1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html> 3<head> 4<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 5<title>Class template polymorphic_allocator</title> 6<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css"> 7<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 8<link rel="home" href="../../../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> 9<link rel="up" href="../../../boost_container_header_reference.html#header.boost.container.pmr.polymorphic_allocator_hpp" title="Header <boost/container/pmr/polymorphic_allocator.hpp>"> 10<link rel="prev" href="monotonic_buffer_resource.html" title="Class monotonic_buffer_resource"> 11<link rel="next" href="operator__.html" title="Function template operator=="> 12</head> 13<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 14<table cellpadding="2" 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accesskey="n" href="operator__.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 25</div> 26<div class="refentry"> 27<a name="boost.container.pmr.polymorphic_allocator"></a><div class="titlepage"></div> 28<div class="refnamediv"> 29<h2><span class="refentrytitle">Class template polymorphic_allocator</span></h2> 30<p>boost::container::pmr::polymorphic_allocator</p> 31</div> 32<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2> 33<div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: <<a class="link" href="../../../boost_container_header_reference.html#header.boost.container.pmr.polymorphic_allocator_hpp" title="Header <boost/container/pmr/polymorphic_allocator.hpp>">boost/container/pmr/polymorphic_allocator.hpp</a>> 34 35</span><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> T<span class="special">></span> 36<span class="keyword">class</span> <a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a> <span class="special">{</span> 37<span class="keyword">public</span><span class="special">:</span> 38 <span class="comment">// types</span> 39 <span class="keyword">typedef</span> <span class="identifier">T</span> <a name="boost.container.pmr.polymorphic_allocator.value_type"></a><span class="identifier">value_type</span><span class="special">;</span> 40 41 <span class="comment">// <a class="link" href="polymorphic_allocator.html#boost.container.pmr.polymorphic_allocatorconstruct-copy-destruct">construct/copy/destruct</a></span> 42 <a class="link" href="polymorphic_allocator.html#idm45641212504720-bb"><span class="identifier">polymorphic_allocator</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span> 43 <a class="link" href="polymorphic_allocator.html#idm45641212502736-bb"><span class="identifier">polymorphic_allocator</span></a><span class="special">(</span><a class="link" href="memory_resource.html" title="Class memory_resource">memory_resource</a> <span class="special">*</span><span class="special">)</span><span class="special">;</span> 44 <a class="link" href="polymorphic_allocator.html#idm45641212497808-bb"><span class="identifier">polymorphic_allocator</span></a><span class="special">(</span><span class="keyword">const</span> <a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a> <span class="special">&</span><span class="special">)</span><span class="special">;</span> 45 <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> U<span class="special">></span> 46 <a class="link" href="polymorphic_allocator.html#idm45641212495392-bb"><span class="identifier">polymorphic_allocator</span></a><span class="special">(</span><span class="keyword">const</span> <a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a><span class="special"><</span> <span class="identifier">U</span> <span class="special">></span> <span class="special">&</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span> 47 <a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a> <span class="special">&</span> <a class="link" href="polymorphic_allocator.html#idm45641212491856-bb"><span class="keyword">operator</span><span class="special">=</span></a><span class="special">(</span><span class="keyword">const</span> <a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a> <span class="special">&</span><span class="special">)</span><span class="special">;</span> 48 49 <span class="comment">// <a class="link" href="polymorphic_allocator.html#idm45641212531040-bb">public member functions</a></span> 50 <span class="identifier">T</span> <span class="special">*</span> <a class="link" href="polymorphic_allocator.html#idm45641212530480-bb"><span class="identifier">allocate</span></a><span class="special">(</span><span class="identifier">size_t</span><span class="special">)</span><span class="special">;</span> 51 <span class="keyword">void</span> <a class="link" href="polymorphic_allocator.html#idm45641212527472-bb"><span class="identifier">deallocate</span></a><span class="special">(</span><span class="identifier">T</span> <span class="special">*</span><span class="special">,</span> <span class="identifier">size_t</span><span class="special">)</span><span class="special">;</span> 52 <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> U<span class="special">,</span> <span class="keyword">class</span> <span class="special">...</span> Args<span class="special">></span> <span class="keyword">void</span> <a class="link" href="polymorphic_allocator.html#idm45641212522000-bb"><span class="identifier">construct</span></a><span class="special">(</span><span class="identifier">U</span> <span class="special">*</span><span class="special">,</span> <span class="identifier">Args</span> <span class="special">&&</span><span class="special">...</span><span class="special">)</span><span class="special">;</span> 53 <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> U<span class="special">></span> <span class="keyword">void</span> <a class="link" href="polymorphic_allocator.html#idm45641212513312-bb"><span class="identifier">destroy</span></a><span class="special">(</span><span class="identifier">U</span> <span class="special">*</span><span class="special">)</span><span class="special">;</span> 54 <a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a> <a class="link" href="polymorphic_allocator.html#idm45641212509952-bb"><span class="identifier">select_on_container_copy_construction</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span> 55 <a class="link" href="memory_resource.html" title="Class memory_resource">memory_resource</a> <span class="special">*</span> <a class="link" href="polymorphic_allocator.html#idm45641212507264-bb"><span class="identifier">resource</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span> 56<span class="special">}</span><span class="special">;</span></pre></div> 57<div class="refsect1"> 58<a name="id-1.3.10.14.23.3.4"></a><h2>Description</h2> 59<p>A specialization of class template <code class="computeroutput"><a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a></code> conforms to the Allocator requirements. Constructed with different memory resources, different instances of the same specialization of <code class="computeroutput"><a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a></code> can exhibit entirely different allocation behavior. This runtime polymorphism allows objects that use <a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a> to behave as if they used different allocator types at run time even though they use the same static allocator type. </p> 60<div class="refsect2"> 61<a name="id-1.3.10.14.23.3.4.3"></a><h3> 62<a name="boost.container.pmr.polymorphic_allocatorconstruct-copy-destruct"></a><code class="computeroutput">polymorphic_allocator</code> 63 public 64 construct/copy/destruct</h3> 65<div class="orderedlist"><ol class="orderedlist" type="1"> 66<li class="listitem"> 67<pre class="literallayout"><a name="idm45641212504720-bb"></a><span class="identifier">polymorphic_allocator</span><span class="special">(</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></pre> 68<p><span class="bold"><strong>Effects</strong></span>: Sets m_resource to <code class="computeroutput">get_default_resource()</code>. </p> 69</li> 70<li class="listitem"> 71<pre class="literallayout"><a name="idm45641212502736-bb"></a><span class="identifier">polymorphic_allocator</span><span class="special">(</span><a class="link" href="memory_resource.html" title="Class memory_resource">memory_resource</a> <span class="special">*</span> r<span class="special">)</span><span class="special">;</span></pre> 72<p><span class="bold"><strong>Requires</strong></span>: r is non-null.</p> 73<p><span class="bold"><strong>Effects</strong></span>: Sets m_resource to r.</p> 74<p><span class="bold"><strong>Throws</strong></span>: Nothing</p> 75<p><span class="bold"><strong>Notes</strong></span>: This constructor provides an implicit conversion from memory_resource*. Non-standard extension: if r is null m_resource is set to get_default_resource(). </p> 76</li> 77<li class="listitem"> 78<pre class="literallayout"><a name="idm45641212497808-bb"></a><span class="identifier">polymorphic_allocator</span><span class="special">(</span><span class="keyword">const</span> <a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a> <span class="special">&</span> other<span class="special">)</span><span class="special">;</span></pre> 79<p><span class="bold"><strong>Effects</strong></span>: Sets m_resource to other.resource(). </p> 80</li> 81<li class="listitem"> 82<pre class="literallayout"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> U<span class="special">></span> 83 <a name="idm45641212495392-bb"></a><span class="identifier">polymorphic_allocator</span><span class="special">(</span><span class="keyword">const</span> <a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a><span class="special"><</span> <span class="identifier">U</span> <span class="special">></span> <span class="special">&</span> other<span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></pre> 84<p><span class="bold"><strong>Effects</strong></span>: Sets m_resource to other.resource(). </p> 85</li> 86<li class="listitem"> 87<pre class="literallayout"><a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a> <span class="special">&</span> <a name="idm45641212491856-bb"></a><span class="keyword">operator</span><span class="special">=</span><span class="special">(</span><span class="keyword">const</span> <a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a> <span class="special">&</span> other<span class="special">)</span><span class="special">;</span></pre> 88<p><span class="bold"><strong>Effects</strong></span>: Sets m_resource to other.resource(). </p> 89</li> 90</ol></div> 91</div> 92<div class="refsect2"> 93<a name="id-1.3.10.14.23.3.4.4"></a><h3> 94<a name="idm45641212531040-bb"></a><code class="computeroutput">polymorphic_allocator</code> public member functions</h3> 95<div class="orderedlist"><ol class="orderedlist" type="1"> 96<li class="listitem"> 97<pre class="literallayout"><span class="identifier">T</span> <span class="special">*</span> <a name="idm45641212530480-bb"></a><span class="identifier">allocate</span><span class="special">(</span><span class="identifier">size_t</span> n<span class="special">)</span><span class="special">;</span></pre> 98<p><span class="bold"><strong>Returns</strong></span>: Equivalent to <code class="computeroutput">static_cast<T*>(m_resource->allocate(n * sizeof(T), alignof(T)))</code>. </p> 99</li> 100<li class="listitem"> 101<pre class="literallayout"><span class="keyword">void</span> <a name="idm45641212527472-bb"></a><span class="identifier">deallocate</span><span class="special">(</span><span class="identifier">T</span> <span class="special">*</span> p<span class="special">,</span> <span class="identifier">size_t</span> n<span class="special">)</span><span class="special">;</span></pre> 102<p><span class="bold"><strong>Requires</strong></span>: p was allocated from a memory resource, x, equal to *m_resource, using <code class="computeroutput">x.allocate(n * sizeof(T), alignof(T))</code>.</p> 103<p><span class="bold"><strong>Effects</strong></span>: Equivalent to m_resource->deallocate(p, n * sizeof(T), alignof(T)).</p> 104<p><span class="bold"><strong>Throws</strong></span>: Nothing. </p> 105</li> 106<li class="listitem"> 107<pre class="literallayout"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> U<span class="special">,</span> <span class="keyword">class</span> <span class="special">...</span> Args<span class="special">></span> <span class="keyword">void</span> <a name="idm45641212522000-bb"></a><span class="identifier">construct</span><span class="special">(</span><span class="identifier">U</span> <span class="special">*</span> p<span class="special">,</span> <span class="identifier">Args</span> <span class="special">&&</span><span class="special">...</span> args<span class="special">)</span><span class="special">;</span></pre> 108<p><span class="bold"><strong>Requires</strong></span>: Uses-allocator construction of T with allocator <code class="computeroutput">*this</code> and constructor arguments <code class="computeroutput">std::forward<Args>(args)...</code> is well-formed. [Note: uses-allocator construction is always well formed for types that do not use allocators. - end note]</p> 109<p><span class="bold"><strong>Effects</strong></span>: Construct a T object at p by uses-allocator construction with allocator <code class="computeroutput">*this</code> and constructor arguments <code class="computeroutput">std::forward<Args>(args)...</code>.</p> 110<p><span class="bold"><strong>Throws</strong></span>: Nothing unless the constructor for T throws. </p> 111</li> 112<li class="listitem"> 113<pre class="literallayout"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> U<span class="special">></span> <span class="keyword">void</span> <a name="idm45641212513312-bb"></a><span class="identifier">destroy</span><span class="special">(</span><span class="identifier">U</span> <span class="special">*</span> p<span class="special">)</span><span class="special">;</span></pre> 114<p><span class="bold"><strong>Effects</strong></span>: p->~U(). </p> 115</li> 116<li class="listitem"> 117<pre class="literallayout"><a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a> <a name="idm45641212509952-bb"></a><span class="identifier">select_on_container_copy_construction</span><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre> 118<p><span class="bold"><strong>Returns</strong></span>: Equivalent to <code class="computeroutput">polymorphic_allocator()</code>. </p> 119</li> 120<li class="listitem"> 121<pre class="literallayout"><a class="link" href="memory_resource.html" title="Class memory_resource">memory_resource</a> <span class="special">*</span> <a name="idm45641212507264-bb"></a><span class="identifier">resource</span><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre> 122<p><span class="bold"><strong>Returns</strong></span>: m_resource. </p> 123</li> 124</ol></div> 125</div> 126</div> 127</div> 128<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 129<td align="left"></td> 130<td align="right"><div class="copyright-footer">Copyright © 2009-2018 Ion Gaztanaga<p> 131 Distributed under the Boost Software License, Version 1.0. (See accompanying 132 file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) 133 </p> 134</div></td> 135</tr></table> 136<hr> 137<div class="spirit-nav"> 138<a accesskey="p" href="monotonic_buffer_resource.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../boost_container_header_reference.html#header.boost.container.pmr.polymorphic_allocator_hpp"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="operator__.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 139</div> 140</body> 141</html> 142
