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| 6 | <title>Boost.Flyweight Documentation - Tracking policies reference</title> | |
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| 14 | <body> | |
| 15 | <h1><img src="../../../../boost.png" alt="Boost logo" align= | |
| 16 | "middle" width="277" height="86">Boost.Flyweight | |
| 17 | Tracking policies reference</h1> | |
| 18 | ||
| 19 | <div class="prev_link"><a href="locking.html"><img src="../prev.gif" alt="locking policies" border="0"><br> | |
| 20 | Locking policies | |
| 21 | </a></div> | |
| 22 | <div class="up_link"><a href="index.html"><img src="../up.gif" alt="Boost.Flyweight reference" border="0"><br> | |
| 23 | Boost.Flyweight reference | |
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| 26 | Performance | |
| 27 | </a></div><br clear="all" style="clear: all;"> | |
| 28 | ||
| 29 | <hr> | |
| 30 | ||
| 31 | <h2>Contents</h2> | |
| 32 | ||
| 33 | <ul> | |
| 34 | <li><a href="#preliminary">Preliminary concepts</a></li> | |
| 35 | <li><a href="#tracking">Tracking policies</a></li> | |
| 36 | <li><a href="#tracking_tag_synopsis">Header | |
| 37 | <code>"boost/flyweight/tracking_tag.hpp"</code> synopsis</a> | |
| 38 | <ul> | |
| 39 | <li><a href="#is_tracking">Class template <code>is_tracking</code></a></li> | |
| 40 | <li><a href="#tracking_construct">Class template <code>tracking</code></a></li> | |
| 41 | </ul> | |
| 42 | </li> | |
| 43 | <li><a href="#refcounted_fwd_synopsis">Header | |
| 44 | <code>"boost/flyweight/refcounted_fwd.hpp"</code> synopsis</a> | |
| 45 | </li> | |
| 46 | <li><a href="#refcounted_synopsis">Header | |
| 47 | <code>"boost/flyweight/refcounted.hpp"</code> synopsis</a> | |
| 48 | <ul> | |
| 49 | <li><a href="#refcounted">Class <code>refcounted</code></a></li> | |
| 50 | </ul> | |
| 51 | </li> | |
| 52 | <li><a href="#no_tracking_fwd_synopsis">Header | |
| 53 | <code>"boost/flyweight/no_tracking_fwd.hpp"</code> synopsis</a> | |
| 54 | </li> | |
| 55 | <li><a href="#no_tracking_synopsis">Header | |
| 56 | <code>"boost/flyweight/no_tracking.hpp"</code> synopsis</a> | |
| 57 | <ul> | |
| 58 | <li><a href="#no_tracking">Class <code>no_tracking</code></a></li> | |
| 59 | </ul> | |
| 60 | </li> | |
| 61 | </ul> | |
| 62 | ||
| 63 | <h2><a name="preliminary">Preliminary concepts</a></h2> | |
| 64 | ||
| 65 | <p> | |
| 66 | A <i>tracking policy helper</i> provides access to some of the functionality | |
| 67 | of a <a href="factories.html#factory">factory</a> so as to be used | |
| 68 | in the implementation of an associated <a href="#tracking"><code>Tracking Policy</code></a>. | |
| 69 | In the following table, <code>TrackingHelper</code> is a tracking policy | |
| 70 | helper associated to a <a href="factories.html#factory">factory</a> type | |
| 71 | <code>Factory</code> of elements of type <code>Entry</code>, <code>h</code> | |
| 72 | is a value of | |
| 73 | <code>Factory::handle_type</code> associated to a <code>Factory</code> <code>f</code> | |
| 74 | and <code>check</code> is a value of | |
| 75 | a <a href="http://www.sgi.com/tech/stl/Predicate.html"><code>Predicate</code></a> | |
| 76 | type <code>Checker</code> with argument of type <code>Factory::handle_type</code>. | |
| 77 | </p> | |
| 78 | ||
| 79 | <p align="center"> | |
| 80 | <table cellspacing="0"> | |
| 81 | <caption><b>Tracking Policy Helper requirements.</b></caption> | |
| 82 | <tr> | |
| 83 | <th align="center">expression</th> | |
| 84 | <th align="center">return type</th> | |
| 85 | <th align="center">assertion/note<br>pre/post-condition</th> | |
| 86 | </tr> | |
| 87 | <tr> | |
| 88 | <td><code>TrackingHelper::entry(h);</code></td> | |
| 89 | <td><code>const Entry&</code></td> | |
| 90 | <td>Returns <code>f.entry(h)</code>.</td> | |
| 91 | </tr> | |
| 92 | <tr class="odd_tr"> | |
| 93 | <td><code>TrackingHelper::erase(h,check);</code></td> | |
| 94 | <td><code>void</code></td> | |
| 95 | <td>If <code>check(h)</code>, invokes <code>f.erase(h)</code>.</td> | |
| 96 | </tr> | |
| 97 | </table> | |
| 98 | </p> | |
| 99 | ||
| 100 | <p> | |
| 101 | The execution of <code>TrackingHelper::erase</code> (including the | |
| 102 | invocation of <code>check(h)</code>) is done in a | |
| 103 | synchronized manner so as to prevent any other thread of execution from | |
| 104 | simultaneously accessing the factory's insertion or deletion facilities. | |
| 105 | </p> | |
| 106 | ||
| 107 | <h2><a name="tracking">Tracking policies</a></h2> | |
| 108 | ||
| 109 | <p> | |
| 110 | A <i>tracking policy</i> defines the strategy to be followed by a | |
| 111 | <a href="flyweight.html#flyweight"><code>flyweight</code></a> instantiation when | |
| 112 | all the flyweight objects associated to a given value are destroyed. | |
| 113 | The tracking policy contributes some type information necessary for the | |
| 114 | definition of the <code>flyweight</code> internal | |
| 115 | <a href="factories.html#factory">factory</a>. | |
| 116 | </p> | |
| 117 | ||
| 118 | <p> | |
| 119 | A type <code>Tracking</code> is a tracking policy if: | |
| 120 | <ul> | |
| 121 | <li>One of the following conditions is satisfied: | |
| 122 | <ol type="a"> | |
| 123 | <li><a href="#is_tracking"><code>is_tracking<Tracking>::type</code></a> is | |
| 124 | <a href="../../../mpl/doc/refmanual/bool.html"><code>boost::mpl::true_</code></a>,</li> | |
| 125 | <li><code>Tracking</code> is of the form | |
| 126 | <a href="#tracking_construct"><code>tracking<Tracking'></code></a>.</li> | |
| 127 | </ol> | |
| 128 | </li> | |
| 129 | <li>The expression <code>Tracking::entry_type</code> (or | |
| 130 | <code>Tracking'::entry_type</code> if (b) applies) is an | |
| 131 | <a href="../../../mpl/doc/refmanual/lambda-expression.html"><code>MPL Lambda | |
| 132 | Expression</code></a> that resolves, when invoked with different types | |
| 133 | (<code>Value</code>,<code>Key</code>) such that <code>Value</code> is | |
| 134 | <a href="http://www.sgi.com/tech/stl/Assignable.html"><code>Assignable</code></a> | |
| 135 | and implicitly convertible to <code>const Key&</code>, to an | |
| 136 | <a href="http://www.sgi.com/tech/stl/Assignable.html"><code>Assignable</code></a> | |
| 137 | type <code>Entry</code> implicitly convertible to both <code>const Value&</code> | |
| 138 | and <code>const Key&</code>. | |
| 139 | </li> | |
| 140 | <li>The expression <code>Tracking::handle_type</code> (or | |
| 141 | <code>Tracking'::handle_type</code> if (b) applies) is an | |
| 142 | <a href="../../../mpl/doc/refmanual/lambda-expression.html"><code>MPL Lambda | |
| 143 | Expression</code></a>; this expression, when invoked with types | |
| 144 | (<code>InternalHandle</code>,<a href="#preliminary"><code>TrackingHelper</code></a>), | |
| 145 | with <code>InternalHandle</code> being | |
| 146 | <a href="http://www.sgi.com/tech/stl/Assignable.html"><code>Assignable</code></a> | |
| 147 | and providing the nothrow guarantee for copy and assignment, | |
| 148 | resolves to an | |
| 149 | <a href="http://www.sgi.com/tech/stl/Assignable.html"><code>Assignable</code></a> | |
| 150 | type <code>Handle</code> which also provides the nothrow guarantee for | |
| 151 | copy and assignment and is constructible from and implicitly | |
| 152 | convertible to <code>InternalHandle</code>. | |
| 153 | <code>TrackingHelper</code> is an incomplete type at the time of | |
| 154 | invocation of <code>Tracking::handle_type</code>. | |
| 155 | </li> | |
| 156 | </ul> | |
| 157 | <code>Tracking::handle_type</code> is parameterized by a helper that provides | |
| 158 | access to some of the functionality of the factory associated to the | |
| 159 | tracking policy. This factory's associated entry and handle types are the types | |
| 160 | <code>Entry</code> and <code>Handle</code> defined above, respectively. | |
| 161 | </p> | |
| 162 | ||
| 163 | <h2><a name="tracking_tag_synopsis">Header | |
| 164 | <a href="../../../../boost/flyweight/tracking_tag.hpp"><code>"boost/flyweight/tracking_tag.hpp"</code></a> synopsis</a></h2> | |
| 165 | ||
| 166 | <blockquote><pre> | |
| 167 | <span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span> | |
| 168 | ||
| 169 | <span class=keyword>namespace</span> <span class=identifier>flyweights</span><span class=special>{</span> | |
| 170 | ||
| 171 | <span class=keyword>struct</span> <span class=identifier>tracking_marker</span><span class=special>;</span> | |
| 172 | ||
| 173 | <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>T</span><span class=special>></span> | |
| 174 | <span class=keyword>struct</span> <span class=identifier>is_tracking</span> | |
| 175 | ||
| 176 | <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>T</span><span class=special>></span> | |
| 177 | <span class=keyword>struct</span> <span class=identifier>tracking</span><span class=special>;</span> | |
| 178 | ||
| 179 | <span class=special>}</span> <span class=comment>// namespace boost::flyweights</span> | |
| 180 | ||
| 181 | <span class=special>}</span> <span class=comment>// namespace boost</span> | |
| 182 | </pre></blockquote> | |
| 183 | ||
| 184 | <h3><a name="is_tracking">Class template <code>is_tracking</code></a></h3> | |
| 185 | ||
| 186 | <p> | |
| 187 | Unless specialized by the user, <code>is_tracking<T>::type</code> is | |
| 188 | <a href="../../../mpl/doc/refmanual/bool.html"><code>boost::mpl::true_</code></a> | |
| 189 | if <code>T</code> is derived from <code>tracking_marker</code>, and it is | |
| 190 | <a href="../../../mpl/doc/refmanual/bool.html"><code>boost::mpl::false_</code></a> | |
| 191 | otherwise. | |
| 192 | </p> | |
| 193 | ||
| 194 | <h3><a name="tracking_construct">Class template <code>tracking</code></a></h3> | |
| 195 | ||
| 196 | <p> | |
| 197 | <code>tracking<T></code> is a syntactic construct meant to indicate | |
| 198 | that <code>T</code> is a tracking policy without resorting to the | |
| 199 | mechanisms provided by the <code>is_tracking</code> class template. | |
| 200 | </p> | |
| 201 | ||
| 202 | <h2><a name="refcounted_fwd_synopsis">Header | |
| 203 | <a href="../../../../boost/flyweight/refcounted_fwd.hpp"><code>"boost/flyweight/refcounted_fwd.hpp"</code></a> synopsis</a></h2> | |
| 204 | ||
| 205 | <blockquote><pre> | |
| 206 | <span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span> | |
| 207 | ||
| 208 | <span class=keyword>namespace</span> <span class=identifier>flyweights</span><span class=special>{</span> | |
| 209 | ||
| 210 | <span class=keyword>struct</span> <span class=identifier>refcounted</span><span class=special>;</span> | |
| 211 | ||
| 212 | <span class=special>}</span> <span class=comment>// namespace boost::flyweights</span> | |
| 213 | ||
| 214 | <span class=special>}</span> <span class=comment>// namespace boost</span> | |
| 215 | </pre></blockquote> | |
| 216 | ||
| 217 | <p> | |
| 218 | <code>refcounted_fwd.hpp</code> forward declares the class | |
| 219 | <a href="#refcounted"><code>refcounted</code></a>. | |
| 220 | </p> | |
| 221 | ||
| 222 | <h2><a name="refcounted_synopsis">Header | |
| 223 | <a href="../../../../boost/flyweight/refcounted.hpp"><code>"boost/flyweight/refcounted.hpp"</code></a> synopsis</a></h2> | |
| 224 | ||
| 225 | <h3><a name="refcounted">Class <code>refcounted</code></a></h3> | |
| 226 | ||
| 227 | <p> | |
| 228 | <a href="#tracking"><code>Tracking Policy</code></a> providing | |
| 229 | <a href="flyweight.html#flyweight"><code>flyweight</code></a> | |
| 230 | instantiations with reference counting semantics: when all the flyweight objects | |
| 231 | associated to a given value are destroyed, the corresponding entry is | |
| 232 | erased from <code>flyweight</code>'s internal | |
| 233 | <a href="factories.html#factory">factory</a>. | |
| 234 | </p> | |
| 235 | ||
| 236 | <h2><a name="no_tracking_fwd_synopsis">Header | |
| 237 | <a href="../../../../boost/flyweight/no_tracking_fwd.hpp"><code>"boost/flyweight/no_tracking_fwd.hpp"</code></a> synopsis</a></h2> | |
| 238 | ||
| 239 | <blockquote><pre> | |
| 240 | <span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span> | |
| 241 | ||
| 242 | <span class=keyword>namespace</span> <span class=identifier>flyweights</span><span class=special>{</span> | |
| 243 | ||
| 244 | <span class=keyword>struct</span> <span class=identifier>no_tracking</span><span class=special>;</span> | |
| 245 | ||
| 246 | <span class=special>}</span> <span class=comment>// namespace boost::flyweights</span> | |
| 247 | ||
| 248 | <span class=special>}</span> <span class=comment>// namespace boost</span> | |
| 249 | </pre></blockquote> | |
| 250 | ||
| 251 | <p> | |
| 252 | <code>no_tracking_fwd.hpp</code> forward declares the class | |
| 253 | <a href="#no_tracking"><code>no_tracking</code></a>. | |
| 254 | </p> | |
| 255 | ||
| 256 | <h2><a name="no_tracking_synopsis">Header | |
| 257 | <a href="../../../../boost/flyweight/no_tracking.hpp"><code>"boost/flyweight/no_tracking.hpp"</code></a> synopsis</a></h2> | |
| 258 | ||
| 259 | <h3><a name="no_tracking">Class <code>no_tracking</code></a></h3> | |
| 260 | ||
| 261 | <p> | |
| 262 | Null <a href="#tracking"><code>Tracking Policy</code></a>: elements inserted | |
| 263 | into <code>flyweight</code>'s internal <a href="factories.html#factory">factory</a> | |
| 264 | are not erased until program termination. | |
| 265 | </p> | |
| 266 | ||
| 267 | <hr> | |
| 268 | ||
| 269 | <div class="prev_link"><a href="locking.html"><img src="../prev.gif" alt="locking policies" border="0"><br> | |
| 270 | Locking policies | |
| 271 | </a></div> | |
| 272 | <div class="up_link"><a href="index.html"><img src="../up.gif" alt="Boost.Flyweight reference" border="0"><br> | |
| 273 | Boost.Flyweight reference | |
| 274 | </a></div> | |
| 275 | <div class="next_link"><a href="../performance.html"><img src="../next.gif" alt="performance" border="0"><br> | |
| 276 | Performance | |
| 277 | </a></div><br clear="all" style="clear: all;"> | |
| 278 | ||
| 279 | <br> | |
| 280 | ||
| 281 | <p>Revised August 18th 2008</p> | |
| 282 | ||
| 283 | <p>© Copyright 2006-2008 Joaquín M López Muñoz. | |
| 284 | Distributed under the Boost Software | |
| 285 | License, Version 1.0. (See accompanying file <a href="../../../../LICENSE_1_0.txt"> | |
| 286 | LICENSE_1_0.txt</a> or copy at <a href="http://www.boost.org/LICENSE_1_0.txt"> | |
| 287 | http://www.boost.org/LICENSE_1_0.txt</a>) | |
| 288 | </p> | |
| 289 | ||
| 290 | </body> | |
| 291 | </html> |