1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0.1 Transitional//EN"> 2 3<html> 4<head> 5<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> 6<title>Boost.Flyweight Documentation - Holders reference</title> 7<link rel="stylesheet" href="../style.css" type="text/css"> 8<link rel="start" href="../index.html"> 9<link rel="prev" href="factories.html"> 10<link rel="up" href="index.html"> 11<link rel="next" href="locking.html"> 12</head> 13 14<body> 15<h1><img src="../../../../boost.png" alt="Boost logo" align= 16"middle" width="277" height="86">Boost.Flyweight 17Holders reference</h1> 18 19<div class="prev_link"><a href="factories.html"><img src="../prev.gif" alt="factories" border="0"><br> 20Factories 21</a></div> 22<div class="up_link"><a href="index.html"><img src="../up.gif" alt="Boost.Flyweight reference" border="0"><br> 23Boost.Flyweight reference 24</a></div> 25<div class="next_link"><a href="locking.html"><img src="../next.gif" alt="locking policies" border="0"><br> 26Locking policies 27</a></div><br clear="all" style="clear: all;"> 28 29<hr> 30 31<h2>Contents</h2> 32 33<ul> 34 <li><a href="#holder">Holders and holder specifiers</a></li> 35 <li><a href="#holder_tag_synopsis">Header 36 <code>"boost/flyweight/holder_tag.hpp"</code> synopsis</a> 37 <ul> 38 <li><a href="#is_holder">Class template <code>is_holder</code></a></li> 39 <li><a href="#holder_construct">Class template <code>holder</code></a></li> 40 </ul> 41 </li> 42 <li><a href="#static_holder_fwd_synopsis">Header 43 <code>"boost/flyweight/static_holder_fwd.hpp"</code> synopsis</a> 44 </li> 45 <li><a href="#static_holder_synopsis">Header 46 <code>"boost/flyweight/static_holder.hpp"</code> synopsis</a> 47 <ul> 48 <li><a href="#static_holder_class">Class template <code>static_holder_class</code></a></li> 49 <li><a href="#static_holder">Class <code>static_holder</code></a></li> 50 </ul> 51 </li> 52 <li><a href="#intermodule_holder_fwd_synopsis">Header 53 <code>"boost/flyweight/intermodule_holder_fwd.hpp"</code> synopsis</a> 54 </li> 55 <li><a href="#intermodule_holder_synopsis">Header 56 <code>"boost/flyweight/intermodule_holder.hpp"</code> synopsis</a> 57 <ul> 58 <li><a href="#intermodule_holder_class">Class template <code>intermodule_holder_class</code></a></li> 59 <li><a href="#intermodule_holder">Class <code>intermodule_holder</code></a></li> 60 </ul> 61 </li> 62</ul> 63 64<h2><a name="holder">Holders and holder specifiers</a></h2> 65 66<p> 67Given a type <code>C</code>, a type <code>Holder</code> is said to be a <i>holder 68of <code>C</code></i> if the expression <code>Holder::get()</code> returns 69a reference to a default initialized <code>C</code> object unique to 70<code>Holder</code>. No invocation of <code>Holder::get()</code>, except possibly 71the first one in the program, does throw. 72<a href="flyweight.html#flyweight"><code>flyweight</code></a> 73privately uses a holder to instantiate a <a href="factories.html#factory">factory</a> 74and some additional data (like a <a href="locking.html#preliminary">mutex</a> for 75internal synchronization) unique to each instantiation type of the class template. 76</p> 77 78<p> 79A type <code>S</code> is a <i>holder specifier</i> if: 80<ol> 81 <li>One of the following conditions is satisfied: 82 <ol type="a"> 83 <li><a href="#is_holder"><code>is_holder<S>::type</code></a> is 84 <a href="../../../mpl/doc/refmanual/bool.html"><code>boost::mpl::true_</code></a>,</li> 85 <li><code>S</code> is of the form <a href="#holder_construct"><code>holder<S'></code></a>.</li> 86 </ol> 87 </li> 88 <li><code>S</code>, or <code>S'</code> if (b) applies, is an 89 <a href="../../../mpl/doc/refmanual/lambda-expression.html"><code>MPL Lambda 90 Expression</code></a> such that invoking it with type <code>C</code> resolves to 91 a holder of <code>C</code>. 92 </li> 93</ol> 94</p> 95 96<h2><a name="holder_tag_synopsis">Header 97<a href="../../../../boost/flyweight/holder_tag.hpp"><code>"boost/flyweight/holder_tag.hpp"</code></a> synopsis</a></h2> 98 99<blockquote><pre> 100<span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span> 101 102<span class=keyword>namespace</span> <span class=identifier>flyweights</span><span class=special>{</span> 103 104<span class=keyword>struct</span> <span class=identifier>holder_marker</span><span class=special>;</span> 105 106<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>T</span><span class=special>></span> 107<span class=keyword>struct</span> <span class=identifier>is_holder</span><span class=special>;</span> 108 109<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>T</span><span class=special>></span> 110<span class=keyword>struct</span> <span class=identifier>holder</span><span class=special>;</span> 111 112<span class=special>}</span> <span class=comment>// namespace boost::flyweights</span> 113 114<span class=special>}</span> <span class=comment>// namespace boost</span> 115</pre></blockquote> 116 117<h3><a name="is_holder">Class template <code>is_holder</code></a></h3> 118 119<p> 120Unless specialized by the user, <code>is_holder<T>::type</code> is 121<a href="../../../mpl/doc/refmanual/bool.html"><code>boost::mpl::true_</code></a> 122if <code>T</code> is derived from <code>holder_marker</code>, and it is 123<a href="../../../mpl/doc/refmanual/bool.html"><code>boost::mpl::false_</code></a> 124otherwise. 125</p> 126 127<h3><a name="holder_construct">Class template <code>holder</code></a></h3> 128 129<p> 130<code>holder<T></code> is a syntactic construct meant to indicate 131that <code>T</code> is a holder specifier without resorting to the 132mechanisms provided by the <code>is_holder</code> class template. 133</p> 134 135<h2><a name="static_holder_fwd_synopsis">Header 136<a href="../../../../boost/flyweight/static_holder_fwd.hpp"><code>"boost/flyweight/static_holder_fwd.hpp"</code></a> synopsis</a></h2> 137 138<blockquote><pre> 139<span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span> 140 141<span class=keyword>namespace</span> <span class=identifier>flyweights</span><span class=special>{</span> 142 143<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>C</span><span class=special>></span> 144<span class=keyword>struct</span> <span class=identifier>static_holder_class</span><span class=special>;</span> 145 146<span class=keyword>struct</span> <span class=identifier>static_holder</span><span class=special>;</span> 147 148<span class=special>}</span> <span class=comment>// namespace boost::flyweights</span> 149 150<span class=special>}</span> <span class=comment>// namespace boost</span> 151</pre></blockquote> 152 153<p> 154<code>static_holder_fwd.hpp</code> forward declares 155<a href="#static_holder_class"><code>static_holder_class</code></a> 156and <a href="#static_holder"><code>static_holder</code></a>. 157</p> 158 159<h2><a name="static_holder_synopsis">Header 160<a href="../../../../boost/flyweight/static_holder.hpp"><code>"boost/flyweight/static_holder.hpp"</code></a> synopsis</a></h2> 161 162<h3><a name="static_holder_class">Class template <code>static_holder_class</code></a></h3> 163 164<p> 165<code>static_holder_class<C></code> keeps its unique instance of <code>C</code> as a 166local static object. 167</p> 168 169<h3><a name="static_holder">Class <code>static_holder</code></a></h3> 170 171<p> 172<a href="#holder"><code>Holder Specifier</code></a> for <a href="#static_holder_class"><code>static_holder_class</code></a>. 173</p> 174 175<h2><a name="intermodule_holder_fwd_synopsis">Header 176<a href="../../../../boost/flyweight/intermodule_holder_fwd.hpp"><code>"boost/flyweight/intermodule_holder_fwd.hpp"</code></a> synopsis</a></h2> 177 178<blockquote><pre> 179<span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span> 180 181<span class=keyword>namespace</span> <span class=identifier>flyweights</span><span class=special>{</span> 182 183<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>C</span><span class=special>></span> 184<span class=keyword>struct</span> <span class=identifier>intermodule_holder_class</span><span class=special>;</span> 185 186<span class=keyword>struct</span> <span class=identifier>intermodule_holder</span><span class=special>;</span> 187 188<span class=special>}</span> <span class=comment>// namespace boost::flyweights</span> 189 190<span class=special>}</span> <span class=comment>// namespace boost</span> 191</pre></blockquote> 192 193<p> 194<code>intermodule_holder_fwd.hpp</code> forward declares 195<a href="#intermodule_holder_class"><code>intermodule_holder_class</code></a> 196and <a href="#intermodule_holder"><code>intermodule_holder</code></a>. 197</p> 198 199<h2><a name="intermodule_holder_synopsis">Header 200<a href="../../../../boost/flyweight/intermodule_holder.hpp"><code>"boost/flyweight/intermodule_holder.hpp"</code></a> synopsis</a></h2> 201 202<h3><a name="intermodule_holder_class">Class template <code>intermodule_holder_class</code></a></h3> 203 204<p> 205<code>intermodule_holder_class<C></code> maintains a <code>C</code> 206instance which is unique even across different dynamically linked modules of 207the program using this same type. In general, this guarantee is not provided by 208<a href="#static_holder_class"><code>static_holder_class</code></a>, as most 209C++ implementations are not able to merge duplicates of static variables stored 210in different dynamic modules of a program. 211</p> 212 213<h3><a name="intermodule_holder">Class <code>intermodule_holder</code></a></h3> 214 215<p> 216<a href="#holder"><code>Holder Specifier</code></a> for <a href="#intermodule_holder_class"><code>intermodule_holder_class</code></a>. 217</p> 218 219<hr> 220 221<div class="prev_link"><a href="factories.html"><img src="../prev.gif" alt="factories" border="0"><br> 222Factories 223</a></div> 224<div class="up_link"><a href="index.html"><img src="../up.gif" alt="Boost.Flyweight reference" border="0"><br> 225Boost.Flyweight reference 226</a></div> 227<div class="next_link"><a href="locking.html"><img src="../next.gif" alt="locking policies" border="0"><br> 228Locking policies 229</a></div><br clear="all" style="clear: all;"> 230 231<br> 232 233<p>Revised August 11th 2008</p> 234 235<p>© Copyright 2006-2008 Joaquín M López Muñoz. 236Distributed under the Boost Software 237License, Version 1.0. (See accompanying file <a href="../../../../LICENSE_1_0.txt"> 238LICENSE_1_0.txt</a> or copy at <a href="http://www.boost.org/LICENSE_1_0.txt"> 239http://www.boost.org/LICENSE_1_0.txt</a>) 240</p> 241 242</body> 243</html> 244
