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  27 <a name="interprocess.quick_guide"></a><a class="link" href="quick_guide.html" title="Quick Guide for the Impatient">Quick Guide for the Impatient</a>
  28 </h2></div></div></div>
  29 <div class="toc"><dl class="toc">
  30 <dt><span class="section"><a href="quick_guide.html#interprocess.quick_guide.qg_memory_pool">Using shared
  31       memory as a pool of unnamed memory blocks</a></span></dt>
  32 <dt><span class="section"><a href="quick_guide.html#interprocess.quick_guide.qg_named_interprocess">Creating
  33       named shared memory objects</a></span></dt>
  34 <dt><span class="section"><a href="quick_guide.html#interprocess.quick_guide.qg_offset_ptr">Using an offset
  35       smart pointer for shared memory</a></span></dt>
  36 <dt><span class="section"><a href="quick_guide.html#interprocess.quick_guide.qg_interprocess_container">Creating
  37       vectors in shared memory</a></span></dt>
  38 <dt><span class="section"><a href="quick_guide.html#interprocess.quick_guide.qg_interprocess_map">Creating
  39       maps in shared memory</a></span></dt>
  40 </dl></div>
  41 <div class="section">
  42 <div class="titlepage"><div><div><h3 class="title">
  43 <a name="interprocess.quick_guide.qg_memory_pool"></a><a class="link" href="quick_guide.html#interprocess.quick_guide.qg_memory_pool" title="Using shared memory as a pool of unnamed memory blocks">Using shared
  44       memory as a pool of unnamed memory blocks</a>
  45 </h3></div></div></div>
  46 <p>
  47         You can just allocate a portion of a shared memory segment, copy the message
  48         to that buffer, send the offset of that portion of shared memory to another
  49         process, and you are done. Let's see the example:
  50       </p>
  51 <p>
  52 </p>
  53 <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">interprocess</span><span class="special">/</span><span class="identifier">managed_shared_memory</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
  54 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">cstdlib</span><span class="special">&gt;</span> <span class="comment">//std::system</span>
  55 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">sstream</span><span class="special">&gt;</span>
  56
  57 <span class="keyword">int</span> <span class="identifier">main</span> <span class="special">(</span><span class="keyword">int</span> <span class="identifier">argc</span><span class="special">,</span> <span class="keyword">char</span> <span class="special">*</span><span class="identifier">argv</span><span class="special">[])</span>
  58 <span class="special">{</span>
  59    <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">interprocess</span><span class="special">;</span>
  60    <span class="keyword">if</span><span class="special">(</span><span class="identifier">argc</span> <span class="special">==</span> <span class="number">1</span><span class="special">){</span>  <span class="comment">//Parent process</span>
  61       <span class="comment">//Remove shared memory on construction and destruction</span>
  62       <span class="keyword">struct</span> <span class="identifier">shm_remove</span>
  63       <span class="special">{</span>
  64          <span class="identifier">shm_remove</span><span class="special">()</span> <span class="special">{</span>  <span class="identifier">shared_memory_object</span><span class="special">::</span><span class="identifier">remove</span><span class="special">(</span><span class="string">"MySharedMemory"</span><span class="special">);</span> <span class="special">}</span>
  65          <span class="special">~</span><span class="identifier">shm_remove</span><span class="special">(){</span>  <span class="identifier">shared_memory_object</span><span class="special">::</span><span class="identifier">remove</span><span class="special">(</span><span class="string">"MySharedMemory"</span><span class="special">);</span> <span class="special">}</span>
  66       <span class="special">}</span> <span class="identifier">remover</span><span class="special">;</span>
  67
  68       <span class="comment">//Create a managed shared memory segment</span>
  69       <span class="identifier">managed_shared_memory</span> <span class="identifier">segment</span><span class="special">(</span><span class="identifier">create_only</span><span class="special">,</span> <span class="string">"MySharedMemory"</span><span class="special">,</span> <span class="number">65536</span><span class="special">);</span>
  70
  71       <span class="comment">//Allocate a portion of the segment (raw memory)</span>
  72       <span class="identifier">managed_shared_memory</span><span class="special">::</span><span class="identifier">size_type</span> <span class="identifier">free_memory</span> <span class="special">=</span> <span class="identifier">segment</span><span class="special">.</span><span class="identifier">get_free_memory</span><span class="special">();</span>
  73       <span class="keyword">void</span> <span class="special">*</span> <span class="identifier">shptr</span> <span class="special">=</span> <span class="identifier">segment</span><span class="special">.</span><span class="identifier">allocate</span><span class="special">(</span><span class="number">1024</span><span class="comment">/*bytes to allocate*/</span><span class="special">);</span>
  74
  75       <span class="comment">//Check invariant</span>
  76       <span class="keyword">if</span><span class="special">(</span><span class="identifier">free_memory</span> <span class="special">&lt;=</span> <span class="identifier">segment</span><span class="special">.</span><span class="identifier">get_free_memory</span><span class="special">())</span>
  77          <span class="keyword">return</span> <span class="number">1</span><span class="special">;</span>
  78
  79       <span class="comment">//An handle from the base address can identify any byte of the shared</span>
  80       <span class="comment">//memory segment even if it is mapped in different base addresses</span>
  81       <span class="identifier">managed_shared_memory</span><span class="special">::</span><span class="identifier">handle_t</span> <span class="identifier">handle</span> <span class="special">=</span> <span class="identifier">segment</span><span class="special">.</span><span class="identifier">get_handle_from_address</span><span class="special">(</span><span class="identifier">shptr</span><span class="special">);</span>
  82       <span class="identifier">std</span><span class="special">::</span><span class="identifier">stringstream</span> <span class="identifier">s</span><span class="special">;</span>
  83       <span class="identifier">s</span> <span class="special">&lt;&lt;</span> <span class="identifier">argv</span><span class="special">[</span><span class="number">0</span><span class="special">]</span> <span class="special">&lt;&lt;</span> <span class="string">" "</span> <span class="special">&lt;&lt;</span> <span class="identifier">handle</span><span class="special">;</span>
  84       <span class="identifier">s</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">ends</span><span class="special">;</span>
  85       <span class="comment">//Launch child process</span>
  86       <span class="keyword">if</span><span class="special">(</span><span class="number">0</span> <span class="special">!=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">system</span><span class="special">(</span><span class="identifier">s</span><span class="special">.</span><span class="identifier">str</span><span class="special">().</span><span class="identifier">c_str</span><span class="special">()))</span>
  87          <span class="keyword">return</span> <span class="number">1</span><span class="special">;</span>
  88       <span class="comment">//Check memory has been freed</span>
  89       <span class="keyword">if</span><span class="special">(</span><span class="identifier">free_memory</span> <span class="special">!=</span> <span class="identifier">segment</span><span class="special">.</span><span class="identifier">get_free_memory</span><span class="special">())</span>
  90          <span class="keyword">return</span> <span class="number">1</span><span class="special">;</span>
  91    <span class="special">}</span>
  92    <span class="keyword">else</span><span class="special">{</span>
  93       <span class="comment">//Open managed segment</span>
  94       <span class="identifier">managed_shared_memory</span> <span class="identifier">segment</span><span class="special">(</span><span class="identifier">open_only</span><span class="special">,</span> <span class="string">"MySharedMemory"</span><span class="special">);</span>
  95
  96       <span class="comment">//An handle from the base address can identify any byte of the shared</span>
  97       <span class="comment">//memory segment even if it is mapped in different base addresses</span>
  98       <span class="identifier">managed_shared_memory</span><span class="special">::</span><span class="identifier">handle_t</span> <span class="identifier">handle</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span>
  99
 100       <span class="comment">//Obtain handle value</span>
 101       <span class="identifier">std</span><span class="special">::</span><span class="identifier">stringstream</span> <span class="identifier">s</span><span class="special">;</span> <span class="identifier">s</span> <span class="special">&lt;&lt;</span> <span class="identifier">argv</span><span class="special">[</span><span class="number">1</span><span class="special">];</span> <span class="identifier">s</span> <span class="special">&gt;&gt;</span> <span class="identifier">handle</span><span class="special">;</span>
 102
 103       <span class="comment">//Get buffer local address from handle</span>
 104       <span class="keyword">void</span> <span class="special">*</span><span class="identifier">msg</span> <span class="special">=</span> <span class="identifier">segment</span><span class="special">.</span><span class="identifier">get_address_from_handle</span><span class="special">(</span><span class="identifier">handle</span><span class="special">);</span>
 105
 106       <span class="comment">//Deallocate previously allocated memory</span>
 107       <span class="identifier">segment</span><span class="special">.</span><span class="identifier">deallocate</span><span class="special">(</span><span class="identifier">msg</span><span class="special">);</span>
 108    <span class="special">}</span>
 109    <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
 110 <span class="special">}</span>
 111 </pre>
 112 <p>
 113       </p>
 114 </div>
 115 <div class="section">
 116 <div class="titlepage"><div><div><h3 class="title">
 117 <a name="interprocess.quick_guide.qg_named_interprocess"></a><a class="link" href="quick_guide.html#interprocess.quick_guide.qg_named_interprocess" title="Creating named shared memory objects">Creating
 118       named shared memory objects</a>
 119 </h3></div></div></div>
 120 <p>
 121         You want to create objects in a shared memory segment, giving a string name
 122         to them so that any other process can find, use and delete them from the
 123         segment when the objects are not needed anymore. Example:
 124       </p>
 125 <p>
 126 </p>
 127 <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">interprocess</span><span class="special">/</span><span class="identifier">managed_shared_memory</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
 128 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">cstdlib</span><span class="special">&gt;</span> <span class="comment">//std::system</span>
 129 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">cstddef</span><span class="special">&gt;</span>
 130 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">cassert</span><span class="special">&gt;</span>
 131 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">utility</span><span class="special">&gt;</span>
 132
 133 <span class="keyword">int</span> <span class="identifier">main</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">argc</span><span class="special">,</span> <span class="keyword">char</span> <span class="special">*</span><span class="identifier">argv</span><span class="special">[])</span>
 134 <span class="special">{</span>
 135    <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">interprocess</span><span class="special">;</span>
 136    <span class="keyword">typedef</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special">&lt;</span><span class="keyword">double</span><span class="special">,</span> <span class="keyword">int</span><span class="special">&gt;</span> <span class="identifier">MyType</span><span class="special">;</span>
 137
 138    <span class="keyword">if</span><span class="special">(</span><span class="identifier">argc</span> <span class="special">==</span> <span class="number">1</span><span class="special">){</span>  <span class="comment">//Parent process</span>
 139       <span class="comment">//Remove shared memory on construction and destruction</span>
 140       <span class="keyword">struct</span> <span class="identifier">shm_remove</span>
 141       <span class="special">{</span>
 142          <span class="identifier">shm_remove</span><span class="special">()</span> <span class="special">{</span> <span class="identifier">shared_memory_object</span><span class="special">::</span><span class="identifier">remove</span><span class="special">(</span><span class="string">"MySharedMemory"</span><span class="special">);</span> <span class="special">}</span>
 143          <span class="special">~</span><span class="identifier">shm_remove</span><span class="special">(){</span> <span class="identifier">shared_memory_object</span><span class="special">::</span><span class="identifier">remove</span><span class="special">(</span><span class="string">"MySharedMemory"</span><span class="special">);</span> <span class="special">}</span>
 144       <span class="special">}</span> <span class="identifier">remover</span><span class="special">;</span>
 145
 146       <span class="comment">//Construct managed shared memory</span>
 147       <span class="identifier">managed_shared_memory</span> <span class="identifier">segment</span><span class="special">(</span><span class="identifier">create_only</span><span class="special">,</span> <span class="string">"MySharedMemory"</span><span class="special">,</span> <span class="number">65536</span><span class="special">);</span>
 148
 149       <span class="comment">//Create an object of MyType initialized to {0.0, 0}</span>
 150       <span class="identifier">MyType</span> <span class="special">*</span><span class="identifier">instance</span> <span class="special">=</span> <span class="identifier">segment</span><span class="special">.</span><span class="identifier">construct</span><span class="special">&lt;</span><span class="identifier">MyType</span><span class="special">&gt;</span>
 151          <span class="special">(</span><span class="string">"MyType instance"</span><span class="special">)</span>  <span class="comment">//name of the object</span>
 152          <span class="special">(</span><span class="number">0.0</span><span class="special">,</span> <span class="number">0</span><span class="special">);</span>            <span class="comment">//ctor first argument</span>
 153
 154       <span class="comment">//Create an array of 10 elements of MyType initialized to {0.0, 0}</span>
 155       <span class="identifier">MyType</span> <span class="special">*</span><span class="identifier">array</span> <span class="special">=</span> <span class="identifier">segment</span><span class="special">.</span><span class="identifier">construct</span><span class="special">&lt;</span><span class="identifier">MyType</span><span class="special">&gt;</span>
 156          <span class="special">(</span><span class="string">"MyType array"</span><span class="special">)</span>     <span class="comment">//name of the object</span>
 157          <span class="special">[</span><span class="number">10</span><span class="special">]</span>                 <span class="comment">//number of elements</span>
 158          <span class="special">(</span><span class="number">0.0</span><span class="special">,</span> <span class="number">0</span><span class="special">);</span>            <span class="comment">//Same two ctor arguments for all objects</span>
 159
 160       <span class="comment">//Create an array of 3 elements of MyType initializing each one</span>
 161       <span class="comment">//to a different value {0.0, 0}, {1.0, 1}, {2.0, 2}...</span>
 162       <span class="keyword">float</span> <span class="identifier">float_initializer</span><span class="special">[</span><span class="number">3</span><span class="special">]</span> <span class="special">=</span> <span class="special">{</span> <span class="number">0.0</span><span class="special">,</span> <span class="number">1.0</span><span class="special">,</span> <span class="number">2.0</span> <span class="special">};</span>
 163       <span class="keyword">int</span>   <span class="identifier">int_initializer</span><span class="special">[</span><span class="number">3</span><span class="special">]</span>   <span class="special">=</span> <span class="special">{</span> <span class="number">0</span><span class="special">,</span> <span class="number">1</span><span class="special">,</span> <span class="number">2</span> <span class="special">};</span>
 164
 165       <span class="identifier">MyType</span> <span class="special">*</span><span class="identifier">array_it</span> <span class="special">=</span> <span class="identifier">segment</span><span class="special">.</span><span class="identifier">construct_it</span><span class="special">&lt;</span><span class="identifier">MyType</span><span class="special">&gt;</span>
 166          <span class="special">(</span><span class="string">"MyType array from it"</span><span class="special">)</span>   <span class="comment">//name of the object</span>
 167          <span class="special">[</span><span class="number">3</span><span class="special">]</span>                        <span class="comment">//number of elements</span>
 168          <span class="special">(</span> <span class="special">&amp;</span><span class="identifier">float_initializer</span><span class="special">[</span><span class="number">0</span><span class="special">]</span>    <span class="comment">//Iterator for the 1st ctor argument</span>
 169          <span class="special">,</span> <span class="special">&amp;</span><span class="identifier">int_initializer</span><span class="special">[</span><span class="number">0</span><span class="special">]);</span>    <span class="comment">//Iterator for the 2nd ctor argument</span>
 170
 171       <span class="comment">//Launch child process</span>
 172       <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">s</span><span class="special">(</span><span class="identifier">argv</span><span class="special">[</span><span class="number">0</span><span class="special">]);</span> <span class="identifier">s</span> <span class="special">+=</span> <span class="string">" child "</span><span class="special">;</span>
 173       <span class="keyword">if</span><span class="special">(</span><span class="number">0</span> <span class="special">!=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">system</span><span class="special">(</span><span class="identifier">s</span><span class="special">.</span><span class="identifier">c_str</span><span class="special">()))</span>
 174          <span class="keyword">return</span> <span class="number">1</span><span class="special">;</span>
 175
 176
 177       <span class="comment">//Check child has destroyed all objects</span>
 178       <span class="keyword">if</span><span class="special">(</span><span class="identifier">segment</span><span class="special">.</span><span class="identifier">find</span><span class="special">&lt;</span><span class="identifier">MyType</span><span class="special">&gt;(</span><span class="string">"MyType array"</span><span class="special">).</span><span class="identifier">first</span> <span class="special">||</span>
 179          <span class="identifier">segment</span><span class="special">.</span><span class="identifier">find</span><span class="special">&lt;</span><span class="identifier">MyType</span><span class="special">&gt;(</span><span class="string">"MyType instance"</span><span class="special">).</span><span class="identifier">first</span> <span class="special">||</span>
 180          <span class="identifier">segment</span><span class="special">.</span><span class="identifier">find</span><span class="special">&lt;</span><span class="identifier">MyType</span><span class="special">&gt;(</span><span class="string">"MyType array from it"</span><span class="special">).</span><span class="identifier">first</span><span class="special">)</span>
 181          <span class="keyword">return</span> <span class="number">1</span><span class="special">;</span>
 182    <span class="special">}</span>
 183    <span class="keyword">else</span><span class="special">{</span>
 184       <span class="comment">//Open managed shared memory</span>
 185       <span class="identifier">managed_shared_memory</span> <span class="identifier">segment</span><span class="special">(</span><span class="identifier">open_only</span><span class="special">,</span> <span class="string">"MySharedMemory"</span><span class="special">);</span>
 186
 187       <span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special">&lt;</span><span class="identifier">MyType</span><span class="special">*,</span> <span class="identifier">managed_shared_memory</span><span class="special">::</span><span class="identifier">size_type</span><span class="special">&gt;</span> <span class="identifier">res</span><span class="special">;</span>
 188
 189       <span class="comment">//Find the array</span>
 190       <span class="identifier">res</span> <span class="special">=</span> <span class="identifier">segment</span><span class="special">.</span><span class="identifier">find</span><span class="special">&lt;</span><span class="identifier">MyType</span><span class="special">&gt;</span> <span class="special">(</span><span class="string">"MyType array"</span><span class="special">);</span>
 191       <span class="comment">//Length should be 10</span>
 192       <span class="keyword">if</span><span class="special">(</span><span class="identifier">res</span><span class="special">.</span><span class="identifier">second</span> <span class="special">!=</span> <span class="number">10</span><span class="special">)</span> <span class="keyword">return</span> <span class="number">1</span><span class="special">;</span>
 193
 194       <span class="comment">//Find the object</span>
 195       <span class="identifier">res</span> <span class="special">=</span> <span class="identifier">segment</span><span class="special">.</span><span class="identifier">find</span><span class="special">&lt;</span><span class="identifier">MyType</span><span class="special">&gt;</span> <span class="special">(</span><span class="string">"MyType instance"</span><span class="special">);</span>
 196       <span class="comment">//Length should be 1</span>
 197       <span class="keyword">if</span><span class="special">(</span><span class="identifier">res</span><span class="special">.</span><span class="identifier">second</span> <span class="special">!=</span> <span class="number">1</span><span class="special">)</span> <span class="keyword">return</span> <span class="number">1</span><span class="special">;</span>
 198
 199       <span class="comment">//Find the array constructed from iterators</span>
 200       <span class="identifier">res</span> <span class="special">=</span> <span class="identifier">segment</span><span class="special">.</span><span class="identifier">find</span><span class="special">&lt;</span><span class="identifier">MyType</span><span class="special">&gt;</span> <span class="special">(</span><span class="string">"MyType array from it"</span><span class="special">);</span>
 201       <span class="comment">//Length should be 3</span>
 202       <span class="keyword">if</span><span class="special">(</span><span class="identifier">res</span><span class="special">.</span><span class="identifier">second</span> <span class="special">!=</span> <span class="number">3</span><span class="special">)</span> <span class="keyword">return</span> <span class="number">1</span><span class="special">;</span>
 203
 204       <span class="comment">//We're done, delete all the objects</span>
 205       <span class="identifier">segment</span><span class="special">.</span><span class="identifier">destroy</span><span class="special">&lt;</span><span class="identifier">MyType</span><span class="special">&gt;(</span><span class="string">"MyType array"</span><span class="special">);</span>
 206       <span class="identifier">segment</span><span class="special">.</span><span class="identifier">destroy</span><span class="special">&lt;</span><span class="identifier">MyType</span><span class="special">&gt;(</span><span class="string">"MyType instance"</span><span class="special">);</span>
 207       <span class="identifier">segment</span><span class="special">.</span><span class="identifier">destroy</span><span class="special">&lt;</span><span class="identifier">MyType</span><span class="special">&gt;(</span><span class="string">"MyType array from it"</span><span class="special">);</span>
 208    <span class="special">}</span>
 209    <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
 210 <span class="special">}</span>
 211 </pre>
 212 <p>
 213       </p>
 214 </div>
 215 <div class="section">
 216 <div class="titlepage"><div><div><h3 class="title">
 217 <a name="interprocess.quick_guide.qg_offset_ptr"></a><a class="link" href="quick_guide.html#interprocess.quick_guide.qg_offset_ptr" title="Using an offset smart pointer for shared memory">Using an offset
 218       smart pointer for shared memory</a>
 219 </h3></div></div></div>
 220 <p>
 221         <span class="bold"><strong>Boost.Interprocess</strong></span> offers offset_ptr smart
 222         pointer family as an offset pointer that stores the distance between the
 223         address of the offset pointer itself and the address of the pointed object.
 224         When offset_ptr is placed in a shared memory segment, it can point safely
 225         objects stored in the same shared memory segment, even if the segment is
 226         mapped in different base addresses in different processes.
 227       </p>
 228 <p>
 229         This allows placing objects with pointer members in shared memory. For example,
 230         if we want to create a linked list in shared memory:
 231       </p>
 232 <p>
 233 </p>
 234 <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">interprocess</span><span class="special">/</span><span class="identifier">managed_shared_memory</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
 235 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">interprocess</span><span class="special">/</span><span class="identifier">offset_ptr</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
 236
 237 <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">interprocess</span><span class="special">;</span>
 238
 239 <span class="comment">//Shared memory linked list node</span>
 240 <span class="keyword">struct</span> <span class="identifier">list_node</span>
 241 <span class="special">{</span>
 242    <span class="identifier">offset_ptr</span><span class="special">&lt;</span><span class="identifier">list_node</span><span class="special">&gt;</span> <span class="identifier">next</span><span class="special">;</span>
 243    <span class="keyword">int</span>                   <span class="identifier">value</span><span class="special">;</span>
 244 <span class="special">};</span>
 245
 246 <span class="keyword">int</span> <span class="identifier">main</span> <span class="special">()</span>
 247 <span class="special">{</span>
 248    <span class="comment">//Remove shared memory on construction and destruction</span>
 249    <span class="keyword">struct</span> <span class="identifier">shm_remove</span>
 250    <span class="special">{</span>
 251       <span class="identifier">shm_remove</span><span class="special">()</span> <span class="special">{</span> <span class="identifier">shared_memory_object</span><span class="special">::</span><span class="identifier">remove</span><span class="special">(</span><span class="string">"MySharedMemory"</span><span class="special">);</span> <span class="special">}</span>
 252       <span class="special">~</span><span class="identifier">shm_remove</span><span class="special">(){</span> <span class="identifier">shared_memory_object</span><span class="special">::</span><span class="identifier">remove</span><span class="special">(</span><span class="string">"MySharedMemory"</span><span class="special">);</span> <span class="special">}</span>
 253    <span class="special">}</span> <span class="identifier">remover</span><span class="special">;</span>
 254
 255    <span class="comment">//Create shared memory</span>
 256    <span class="identifier">managed_shared_memory</span> <span class="identifier">segment</span><span class="special">(</span><span class="identifier">create_only</span><span class="special">,</span>
 257                                  <span class="string">"MySharedMemory"</span><span class="special">,</span>  <span class="comment">//segment name</span>
 258                                  <span class="number">65536</span><span class="special">);</span>
 259
 260    <span class="comment">//Create linked list with 10 nodes in shared memory</span>
 261    <span class="identifier">offset_ptr</span><span class="special">&lt;</span><span class="identifier">list_node</span><span class="special">&gt;</span> <span class="identifier">prev</span> <span class="special">=</span> <span class="number">0</span><span class="special">,</span> <span class="identifier">current</span><span class="special">,</span> <span class="identifier">first</span><span class="special">;</span>
 262
 263    <span class="keyword">int</span> <span class="identifier">i</span><span class="special">;</span>
 264    <span class="keyword">for</span><span class="special">(</span><span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> <span class="identifier">i</span> <span class="special">&lt;</span> <span class="number">10</span><span class="special">;</span> <span class="special">++</span><span class="identifier">i</span><span class="special">,</span> <span class="identifier">prev</span> <span class="special">=</span> <span class="identifier">current</span><span class="special">){</span>
 265       <span class="identifier">current</span> <span class="special">=</span> <span class="keyword">static_cast</span><span class="special">&lt;</span><span class="identifier">list_node</span><span class="special">*&gt;(</span><span class="identifier">segment</span><span class="special">.</span><span class="identifier">allocate</span><span class="special">(</span><span class="keyword">sizeof</span><span class="special">(</span><span class="identifier">list_node</span><span class="special">)));</span>
 266       <span class="identifier">current</span><span class="special">-&gt;</span><span class="identifier">value</span> <span class="special">=</span> <span class="identifier">i</span><span class="special">;</span>
 267       <span class="identifier">current</span><span class="special">-&gt;</span><span class="identifier">next</span>  <span class="special">=</span> <span class="number">0</span><span class="special">;</span>
 268
 269       <span class="keyword">if</span><span class="special">(!</span><span class="identifier">prev</span><span class="special">)</span>
 270          <span class="identifier">first</span> <span class="special">=</span> <span class="identifier">current</span><span class="special">;</span>
 271       <span class="keyword">else</span>
 272          <span class="identifier">prev</span><span class="special">-&gt;</span><span class="identifier">next</span> <span class="special">=</span> <span class="identifier">current</span><span class="special">;</span>
 273    <span class="special">}</span>
 274
 275    <span class="comment">//Communicate list to other processes</span>
 276    <span class="comment">//. . .</span>
 277    <span class="comment">//When done, destroy list</span>
 278    <span class="keyword">for</span><span class="special">(</span><span class="identifier">current</span> <span class="special">=</span> <span class="identifier">first</span><span class="special">;</span> <span class="identifier">current</span><span class="special">;</span> <span class="comment">/**/</span><span class="special">){</span>
 279       <span class="identifier">prev</span> <span class="special">=</span> <span class="identifier">current</span><span class="special">;</span>
 280       <span class="identifier">current</span> <span class="special">=</span> <span class="identifier">current</span><span class="special">-&gt;</span><span class="identifier">next</span><span class="special">;</span>
 281       <span class="identifier">segment</span><span class="special">.</span><span class="identifier">deallocate</span><span class="special">(</span><span class="identifier">prev</span><span class="special">.</span><span class="identifier">get</span><span class="special">());</span>
 282    <span class="special">}</span>
 283    <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
 284 <span class="special">}</span>
 285 </pre>
 286 <p>
 287       </p>
 288 <p>
 289         To help with basic data structures, <span class="bold"><strong>Boost.Interprocess</strong></span>
 290         offers containers like vector, list, map, so you can avoid these manual data
 291         structures just like with standard containers.
 292       </p>
 293 </div>
 294 <div class="section">
 295 <div class="titlepage"><div><div><h3 class="title">
 296 <a name="interprocess.quick_guide.qg_interprocess_container"></a><a class="link" href="quick_guide.html#interprocess.quick_guide.qg_interprocess_container" title="Creating vectors in shared memory">Creating
 297       vectors in shared memory</a>
 298 </h3></div></div></div>
 299 <p>
 300         <span class="bold"><strong>Boost.Interprocess</strong></span> allows creating complex
 301         objects in shared memory and memory mapped files. For example, we can construct
 302         STL-like containers in shared memory. To do this, we just need to create
 303         a special (managed) shared memory segment, declare a <span class="bold"><strong>Boost.Interprocess</strong></span>
 304         allocator and construct the vector in shared memory just if it was any other
 305         object.
 306       </p>
 307 <p>
 308         The class that allows this complex structures in shared memory is called
 309         <code class="computeroutput"><a class="link" href="../boost/interprocess/managed_shared_memory.html" title="Type definition managed_shared_memory">boost::interprocess::managed_shared_memory</a></code>
 310         and it's easy to use. Just execute this example without arguments:
 311       </p>
 312 <p>
 313 </p>
 314 <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">interprocess</span><span class="special">/</span><span class="identifier">managed_shared_memory</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
 315 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">interprocess</span><span class="special">/</span><span class="identifier">containers</span><span class="special">/</span><span class="identifier">vector</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
 316 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">interprocess</span><span class="special">/</span><span class="identifier">allocators</span><span class="special">/</span><span class="identifier">allocator</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
 317 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">string</span><span class="special">&gt;</span>
 318 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">cstdlib</span><span class="special">&gt;</span> <span class="comment">//std::system</span>
 319
 320 <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">interprocess</span><span class="special">;</span>
 321
 322 <span class="comment">//Define an STL compatible allocator of ints that allocates from the managed_shared_memory.</span>
 323 <span class="comment">//This allocator will allow placing containers in the segment</span>
 324 <span class="keyword">typedef</span> <span class="identifier">allocator</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">,</span> <span class="identifier">managed_shared_memory</span><span class="special">::</span><span class="identifier">segment_manager</span><span class="special">&gt;</span>  <span class="identifier">ShmemAllocator</span><span class="special">;</span>
 325
 326 <span class="comment">//Alias a vector that uses the previous STL-like allocator so that allocates</span>
 327 <span class="comment">//its values from the segment</span>
 328 <span class="keyword">typedef</span> <span class="identifier">vector</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">,</span> <span class="identifier">ShmemAllocator</span><span class="special">&gt;</span> <span class="identifier">MyVector</span><span class="special">;</span>
 329
 330 <span class="comment">//Main function. For parent process argc == 1, for child process argc == 2</span>
 331 <span class="keyword">int</span> <span class="identifier">main</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">argc</span><span class="special">,</span> <span class="keyword">char</span> <span class="special">*</span><span class="identifier">argv</span><span class="special">[])</span>
 332 <span class="special">{</span>
 333    <span class="keyword">if</span><span class="special">(</span><span class="identifier">argc</span> <span class="special">==</span> <span class="number">1</span><span class="special">){</span> <span class="comment">//Parent process</span>
 334       <span class="comment">//Remove shared memory on construction and destruction</span>
 335       <span class="keyword">struct</span> <span class="identifier">shm_remove</span>
 336       <span class="special">{</span>
 337          <span class="identifier">shm_remove</span><span class="special">()</span> <span class="special">{</span> <span class="identifier">shared_memory_object</span><span class="special">::</span><span class="identifier">remove</span><span class="special">(</span><span class="string">"MySharedMemory"</span><span class="special">);</span> <span class="special">}</span>
 338          <span class="special">~</span><span class="identifier">shm_remove</span><span class="special">(){</span> <span class="identifier">shared_memory_object</span><span class="special">::</span><span class="identifier">remove</span><span class="special">(</span><span class="string">"MySharedMemory"</span><span class="special">);</span> <span class="special">}</span>
 339       <span class="special">}</span> <span class="identifier">remover</span><span class="special">;</span>
 340
 341       <span class="comment">//Create a new segment with given name and size</span>
 342       <span class="identifier">managed_shared_memory</span> <span class="identifier">segment</span><span class="special">(</span><span class="identifier">create_only</span><span class="special">,</span> <span class="string">"MySharedMemory"</span><span class="special">,</span> <span class="number">65536</span><span class="special">);</span>
 343
 344       <span class="comment">//Initialize shared memory STL-compatible allocator</span>
 345       <span class="keyword">const</span> <span class="identifier">ShmemAllocator</span> <span class="identifier">alloc_inst</span> <span class="special">(</span><span class="identifier">segment</span><span class="special">.</span><span class="identifier">get_segment_manager</span><span class="special">());</span>
 346
 347       <span class="comment">//Construct a vector named "MyVector" in shared memory with argument alloc_inst</span>
 348       <span class="identifier">MyVector</span> <span class="special">*</span><span class="identifier">myvector</span> <span class="special">=</span> <span class="identifier">segment</span><span class="special">.</span><span class="identifier">construct</span><span class="special">&lt;</span><span class="identifier">MyVector</span><span class="special">&gt;(</span><span class="string">"MyVector"</span><span class="special">)(</span><span class="identifier">alloc_inst</span><span class="special">);</span>
 349
 350       <span class="keyword">for</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> <span class="identifier">i</span> <span class="special">&lt;</span> <span class="number">100</span><span class="special">;</span> <span class="special">++</span><span class="identifier">i</span><span class="special">)</span>  <span class="comment">//Insert data in the vector</span>
 351          <span class="identifier">myvector</span><span class="special">-&gt;</span><span class="identifier">push_back</span><span class="special">(</span><span class="identifier">i</span><span class="special">);</span>
 352
 353       <span class="comment">//Launch child process</span>
 354       <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">s</span><span class="special">(</span><span class="identifier">argv</span><span class="special">[</span><span class="number">0</span><span class="special">]);</span> <span class="identifier">s</span> <span class="special">+=</span> <span class="string">" child "</span><span class="special">;</span>
 355       <span class="keyword">if</span><span class="special">(</span><span class="number">0</span> <span class="special">!=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">system</span><span class="special">(</span><span class="identifier">s</span><span class="special">.</span><span class="identifier">c_str</span><span class="special">()))</span>
 356          <span class="keyword">return</span> <span class="number">1</span><span class="special">;</span>
 357
 358       <span class="comment">//Check child has destroyed the vector</span>
 359       <span class="keyword">if</span><span class="special">(</span><span class="identifier">segment</span><span class="special">.</span><span class="identifier">find</span><span class="special">&lt;</span><span class="identifier">MyVector</span><span class="special">&gt;(</span><span class="string">"MyVector"</span><span class="special">).</span><span class="identifier">first</span><span class="special">)</span>
 360          <span class="keyword">return</span> <span class="number">1</span><span class="special">;</span>
 361    <span class="special">}</span>
 362    <span class="keyword">else</span><span class="special">{</span> <span class="comment">//Child process</span>
 363       <span class="comment">//Open the managed segment</span>
 364       <span class="identifier">managed_shared_memory</span> <span class="identifier">segment</span><span class="special">(</span><span class="identifier">open_only</span><span class="special">,</span> <span class="string">"MySharedMemory"</span><span class="special">);</span>
 365
 366       <span class="comment">//Find the vector using the c-string name</span>
 367       <span class="identifier">MyVector</span> <span class="special">*</span><span class="identifier">myvector</span> <span class="special">=</span> <span class="identifier">segment</span><span class="special">.</span><span class="identifier">find</span><span class="special">&lt;</span><span class="identifier">MyVector</span><span class="special">&gt;(</span><span class="string">"MyVector"</span><span class="special">).</span><span class="identifier">first</span><span class="special">;</span>
 368
 369       <span class="comment">//Use vector in reverse order</span>
 370       <span class="identifier">std</span><span class="special">::</span><span class="identifier">sort</span><span class="special">(</span><span class="identifier">myvector</span><span class="special">-&gt;</span><span class="identifier">rbegin</span><span class="special">(),</span> <span class="identifier">myvector</span><span class="special">-&gt;</span><span class="identifier">rend</span><span class="special">());</span>
 371
 372       <span class="comment">//When done, destroy the vector from the segment</span>
 373       <span class="identifier">segment</span><span class="special">.</span><span class="identifier">destroy</span><span class="special">&lt;</span><span class="identifier">MyVector</span><span class="special">&gt;(</span><span class="string">"MyVector"</span><span class="special">);</span>
 374    <span class="special">}</span>
 375
 376    <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
 377 <span class="special">}</span>
 378 </pre>
 379 <p>
 380       </p>
 381 <p>
 382         The parent process will create an special shared memory class that allows
 383         easy construction of many complex data structures associated with a name.
 384         The parent process executes the same program with an additional argument
 385         so the child process opens the shared memory and uses the vector and erases
 386         it.
 387       </p>
 388 </div>
 389 <div class="section">
 390 <div class="titlepage"><div><div><h3 class="title">
 391 <a name="interprocess.quick_guide.qg_interprocess_map"></a><a class="link" href="quick_guide.html#interprocess.quick_guide.qg_interprocess_map" title="Creating maps in shared memory">Creating
 392       maps in shared memory</a>
 393 </h3></div></div></div>
 394 <p>
 395         Just like a vector, <span class="bold"><strong>Boost.Interprocess</strong></span> allows
 396         creating maps in shared memory and memory mapped files. The only difference
 397         is that like standard associative containers, <span class="bold"><strong>Boost.Interprocess</strong></span>'s
 398         map needs also the comparison functor when an allocator is passed in the
 399         constructor:
 400       </p>
 401 <p>
 402 </p>
 403 <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">interprocess</span><span class="special">/</span><span class="identifier">managed_shared_memory</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
 404 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">interprocess</span><span class="special">/</span><span class="identifier">containers</span><span class="special">/</span><span class="identifier">map</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
 405 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">interprocess</span><span class="special">/</span><span class="identifier">allocators</span><span class="special">/</span><span class="identifier">allocator</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
 406 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">functional</span><span class="special">&gt;</span>
 407 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">utility</span><span class="special">&gt;</span>
 408
 409 <span class="keyword">int</span> <span class="identifier">main</span> <span class="special">()</span>
 410 <span class="special">{</span>
 411    <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">interprocess</span><span class="special">;</span>
 412
 413    <span class="comment">//Remove shared memory on construction and destruction</span>
 414    <span class="keyword">struct</span> <span class="identifier">shm_remove</span>
 415    <span class="special">{</span>
 416       <span class="identifier">shm_remove</span><span class="special">()</span> <span class="special">{</span> <span class="identifier">shared_memory_object</span><span class="special">::</span><span class="identifier">remove</span><span class="special">(</span><span class="string">"MySharedMemory"</span><span class="special">);</span> <span class="special">}</span>
 417       <span class="special">~</span><span class="identifier">shm_remove</span><span class="special">(){</span> <span class="identifier">shared_memory_object</span><span class="special">::</span><span class="identifier">remove</span><span class="special">(</span><span class="string">"MySharedMemory"</span><span class="special">);</span> <span class="special">}</span>
 418    <span class="special">}</span> <span class="identifier">remover</span><span class="special">;</span>
 419
 420    <span class="comment">//Shared memory front-end that is able to construct objects</span>
 421    <span class="comment">//associated with a c-string. Erase previous shared memory with the name</span>
 422    <span class="comment">//to be used and create the memory segment at the specified address and initialize resources</span>
 423    <span class="identifier">managed_shared_memory</span> <span class="identifier">segment</span>
 424       <span class="special">(</span><span class="identifier">create_only</span>
 425       <span class="special">,</span><span class="string">"MySharedMemory"</span> <span class="comment">//segment name</span>
 426       <span class="special">,</span><span class="number">65536</span><span class="special">);</span>          <span class="comment">//segment size in bytes</span>
 427
 428    <span class="comment">//Note that map&lt;Key, MappedType&gt;'s value_type is std::pair&lt;const Key, MappedType&gt;,</span>
 429    <span class="comment">//so the allocator must allocate that pair.</span>
 430    <span class="keyword">typedef</span> <span class="keyword">int</span>    <span class="identifier">KeyType</span><span class="special">;</span>
 431    <span class="keyword">typedef</span> <span class="keyword">float</span>  <span class="identifier">MappedType</span><span class="special">;</span>
 432    <span class="keyword">typedef</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special">&lt;</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">,</span> <span class="keyword">float</span><span class="special">&gt;</span> <span class="identifier">ValueType</span><span class="special">;</span>
 433
 434    <span class="comment">//Alias an STL compatible allocator of for the map.</span>
 435    <span class="comment">//This allocator will allow to place containers</span>
 436    <span class="comment">//in managed shared memory segments</span>
 437    <span class="keyword">typedef</span> <span class="identifier">allocator</span><span class="special">&lt;</span><span class="identifier">ValueType</span><span class="special">,</span> <span class="identifier">managed_shared_memory</span><span class="special">::</span><span class="identifier">segment_manager</span><span class="special">&gt;</span>
 438       <span class="identifier">ShmemAllocator</span><span class="special">;</span>
 439
 440    <span class="comment">//Alias a map of ints that uses the previous STL-like allocator.</span>
 441    <span class="comment">//Note that the third parameter argument is the ordering function</span>
 442    <span class="comment">//of the map, just like with std::map, used to compare the keys.</span>
 443    <span class="keyword">typedef</span> <span class="identifier">map</span><span class="special">&lt;</span><span class="identifier">KeyType</span><span class="special">,</span> <span class="identifier">MappedType</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">less</span><span class="special">&lt;</span><span class="identifier">KeyType</span><span class="special">&gt;,</span> <span class="identifier">ShmemAllocator</span><span class="special">&gt;</span> <span class="identifier">MyMap</span><span class="special">;</span>
 444
 445    <span class="comment">//Initialize the shared memory STL-compatible allocator</span>
 446    <span class="identifier">ShmemAllocator</span> <span class="identifier">alloc_inst</span> <span class="special">(</span><span class="identifier">segment</span><span class="special">.</span><span class="identifier">get_segment_manager</span><span class="special">());</span>
 447
 448    <span class="comment">//Construct a shared memory map.</span>
 449    <span class="comment">//Note that the first parameter is the comparison function,</span>
 450    <span class="comment">//and the second one the allocator.</span>
 451    <span class="comment">//This the same signature as std::map's constructor taking an allocator</span>
 452    <span class="identifier">MyMap</span> <span class="special">*</span><span class="identifier">mymap</span> <span class="special">=</span>
 453       <span class="identifier">segment</span><span class="special">.</span><span class="identifier">construct</span><span class="special">&lt;</span><span class="identifier">MyMap</span><span class="special">&gt;(</span><span class="string">"MyMap"</span><span class="special">)</span>      <span class="comment">//object name</span>
 454                                  <span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">less</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;()</span> <span class="comment">//first  ctor parameter</span>
 455                                  <span class="special">,</span><span class="identifier">alloc_inst</span><span class="special">);</span>     <span class="comment">//second ctor parameter</span>
 456
 457    <span class="comment">//Insert data in the map</span>
 458    <span class="keyword">for</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> <span class="identifier">i</span> <span class="special">&lt;</span> <span class="number">100</span><span class="special">;</span> <span class="special">++</span><span class="identifier">i</span><span class="special">){</span>
 459       <span class="identifier">mymap</span><span class="special">-&gt;</span><span class="identifier">insert</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special">&lt;</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">,</span> <span class="keyword">float</span><span class="special">&gt;(</span><span class="identifier">i</span><span class="special">,</span> <span class="special">(</span><span class="keyword">float</span><span class="special">)</span><span class="identifier">i</span><span class="special">));</span>
 460    <span class="special">}</span>
 461    <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
 462 <span class="special">}</span>
 463 </pre>
 464 <p>
 465       </p>
 466 <p>
 467         For a more advanced example including containers of containers, see the section
 468         <a class="link" href="allocators_containers.html#interprocess.allocators_containers.containers_explained.containers_of_containers" title="Containers of containers">Containers
 469         of containers</a>.
 470       </p>
 471 </div>
 472 </div>
 473 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 474 <td align="left"></td>
 475 <td align="right"><div class="copyright-footer">Copyright &#169; 2005-2012 Ion Gaztanaga<p>
 476         Distributed under the Boost Software License, Version 1.0. (See accompanying
 477         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>)
 478       </p>
 479 </div></td>
 480 </tr></table>
 481 <hr>
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