code>xml_node</code> type, known as null node or empty node (such nodes have type <code>node_null</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&#8217;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>node.parent().parent()</code>; if a node is a null node or it does not have a parent, the first <code>parent()</code> call returns null node; the second <code>parent()</code> call then also returns null node, which makes error handling easier.</p>
</div>
<div id="xml_attribute" class="paragraph">
<p><code>xml_attribute</code> is the handle to an XML attribute; it has the same semantics as <code>xml_node</code>, i.e. there can be several <code>xml_attribute</code> handles pointing to the same underlying object and there is a special null attribute value, which propagates to function results.</p>
</div>
<div class="paragraph">
<p><a id="xml_attribute::ctor"></a><a id="xml_node::ctor"></a>
Both <code>xml_node</code> and <code>xml_attribute</code> have the default constructor which initializes them to null objects.</p>
</div>
<div class="paragraph">
<p><a id="xml_attribute::comparison"></a><a id="xml_node::comparison"></a>
<code>xml_node</code> and <code>xml_attribute</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 null handles. 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>
</div>
<div class="paragraph">
<p><a id="xml_attribute::hash_value"></a><a id="xml_node::hash_value"></a>
If you want to use <code>xml_node</code> or <code>xml_attribute</code> objects as keys in hash-based associative containers, you can use the <code>hash_value</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. Note that hash value does not depend on the content of the node, only on the location of the underlying structure in memory - this means that loading the same document twice will likely produce different hash values, and copying the node will not preserve the hash.</p>
</div>
<div class="paragraph">
<p><a id="xml_attribute::unspecified_bool_type"></a><a id="xml_node::unspecified_bool_type"></a><a id="xml_attribute::empty"></a><a id="xml_node::empty"></a>
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>if (node) { &#8230;&#8203; }</code> or <code>if (!node) { &#8230;&#8203; } else { &#8230;&#8203; }</code>. Alternatively you can check if a given <code>xml_node</code>/<code>xml_attribute</code> handle is null by calling the following methods:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c++"><span></span><span class="tok-kt">bool</span> <span class="tok-n">xml_attribute</span><span class="tok-o">::</span><span class="tok-n">empty</span><span class="tok-p">()</span> <span class="tok-k">const</span><span class="tok-p">;</span>
<span class="tok-kt">bool</span> <span class="tok-n">xml_node</span><span class="tok-o">::</span><span class="tok-n">empty</span><span class="tok-p">()</span> <span class="tok-k">const</span><span class="tok-p">;</span></code></pre>
</div>
</div>
<div class="paragraph">
<p>Nodes and attributes do not exist without a document tree, so you can&#8217;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 href="#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>
<div class="sect2">
<h3 id="dom.unicode"><a class="anchor" href="#dom.unicode"></a><a class="link" href="#dom.unicode">3.3. Unicode interface</a></h3>
<div class="paragraph">
<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 href="#PUGIXML_WCHAR_MODE">PUGIXML_WCHAR_MODE</a> define; you can set it via <code>pugiconfig.hpp</code> or via preprocessor options, as discussed in <a href="#install.building.config">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>wchar_t</code> type.</p>
</div>
<div class="admonitionblock note">
<table>
<tr>
<td class="icon">
<div class="title">Note</div>
</td>
<td class="content">
If the size of <code>wchar_t</code> is 2, pugixml assumes UTF-16 encoding instead of UCS-2, which means that some characters are represented as two code points.
</td>
</tr>
</table>
</div>
<div class="paragraph">
<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>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c++"><span></span><span class="tok-k">const</span> <span class="tok-kt">char</span><span class="tok-o">*</span> <span class="tok-n">xml_node</span><span class="tok-o">::</span><span class="tok-n">name</span><span class="tok-p">()</span> <span class="tok-k">const</span><span class="tok-p">;</span>
<span class="tok-kt">bool</span> <span class="tok-n">xml_node</span><span class="tok-o">::</span><span class="tok-n">set_name</span><span class="tok-p">(</span><span class="tok-k">const</span> <span class="tok-kt">char</span><span class="tok-o">*</span> <span class="tok-n">value</span><span class="tok-p">);</span></code></pre>
</div>
</div>
<div class="paragraph">
<p>and like this in wchar_t mode:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c++"><span></span><span class="tok-k">const</span> <span class="tok-kt">wchar_t</span><span class="tok-o">*</span> <span class="tok-n">xml_node</span><span class="tok-o">::</span><span class="tok-n">name</span><span class="tok-p">()</span> <span class="tok-k">const</span><span class="tok-p">;</span>
<span class="tok-kt">bool</span> <span class="tok-n">xml_node</span><span class="tok-o">::</span><span class="tok-n">set_name</span><span class="tok-p">(</span><span class="tok-k">const</span> <span class="tok-kt">wchar_t</span><span class="tok-o">*</span> <span class="tok-n">value</span><span class="tok-p">);</span></code></pre>
</div>
</div>
<div class="paragraph">
<p><a id="char_t"></a><a id="string_t"></a>
There is a special type, <code>pugi::char_t</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>pugi::string_t</code>, which is defined as the STL string of the character type; it corresponds to <code>std::string</code> in char mode and to <code>std::wstring</code> in wchar_t mode.</p>
</div>
<div class="paragraph">
<p>In addition to the interface, the internal implementation changes to store XML data as <code>pugi::char_t</code>; this means that these two modes have different memory usage characteristics - generally UTF-8 mode is more memory and performance efficient, especially if <code>sizeof(wchar_t)</code> is 4. The conversion to <code>pugi::char_t</code> upon document loading and from <code>pugi::char_t</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>
</div>
<div class="paragraph">
<p><a id="as_utf8"></a><a id="as_wide"></a>
There are cases when you&#8217;ll have to convert string data between UTF-8 and wchar_t encodings; the following helper functions are provided for such purposes:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c++"><span></span><span class="tok-n">std</span><span class="tok-o">::</span><span class="tok-n">string</span> <span class="tok-n">as_utf8</span><span class="tok-p">(</span><span class="tok-k">const</span> <span class="tok-kt">wchar_t</span><span class="tok-o">*</span> <span class="tok-n">str</span><span class="tok-p">);</span>
<span class="tok-n">std</span><span class="tok-o">::</span><span class="tok-n">wstring</span> <span class="tok-n">as_wide</span><span class="tok-p">(</span><span class="tok-k">const</span> <span class="tok-kt">char</span><span class="tok-o">*</span> <span class="tok-n">str</span><span class="tok-p">);</span></code></pre>
</div>
</div>
<div class="paragraph">
<p>Both functions accept a null-terminated string as an argument <code>str</code>, and return the converted string. <code>as_utf8</code> performs conversion from UTF-16/32 to UTF-8; <code>as_wide</code> performs conversion from UTF-8 to UTF-16/32. Invalid UTF sequences are silently discarded upon conversion. <code>str</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>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c++"><span></span><span class="tok-n">std</span><span class="tok-o">::</span><span class="tok-n">string</span> <span class="tok-n">as_utf8</span><span class="tok-p">(</span><span class="tok-k">const</span> <span class="tok-n">std</span><span class="tok-o">::</span><span class="tok-n">wstring</span><span class="tok-o">&amp;</span> <span class="tok-n">str</span><span class="tok-p">);</span>
<span class="tok-n">std</span><span class="tok-o">::</span><span class="tok-n">wstring</span> <span class="tok-n">as_wide</span><span class="tok-p">(</span><span class="tok-k">const</span> <span class="tok-n">std</span><span class="tok-o">::</span><span class="tok-n">string</span><span class="tok-o">&amp;</span> <span class="tok-n">str</span><span class="tok-p">);</span></code></pre>
</div>
</div>
<div class="admonitionblock note">
<table>
<tr>
<td class="icon">
<div class="title">Note</div>
</td>
<td class="content">
<div class="paragraph">
<p>Most examples in this documentation assume char interface and therefore will not compile with <a href="#PUGIXML_WCHAR_MODE">PUGIXML_WCHAR_MODE</a>. This is done to simplify the documentation; usually the only changes you&#8217;ll have to make is to pass <code>wchar_t</code> string literals, i.e. instead of</p>
</div>
<div class="paragraph">
<p><code>xml_node node = doc.child("bookstore").find_child_by_attribute("book", "id", "12345");</code></p>
</div>
<div class="paragraph">
<p>you&#8217;ll have to use</p>
</div>
<div class="paragraph">
<p><code>xml_node node = doc.child(L"bookstore").find_child_by_attribute(L"book", L"id", L"12345");</code></p>
</div>
</td>
</tr>
</table>
</div>
</div>
<div class="sect2">
<h3 id="dom.thread"><a class="anchor" href="#dom.thread"></a><a class="link" href="#dom.thread">3.4. Thread-safety guarantees</a></h3>
<div class="paragraph">
<p>Almost all functions in pugixml have the following thread-safety guarantees:</p>
</div>
<div class="ulist">
<ul>
<li>
<p>it is safe to call free (non-member) functions from multiple threads</p>
</li>
<li>
<p>it is safe to perform concurrent read-only accesses to the same tree (all constant member functions do not modify the tree)</p>
</li>
<li>
<p>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</p>
</li>
</ul>
</div>
<div class="paragraph">
<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>
</div>
<div class="paragraph">
<p>The only exception is <a href="#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 href="#dom.memory.custom">Custom memory allocation/deallocation functions</a>.</p>
</div>
</div>
<div class="sect2">
<h3 id="dom.exception"><a class="anchor" href="#dom.exception"></a><a class="link" href="#dom.exception">3.5. Exception guarantees</a></h3>
<div class="paragraph">
<p>With the exception of XPath, pugixml itself does not throw any exceptions. Additionally, most pugixml functions have a no-throw exception guarantee.</p>
</div>
<div class="paragraph">
<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 href="#xml_node::traverse">xml_node::traverse</a> or <a href="#xml_node::find_node">xml_node::find_node</a>) do not provide any exception guarantees beyond the ones provided by the callback.</p>
</div>
<div class="paragraph">
<p>If exception handling is not disabled with <a href="#PUGIXML_NO_EXCEPTIONS">PUGIXML_NO_EXCEPTIONS</a> define, XPath functions may throw <a href="#xpath_exception">xpath_exception</a> on parsing errors; also, XPath functions may throw <code>std::bad_alloc</code> in low memory conditions. Still, XPath functions provide strong exception guarantee.</p>
</div>
</div>
<div class="sect2">
<h3 id="dom.memory"><a class="anchor" href="#dom.memory"></a><a class="link" href="#dom.memory">3.6. Memory management</a></h3>
<div class="paragraph">
<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>
<div class="sect3">
<h4 id="dom.memory.custom"><a class="anchor" href="#dom.memory.custom"></a><a class="link" href="#dom.memory.custom">3.6.1. Custom memory allocation/deallocation functions</a></h4>
<div class="paragraph">
<p><a id="allocation_function"></a><a id="deallocation_function"></a>
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>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c++"><span></span><span class="tok-k">typedef</span> <span class="tok-kt">void</span><span class="tok-o">*</span> <span class="tok-p">(</span><span class="tok-o">*</span><span class="tok-n">allocation_function</span><span class="tok-p">)(</span><span class="tok-kt">size_t</span> <span class="tok-n">size</span><span class="tok-p">);</span>
<span class="tok-k">typedef</span> <span class="tok-nf">void</span> <span class="tok-p">(</span><span class="tok-o">*</span><span class="tok-n">deallocation_function</span><span class="tok-p">)(</span><span class="tok-kt">void</span><span class="tok-o">*</span> <span class="tok-n">ptr</span><span class="tok-p">);</span></code></pre>
</div>
</div>
<div class="paragraph">
<p><a id="set_memory_management_functions"></a><a id="get_memory_allocation_function"></a><a id="get_memory_deallocation_function"></a>
You can use the following accessor functions to change or get current memory management functions:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c++"><span></span><span class="tok-kt">void</span> <span class="tok-nf">set_memory_management_functions</span><span class="tok-p">(</span><span class="tok-n">allocation_function</span> <span class="tok-n">allocate</span><span class="tok-p">,</span> <span class="tok-n">deallocation_function</span> <span class="tok-n">deallocate</span><span class="tok-p">);</span>
<span class="tok-n">allocation_function</span> <span class="tok-nf">get_memory_allocation_function</span><span class="tok-p">();</span>
<span class="tok-n">deallocation_function</span> <span class="tok-nf">get_memory_deallocation_function</span><span class="tok-p">();</span></code></pre>
</div>
</div>
<div class="paragraph">
<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>void*</code> and <code>double</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 either return null pointer or to throw an exception.</p>
</div>
<div class="paragraph">
<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>
</div>
<div class="paragraph">
<p>This is a simple example of custom memory management (<a href="samples/custom_memory_management.cpp" class="bare">samples/custom_memory_management.cpp</a>):</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c++"><span></span><span class="tok-kt">void</span><span class="tok-o">*</span> <span class="tok-nf">custom_allocate</span><span class="tok-p">(</span><span class="tok-kt">size_t</span> <span class="tok-n">size</span><span class="tok-p">)</span>
<span class="tok-p">{</span>
    <span class="tok-k">return</span> <span class="tok-k">new</span> <span class="tok-p">(</span><span class="tok-n">std</span><span class="tok-o">::</span><span class="tok-n">nothrow</span><span class="tok-p">)</span> <span class="tok-kt">char</span><span class="tok-p">[</span><span class="tok-n">size</span><span class="tok-p">];</span>
<span class="tok-p">}</span>

<span class="tok-kt">void</span> <span class="tok-nf">custom_deallocate</span><span class="tok-p">(</span><span class="tok-kt">void</span><span class="tok-o">*</span> <span class="tok-n">ptr</span><span class="tok-p">)</span>
<span class="tok-p">{</span>
    <span class="tok-k">delete</span><span class="tok-p">[]</span> <span class="tok-k">static_cast</span><span class="tok-o">&lt;</span><span class="tok-kt">char</span><span class="tok-o">*&gt;</span><span class="tok-p">(</span><span class="tok-n">ptr</span><span class="tok-p">);</span>
<span class="tok-p">}</span></code></pre>
</div>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c++"><span></span><span class="tok-n">pugi</span><span class="tok-o">::</span><span class="tok-n">set_memory_management_functions</span><span class="tok-p">(</span><span class="tok-n">custom_allocate</span><span class="tok-p">,</span> <span class="tok-n">custom_deallocate</span><span class="tok-p">);</span></code></pre>
</div>
</div>
<div class="paragraph">
<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>
<div class="sect3">
<h4 id="dom.memory.tuning"><a class="anchor" href="#dom.memory.tuning"></a><a class="link" href="#dom.memory.tuning">3.6.2. Memory consumption tuning</a></h4>
<div class="paragraph">
<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>
</div>
<div class="paragraph">
<p>These constants can be tuned via configuration defines, as discussed in <a href="#install.building.config">Additional configuration options</a>; it is recommended to set them in <code>pugiconfig.hpp</code>.</p>
</div>
<div class="ulist">
<ul>
<li>
<p><code>PUGIXML_MEMORY_PAGE_SIZE</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.</p>
</li>
<li>
<p><code>PUGIXML_MEMORY_OUTPUT_STACK</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&#8217;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.</p>
</li>
<li>
<p><code>PUGIXML_MEMORY_XPATH_PAGE_SIZE</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.</p>
</li>
</ul>
</div>
</div>
<div class="sect3">
<h4 id="dom.memory.internals"><a class="anchor" href="#dom.memory.internals"></a><a class="link" href="#dom.memory.internals">3.6.3. Document memory management internals</a></h4>
<div class="paragraph">
<p>Constructing a document object using the default constructor does not result in any allocations; document node is stored inside the <a href="#xml_document">xml_document</a> object.</p>
</div>
<div class="paragraph">
<p>When the document is loaded from file/buffer, unless an inplace loading function is used (see <a href="#loading.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 href="#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>
</div>
<div class="paragraph">
<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 Kb; 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 class="sect3">
<h4 id="dom.memory.compact"><a class="anchor" href="#dom.memory.compact"></a><a class="link" href="#dom.memory.compact">3.6.4. Compact mode</a></h4>
<div class="paragraph">
<p>By default nodes and attributes are optimized for efficiency of access. This can cause them to take a significant amount of memory - for documents with a lot of nodes and not a lot of contents (short attribute values/node text), and depending on the pointer size, the document structure can take noticeably more memory than the document itself (e.g. on a 64-bit platform in UTF-8 mode a markup-heavy document with the file size of 2.1 Mb can use 2.1 Mb for document buffer and 8.3 Mb for document structure).</p>
</div>
<div class="paragraph">
<p>If you are processing big documents or your platform is memory constrained and you&#8217;re willing to sacrifice a bit of performance for memory, you can compile pugixml with <code>PUGIXML_COMPACT</code> define which will activate compact mode. Compact mode uses a different representation of the document structure that assumes locality of reference between nodes and attributes to optimize memory usage. As a result you get significantly smaller node/attribute objects; usually most objects in most documents don&#8217;t require additional storage, but in the worst case - if assumptions about locality of reference don&#8217;t hold - additional memory will be allocated to store the extra data required.</p>
</div>
<div class="paragraph">
<p>The compact storage supports all existing operations - including tree modification - with the same amortized complexity (that is, all basic document manipulations are still O(1) on average). The operations are slightly slower; you can usually expect 10-50% slowdown in terms of processing time unless your processing was memory-bound.</p>
</div>
<div class="paragraph">
<p>On 32-bit architectures document structure in compact mode is typically reduced by around 2.5x; on 64-bit architectures the ratio is around 5x. Thus for big markup-heavy documents compact mode can make the difference between the processing of a multi-gigabyte document running completely from RAM vs requiring swapping to disk. Even if the document fits into memory, compact storage can use CPU caches more efficiently by taking less space and causing less cache/TLB misses.</p>
</div>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="loading"><a class="anchor" href="#loading"></a><a class="link" href="#loading">4. Loading document</a></h2>
<div class="sectionbody">
<div class="paragraph">
<p>pugixml provides several functions for loading XML data from various places - files, C&#43;&#43; iostreams, memory buffers. All functions use an extremely fast non-validating parser. This parser is not fully W3C conformant - it can load any valid XML document, but does not perform some well-formedness checks. While considerable effort is made to reject invalid XML documents, some validation is not performed for performance reasons. Also some XML transformations (i.e. EOL handling or attribute value normalization) can impact parsing speed and thus can be disabled. However for vast majority of XML documents there is no performance difference between different parsing options. Parsing options also control whether certain XML nodes are parsed; see <a href="#loading.options">Parsing options</a> for more information.</p>
</div>
<div class="paragraph">
<p>XML data is always converted to internal character format (see <a href="#dom.unicode">Unicode interface</a>) before parsing. pugixml supports all popular Unicode encodings (UTF-8, UTF-16 (big and little endian), UTF-32 (big and little endian); UCS-2 is naturally supported since it&#8217;s a strict subset of UTF-16) as well as some non-Unicode encodings (Latin-1) and handles all encoding conversions automatically. Unless explicit encoding is specified, loading functions perform automatic encoding detection based on source XML data, so in most cases you do not have to specify document encoding. Encoding conversion is described in more detail in <a href="#loading.encoding">Encodings</a>.</p>
</div>
<div class="sect2">
<h3 id="loading.file"><a class="anchor" href="#loading.file"></a><a class="link" href="#loading.file">4.1. Loading document from file</a></h3>
<div class="paragraph">
<p><a id="xml_document::load_file"></a><a id="xml_document::load_file_wide"></a>
The most common source of XML data is files; pugixml provides dedicated functions for loading an XML document from file:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c++"><span></span><span class="tok-n">xml_parse_result</span> <span class="tok-n">xml_document</span><span class="tok-o">::</span><span class="tok-n">load_file</span><span class="tok-p">(</span><span class="tok-k">const</span> <span class="tok-kt">char</span><span class="tok-o">*</span> <span class="tok-n">path</span><span class="tok-p">,</span> <span class="tok-kt">unsigned</span> <span class="tok-kt">int</span> <span class="tok-n">options</span> <span class="tok-o">=</span> <span class="tok-n">parse_default</span><span class="tok-p">,</span> <span class="tok-n">xml_encoding</span> <span class="tok-n">encoding</span> <span class="tok-o">=</span> <span class="tok-n">encoding_auto</span><span class="tok-p">);</span>
<span class="tok-n">xml_parse_result</span> <span class="tok-n">xml_document</span><span class="tok-o">::</span><span class="tok-n">load_file</span><span class="tok-p">(</span><span class="tok-k">const</span> <span class="tok-kt">wchar_t</span><span class="tok-o">*</span> <span class="tok-n">path</span><span class="tok-p">,</span> <span class="tok-kt">unsigned</span> <span class="tok-kt">int</span> <span class="tok-n">options</span> <span class="tok-o">=</span> <span class="tok-n">parse_default</span><span class="tok-p">,</span> <span class="tok-n">xml_encoding</span> <span class="tok-n">encoding</span> <span class="tok-o">=</span> <span class="tok-n">encoding_auto</span><span class="tok-p">);</span></code></pre>
</div>
</div>
<div class="paragraph">
<p>These functions accept the file path as its first argument, and also two optional arguments, which specify parsing options (see <a href="#loading.options">Parsing options</a>) and input data encoding (see <a href="#loading.encoding">Encodings</a>). The path has the target operating system format, so it can be a relative or absolute one, it should have the delimiters of the target system, it should have the exact case if the target file system is case-sensitive, etc.</p>
</div>
<div class="paragraph">
<p>File path is passed to the system file opening function as is in case of the first function (which accepts <code>const char* path</code>); the second function either uses a special file opening function if it is provided by the runtime library or converts the path to UTF-8 and uses the system file opening function.</p>
</div>
<div class="paragraph">
<p><code>load_file</code> destroys the existing document tree and then tries to load the new tree from the specified file. The result of the operation is returned in an <a href="#xml_parse_result">xml_parse_result</a> object; this object contains the operation status and the related information (i.e. last successfully parsed position in the input file, if parsing fails). See <a href="#loading.errors">Handling parsing errors</a> for error handling details.</p>
</div>
<div class="paragraph">
<p>This is an example of loading XML document from file (<a href="samples/load_file.cpp" class="bare">samples/load_file.cpp</a>):</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c++"><span></span><span class="tok-n">pugi</span><span class="tok-o">::</span><span class="tok-n">xml_document</span> <span class="tok-n">doc</span><span class="tok-p">;</span>

<span class="tok-n">pugi</span><span class="tok-o">::</span><span class="tok-n">xml_parse_result</span> <span class="tok-n">result</span> <span class="tok-o">=</span> <span class="tok-n">doc</span><span class="tok-p">.</span><span class="tok-n">load_file</span><span class="tok-p">(</span><span class="tok-s">&quot;tree.xml&quot;</span><span class="tok-p">);</span>

<span class="tok-n">std</span><span class="tok-o">::</span><span class="tok-n">cout</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-s">&quot;Load result: &quot;</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-n">result</span><span class="tok-p">.</span><span class="tok-n">description</span><span class="tok-p">()</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-s">&quot;, mesh name: &quot;</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-n">doc</span><span class="tok-p">.</span><span class="tok-n">child</span><span class="tok-p">(</span><span class="tok-s">&quot;mesh&quot;</span><span class="tok-p">).</span><span class="tok-n">attribute</span><span class="tok-p">(</span><span class="tok-s">&quot;name&quot;</span><span class="tok-p">).</span><span class="tok-n">value</span><span class="tok-p">()</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-n">std</span><span class="tok-o">::</span><span class="tok-n">endl</span><span class="tok-p">;</span></code></pre>
</div>
</div>
</div>
<div class="sect2">
<h3 id="loading.memory"><a class="anchor" href="#loading.memory"></a><a class="link" href="#loading.memory">4.2. Loading document from memory</a></h3>
<div class="paragraph">
<p><a id="xml_document::load_buffer"></a><a id="xml_document::load_buffer_inplace"></a><a id="xml_document::load_buffer_inplace_own"></a>
Sometimes XML data should be loaded from some other source than a file, i.e. HTTP URL; also you may want to load XML data from file using non-standard functions, i.e. to use your virtual file system facilities or to load XML from GZip-compressed files. All these scenarios require loading document from memory. First you should prepare a contiguous memory block with all XML data; then you have to invoke one of buffer loading functions. These functions will handle the necessary encoding conversions, if any, and then will parse the data into the corresponding XML tree. There are several buffer loading functions, which differ in the behavior and thus in performance/memory usage:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c++"><span></span><span class="tok-n">xml_parse_result</span> <span class="tok-n">xml_document</span><span class="tok-o">::</span><span class="tok-n">load_buffer</span><span class="tok-p">(</span><span class="tok-k">const</span> <span class="tok-kt">void</span><span class="tok-o">*</span> <span class="tok-n">contents</span><span class="tok-p">,</span> <span class="tok-kt">size_t</span> <span class="tok-n">size</span><span class="tok-p">,</span> <span class="tok-kt">unsigned</span> <span class="tok-kt">int</span> <span class="tok-n">options</span> <span class="tok-o">=</span> <span class="tok-n">parse_default</span><span class="tok-p">,</span> <span class="tok-n">xml_encoding</span> <span class="tok-n">encoding</span> <span class="tok-o">=</span> <span class="tok-n">encoding_auto</span><span class="tok-p">);</span>
<span class="tok-n">xml_parse_result</span> <span class="tok-n">xml_document</span><span class="tok-o">::</span><span class="tok-n">load_buffer_inplace</span><span class="tok-p">(</span><span class="tok-kt">void</span><span class="tok-o">*</span> <span class="tok-n">contents</span><span class="tok-p">,</span> <span class="tok-kt">size_t</span> <span class="tok-n">size</span><span class="tok-p">,</span> <span class="tok-kt">unsigned</span> <span class="tok-kt">int</span> <span class="tok-n">options</span> <span class="tok-o">=</span> <span class="tok-n">parse_default</span><span class="tok-p">,</span> <span class="tok-n">xml_encoding</span> <span class="tok-n">encoding</span> <span class="tok-o">=</span> <span class="tok-n">encoding_auto</span><span class="tok-p">);</span>
<span class="tok-n">xml_parse_result</span> <span class="tok-n">xml_document</span><span class="tok-o">::</span><span class="tok-n">load_buffer_inplace_own</span><span class="tok-p">(</span><span class="tok-kt">void</span><span class="tok-o">*</span> <span class="tok-n">contents</span><span class="tok-p">,</span> <span class="tok-kt">size_t</span> <span class="tok-n">size</span><span class="tok-p">,</span> <span class="tok-kt">unsigned</span> <span class="tok-kt">int</span> <span class="tok-n">options</span> <span class="tok-o">=</span> <span class="tok-n">parse_default</span><span class="tok-p">,</span> <span class="tok-n">xml_encoding</span> <span class="tok-n">encoding</span> <span class="tok-o">=</span> <span class="tok-n">encoding_auto</span><span class="tok-p">);</span></code></pre>
</div>
</div>
<div class="paragraph">
<p>All functions accept the buffer which is represented by a pointer to XML data, <code>contents</code>, and data size in bytes. Also there are two optional arguments, which specify parsing options (see <a href="#loading.options">Parsing options</a>) and input data encoding (see <a href="#loading.encoding">Encodings</a>). The buffer does not have to be zero-terminated.</p>
</div>
<div class="paragraph">
<p><code>load_buffer</code> function works with immutable buffer - it does not ever modify the buffer. Because of this restriction it has to create a private buffer and copy XML data to it before parsing (applying encoding conversions if necessary). This copy operation carries a performance penalty, so inplace functions are provided - <code>load_buffer_inplace</code> and <code>load_buffer_inplace_own</code> store the document data in the buffer, modifying it in the process. In order for the document to stay valid, you have to make sure that the buffer&#8217;s lifetime exceeds that of the tree if you&#8217;re using inplace functions. In addition to that, <code>load_buffer_inplace</code> does not assume ownership of the buffer, so you&#8217;ll have to destroy it yourself; <code>load_buffer_inplace_own</code> assumes ownership of the buffer and destroys it once it is not needed. This means that if you&#8217;re using <code>load_buffer_inplace_own</code>, you have to allocate memory with pugixml allocation function (you can get it via <a href="#get_memory_allocation_function">get_memory_allocation_function</a>).</p>
</div>
<div class="paragraph">
<p>The best way from the performance/memory point of view is to load document using <code>load_buffer_inplace_own</code>; this function has maximum control of the buffer with XML data so it is able to avoid redundant copies and reduce peak memory usage while parsing. This is the recommended function if you have to load the document from memory and performance is critical.</p>
</div>
<div id="xml_document::load_string" class="paragraph">
<p>There is also a simple helper function for cases when you want to load the XML document from null-terminated character string:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c++"><span></span><span class="tok-n">xml_parse_result</span> <span class="tok-n">xml_document</span><span class="tok-o">::</span><span class="tok-n">load_string</span><span class="tok-p">(</span><span class="tok-k">const</span> <span class="tok-n">char_t</span><span class="tok-o">*</span> <span class="tok-n">contents</span><span class="tok-p">,</span> <span class="tok-kt">unsigned</span> <span class="tok-kt">int</span> <span class="tok-n">options</span> <span class="tok-o">=</span> <span class="tok-n">parse_default</span><span class="tok-p">);</span></code></pre>
</div>
</div>
<div class="paragraph">
<p>It is equivalent to calling <code>load_buffer</code> with <code>size</code> being either <code>strlen(contents)</code> or <code>wcslen(contents) * sizeof(wchar_t)</code>, depending on the character type. This function assumes native encoding for input data, so it does not do any encoding conversion. In general, this function is fine for loading small documents from string literals, but has more overhead and less functionality than the buffer loading functions.</p>
</div>
<div class="paragraph">
<p>This is an example of loading XML document from memory using different functions (<a href="samples/load_memory.cpp" class="bare">samples/load_memory.cpp</a>):</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c++"><span></span><span class="tok-k">const</span> <span class="tok-kt">char</span> <span class="tok-n">source</span><span class="tok-p">[]</span> <span class="tok-o">=</span> <span class="tok-s">&quot;&lt;mesh name=&#39;sphere&#39;&gt;&lt;bounds&gt;0 0 1 1&lt;/bounds&gt;&lt;/mesh&gt;&quot;</span><span class="tok-p">;</span>
<span class="tok-kt">size_t</span> <span class="tok-n">size</span> <span class="tok-o">=</span> <span class="tok-k">sizeof</span><span class="tok-p">(</span><span class="tok-n">source</span><span class="tok-p">);</span></code></pre>
</div>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c++"><span></span><span class="tok-c1">// You can use load_buffer to load document from immutable memory block:</span>
<span class="tok-n">pugi</span><span class="tok-o">::</span><span class="tok-n">xml_parse_result</span> <span class="tok-n">result</span> <span class="tok-o">=</span> <span class="tok-n">doc</span><span class="tok-p">.</span><span class="tok-n">load_buffer</span><span class="tok-p">(</span><span class="tok-n">source</span><span class="tok-p">,</span> <span class="tok-n">size</span><span class="tok-p">);</span></code></pre>
</div>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c++"><span></span><span class="tok-c1">// You can use load_buffer_inplace to load document from mutable memory block; the block&#39;s lifetime must exceed that of document</span>
<span class="tok-kt">char</span><span class="tok-o">*</span> <span class="tok-n">buffer</span> <span class="tok-o">=</span> <span class="tok-k">new</span> <span class="tok-kt">char</span><span class="tok-p">[</span><span class="tok-n">size</span><span class="tok-p">];</span>
<span class="tok-n">memcpy</span><span class="tok-p">(</span><span class="tok-n">buffer</span><span class="tok-p">,</span> <span class="tok-n">source</span><span class="tok-p">,</span> <span class="tok-n">size</span><span class="tok-p">);</span>

<span class="tok-c1">// The block can be allocated by any method; the block is modified during parsing</span>
<span class="tok-n">pugi</span><span class="tok-o">::</span><span class="tok-n">xml_parse_result</span> <span class="tok-n">result</span> <span class="tok-o">=</span> <span class="tok-n">doc</span><span class="tok-p">.</span><span class="tok-n">load_buffer_inplace</span><span class="tok-p">(</span><span class="tok-n">buffer</span><span class="tok-p">,</span> <span class="tok-n">size</span><span class="tok-p">);</span>

<span class="tok-c1">// You have to destroy the block yourself after the document is no longer used</span>
<span class="tok-k">delete</span><span class="tok-p">[]</span> <span class="tok-n">buffer</span><span class="tok-p">;</span></code></pre>
</div>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c++"><span></span><span class="tok-c1">// You can use load_buffer_inplace_own to load document from mutable memory block and to pass the ownership of this block</span>
<span class="tok-c1">// The block has to be allocated via pugixml allocation function - using i.e. operator new here is incorrect</span>
<span class="tok-kt">char</span><span class="tok-o">*</span> <span class="tok-n">buffer</span> <span class="tok-o">=</span> <span class="tok-k">static_cast</span><span class="tok-o">&lt;</span><span class="tok-kt">char</span><span class="tok-o">*&gt;</span><span class="tok-p">(</span><span class="tok-n">pugi</span><span class="tok-o">::</span><span class="tok-n">get_memory_allocation_function</span><span class="tok-p">()(</span><span class="tok-n">size</span><span class="tok-p">));</span>
<span class="tok-n">memcpy</span><span class="tok-p">(</span><span class="tok-n">buffer</span><span class="tok-p">,</span> <span class="tok-n">source</span><span class="tok-p">,</span> <span class="tok-n">size</span><span class="tok-p">);</span>

<span class="tok-c1">// The block will be deleted by the document</span>
<span class="tok-n">pugi</span><span class="tok-o">::</span><span class="tok-n">xml_parse_result</span> <span class="tok-n">result</span> <span class="tok-o">=</span> <span class="tok-n">doc</span><span class="tok-p">.</span><span class="tok-n">load_buffer_inplace_own</span><span class="tok-p">(</span><span class="tok-n">buffer</span><span class="tok-p">,</span> <span class="tok-n">size</span><span class="tok-p">);</span></code></pre>
</div>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c++"><span></span><span class="tok-c1">// You can use load to load document from null-terminated strings, for example literals:</span>
<span class="tok-n">pugi</span><span class="tok-o">::</span><span class="tok-n">xml_parse_result</span> <span class="tok-n">result</span> <span class="tok-o">=</span> <span class="tok-n">doc</span><span class="tok-p">.</span><span class="tok-n">load_string</span><span class="tok-p">(</span><span class="tok-s">&quot;&lt;mesh name=&#39;sphere&#39;&gt;&lt;bounds&gt;0 0 1 1&lt;/bounds&gt;&lt;/mesh&gt;&quot;</span><span class="tok-p">);</span></code></pre>
</div>
</div>
</div>
<div class="sect2">
<h3 id="loading.stream"><a class="anchor" href="#loading.stream"></a><a class="link" href="#loading.stream">4.3. Loading document from C&#43;&#43; IOstreams</a></h3>
<div id="xml_document::load_stream" class="paragraph">
<p>To enhance interoperability, pugixml provides functions for loading document from any object which implements C&#43;&#43; <code>std::istream</code> interface. This allows you to load documents from any standard C&#43;&#43; stream (i.e. file stream) or any third-party compliant implementation (i.e. Boost Iostreams). There are two functions, one works with narrow character streams, another handles wide character ones:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c++"><span></span><span class="tok-n">xml_parse_result</span> <span class="tok-n">xml_document</span><span class="tok-o">::</span><span class="tok-n">load</span><span class="tok-p">(</span><span class="tok-n">std</span><span class="tok-o">::</span><span class="tok-n">istream</span><span class="tok-o">&amp;</span> <span class="tok-n">stream</span><span class="tok-p">,</span> <span class="tok-kt">unsigned</span> <span class="tok-kt">int</span> <span class="tok-n">options</span> <span class="tok-o">=</span> <span class="tok-n">parse_default</span><span class="tok-p">,</span> <span class="tok-n">xml_encoding</span> <span class="tok-n">encoding</span> <span class="tok-o">=</span> <span class="tok-n">encoding_auto</span><span class="tok-p">);</span>
<span class="tok-n">xml_parse_result</span> <span class="tok-n">xml_document</span><span class="tok-o">::</span><span class="tok-n">load</span><span class="tok-p">(</span><span class="tok-n">std</span><span class="tok-o">::</span><span class="tok-n">wistream</span><span class="tok-o">&amp;</span> <span class="tok-n">stream</span><span class="tok-p">,</span> <span class="tok-kt">unsigned</span> <span class="tok-kt">int</span> <span class="tok-n">options</span> <span class="tok-o">=</span> <span class="tok-n">parse_default</span><span class="tok-p">);</span></code></pre>
</div>
</div>
<div class="paragraph">
<p><code>load</code> with <code>std::istream</code> argument loads the document from stream from the current read position to the end, treating the stream contents as a byte stream of the specified encoding (with encoding autodetection as necessary). Thus calling <code>xml_document::load</code> on an opened <code>std::ifstream</code> object is equivalent to calling <code>xml_document::load_file</code>.</p>
</div>
<div class="paragraph">
<p><code>load</code> with <code>std::wstream</code> argument treats the stream contents as a wide character stream (encoding is always <a href="#encoding_wchar">encoding_wchar</a>). Because of this, using <code>load</code> with wide character streams requires careful (usually platform-specific) stream setup (i.e. using the <code>imbue</code> function). Generally use of wide streams is discouraged, however it provides you the ability to load documents from non-Unicode encodings, i.e. you can load Shift-JIS encoded data if you set the correct locale.</p>
</div>
<div class="paragraph">
<p>This is a simple example of loading XML document from file using streams (<a href="samples/load_stream.cpp" class="bare">samples/load_stream.cpp</a>); read the sample code for more complex examples involving wide streams and locales:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c++"><span></span><span class="tok-n">std</span><span class="tok-o">::</span><span class="tok-n">ifstream</span> <span class="tok-n">stream</span><span class="tok-p">(</span><span class="tok-s">&quot;weekly-utf-8.xml&quot;</span><span class="tok-p">);</span>
<span class="tok-n">pugi</span><span class="tok-o">::</span><span class="tok-n">xml_parse_result</span> <span class="tok-n">result</span> <span class="tok-o">=</span> <span class="tok-n">doc</span><span class="tok-p">.</span><span class="tok-n">load</span><span class="tok-p">(</span><span class="tok-n">stream</span><span class="tok-p">);</span></code></pre>
</div>
</div>
</div>
<div class="sect2">
<h3 id="loading.errors"><a class="anchor" href="#loading.errors"></a><a class="link" href="#loading.errors">4.4. Handling parsing errors</a></h3>
<div id="xml_parse_result" class="paragraph">
<p>All document loading functions return the parsing result via <code>xml_parse_result</code> object. It contains parsing status, the offset of last successfully parsed character from the beginning of the source stream, and the encoding of the source stream:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c++"><span></span><span class="tok-k">struct</span> <span class="tok-n">xml_parse_result</span>
<span class="tok-p">{</span>
    <span class="tok-n">xml_parse_status</span> <span class="tok-n">status</span><span class="tok-p">;</span>
    <span class="tok-kt">ptrdiff_t</span> <span class="tok-n">offset</span><span class="tok-p">;</span>
    <span class="tok-n">xml_encoding</span> <span class="tok-n">encoding</span><span class="tok-p">;</span>

    <span class="tok-k">operator</span> <span class="tok-nf">bool</span><span class="tok-p">()</span> <span class="tok-k">const</span><span class="tok-p">;</span>
    <span class="tok-k">const</span> <span class="tok-kt">char</span><span class="tok-o">*</span> <span class="tok-nf">description</span><span class="tok-p">()</span> <span class="tok-k">const</span><span class="tok-p">;</span>
<span class="tok-p">};</span></code></pre>
</div>
</div>
<div class="paragraph">
<p><a id="xml_parse_status"></a><a id="xml_parse_result::status"></a>
Parsing status is represented as the <code>xml_parse_status</code> enumeration and can be one of the following:</p>
</div>
<div class="ulist">
<ul>
<li>
<p><a id="status_ok"></a><code>status_ok</code> means that no error was encountered during parsing; the source stream represents the valid XML document which was fully parsed and converted to a tree.</p>
</li>
<li>
<p><a id="status_file_not_found"></a><code>status_file_not_found</code> is only returned by <code>load_file</code> function and means that file could not be opened.</p>
</li>
<li>
<p><a id="status_io_error"></a><code>status_io_error</code> is returned by <code>load_file</code> function and by <code>load</code> functions with <code>std::istream</code>/<code>std::wstream</code> arguments; it means that some I/O error has occurred during reading the file/stream.</p>
</li>
<li>
<p><a id="status_out_of_memory"></a><code>status_out_of_memory</code> means that there was not enough memory during some allocation; any allocation failure during parsing results in this error.</p>
</li>
<li>
<p><a id="status_internal_error"></a><code>status_internal_error</code> means that something went horribly wrong; currently this error does not occur</p>
</li>
<li>
<p><a id="status_unrecognized_tag"></a><code>status_unrecognized_tag</code> means that parsing stopped due to a tag with either an empty name or a name which starts with incorrect character, such as <code>#</code>.</p>
</li>
<li>
<p><a id="status_bad_pi"></a><code>status_bad_pi</code> means that parsing stopped due to incorrect document declaration/processing instruction</p>
</li>
<li>
<p><a id="status_bad_comment"></a><code>status_bad_comment</code>, <a id="status_bad_cdata"></a><code>status_bad_cdata</code>, <a id="status_bad_doctype"></a><code>status_bad_doctype</code> and <a id="status_bad_pcdata"></a><code>status_bad_pcdata</code> mean that parsing stopped due to the invalid construct of the respective type</p>
</li>
<li>
<p><a id="status_bad_start_element"></a><code>status_bad_start_element</code> means that parsing stopped because starting tag either had no closing <code>&gt;</code> symbol or contained some incorrect symbol</p>
</li>
<li>
<p><a id="status_bad_attribute"></a><code>status_bad_attribute</code> means that parsing stopped because there was an incorrect attribute, such as an attribute without value or with value that is not quoted (note that <code>&lt;node attr=1&gt;</code> is incorrect in XML)</p>
</li>
<li>
<p><a id="status_bad_end_element"></a><code>status_bad_end_element</code> means that parsing stopped because ending tag had incorrect syntax (i.e. extra non-whitespace symbols between tag name and <code>&gt;</code>)</p>
</li>
<li>
<p><a id="status_end_element_mismatch"></a><code>status_end_element_mismatch</code> means that parsing stopped because the closing tag did not match the opening one (i.e. <code>&lt;node&gt;&lt;/nedo&gt;</code>) or because some tag was not closed at all</p>
</li>
<li>
<p><a id="status_no_document_element"></a><code>status_no_document_element</code> means that no element nodes were discovered during parsing; this usually indicates an empty or invalid document</p>
</li>
</ul>
</div>
<div id="xml_parse_result::description" class="paragraph">
<p><code>description()</code> member function can be used to convert parsing status to a string; the returned message is always in English, so you&#8217;ll have to write your own function if you need a localized string. However please note that the exact messages returned by <code>description()</code> function may change from version to version, so any complex status handling should be based on <code>status</code> value. Note that <code>description()</code> returns a <code>char</code> string even in <code>PUGIXML_WCHAR_MODE</code>; you&#8217;ll have to call <a href="#as_wide">as_wide</a> to get the <code>wchar_t</code> string.</p>
</div>
<div class="paragraph">
<p>If parsing failed because the source data was not a valid XML, the resulting tree is not destroyed - despite the fact that load function returns error, you can use the part of the tree that was successfully parsed. Obviously, the last element may have an unexpected name/value; for example, if the attribute value does not end with the necessary quotation mark, like in <code>&lt;node attr="value&gt;some data&lt;/node&gt;</code> example, the value of attribute <code>attr</code> will contain the string <code>value&gt;some data&lt;/node&gt;</code>.</p>
</div>
<div id="xml_parse_result::offset" class="paragraph">
<p>In addition to the status code, parsing result has an <code>offset</code> member, which contains the offset of last successfully parsed character if parsing failed because of an error in source data; otherwise <code>offset</code> is 0. For parsing efficiency reasons, pugixml does not track the current line during parsing; this offset is in units of <a href="#char_t">pugi::char_t</a> (bytes for character mode, wide characters for wide character mode). Many text editors support 'Go To Position' feature - you can use it to locate the exact error position. Alternatively, if you&#8217;re loading the document from memory, you can display the error chunk along with the error description (see the example code below).</p>
</div>
<div class="admonitionblock caution">
<table>
<tr>
<td class="icon">
<div class="title">Caution</div>
</td>
<td class="content">
Offset is calculated in the XML buffer in native encoding; if encoding conversion is performed during parsing, offset can not be used to reliably track the error position.
</td>
</tr>
</table>
</div>
<div id="xml_parse_result::encoding" class="paragraph">
<p>Parsing result also has an <code>encoding</code> member, which can be used to check that the source data encoding was correctly guessed. It is equal to the exact encoding used during parsing (i.e. with the exact endianness); see <a href="#loading.encoding">Encodings</a> for more information.</p>
</div>
<div id="xml_parse_result::bool" class="paragraph">
<p>Parsing result object can be implicitly converted to <code>bool</code>; if you do not want to handle parsing errors thoroughly, you can just check the return value of load functions as if it was a <code>bool</code>: <code>if (doc.load_file("file.xml")) { &#8230;&#8203; } else { &#8230;&#8203; }</code>.</p>
</div>
<div class="paragraph">
<p>This is an example of handling loading errors (<a href="samples/load_error_handling.cpp" class="bare">samples/load_error_handling.cpp</a>):</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c++"><span></span><span class="tok-n">pugi</span><span class="tok-o">::</span><span class="tok-n">xml_document</span> <span class="tok-n">doc</span><span class="tok-p">;</span>
<span class="tok-n">pugi</span><span class="tok-o">::</span><span class="tok-n">xml_parse_result</span> <span class="tok-n">result</span> <span class="tok-o">=</span> <span class="tok-n">doc</span><span class="tok-p">.</span><span class="tok-n">load_string</span><span class="tok-p">(</span><span class="tok-n">source</span><span class="tok-p">);</span>

<span class="tok-k">if</span> <span class="tok-p">(</span><span class="tok-n">result</span><span class="tok-p">)</span>
<span class="tok-p">{</span>
    <span class="tok-n">std</span><span class="tok-o">::</span><span class="tok-n">cout</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-s">&quot;XML [&quot;</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-n">source</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-s">&quot;] parsed without errors, attr value: [&quot;</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-n">doc</span><span class="tok-p">.</span><span class="tok-n">child</span><span class="tok-p">(</span><span class="tok-s">&quot;node&quot;</span><span class="tok-p">).</span><span class="tok-n">attribute</span><span class="tok-p">(</span><span class="tok-s">&quot;attr&quot;</span><span class="tok-p">).</span><span class="tok-n">value</span><span class="tok-p">()</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-s">&quot;]</span><span class="tok-se">\n\n</span><span class="tok-s">&quot;</span><span class="tok-p">;</span>
<span class="tok-p">}</span>
<span class="tok-k">else</span>
<span class="tok-p">{</span>
    <span class="tok-n">std</span><span class="tok-o">::</span><span class="tok-n">cout</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-s">&quot;XML [&quot;</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-n">source</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-s">&quot;] parsed with errors, attr value: [&quot;</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-n">doc</span><span class="tok-p">.</span><span class="tok-n">child</span><span class="tok-p">(</span><span class="tok-s">&quot;node&quot;</span><span class="tok-p">).</span><span class="tok-n">attribute</span><span class="tok-p">(</span><span class="tok-s">&quot;attr&quot;</span><span class="tok-p">).</span><span class="tok-n">value</span><span class="tok-p">()</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-s">&quot;]</span><span class="tok-se">\n</span><span class="tok-s">&quot;</span><span class="tok-p">;</span>
    <span class="tok-n">std</span><span class="tok-o">::</span><span class="tok-n">cout</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-s">&quot;Error description: &quot;</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-n">result</span><span class="tok-p">.</span><span class="tok-n">description</span><span class="tok-p">()</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-s">&quot;</span><span class="tok-se">\n</span><span class="tok-s">&quot;</span><span class="tok-p">;</span>
    <span class="tok-n">std</span><span class="tok-o">::</span><span class="tok-n">cout</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-s">&quot;Error offset: &quot;</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-n">result</span><span class="tok-p">.</span><span class="tok-n">offset</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-s">&quot; (error at [...&quot;</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-p">(</span><span class="tok-n">source</span> <span class="tok-o">+</span> <span class="tok-n">result</span><span class="tok-p">.</span><span class="tok-n">offset</span><span class="tok-p">)</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-s">&quot;]</span><span class="tok-se">\n\n</span><span class="tok-s">&quot;</span><span class="tok-p">;</span>
<span class="tok-p">}</span></code></pre>
</div>
</div>
</div>
<div class="sect2">
<h3 id="loading.options"><a class="anchor" href="#loading.options"></a><a class="link" href="#loading.options">4.5. Parsing options</a></h3>
<div class="paragraph">
<p>All document loading functions accept the optional parameter <code>options</code>. This is a bitmask that customizes the parsing process: you can select the node types that are parsed and various transformations that are performed with the XML text. Disabling certain transformations can improve parsing performance for some documents; however, the code for all transformations is very well optimized, and thus the majority of documents won&#8217;t get any performance benefit. As a rule of thumb, only modify parsing flags if you want to get some nodes in the document that are excluded by default (i.e. declaration or comment nodes).</p>
</div>
<div class="admonitionblock note">
<table>
<tr>
<td class="icon">
<div class="title">Note</div>
</td>
<td class="content">
You should use the usual bitwise arithmetics to manipulate the bitmask: to enable a flag, use <code>mask | flag</code>; to disable a flag, use <code>mask &amp; ~flag</code>.
</td>
</tr>
</table>
</div>
<div class="paragraph">
<p>These flags control the resulting tree contents:</p>
</div>
<div class="ulist">
<ul>
<li>
<p><a id="parse_declaration"></a><code>parse_declaration</code> determines if XML document declaration (node with type <a href="#node_declaration">node_declaration</a>) is to be put in DOM tree. If this flag is off, it is not put in the tree, but is still parsed and checked for correctness. This flag is <strong>off</strong> by default.</p>
</li>
<li>
<p><a id="parse_doctype"></a><code>parse_doctype</code> determines if XML document type declaration (node with type <a href="#node_doctype">node_doctype</a>) is to be put in DOM tree. If this flag is off, it is not put in the tree, but is still parsed and checked for correctness. This flag is <strong>off</strong> by default.</p>
</li>
<li>
<p><a id="parse_pi"></a><code>parse_pi</code> determines if processing instructions (nodes with type <a href="#node_pi">node_pi</a>) are to be put in DOM tree. If this flag is off, they are not put in the tree, but are still parsed and checked for correctness. Note that <code>&lt;?xml &#8230;&#8203;?&gt;</code> (document declaration) is not considered to be a PI. This flag is <strong>off</strong> by default.</p>
</li>
<li>
<p><a id="parse_comments"></a><code>parse_comments</code> determines if comments (nodes with type <a href="#node_comment">node_comment</a>) are to be put in DOM tree. If this flag is off, they are not put in the tree, but are still parsed and checked for correctness. This flag is <strong>off</strong> by default.</p>
</li>
<li>
<p><a id="parse_cdata"></a><code>parse_cdata</code> determines if CDATA sections (nodes with type <a href="#node_cdata">node_cdata</a>) are to be put in DOM tree. If this flag is off, they are not put in the tree, but are still parsed and checked for correctness. This flag is <strong>on</strong> by default.</p>
</li>
<li>
<p><a id="parse_trim_pcdata"></a><code>parse_trim_pcdata</code> determines if leading and trailing whitespace characters are to be removed from PCDATA nodes. While for some applications leading/trailing whitespace is significant, often the application only cares about the non-whitespace contents so it&#8217;s easier to trim whitespace from text during parsing. This flag is <strong>off</strong> by default.</p>
</li>
<li>
<p><a id="parse_ws_pcdata"></a><code>parse_ws_pcdata</code> determines if PCDATA nodes (nodes with type <a href="#node_pcdata">node_pcdata</a>) that consist only of whitespace characters are to be put in DOM tree. Often whitespace-only data is not significant for the application, and the cost of allocating and storing such nodes (both memory and speed-wise) can be significant. For example, after parsing XML string <code>&lt;node&gt; &lt;a/&gt; &lt;/node&gt;</code>, <code>&lt;node&gt;</code> element will have three children when <code>parse_ws_pcdata</code> is set (child with type <a href="#node_pcdata">node_pcdata</a> and value <code>" "</code>, child with type <a href="#node_element">node_element</a> and name <code>"a"</code>, and another child with type <a href="#node_pcdata">node_pcdata</a> and value <code>" "</code>), and only one child when <code>parse_ws_pcdata</code> is not set. This flag is <strong>off</strong> by default.</p>
</li>
<li>
<p><a id="parse_ws_pcdata_single"></a><code>parse_ws_pcdata_single</code> determines if whitespace-only PCDATA nodes that have no sibling nodes are to be put in DOM tree. In some cases application needs to parse the whitespace-only contents of nodes, i.e. <code>&lt;node&gt;  &lt;/node&gt;</code>, but is not interested in whitespace markup elsewhere. It is possible to use <a href="#parse_ws_pcdata">parse_ws_pcdata</a> flag in this case, but it results in excessive allocations and complicates document processing; this flag can be used to avoid that. As an example, after parsing XML string <code>&lt;node&gt; &lt;a&gt;  &lt;/a&gt; &lt;/node&gt;</code> with <code>parse_ws_pcdata_single</code> flag set, <code>&lt;node&gt;</code> element will have one child <code>&lt;a&gt;</code>, and <code>&lt;a&gt;</code> element will have one child with type <a href="#node_pcdata">node_pcdata</a> and value <code>"  "</code>. This flag has no effect if <a href="#parse_ws_pcdata">parse_ws_pcdata</a> is enabled. This flag is <strong>off</strong> by default.</p>
</li>
<li>
<p><a id="parse_embed_pcdata"></a><code>parse_embed_pcdata</code> determines if PCDATA contents is to be saved as element values. Normally element nodes have names but not values; this flag forces the parser to store the contents as a value if PCDATA is the first child of the element node (otherwise PCDATA node is created as usual). This can significantly reduce the memory required for documents with many PCDATA nodes. To retrieve the data you can use <code>xml_node::value()</code> on the element nodes or any of the higher-level functions like <code>child_value</code> or <code>text</code>. This flag is <strong>off</strong> by default.
Since this flag significantly changes the DOM structure it is only recommended for parsing documents with many PCDATA nodes in memory-constrained environments. This flag is <strong>off</strong> by default.</p>
</li>
<li>
<p><a id="parse_fragment"></a><code>parse_fragment</code> determines if document should be treated as a fragment of a valid XML. Parsing document as a fragment leads to top-level PCDATA content (i.e. text that is not located inside a node) to be added to a tree, and additionally treats documents without element nodes as valid. This flag is <strong>off</strong> by default.</p>
</li>
</ul>
</div>
<div class="admonitionblock caution">
<table>
<tr>
<td class="icon">
<div class="title">Caution</div>
</td>
<td class="content">
Using in-place parsing (<a href="#xml_document::load_buffer_inplace">load_buffer_inplace</a>) with <code>parse_fragment</code> flag may result in the loss of the last character of the buffer if it is a part of PCDATA. Since PCDATA values are null-terminated strings, the only way to resolve this is to provide a null-terminated buffer as an input to <code>load_buffer_inplace</code> - i.e. <code>doc.load_buffer_inplace("test\0", 5, pugi::parse_default | pugi::parse_fragment)</code>.
</td>
</tr>
</table>
</div>
<div class="paragraph">
<p>These flags control the transformation of tree element contents:</p>
</div>
<div class="ulist">
<ul>
<li>
<p><a id="parse_escapes"></a><code>parse_escapes</code> determines if character and entity references are to be expanded during the parsing process. Character references have the form <code>&amp;#&#8230;&#8203;;</code> or <code>&amp;#x&#8230;&#8203;;</code> (<code>&#8230;&#8203;</code> is Unicode numeric representation of character in either decimal (<code>&amp;#&#8230;&#8203;;</code>) or hexadecimal (<code>&amp;#x&#8230;&#8203;;</code>) form), entity references are <code>&amp;lt;</code>, <code>&amp;gt;</code>, <code>&amp;amp;</code>, <code>&amp;apos;</code> and <code>&amp;quot;</code> (note that as pugixml does not handle DTD, the only allowed entities are predefined ones). If character/entity reference can not be expanded, it is left as is, so you can do additional processing later. Reference expansion is performed on attribute values and PCDATA content. This flag is <strong>on</strong> by default.</p>
</li>
<li>
<p><a id="parse_eol"></a><code>parse_eol</code> determines if EOL handling (that is, replacing sequences <code>\r\n</code> by a single <code>\n</code> character, and replacing all standalone <code>\r</code> characters by <code>\n</code>) is to be performed on input data (that is, comment contents, PCDATA/CDATA contents and attribute values). This flag is <strong>on</strong> by default.</p>
</li>
<li>
<p><a id="parse_wconv_attribute"></a><code>parse_wconv_attribute</code> determines if attribute value normalization should be performed for all attributes. This means, that whitespace characters (new line, tab and space) are replaced with space (<code>' '</code>). New line characters are always treated as if <a href="#parse_eol">parse_eol</a> is set, i.e. <code>\r\n</code> is converted to a single space.  This flag is <strong>on</strong> by default.</p>
</li>
<li>
<p><a id="parse_wnorm_attribute"></a><code>parse_wnorm_attribute</code> determines if extended attribute value normalization should be performed for all attributes. This means, that after attribute values are normalized as if <a href="#parse_wconv_attribute">parse_wconv_attribute</a> was set, leading and trailing space characters are removed, and all sequences of space characters are replaced by a single space character. <a href="#parse_wconv_attribute">parse_wconv_attribute</a> has no effect if this flag is on. This flag is <strong>off</strong> by default.</p>
</li>
</ul>
</div>
<div class="admonitionblock note">
<table>
<tr>
<td class="icon">
<div class="title">Note</div>
</td>
<td class="content">
<code>parse_wconv_attribute</code> option performs transformations that are required by W3C specification for attributes that are declared as CDATA; <a href="#parse_wnorm_attribute">parse_wnorm_attribute</a> performs transformations required for NMTOKENS attributes. In the absence of document type declaration all attributes should behave as if they are declared as CDATA, thus <a href="#parse_wconv_attribute">parse_wconv_attribute</a> is the default option.
</td>
</tr>
</table>
</div>
<div class="paragraph">
<p>Additionally there are three predefined option masks:</p>
</div>
<div class="ulist">
<ul>
<li>
<p><a id="parse_minimal"></a><code>parse_minimal</code> has all options turned off. This option mask means that pugixml does not add declaration nodes, document type declaration nodes, PI nodes, CDATA sections and comments to the resulting tree and does not perform any conversion for input data, so theoretically it is the fastest mode. However, as mentioned above, in practice <a href="#parse_default">parse_default</a> is usually equally fast.</p>
</li>
<li>
<p><a id="parse_default"></a><code>parse_default</code> is the default set of flags, i.e. it has all options set to their default values. It includes parsing CDATA sections (comments/PIs are not parsed), performing character and entity reference expansion, replacing whitespace characters with spaces in attribute values and performing EOL handling. Note, that PCDATA sections consisting only of whitespace characters are not parsed (by default) for performance reasons.</p>
</li>
<li>
<p><a id="parse_full"></a><code>parse_full</code> is the set of flags which adds nodes of all types to the resulting tree and performs default conversions for input data. It includes parsing CDATA sections, comments, PI nodes, document declaration node and document type declaration node, performing character and entity reference expansion, replacing whitespace characters with spaces in attribute values and performing EOL handling. Note, that PCDATA sections consisting only of whitespace characters are not parsed in this mode.</p>
</li>
</ul>
</div>
<div class="paragraph">
<p>This is an example of using different parsing options (<a href="samples/load_options.cpp" class="bare">samples/load_options.cpp</a>):</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c++"><span></span><span class="tok-k">const</span> <span class="tok-kt">char</span><span class="tok-o">*</span> <span class="tok-n">source</span> <span class="tok-o">=</span> <span class="tok-s">&quot;&lt;!--comment--&gt;&lt;node&gt;&amp;lt;&lt;/node&gt;&quot;</span><span class="tok-p">;</span>

<span class="tok-c1">// Parsing with default options; note that comment node is not added to the tree, and entity reference &amp;lt; is expanded</span>
<span class="tok-n">doc</span><span class="tok-p">.</span><span class="tok-n">load_string</span><span class="tok-p">(</span><span class="tok-n">source</span><span class="tok-p">);</span>
<span class="tok-n">std</span><span class="tok-o">::</span><span class="tok-n">cout</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-s">&quot;First node value: [&quot;</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-n">doc</span><span class="tok-p">.</span><span class="tok-n">first_child</span><span class="tok-p">().</span><span class="tok-n">value</span><span class="tok-p">()</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-s">&quot;], node child value: [&quot;</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-n">doc</span><span class="tok-p">.</span><span class="tok-n">child_value</span><span class="tok-p">(</span><span class="tok-s">&quot;node&quot;</span><span class="tok-p">)</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-s">&quot;]</span><span class="tok-se">\n</span><span class="tok-s">&quot;</span><span class="tok-p">;</span>

<span class="tok-c1">// Parsing with additional parse_comments option; comment node is now added to the tree</span>
<span class="tok-n">doc</span><span class="tok-p">.</span><span class="tok-n">load_string</span><span class="tok-p">(</span><span class="tok-n">source</span><span class="tok-p">,</span> <span class="tok-n">pugi</span><span class="tok-o">::</span><span class="tok-n">parse_default</span> <span class="tok-o">|</span> <span class="tok-n">pugi</span><span class="tok-o">::</span><span class="tok-n">parse_comments</span><span class="tok-p">);</span>
<span class="tok-n">std</span><span class="tok-o">::</span><span class="tok-n">cout</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-s">&quot;First node value: [&quot;</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-n">doc</span><span class="tok-p">.</span><span class="tok-n">first_child</span><span class="tok-p">().</span><span class="tok-n">value</span><span class="tok-p">()</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-s">&quot;], node child value: [&quot;</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-n">doc</span><span class="tok-p">.</span><span class="tok-n">child_value</span><span class="tok-p">(</span><span class="tok-s">&quot;node&quot;</span><span class="tok-p">)</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-s">&quot;]</span><span class="tok-se">\n</span><span class="tok-s">&quot;</span><span class="tok-p">;</span>

<span class="tok-c1">// Parsing with additional parse_comments option and without the (default) parse_escapes option; &amp;lt; is not expanded</span>
<span class="tok-n">doc</span><span class="tok-p">.</span><span class="tok-n">load_string</span><span class="tok-p">(</span><span class="tok-n">source</span><span class="tok-p">,</span> <span class="tok-p">(</span><span class="tok-n">pugi</span><span class="tok-o">::</span><span class="tok-n">parse_default</span> <span class="tok-o">|</span> <span class="tok-n">pugi</span><span class="tok-o">::</span><span class="tok-n">parse_comments</span><span class="tok-p">)</span> <span class="tok-o">&amp;</span> <span class="tok-o">~</span><span class="tok-n">pugi</span><span class="tok-o">::</span><span class="tok-n">parse_escapes</span><span class="tok-p">);</span>
<span class="tok-n">std</span><span class="tok-o">::</span><span class="tok-n">cout</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-s">&quot;First node value: [&quot;</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-n">doc</span><span class="tok-p">.</span><span class="tok-n">first_child</span><span class="tok-p">().</span><span class="tok-n">value</span><span class="tok-p">()</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-s">&quot;], node child value: [&quot;</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-n">doc</span><span class="tok-p">.</span><span class="tok-n">child_value</span><span class="tok-p">(</span><span class="tok-s">&quot;node&quot;</span><span class="tok-p">)</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-s">&quot;]</span><span class="tok-se">\n</span><span class="tok-s">&quot;</span><span class="tok-p">;</span>

<span class="tok-c1">// Parsing with minimal option mask; comment node is not added to the tree, and &amp;lt; is not expanded</span>
<span class="tok-n">doc</span><span class="tok-p">.</span><span class="tok-n">load_string</span><span class="tok-p">(</span><span class="tok-n">source</span><span class="tok-p">,</span> <span class="tok-n">pugi</span><span class="tok-o">::</span><span class="tok-n">parse_minimal</span><span class="tok-p">);</span>
<span class="tok-n">std</span><span class="tok-o">::</span><span class="tok-n">cout</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-s">&quot;First node value: [&quot;</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-n">doc</span><span class="tok-p">.</span><span class="tok-n">first_child</span><span class="tok-p">().</span><span class="tok-n">value</span><span class="tok-p">()</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-s">&quot;], node child value: [&quot;</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-n">doc</span><span class="tok-p">.</span><span class="tok-n">child_value</span><span class="tok-p">(</span><span class="tok-s">&quot;node&quot;</span><span class="tok-p">)</span> <span class="tok-o">&lt;&lt;</span> <span class="tok-s">&quot;]</span><span class="tok-se">\n</span><span class="tok-s">&quot;</span><span class="tok-p">;</span></code></pre>
</div>
</div>
</div>
<div class="sect2">
<h3 id="loading.encoding"><a class="anchor" href="#loading.encoding"></a><a class="link" href="#loading.encoding">4.6. Encodings</a></h3>
<div id="xml_encoding" class="paragraph">
<p>pugixml supports all popular Unicode encodings (UTF-8, UTF-16 (big and little endian), UTF-32 (big and little endian); UCS-2 is naturally supported since it&#8217;s a strict subset of UTF-16) as well as some non-Unicode encodings (Latin-1) and handles all encoding conversions. Most loading functions accept the optional parameter <code>encoding</code>. This is a value of enumeration type <code>xml_encoding</code>, that can have the following values:</p>
</div>
<div class="ulist">
<ul>
<li>
<p><a id="encoding_auto"></a><code>encoding_auto</code> means that pugixml will try to guess the encoding based on source XML data. The algorithm is a modified version of the one presented in <a href="http://www.w3.org/TR/REC-xml/#sec-guessing">Appendix F of XML recommendation</a>. It tries to find a Byte Order Mark of one of the supported encodings first; if that fails, it checks if the first few bytes of the input data look like a representation of <code>&lt;</code> or <code>&lt;?</code> in one of UTF-16 or UTF-32 variants; if that fails as well, encoding is assumed to be either UTF-8 or one of the non-Unicode encodings - to make the final decision the algorithm tries to parse the <code>encoding</code> attribute of the XML document declaration, ultimately falling back to UTF-8 if document declaration is not present or does not specify a supported encoding.</p>
</li>
<li>
<p><a id="encoding_utf8"></a><code>encoding_utf8</code> corresponds to UTF-8 encoding as defined in the Unicode standard; UTF-8 sequences with length equal to 5 or 6 are not standard and are rejected.</p>
</li>
<li>
<p><a id="encoding_utf16_le"></a><code>encoding_utf16_le</code> corresponds to little-endian UTF-16 encoding as defined in the Unicode standard; surrogate pairs are supported.</p>
</li>
<li>
<p><a id="encoding_utf16_be"></a><code>encoding_utf16_be</code> corresponds to big-endian UTF-16 encoding as defined in the Unicode standard; surrogate pairs are supported.</p>
</li>
<li>
<p><a id="encoding_utf16"></a><code>encoding_utf16</code> corresponds to UTF-16 encoding as defined in the Unicode standard; the endianness is assumed to be that of the target platform.</p>
</li>
<li>
<p><a id="encoding_utf32_le"></a><code>encoding_utf32_le</code> corresponds to little-endian UTF-32 encoding as defined in the Unicode standard.</p>
</li>
<li>
<p><a id="encoding_utf32_be"></a><code>encoding_utf32_be</code> corresponds to big-endian UTF-32 encoding as defined in the Unicode standard.</p>
</li>
<li>
<p><a id="encoding_utf32"></a><code>encoding_utf32</code> corresponds to UTF-32 encoding as defined in the Unicode standard; the endianness is assumed to be that of the target platform.</p>
</li>
<li>
<p><a id="encoding_wchar"></a><code>encoding_wchar</code> corresponds to the encoding of <code>wchar_t</code> type; it has the same meaning as either <code>encoding_utf16</code> or <code>encoding_utf32</code>, depending on <code>wchar_t</code> size.</p>
</li>
<li>
<p><a id="encoding_latin1"></a><code>encoding_latin1</code> corresponds to ISO-8859-1 encoding (also known as Latin-1).</p>
</li>
</ul>
</div>
<div class="paragraph">
<p>The algorithm used for <code>encoding_auto</code> correctly detects any supported Unicode encoding for all well-formed XML documents (since they start with document declaration) and for all other XML documents that start with <code>&lt;</code>; if your XML document does not start with <code>&lt;</code> and has encoding that is different from UTF-8, use the specific encoding.</p>
</div>
<div class="admonitionblock note">
<table>
<tr>
<td class="icon">
<div class="title">Note</div>
</td>
<td class="content">
The current behavior for Unicode conversion is to skip all invalid UTF sequences during conversion. This behavior should not be relied upon; moreover, in case no encoding conversion is performed, the invalid sequences are not removed, so you&#8217;ll get them as is in node/attribute contents.
</td>
</tr>
</table>
</div>
</div>
<div class="sect2">
<h3 id="loading.w3c"><a class="anchor" href="#loading.w3c"></a><a class="link" href="#loading.w3c">4.7. Conformance to W3C specification</a></h3>
<div class="paragraph">
<p>pugixml is not fully W3C conformant - it can load any valid XML document, but does not perform some well-formedness checks. While considerable effort is made to reject invalid XML documents, some validation is not performed because of performance reasons.</p>
</div>
<div class="paragraph">
<p>There is only one non-conformant behavior when dealing with valid XML documents: pugixml does not use information supplied in document type declaration for parsing. This means that entities declared in DOCTYPE are not expanded, and all attribute/PCDATA values are always processed in a uniform way that depends only on parsing options.</p>
</div>
<div class="paragraph">
<p>As for rejecting invalid XML documents, there are a number of incompatibilities with W3C specification, including:</p>
</div>
<div class="ulist">
<ul>
<li>
<p>Multiple attributes of the same node can have equal names.</p>
</li>
<li>
<p>Tag and attribute names are not fully validated for consisting of allowed characters, so some invalid tags are not rejected</p>
</li>
<li>
<p>Attribute values which contain <code>&lt;</code> are not rejected.</p>
</li>
<li>
<p>Invalid entity/character references are not rejected and are instead left as is.</p>
</li>
<li>
<p>Comment values can contain <code>--</code>.</p>
</li>
<li>
<p>XML data is not required to begin with document declaration; additionally, document declaration can appear after comments and other nodes.</p>
</li>
<li>
<p>Invalid document type declarations are silently ignored in some cases.</p>
</li>
<li>
<p>Unicode validation is not performed so invalid UTF sequences are not rejected.</p>
</li>
</ul>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="access"><a class="anchor" href="#access"></a><a class="link" href="#access">5. Accessing document data</a></h2>
<div class="sectionbody">
<div class="paragraph">
<p>pugixml features an extensive interface for getting various types of data from the document and for traversing the document. This section provides documentation for all such functions that do not modify the tree except for XPath-related functions; see <a href="#xpath">XPath</a> for XPath reference. As discussed in <a href="#dom.cpp">C&#43;&#43; interface</a>, there are two types of handles to tree data - <a href="#xml_node">xml_node</a> and <a href="#xml_attribute">xml_attribute</a>. The handles have special null (empty) values which propagate through various functions and thus are useful for writing more concise code; see <a href="#node_null">this description</a> for details. The documentation in this section will explicitly state the results of all function in case of null inputs.</p>
</div>
<div class="sect2">
<h3 id="access.basic"><a class="anchor" href="#access.basic"></a><a class="link" href="#access.basic">Basic traversal functions</a></h3>
<div class="paragraph">
<p><a id="xml_node::parent"></a><a id="xml_node::first_child"></a><a id="xml_node::last_child"></a><a id="xml_node::next_sibling"></a><a id="xml_node::previous_sibling"></a><a id="xml_node::first_attribute"></a><a id="xml_node::last_attribute"></a><a id="xml_attribute::next_attribute"></a><a id="xml_attribute::previous_attribute"></a>
The internal representation of the document is a tree, where each node has a list of child nodes (the order of children corresponds to their order in the XML representation), and additionally element nodes have a list of attributes, which is also ordered. Several functions are provided in order to let you get from one node in the tree to the other. These functions roughly correspond to the internal representation, and thus are usually building blocks for other methods of traversing (i.e. XPath traversals are based on these functions).</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c++"><span></span><span class="tok-n">xml_node</span> <span class="tok-n">xml_node</span><span class="tok-o">::</span><span class="tok-n">parent</span><span class="tok-p">()</span> <span class="tok-k">const</span><span class="tok-p">;</span>
<span class="tok-n">xml_node</span> <span class="tok-n">xml_node</span><span class="tok-o">::</span><span class="tok-n">first_child</span><span class="tok-p">()</span> <span class="tok-k">const</span><span class="tok-p">;</span>
<span class="tok-n">xml_node</span> <span class="tok-n">xml_node</span><span class="tok-o">::</span><span class="tok-n">last_child</span><span class="tok-p">()</span> <span class="tok-k">const</span><span class="tok-p">;</span>
<span class="tok-n">xml_node</span> <span class="tok-n">xml_node</span><span class="tok-o">::</span><span class="tok-n">next_sibling</span><span class="tok-p">()</span> <span class="tok-k">const</span><span class="tok-p">;</span>
<span class="tok-n">xml_node</span> <span class="tok-n">xml_node</span><span class="tok-o">::</span><span class="tok-n">previous_sibling</span><span class="tok-p">()</span> <span class="tok-k">const</span><span class="tok-p">;</span>

<span class="tok-n">xml_attribute</span> <span class="tok-n">xml_node</span><span class="tok-o">::</span><span class="tok-n">first_attribute</span><span class="tok-p">()</span> <span class="tok-k">const</span><span class="tok-p">;</span>