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  26 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
  27 <a name="context.ccontext"></a><a name="ccontext"></a><a class="link" href="ccontext.html" title="Class captured_context">Class captured_context</a>
  28 </h2></div></div></div>
  29 <p>
  30       Class <span class="emphasis"><em>captured_context</em></span> encapsulates context switching
  31       and manages the associated context' stack (allocation/deallocation).
  32     </p>
  33 <p>
  34       <span class="emphasis"><em>captured_context</em></span> allocates the context stack (using its
  35       <a class="link" href="stack.html#stack"><span class="emphasis"><em>StackAllocator</em></span></a> argument)
  36       and creates a control structure on top of it. This structure is responsible
  37       for managing context' stack. The address of the control structure is stored
  38       in the first frame of context' stack (e.g. it can not directly accessed from
  39       within <span class="emphasis"><em>captured_context</em></span>). In contrast to <span class="emphasis"><em>execution_context</em></span>
  40       the ownership of the control structure is not shared (no member variable to
  41       control structure in <span class="emphasis"><em>captured_context</em></span>). <span class="emphasis"><em>captured_context</em></span>
  42       keeps internally a state that is moved by a call of <span class="emphasis"><em>captured_context::operator()</em></span>
  43       (<code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
  44       will be invalidated), e.g. after a calling <span class="emphasis"><em>captured_context::operator()</em></span>,
  45       <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
  46       can not be used for an additional context switch.
  47     </p>
  48 <p>
  49       <span class="emphasis"><em>captured_context</em></span> is only move-constructible and move-assignable.
  50     </p>
  51 <p>
  52       The moved state is assigned to a new instance of <span class="emphasis"><em>captured_context</em></span>.
  53       This object becomes the first argument of the context-function, if the context
  54       was resumed the first time or the object becomes the first element in a tuple
  55       returned by <span class="emphasis"><em>captured_context::operator()</em></span> that has been
  56       called in the resumed context. In contrast to <a class="link" href="econtext.html#econtext"><span class="emphasis"><em>execution_context</em></span></a>,
  57       the context switch is faster because no global pointer etc. is involved (that's
  58       the reason why segmented stacks are not supported by <span class="emphasis"><em>captured_context</em></span>).
  59     </p>
  60 <p>
  61       If an instance with valid state goes out of scope, the stack is traversed in
  62       order to access the control structure (address stored at the first stack frame)
  63       and to deallocate context' stack via the <span class="emphasis"><em>StackAllocator</em></span>.
  64       The stack walking makes the destruction of <span class="emphasis"><em>captured_context</em></span>
  65       very slow compared to <span class="emphasis"><em>execution_context</em></span>.
  66     </p>
  67 <p>
  68       <span class="emphasis"><em>captured_context</em></span> expects a function/functor with signature
  69       <code class="computeroutput"><span class="identifier">captured_context</span><span class="special">(</span><span class="identifier">captured_context</span> <span class="identifier">ctx</span><span class="special">,</span> <span class="keyword">void</span><span class="special">*</span>
  70       <span class="identifier">vp</span><span class="special">)</span></code>.
  71       The parameter <code class="computeroutput"><span class="identifier">ctx</span></code> represents
  72       the context from which this context was resumed (e.g. that has called <span class="emphasis"><em>captured_context::operator()</em></span>
  73       on <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>)
  74       and <code class="computeroutput"><span class="identifier">vp</span></code> is the data passed to
  75       <span class="emphasis"><em>captured_context::operator()</em></span>. The return value is the
  76       captured_context that has to be resumed, while this context terminates.
  77     </p>
  78 <div class="important"><table border="0" summary="Important">
  79 <tr>
  80 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Important]" src="../../../../../doc/src/images/important.png"></td>
  81 <th align="left">Important</th>
  82 </tr>
  83 <tr><td align="left" valign="top"><p>
  84         Segmented stacks are not supported by <span class="emphasis"><em>captured_context</em></span>.
  85       </p></td></tr>
  86 </table></div>
  87 <h4>
  88 <a name="context.ccontext.h0"></a>
  89       <span><a name="context.ccontext.usage_of__emphasis_captured_context__emphasis_"></a></span><a class="link" href="ccontext.html#context.ccontext.usage_of__emphasis_captured_context__emphasis_">usage
  90       of <span class="emphasis"><em>captured_context</em></span></a>
  91     </h4>
  92 <pre class="programlisting"><span class="keyword">int</span> <span class="identifier">n</span><span class="special">=</span><span class="number">35</span><span class="special">;</span>
  93 <span class="identifier">ctx</span><span class="special">::</span><span class="identifier">captured_context</span> <span class="identifier">source</span><span class="special">(</span>
  94     <span class="special">[</span><span class="identifier">n</span><span class="special">](</span><span class="identifier">ctx</span><span class="special">::</span><span class="identifier">captured_context</span> <span class="identifier">sink</span><span class="special">,</span><span class="keyword">void</span><span class="special">*)</span><span class="keyword">mutable</span><span class="special">{</span>
  95         <span class="keyword">int</span> <span class="identifier">a</span><span class="special">=</span><span class="number">0</span><span class="special">;</span>
  96         <span class="keyword">int</span> <span class="identifier">b</span><span class="special">=</span><span class="number">1</span><span class="special">;</span>
  97         <span class="keyword">while</span><span class="special">(</span><span class="identifier">n</span><span class="special">--&gt;</span><span class="number">0</span><span class="special">){</span>
  98             <span class="keyword">auto</span> <span class="identifier">result</span><span class="special">=</span><span class="identifier">sink</span><span class="special">(&amp;</span><span class="identifier">a</span><span class="special">);</span>
  99             <span class="identifier">sink</span><span class="special">=</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">get</span><span class="special">&lt;</span><span class="number">0</span><span class="special">&gt;(</span><span class="identifier">result</span><span class="special">));</span>
 100             <span class="keyword">auto</span> <span class="identifier">next</span><span class="special">=</span><span class="identifier">a</span><span class="special">+</span><span class="identifier">b</span><span class="special">;</span>
 101             <span class="identifier">a</span><span class="special">=</span><span class="identifier">b</span><span class="special">;</span>
 102             <span class="identifier">b</span><span class="special">=</span><span class="identifier">next</span><span class="special">;</span>
 103         <span class="special">}</span>
 104         <span class="keyword">return</span> <span class="identifier">sink</span><span class="special">;</span>
 105     <span class="special">});</span>
 106 <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">10</span><span class="special">;++</span><span class="identifier">i</span><span class="special">){</span>
 107     <span class="keyword">auto</span> <span class="identifier">result</span><span class="special">=</span><span class="identifier">source</span><span class="special">();</span>
 108     <span class="identifier">source</span><span class="special">=</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">get</span><span class="special">&lt;</span><span class="number">0</span><span class="special">&gt;(</span><span class="identifier">result</span><span class="special">));</span>
 109     <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span><span class="special">&lt;&lt;*(</span><span class="keyword">int</span><span class="special">*)</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">get</span><span class="special">&lt;</span><span class="number">1</span><span class="special">&gt;(</span><span class="identifier">result</span><span class="special">)&lt;&lt;</span><span class="string">" "</span><span class="special">;</span>
 110 <span class="special">}</span>
 111
 112 <span class="identifier">output</span><span class="special">:</span>
 113     <span class="number">0</span> <span class="number">1</span> <span class="number">1</span> <span class="number">2</span> <span class="number">3</span> <span class="number">5</span> <span class="number">8</span> <span class="number">13</span> <span class="number">21</span> <span class="number">34</span>
 114 </pre>
 115 <p>
 116       This simple example demonstrates the basic usage of <span class="emphasis"><em>captured_context</em></span>.
 117       The context <code class="computeroutput"><span class="identifier">sink</span></code> represents
 118       the <span class="emphasis"><em>main</em></span>-context (function <span class="emphasis"><em>main()</em></span>
 119       running). <code class="computeroutput"><span class="identifier">sink</span></code> is generated
 120       by the framework (first element of lambda's parameter list). Because the state
 121       is invalidated (== changed) by each call of <span class="emphasis"><em>captured_context::operator()</em></span>,
 122       <code class="computeroutput"><span class="identifier">sink</span></code> has to be assigned the
 123       new state of the <span class="emphasis"><em>captured_context</em></span> returned by <span class="emphasis"><em>captured_context::operator()</em></span>.
 124     </p>
 125 <p>
 126       The lambda that calculates the Fibonacci numbers is executed inside the context
 127       represented by <code class="computeroutput"><span class="identifier">source</span></code>. Calculated
 128       Fibonacci numbers are transferred between the two context' via expression
 129       <span class="emphasis"><em>sink(&amp;a)</em></span> (and returned by <span class="emphasis"><em>source()</em></span>).
 130     </p>
 131 <p>
 132       The locale variables <code class="computeroutput"><span class="identifier">a</span></code>, <code class="computeroutput"><span class="identifier">b</span></code> and <code class="computeroutput"> <span class="identifier">next</span></code>
 133       remain their values during each context switch (<span class="emphasis"><em>yield(a)</em></span>).
 134       This is possible due <code class="computeroutput"><span class="identifier">ctx</span></code> has
 135       its own stack and the stack is exchanged by each context switch.
 136     </p>
 137 <h4>
 138 <a name="context.ccontext.h1"></a>
 139       <span><a name="context.ccontext.inverting_the_control_flow"></a></span><a class="link" href="ccontext.html#context.ccontext.inverting_the_control_flow">inverting
 140       the control flow</a>
 141     </h4>
 142 <pre class="programlisting"><span class="comment">/*
 143  * grammar:
 144  *   P ---&gt; E '\0'
 145  *   E ---&gt; T {('+'|'-') T}
 146  *   T ---&gt; S {('*'|'/') S}
 147  *   S ---&gt; digit | '(' E ')'
 148  */</span>
 149 <span class="keyword">class</span> <span class="identifier">Parser</span><span class="special">{</span>
 150     <span class="comment">// implementation omitted; see examples directory</span>
 151 <span class="special">};</span>
 152
 153 <span class="identifier">std</span><span class="special">::</span><span class="identifier">istringstream</span> <span class="identifier">is</span><span class="special">(</span><span class="string">"1+1"</span><span class="special">);</span>
 154 <span class="keyword">bool</span> <span class="identifier">done</span><span class="special">=</span><span class="keyword">false</span><span class="special">;</span>
 155 <span class="identifier">std</span><span class="special">::</span><span class="identifier">exception_ptr</span> <span class="identifier">except</span><span class="special">;</span>
 156
 157 <span class="comment">// execute parser in new execution context</span>
 158 <span class="identifier">boost</span><span class="special">::</span><span class="identifier">context</span><span class="special">::</span><span class="identifier">captured_context</span> <span class="identifier">source</span><span class="special">(</span>
 159         <span class="special">[&amp;</span><span class="identifier">is</span><span class="special">,&amp;</span><span class="identifier">done</span><span class="special">,&amp;</span><span class="identifier">except</span><span class="special">](</span><span class="identifier">ctx</span><span class="special">::</span><span class="identifier">captured_context</span> <span class="identifier">sink</span><span class="special">,</span><span class="keyword">void</span><span class="special">*){</span>
 160         <span class="comment">// create parser with callback function</span>
 161         <span class="identifier">Parser</span> <span class="identifier">p</span><span class="special">(</span> <span class="identifier">is</span><span class="special">,</span>
 162                   <span class="special">[&amp;</span><span class="identifier">sink</span><span class="special">](</span><span class="keyword">char</span> <span class="identifier">ch</span><span class="special">){</span>
 163                         <span class="comment">// resume main execution context</span>
 164                         <span class="keyword">auto</span> <span class="identifier">result</span> <span class="special">=</span> <span class="identifier">sink</span><span class="special">(&amp;</span><span class="identifier">ch</span><span class="special">);</span>
 165                         <span class="identifier">sink</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">get</span><span class="special">&lt;</span><span class="number">0</span><span class="special">&gt;(</span><span class="identifier">result</span><span class="special">));</span>
 166                 <span class="special">});</span>
 167             <span class="keyword">try</span> <span class="special">{</span>
 168                 <span class="comment">// start recursive parsing</span>
 169                 <span class="identifier">p</span><span class="special">.</span><span class="identifier">run</span><span class="special">();</span>
 170             <span class="special">}</span> <span class="keyword">catch</span> <span class="special">(...)</span> <span class="special">{</span>
 171                 <span class="comment">// store other exceptions in exception-pointer</span>
 172                 <span class="identifier">except</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">current_exception</span><span class="special">();</span>
 173             <span class="special">}</span>
 174             <span class="comment">// set termination flag</span>
 175             <span class="identifier">done</span><span class="special">=</span><span class="keyword">true</span><span class="special">;</span>
 176             <span class="comment">// resume main execution context</span>
 177             <span class="keyword">return</span> <span class="identifier">sink</span><span class="special">;</span>
 178         <span class="special">});</span>
 179
 180 <span class="comment">// user-code pulls parsed data from parser</span>
 181 <span class="comment">// invert control flow</span>
 182 <span class="keyword">auto</span> <span class="identifier">result</span> <span class="special">=</span> <span class="identifier">source</span><span class="special">();</span>
 183 <span class="identifier">source</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">get</span><span class="special">&lt;</span><span class="number">0</span><span class="special">&gt;(</span><span class="identifier">result</span><span class="special">));</span>
 184 <span class="keyword">void</span> <span class="special">*</span> <span class="identifier">vp</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">get</span><span class="special">&lt;</span><span class="number">1</span><span class="special">&gt;(</span><span class="identifier">result</span><span class="special">);</span>
 185 <span class="keyword">if</span> <span class="special">(</span> <span class="identifier">except</span><span class="special">)</span> <span class="special">{</span>
 186     <span class="identifier">std</span><span class="special">::</span><span class="identifier">rethrow_exception</span><span class="special">(</span><span class="identifier">except</span><span class="special">);</span>
 187 <span class="special">}</span>
 188 <span class="keyword">while</span><span class="special">(</span> <span class="special">!</span> <span class="identifier">done</span><span class="special">)</span> <span class="special">{</span>
 189     <span class="identifier">printf</span><span class="special">(</span><span class="string">"Parsed: %c\n"</span><span class="special">,*</span> <span class="keyword">static_cast</span><span class="special">&lt;</span><span class="keyword">char</span><span class="special">*&gt;(</span><span class="identifier">vp</span><span class="special">));</span>
 190     <span class="identifier">std</span><span class="special">::</span><span class="identifier">tie</span><span class="special">(</span><span class="identifier">source</span><span class="special">,</span><span class="identifier">vp</span><span class="special">)</span> <span class="special">=</span> <span class="identifier">source</span><span class="special">();</span>
 191     <span class="keyword">if</span> <span class="special">(</span><span class="identifier">except</span><span class="special">)</span> <span class="special">{</span>
 192         <span class="identifier">std</span><span class="special">::</span><span class="identifier">rethrow_exception</span><span class="special">(</span><span class="identifier">except</span><span class="special">);</span>
 193     <span class="special">}</span>
 194 <span class="special">}</span>
 195
 196 <span class="identifier">output</span><span class="special">:</span>
 197     <span class="identifier">Parsed</span><span class="special">:</span> <span class="number">1</span>
 198     <span class="identifier">Parsed</span><span class="special">:</span> <span class="special">+</span>
 199     <span class="identifier">Parsed</span><span class="special">:</span> <span class="number">1</span>
 200 </pre>
 201 <p>
 202       In this example a recursive descent parser uses a callback to emit a newly
 203       passed symbol. Using <span class="emphasis"><em>captured_context</em></span> the control flow
 204       can be inverted, e.g. the user-code pulls parsed symbols from the parser -
 205       instead to get pushed from the parser (via callback).
 206     </p>
 207 <p>
 208       The data (character) is transferred between the two <span class="emphasis"><em>captured_context</em></span>.
 209     </p>
 210 <p>
 211       If the code executed by <span class="emphasis"><em>captured_context</em></span> emits an exception,
 212       the application is terminated. <span class="emphasis"><em>std::exception_ptr</em></span> can
 213       be used to transfer exceptions between different execution contexts.
 214     </p>
 215 <p>
 216       Sometimes it is necessary to unwind the stack of an unfinished context to destroy
 217       local stack variables so they can release allocated resources (RAII pattern).
 218       The user is responsible for this task.
 219     </p>
 220 <a name="cc_prealloc"></a><h4>
 221 <a name="context.ccontext.h2"></a>
 222       <span><a name="context.ccontext.allocating_control_structures_on_top_of_stack"></a></span><a class="link" href="ccontext.html#context.ccontext.allocating_control_structures_on_top_of_stack">allocating
 223       control structures on top of stack</a>
 224     </h4>
 225 <p>
 226       Allocating control structures on top of the stack requires to allocated the
 227       <span class="emphasis"><em>stack_context</em></span> and create the control structure with placement
 228       new before <span class="emphasis"><em>captured_context</em></span> is created.
 229     </p>
 230 <div class="note"><table border="0" summary="Note">
 231 <tr>
 232 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../doc/src/images/note.png"></td>
 233 <th align="left">Note</th>
 234 </tr>
 235 <tr><td align="left" valign="top"><p>
 236         The user is responsible for destructing the control structure at the top
 237         of the stack.
 238       </p></td></tr>
 239 </table></div>
 240 <pre class="programlisting"><span class="comment">// stack-allocator used for (de-)allocating stack</span>
 241 <span class="identifier">fixedsize_stack</span> <span class="identifier">salloc</span><span class="special">(</span> <span class="number">4048</span><span class="special">);</span>
 242 <span class="comment">// allocate stack space</span>
 243 <span class="identifier">stack_context</span> <span class="identifier">sctx</span><span class="special">(</span> <span class="identifier">salloc</span><span class="special">.</span><span class="identifier">allocate</span><span class="special">()</span> <span class="special">);</span>
 244 <span class="comment">// reserve space for control structure on top of the stack</span>
 245 <span class="keyword">void</span> <span class="special">*</span> <span class="identifier">sp</span> <span class="special">=</span> <span class="keyword">static_cast</span><span class="special">&lt;</span> <span class="keyword">char</span> <span class="special">*</span> <span class="special">&gt;(</span> <span class="identifier">sctx</span><span class="special">.</span><span class="identifier">sp</span><span class="special">)</span> <span class="special">-</span> <span class="keyword">sizeof</span><span class="special">(</span> <span class="identifier">my_control_structure</span><span class="special">);</span>
 246 <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">size</span> <span class="special">=</span> <span class="identifier">sctx</span><span class="special">.</span><span class="identifier">size</span> <span class="special">-</span> <span class="keyword">sizeof</span><span class="special">(</span> <span class="identifier">my_control_structure</span><span class="special">);</span>
 247 <span class="comment">// placement new creates control structure on reserved space</span>
 248 <span class="identifier">my_control_structure</span> <span class="special">*</span> <span class="identifier">cs</span> <span class="special">=</span> <span class="keyword">new</span> <span class="special">(</span> <span class="identifier">sp</span><span class="special">)</span> <span class="identifier">my_control_structure</span><span class="special">(</span> <span class="identifier">sp</span><span class="special">,</span> <span class="identifier">size</span><span class="special">,</span> <span class="identifier">sctx</span><span class="special">,</span> <span class="identifier">salloc</span><span class="special">);</span>
 249 <span class="special">...</span>
 250 <span class="comment">// destructing the control structure</span>
 251 <span class="identifier">cs</span><span class="special">-&gt;~</span><span class="identifier">my_control_structure</span><span class="special">();</span>
 252 <span class="special">...</span>
 253 <span class="keyword">struct</span> <span class="identifier">my_control_structure</span>  <span class="special">{</span>
 254     <span class="comment">// captured context</span>
 255     <span class="identifier">captured_context</span> <span class="identifier">cctx</span><span class="special">;</span>
 256
 257     <span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">StackAllocator</span> <span class="special">&gt;</span>
 258     <span class="identifier">my_control_structure</span><span class="special">(</span> <span class="keyword">void</span> <span class="special">*</span> <span class="identifier">sp</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">size</span><span class="special">,</span> <span class="identifier">stack_context</span> <span class="identifier">sctx</span><span class="special">,</span> <span class="identifier">StackAllocator</span> <span class="identifier">salloc</span><span class="special">)</span> <span class="special">:</span>
 259         <span class="comment">// create captured context</span>
 260         <span class="identifier">cctx</span><span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">allocator_arg</span><span class="special">,</span> <span class="identifier">preallocated</span><span class="special">(</span> <span class="identifier">sp</span><span class="special">,</span> <span class="identifier">size</span><span class="special">,</span> <span class="identifier">sctx</span><span class="special">),</span> <span class="identifier">salloc</span><span class="special">,</span> <span class="identifier">entry_func</span><span class="special">)</span> <span class="special">{</span>
 261     <span class="special">}</span>
 262     <span class="special">...</span>
 263 <span class="special">};</span>
 264 </pre>
 265 <h4>
 266 <a name="context.ccontext.h3"></a>
 267       <span><a name="context.ccontext.exception_handling"></a></span><a class="link" href="ccontext.html#context.ccontext.exception_handling">exception
 268       handling</a>
 269     </h4>
 270 <p>
 271       If the function executed inside a <span class="emphasis"><em>captured_context</em></span> emits
 272       ans exception, the application is terminated by calling <span class="emphasis"><em>std::terminate()</em></span>.
 273       <span class="emphasis"><em>std::exception_ptr</em></span> can be used to transfer exceptions
 274       between different execution contexts.
 275     </p>
 276 <h4>
 277 <a name="context.ccontext.h4"></a>
 278       <span><a name="context.ccontext.parameter_passing"></a></span><a class="link" href="ccontext.html#context.ccontext.parameter_passing">parameter
 279       passing</a>
 280     </h4>
 281 <p>
 282       The void pointer argument passed to <span class="emphasis"><em>captured_context::operator()</em></span>,
 283       in one context, is passed as the last argument of the <span class="emphasis"><em>context-function</em></span>
 284       if the context is started for the first time. In all following invocations
 285       of <span class="emphasis"><em>captured_context::operator()</em></span> the void pointer passed
 286       to <span class="emphasis"><em>captured_context::operator()</em></span>, in one context, is returned
 287       by <span class="emphasis"><em>captured_context::operator()</em></span> in the other context.
 288     </p>
 289 <pre class="programlisting"><span class="keyword">class</span> <span class="identifier">X</span> <span class="special">{</span>
 290 <span class="keyword">private</span><span class="special">:</span>
 291     <span class="identifier">std</span><span class="special">::</span><span class="identifier">exception_ptr</span> <span class="identifier">excptr_</span><span class="special">;</span>
 292     <span class="identifier">boost</span><span class="special">::</span><span class="identifier">context</span><span class="special">::</span><span class="identifier">captured_context</span> <span class="identifier">ctx_</span><span class="special">;</span>
 293
 294 <span class="keyword">public</span><span class="special">:</span>
 295     <span class="identifier">X</span><span class="special">()</span> <span class="special">:</span>
 296         <span class="identifier">excptr_</span><span class="special">(),</span>
 297         <span class="identifier">ctx_</span><span class="special">([=](</span><span class="identifier">ctx</span><span class="special">::</span><span class="identifier">captured_context</span> <span class="identifier">ctx</span><span class="special">,</span> <span class="keyword">void</span><span class="special">*</span> <span class="identifier">vp</span><span class="special">)</span><span class="keyword">mutable</span><span class="special">{</span>
 298                     <span class="keyword">try</span> <span class="special">{</span>
 299                         <span class="keyword">for</span> <span class="special">(;;)</span> <span class="special">{</span>
 300                             <span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="special">*</span> <span class="keyword">static_cast</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">*&gt;(</span><span class="identifier">vp</span><span class="special">);</span>
 301                             <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">str</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">lexical_cast</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&gt;(</span><span class="identifier">i</span><span class="special">);</span>
 302                             <span class="keyword">auto</span> <span class="identifier">result</span> <span class="special">=</span> <span class="identifier">ctx</span><span class="special">(&amp;</span> <span class="identifier">str</span><span class="special">);</span>
 303                             <span class="identifier">ctx</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">get</span><span class="special">&lt;</span><span class="number">0</span><span class="special">&gt;(</span><span class="identifier">result</span><span class="special">)</span> <span class="special">);</span>
 304                             <span class="identifier">vp</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">get</span><span class="special">&lt;</span><span class="number">1</span><span class="special">&gt;(</span><span class="identifier">result</span><span class="special">);</span>
 305                         <span class="special">}</span>
 306                     <span class="special">}</span> <span class="keyword">catch</span> <span class="special">(</span><span class="identifier">ctx</span><span class="special">::</span><span class="identifier">detail</span><span class="special">::</span><span class="identifier">forced_unwind</span> <span class="keyword">const</span><span class="special">&amp;)</span> <span class="special">{</span>
 307                         <span class="keyword">throw</span><span class="special">;</span>
 308                     <span class="special">}</span> <span class="keyword">catch</span> <span class="special">(...)</span> <span class="special">{</span>
 309                         <span class="identifier">excptr_</span><span class="special">=</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">current_exception</span><span class="special">();</span>
 310                     <span class="special">}</span>
 311                     <span class="keyword">return</span> <span class="identifier">ctx</span><span class="special">;</span>
 312              <span class="special">})</span>
 313     <span class="special">{}</span>
 314
 315     <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="keyword">operator</span><span class="special">()(</span><span class="keyword">int</span> <span class="identifier">i</span><span class="special">)</span> <span class="special">{</span>
 316         <span class="keyword">auto</span> <span class="identifier">result</span> <span class="special">=</span> <span class="identifier">ctx_</span><span class="special">(&amp;</span><span class="identifier">i</span><span class="special">);</span>
 317         <span class="identifier">ctx_</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">get</span><span class="special">&lt;</span><span class="number">0</span><span class="special">&gt;(</span><span class="identifier">result</span><span class="special">));</span>
 318         <span class="keyword">void</span> <span class="special">*</span> <span class="identifier">ret</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">get</span><span class="special">&lt;</span><span class="number">1</span><span class="special">&gt;(</span><span class="identifier">result</span><span class="special">);</span>
 319         <span class="keyword">if</span><span class="special">(</span><span class="identifier">excptr_</span><span class="special">){</span>
 320             <span class="identifier">std</span><span class="special">::</span><span class="identifier">rethrow_exception</span><span class="special">(</span><span class="identifier">excptr_</span><span class="special">);</span>
 321         <span class="special">}</span>
 322         <span class="keyword">return</span> <span class="special">*</span> <span class="keyword">static_cast</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">*&gt;(</span><span class="identifier">ret</span><span class="special">);</span>
 323     <span class="special">}</span>
 324 <span class="special">};</span>
 325
 326 <span class="identifier">X</span> <span class="identifier">x</span><span class="special">;</span>
 327 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">x</span><span class="special">(</span> <span class="number">7</span><span class="special">)</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
 328
 329 <span class="identifier">output</span><span class="special">:</span>
 330 <span class="number">7</span>
 331 </pre>
 332 <h4>
 333 <a name="context.ccontext.h5"></a>
 334       <span><a name="context.ccontext.class__code__phrase_role__identifier__captured_context__phrase___code_"></a></span><a class="link" href="ccontext.html#context.ccontext.class__code__phrase_role__identifier__captured_context__phrase___code_">Class
 335       <code class="computeroutput"><span class="identifier">captured_context</span></code></a>
 336     </h4>
 337 <pre class="programlisting"><span class="keyword">class</span> <span class="identifier">captured_context</span> <span class="special">{</span>
 338 <span class="keyword">public</span><span class="special">:</span>
 339     <span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">Fn</span><span class="special">,</span> <span class="keyword">typename</span> <span class="special">...</span> <span class="identifier">Args</span> <span class="special">&gt;</span>
 340     <span class="identifier">captured_context</span><span class="special">(</span> <span class="identifier">Fn</span> <span class="special">&amp;&amp;</span> <span class="identifier">fn</span><span class="special">,</span> <span class="identifier">Args</span> <span class="special">&amp;&amp;</span> <span class="special">...</span> <span class="identifier">args</span><span class="special">);</span>
 341
 342     <span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">StackAlloc</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Fn</span><span class="special">,</span> <span class="keyword">typename</span> <span class="special">...</span> <span class="identifier">Args</span> <span class="special">&gt;</span>
 343     <span class="identifier">captured_context</span><span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">allocator_arg_t</span><span class="special">,</span> <span class="identifier">StackAlloc</span> <span class="identifier">salloc</span><span class="special">,</span> <span class="identifier">Fn</span> <span class="special">&amp;&amp;</span> <span class="identifier">fn</span><span class="special">,</span> <span class="identifier">Args</span> <span class="special">&amp;&amp;</span> <span class="special">...</span> <span class="identifier">args</span><span class="special">);</span>
 344
 345     <span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">StackAlloc</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Fn</span><span class="special">,</span> <span class="keyword">typename</span> <span class="special">...</span> <span class="identifier">Args</span> <span class="special">&gt;</span>
 346     <span class="identifier">captured_context</span><span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">allocator_arg_t</span><span class="special">,</span> <span class="identifier">preallocated</span> <span class="identifier">palloc</span><span class="special">,</span> <span class="identifier">StackAlloc</span> <span class="identifier">salloc</span><span class="special">,</span> <span class="identifier">Fn</span> <span class="special">&amp;&amp;</span> <span class="identifier">fn</span><span class="special">,</span> <span class="identifier">Args</span> <span class="special">&amp;&amp;</span> <span class="special">...</span> <span class="identifier">args</span><span class="special">);</span>
 347
 348     <span class="special">~</span><span class="identifier">captured_context</span><span class="special">();</span>
 349
 350     <span class="identifier">captured_context</span><span class="special">(</span> <span class="identifier">captured_context</span> <span class="special">&amp;&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span>
 351     <span class="identifier">captured_context</span> <span class="special">&amp;</span> <span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">captured_context</span> <span class="special">&amp;&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span>
 352
 353     <span class="identifier">captured_context</span><span class="special">(</span> <span class="identifier">captured_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">=</span> <span class="keyword">delete</span><span class="special">;</span>
 354     <span class="identifier">captured_context</span> <span class="special">&amp;</span> <span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">captured_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">=</span> <span class="keyword">delete</span><span class="special">;</span>
 355
 356     <span class="keyword">explicit</span> <span class="keyword">operator</span> <span class="keyword">bool</span><span class="special">()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 357     <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">!()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 358
 359     <span class="identifier">std</span><span class="special">::</span><span class="identifier">tuple</span><span class="special">&lt;</span> <span class="identifier">captured_context</span><span class="special">,</span> <span class="keyword">void</span> <span class="special">*</span> <span class="special">&gt;</span> <span class="keyword">operator</span><span class="special">()(</span> <span class="keyword">void</span> <span class="special">*</span> <span class="identifier">data</span> <span class="special">=</span> <span class="keyword">nullptr</span><span class="special">);</span>
 360
 361     <span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">Fn</span><span class="special">,</span> <span class="keyword">typename</span> <span class="special">...</span> <span class="identifier">Args</span> <span class="special">&gt;</span>
 362     <span class="identifier">std</span><span class="special">::</span><span class="identifier">tuple</span><span class="special">&lt;</span> <span class="identifier">captured_context</span><span class="special">,</span> <span class="keyword">void</span> <span class="special">*</span> <span class="special">&gt;</span> <span class="keyword">operator</span><span class="special">()(</span> <span class="identifier">exec_ontop_arg_t</span><span class="special">,</span> <span class="identifier">Fn</span> <span class="special">&amp;&amp;</span> <span class="identifier">fn</span><span class="special">,</span> <span class="identifier">Args</span> <span class="special">&amp;&amp;</span> <span class="special">...</span> <span class="identifier">args</span><span class="special">);</span>
 363
 364     <span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">Fn</span><span class="special">,</span> <span class="keyword">typename</span> <span class="special">...</span> <span class="identifier">Args</span> <span class="special">&gt;</span>
 365     <span class="identifier">std</span><span class="special">::</span><span class="identifier">tuple</span><span class="special">&lt;</span> <span class="identifier">captured_context</span><span class="special">,</span> <span class="keyword">void</span> <span class="special">*</span> <span class="special">&gt;</span> <span class="keyword">operator</span><span class="special">()(</span> <span class="keyword">void</span> <span class="special">*</span> <span class="identifier">data</span><span class="special">,</span> <span class="identifier">exec_ontop_arg_t</span><span class="special">,</span> <span class="identifier">Fn</span> <span class="special">&amp;&amp;</span> <span class="identifier">fn</span><span class="special">,</span> <span class="identifier">Args</span> <span class="special">&amp;&amp;</span> <span class="special">...</span> <span class="identifier">args</span><span class="special">);</span>
 366
 367     <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">==(</span> <span class="identifier">captured_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 368
 369     <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">!=(</span> <span class="identifier">captured_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 370
 371     <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">&lt;(</span> <span class="identifier">captured_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 372
 373     <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">&gt;(</span> <span class="identifier">captured_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 374
 375     <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">&lt;=(</span> <span class="identifier">captured_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 376
 377     <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">&gt;=(</span> <span class="identifier">captured_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 378
 379     <span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">charT</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">traitsT</span> <span class="special">&gt;</span>
 380     <span class="keyword">friend</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_ostream</span><span class="special">&lt;</span> <span class="identifier">charT</span><span class="special">,</span> <span class="identifier">traitsT</span> <span class="special">&gt;</span> <span class="special">&amp;</span>
 381     <span class="keyword">operator</span><span class="special">&lt;&lt;(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_ostream</span><span class="special">&lt;</span> <span class="identifier">charT</span><span class="special">,</span> <span class="identifier">traitsT</span> <span class="special">&gt;</span> <span class="special">&amp;</span> <span class="identifier">os</span><span class="special">,</span> <span class="identifier">captured_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">);</span>
 382 <span class="special">};</span>
 383 </pre>
 384 <p>
 385       </p>
 386 <h5>
 387 <a name="captured_context_constructor_bridgehead"></a>
 388   <span><a name="captured_context_constructor"></a></span>
 389   <a class="link" href="ccontext.html#captured_context_constructor">Constructor</a>
 390 </h5>
 391 <p>
 392     </p>
 393 <pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">Fn</span><span class="special">,</span> <span class="keyword">typename</span> <span class="special">...</span> <span class="identifier">Args</span> <span class="special">&gt;</span>
 394 <span class="identifier">captured_context</span><span class="special">(</span> <span class="identifier">Fn</span> <span class="special">&amp;&amp;</span> <span class="identifier">fn</span><span class="special">,</span> <span class="identifier">Args</span> <span class="special">&amp;&amp;</span> <span class="special">...</span> <span class="identifier">args</span><span class="special">);</span>
 395
 396 <span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">StackAlloc</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Fn</span><span class="special">,</span> <span class="keyword">typename</span> <span class="special">...</span> <span class="identifier">Args</span> <span class="special">&gt;</span>
 397 <span class="identifier">captured_context</span><span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">allocator_arg_t</span><span class="special">,</span> <span class="identifier">StackAlloc</span> <span class="identifier">salloc</span><span class="special">,</span> <span class="identifier">Fn</span> <span class="special">&amp;&amp;</span> <span class="identifier">fn</span><span class="special">,</span> <span class="identifier">Args</span> <span class="special">&amp;&amp;</span> <span class="special">...</span> <span class="identifier">args</span><span class="special">);</span>
 398
 399 <span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">StackAlloc</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Fn</span><span class="special">,</span> <span class="keyword">typename</span> <span class="special">...</span> <span class="identifier">Args</span> <span class="special">&gt;</span>
 400 <span class="identifier">captured_context</span><span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">allocator_arg_t</span><span class="special">,</span> <span class="identifier">preallocated</span> <span class="identifier">palloc</span><span class="special">,</span> <span class="identifier">StackAlloc</span> <span class="identifier">salloc</span><span class="special">,</span> <span class="identifier">Fn</span> <span class="special">&amp;&amp;</span> <span class="identifier">fn</span><span class="special">,</span> <span class="identifier">Args</span> <span class="special">&amp;&amp;</span> <span class="special">...</span> <span class="identifier">args</span><span class="special">);</span>
 401 </pre>
 402 <div class="variablelist">
 403 <p class="title"><b></b></p>
 404 <dl>
 405 <dt><span class="term">Effects:</span></dt>
 406 <dd><p>
 407             Creates a new execution context and prepares the context to execute
 408             <code class="computeroutput"><span class="identifier">fn</span></code>. <code class="computeroutput"><span class="identifier">fixedsize_stack</span></code>
 409             is used as default stack allocator (stack size == fixedsize_stack::traits::default_size()).
 410             The constructor with argument type <code class="computeroutput"><span class="identifier">preallocated</span></code>,
 411             is used to create a user defined data <a class="link" href="econtext.html#ec_prealloc">(for
 412             instance additional control structures)</a> on top of the stack.
 413           </p></dd>
 414 </dl>
 415 </div>
 416 <p>
 417       </p>
 418 <h5>
 419 <a name="captured_context_move%20constructor_bridgehead"></a>
 420   <span><a name="captured_context_move%20constructor"></a></span>
 421   <a class="link" href="ccontext.html#captured_context_move%20constructor">Move constructor</a>
 422 </h5>
 423 <p>
 424     </p>
 425 <pre class="programlisting"><span class="identifier">captured_context</span><span class="special">(</span> <span class="identifier">captured_context</span> <span class="special">&amp;&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span>
 426 </pre>
 427 <div class="variablelist">
 428 <p class="title"><b></b></p>
 429 <dl>
 430 <dt><span class="term">Effects:</span></dt>
 431 <dd><p>
 432             Moves underlying capture record to <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>.
 433           </p></dd>
 434 <dt><span class="term">Throws:</span></dt>
 435 <dd><p>
 436             Nothing.
 437           </p></dd>
 438 </dl>
 439 </div>
 440 <p>
 441       </p>
 442 <h5>
 443 <a name="captured_context_move%20assignment_bridgehead"></a>
 444   <span><a name="captured_context_move%20assignment"></a></span>
 445   <a class="link" href="ccontext.html#captured_context_move%20assignment">Move assignment operator</a>
 446 </h5>
 447 <p>
 448     </p>
 449 <pre class="programlisting"><span class="identifier">captured_context</span> <span class="special">&amp;</span> <span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">captured_context</span> <span class="special">&amp;&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span>
 450 </pre>
 451 <div class="variablelist">
 452 <p class="title"><b></b></p>
 453 <dl>
 454 <dt><span class="term">Effects:</span></dt>
 455 <dd><p>
 456             Moves the state of <code class="computeroutput"><span class="identifier">other</span></code>
 457             to <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
 458             using move semantics.
 459           </p></dd>
 460 <dt><span class="term">Throws:</span></dt>
 461 <dd><p>
 462             Nothing.
 463           </p></dd>
 464 </dl>
 465 </div>
 466 <p>
 467       </p>
 468 <h5>
 469 <a name="captured_context_operator_bool_bridgehead"></a>
 470   <span><a name="captured_context_operator_bool"></a></span>
 471   <a class="link" href="ccontext.html#captured_context_operator_bool">Member
 472       function <code class="computeroutput">operator bool</code>()</a>
 473 </h5>
 474 <p>
 475     </p>
 476 <pre class="programlisting"><span class="keyword">explicit</span> <span class="keyword">operator</span> <span class="keyword">bool</span><span class="special">()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 477 </pre>
 478 <div class="variablelist">
 479 <p class="title"><b></b></p>
 480 <dl>
 481 <dt><span class="term">Returns:</span></dt>
 482 <dd><p>
 483             <code class="computeroutput"><span class="keyword">true</span></code> if <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> points to a capture record.
 484           </p></dd>
 485 <dt><span class="term">Throws:</span></dt>
 486 <dd><p>
 487             Nothing.
 488           </p></dd>
 489 </dl>
 490 </div>
 491 <p>
 492       </p>
 493 <h5>
 494 <a name="captured_context_operator_not_bridgehead"></a>
 495   <span><a name="captured_context_operator_not"></a></span>
 496   <a class="link" href="ccontext.html#captured_context_operator_not">Member
 497       function <code class="computeroutput">operator!</code>()</a>
 498 </h5>
 499 <p>
 500     </p>
 501 <pre class="programlisting"><span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">!()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 502 </pre>
 503 <div class="variablelist">
 504 <p class="title"><b></b></p>
 505 <dl>
 506 <dt><span class="term">Returns:</span></dt>
 507 <dd><p>
 508             <code class="computeroutput"><span class="keyword">true</span></code> if <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not point to a capture record.
 509           </p></dd>
 510 <dt><span class="term">Throws:</span></dt>
 511 <dd><p>
 512             Nothing.
 513           </p></dd>
 514 </dl>
 515 </div>
 516 <p>
 517       </p>
 518 <h5>
 519 <a name="captured_context_operator_call_bridgehead"></a>
 520   <span><a name="captured_context_operator_call"></a></span>
 521   <a class="link" href="ccontext.html#captured_context_operator_call">Member
 522       function <code class="computeroutput">operator()</code>()</a>
 523 </h5>
 524 <p>
 525     </p>
 526 <pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">tuple</span><span class="special">&lt;</span> <span class="identifier">captured_context</span><span class="special">,</span> <span class="keyword">void</span> <span class="special">*</span> <span class="special">&gt;</span> <span class="keyword">operator</span><span class="special">()(</span> <span class="keyword">void</span> <span class="special">*</span> <span class="identifier">data</span> <span class="special">=</span> <span class="keyword">nullptr</span><span class="special">);</span>
 527 </pre>
 528 <div class="variablelist">
 529 <p class="title"><b></b></p>
 530 <dl>
 531 <dt><span class="term">Effects:</span></dt>
 532 <dd><p>
 533             Stores internally the current context data (stack pointer, instruction
 534             pointer, and CPU registers) of the current active context and restores
 535             the context data from <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>, which implies jumping to <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>'s
 536             context. The void pointer argument, <code class="computeroutput"><span class="identifier">vp</span></code>,
 537             is passed to the current context to be returned by the most recent call
 538             to <code class="computeroutput"><span class="identifier">captured_context</span><span class="special">::</span><span class="keyword">operator</span><span class="special">()</span></code>
 539             in the same thread. <code class="computeroutput"><span class="identifier">fn</span></code>
 540             is executed with arguments <code class="computeroutput"><span class="identifier">args</span></code>
 541             on top of the stack of <code class="computeroutput"><span class="keyword">this</span></code>.
 542           </p></dd>
 543 <dt><span class="term">Note:</span></dt>
 544 <dd><p>
 545             The behaviour is undefined if <code class="computeroutput"><span class="keyword">operator</span><span class="special">()()</span></code> is called while <code class="computeroutput"><span class="identifier">captured_context</span><span class="special">::</span><span class="identifier">current</span><span class="special">()</span></code> returns <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> (e.g. resuming an already running
 546             context). If the top-level context function returns, <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">exit</span><span class="special">()</span></code> is called.
 547           </p></dd>
 548 <dt><span class="term">Returns:</span></dt>
 549 <dd><p>
 550             The tuple of void pointer argument passed to the most recent call to
 551             <code class="computeroutput"><span class="identifier">captured_context</span><span class="special">::</span><span class="keyword">operator</span><span class="special">()</span></code>,
 552             if any and a captured_context representing the context that has been
 553             suspended .
 554           </p></dd>
 555 </dl>
 556 </div>
 557 <p>
 558       </p>
 559 <h5>
 560 <a name="captured_context_operator_call_ontop_bridgehead"></a>
 561   <span><a name="captured_context_operator_call_ontop"></a></span>
 562   <a class="link" href="ccontext.html#captured_context_operator_call_ontop">Member
 563       function <code class="computeroutput">operator()</code>()</a>
 564 </h5>
 565 <p>
 566     </p>
 567 <pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">Fn</span><span class="special">,</span> <span class="keyword">typename</span> <span class="special">...</span> <span class="identifier">Args</span> <span class="special">&gt;</span>
 568 <span class="identifier">std</span><span class="special">::</span><span class="identifier">tuple</span><span class="special">&lt;</span> <span class="identifier">captured_context</span><span class="special">,</span> <span class="keyword">void</span> <span class="special">*</span> <span class="special">&gt;</span> <span class="keyword">operator</span><span class="special">()(</span> <span class="identifier">exec_ontop_arg_t</span><span class="special">,</span> <span class="identifier">Fn</span> <span class="special">&amp;&amp;</span> <span class="identifier">fn</span><span class="special">,</span> <span class="identifier">Args</span> <span class="special">&amp;&amp;</span> <span class="special">...</span> <span class="identifier">args</span><span class="special">);</span>
 569
 570 <span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">Fn</span><span class="special">,</span> <span class="keyword">typename</span> <span class="special">...</span> <span class="identifier">Args</span> <span class="special">&gt;</span>
 571 <span class="identifier">std</span><span class="special">::</span><span class="identifier">tuple</span><span class="special">&lt;</span> <span class="identifier">captured_context</span><span class="special">,</span> <span class="keyword">void</span> <span class="special">*</span> <span class="special">&gt;</span> <span class="keyword">operator</span><span class="special">()(</span> <span class="keyword">void</span> <span class="special">*</span> <span class="identifier">data</span><span class="special">,</span> <span class="identifier">exec_ontop_arg_t</span><span class="special">,</span> <span class="identifier">Fn</span> <span class="special">&amp;&amp;</span> <span class="identifier">fn</span><span class="special">,</span> <span class="identifier">Args</span> <span class="special">&amp;&amp;</span> <span class="special">...</span> <span class="identifier">args</span><span class="special">);</span>
 572 </pre>
 573 <div class="variablelist">
 574 <p class="title"><b></b></p>
 575 <dl>
 576 <dt><span class="term">Effects:</span></dt>
 577 <dd><p>
 578             Same as <span class="emphasis"><em>captured_context::operator()</em></span>. Additionally,
 579             function <code class="computeroutput"><span class="identifier">fn</span></code> is executed
 580             with arguments <code class="computeroutput"><span class="identifier">args</span></code> in
 581             the context of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
 582             (e.g. the stack frame of <code class="computeroutput"><span class="identifier">fn</span></code>
 583             is allocated on stack of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>).
 584           </p></dd>
 585 <dt><span class="term">Returns:</span></dt>
 586 <dd><p>
 587             The tuple of void pointer argument passed to the most recent call to
 588             <code class="computeroutput"><span class="identifier">captured_context</span><span class="special">::</span><span class="keyword">operator</span><span class="special">()</span></code>,
 589             if any and a captured_context representing the context that has been
 590             suspended .
 591           </p></dd>
 592 </dl>
 593 </div>
 594 <p>
 595       </p>
 596 <h5>
 597 <a name="captured_context_operator_equal_bridgehead"></a>
 598   <span><a name="captured_context_operator_equal"></a></span>
 599   <a class="link" href="ccontext.html#captured_context_operator_equal">Member
 600       function <code class="computeroutput">operator==</code>()</a>
 601 </h5>
 602 <p>
 603     </p>
 604 <pre class="programlisting"><span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">==(</span> <span class="identifier">captured_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 605 </pre>
 606 <div class="variablelist">
 607 <p class="title"><b></b></p>
 608 <dl>
 609 <dt><span class="term">Returns:</span></dt>
 610 <dd><p>
 611             <code class="computeroutput"><span class="keyword">true</span></code> if <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="identifier">other</span></code>
 612             represent the same execution context, <code class="computeroutput"><span class="keyword">false</span></code>
 613             otherwise.
 614           </p></dd>
 615 <dt><span class="term">Throws:</span></dt>
 616 <dd><p>
 617             Nothing.
 618           </p></dd>
 619 </dl>
 620 </div>
 621 <p>
 622       </p>
 623 <h5>
 624 <a name="captured_context_operator_notequal_bridgehead"></a>
 625   <span><a name="captured_context_operator_notequal"></a></span>
 626   <a class="link" href="ccontext.html#captured_context_operator_notequal">Member
 627       function <code class="computeroutput">operator!=</code>()</a>
 628 </h5>
 629 <p>
 630     </p>
 631 <pre class="programlisting"><span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">!=(</span> <span class="identifier">captured_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 632 </pre>
 633 <div class="variablelist">
 634 <p class="title"><b></b></p>
 635 <dl>
 636 <dt><span class="term">Returns:</span></dt>
 637 <dd><p>
 638             <code class="computeroutput">! (other == * this)</code>
 639           </p></dd>
 640 <dt><span class="term">Throws:</span></dt>
 641 <dd><p>
 642             Nothing.
 643           </p></dd>
 644 </dl>
 645 </div>
 646 <p>
 647       </p>
 648 <h5>
 649 <a name="captured_context_operator_less_bridgehead"></a>
 650   <span><a name="captured_context_operator_less"></a></span>
 651   <a class="link" href="ccontext.html#captured_context_operator_less">Member
 652       function <code class="computeroutput">operator&lt;</code>()</a>
 653 </h5>
 654 <p>
 655     </p>
 656 <pre class="programlisting"><span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">&lt;(</span> <span class="identifier">captured_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 657 </pre>
 658 <div class="variablelist">
 659 <p class="title"><b></b></p>
 660 <dl>
 661 <dt><span class="term">Returns:</span></dt>
 662 <dd><p>
 663             <code class="computeroutput"><span class="keyword">true</span></code> if <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span> <span class="special">!=</span> <span class="identifier">other</span></code> is true and the implementation-defined
 664             total order of <code class="computeroutput"><span class="identifier">captured_context</span></code>
 665             values places <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
 666             before <code class="computeroutput"><span class="identifier">other</span></code>, false otherwise.
 667           </p></dd>
 668 <dt><span class="term">Throws:</span></dt>
 669 <dd><p>
 670             Nothing.
 671           </p></dd>
 672 </dl>
 673 </div>
 674 <p>
 675       </p>
 676 <h5>
 677 <a name="captured_context_operator_greater_bridgehead"></a>
 678   <span><a name="captured_context_operator_greater"></a></span>
 679   <a class="link" href="ccontext.html#captured_context_operator_greater">Member
 680       function <code class="computeroutput">operator&gt;</code>()</a>
 681 </h5>
 682 <p>
 683     </p>
 684 <pre class="programlisting"><span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">&gt;(</span> <span class="identifier">captured_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 685 </pre>
 686 <div class="variablelist">
 687 <p class="title"><b></b></p>
 688 <dl>
 689 <dt><span class="term">Returns:</span></dt>
 690 <dd><p>
 691             <code class="computeroutput"><span class="identifier">other</span> <span class="special">&lt;</span>
 692             <span class="special">*</span> <span class="keyword">this</span></code>
 693           </p></dd>
 694 <dt><span class="term">Throws:</span></dt>
 695 <dd><p>
 696             Nothing.
 697           </p></dd>
 698 </dl>
 699 </div>
 700 <p>
 701       </p>
 702 <h5>
 703 <a name="captured_context_operator_lesseq_bridgehead"></a>
 704   <span><a name="captured_context_operator_lesseq"></a></span>
 705   <a class="link" href="ccontext.html#captured_context_operator_lesseq">Member
 706       function <code class="computeroutput">operator&lt;=</code>()</a>
 707 </h5>
 708 <p>
 709     </p>
 710 <pre class="programlisting"><span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">&lt;=(</span> <span class="identifier">captured_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 711 </pre>
 712 <div class="variablelist">
 713 <p class="title"><b></b></p>
 714 <dl>
 715 <dt><span class="term">Returns:</span></dt>
 716 <dd><p>
 717             <code class="computeroutput"><span class="special">!</span> <span class="special">(</span><span class="identifier">other</span> <span class="special">&lt;</span>
 718             <span class="special">*</span> <span class="keyword">this</span><span class="special">)</span></code>
 719           </p></dd>
 720 <dt><span class="term">Throws:</span></dt>
 721 <dd><p>
 722             Nothing.
 723           </p></dd>
 724 </dl>
 725 </div>
 726 <p>
 727       </p>
 728 <h5>
 729 <a name="captured_context_operator_greatereq_bridgehead"></a>
 730   <span><a name="captured_context_operator_greatereq"></a></span>
 731   <a class="link" href="ccontext.html#captured_context_operator_greatereq">Member
 732       function <code class="computeroutput">operator&gt;=</code>()</a>
 733 </h5>
 734 <p>
 735     </p>
 736 <pre class="programlisting"><span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">&gt;=(</span> <span class="identifier">captured_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 737 </pre>
 738 <div class="variablelist">
 739 <p class="title"><b></b></p>
 740 <dl>
 741 <dt><span class="term">Returns:</span></dt>
 742 <dd><p>
 743             <code class="computeroutput"><span class="special">!</span> <span class="special">(*</span>
 744             <span class="keyword">this</span> <span class="special">&lt;</span>
 745             <span class="identifier">other</span><span class="special">)</span></code>
 746           </p></dd>
 747 <dt><span class="term">Throws:</span></dt>
 748 <dd><p>
 749             Nothing.
 750           </p></dd>
 751 </dl>
 752 </div>
 753 <p>
 754       </p>
 755 <h5>
 756 <a name="captured_context_bridgehead"></a>
 757   <span><a name="captured_context"></a></span>
 758   <a class="link" href="ccontext.html#captured_context">Non-member function
 759       <code class="computeroutput">operator&lt;&lt;()</code></a>
 760 </h5>
 761 <p>
 762     </p>
 763 <pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">charT</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">traitsT</span> <span class="special">&gt;</span>
 764 <span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_ostream</span><span class="special">&lt;</span> <span class="identifier">charT</span><span class="special">,</span> <span class="identifier">traitsT</span> <span class="special">&gt;</span> <span class="special">&amp;</span>
 765 <span class="keyword">operator</span><span class="special">&lt;&lt;(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_ostream</span><span class="special">&lt;</span> <span class="identifier">charT</span><span class="special">,</span> <span class="identifier">traitsT</span> <span class="special">&gt;</span> <span class="special">&amp;</span> <span class="identifier">os</span><span class="special">,</span> <span class="identifier">captured_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">);</span>
 766 </pre>
 767 <div class="variablelist">
 768 <p class="title"><b></b></p>
 769 <dl>
 770 <dt><span class="term">Efects:</span></dt>
 771 <dd><p>
 772             Writes the representation of <code class="computeroutput"><span class="identifier">other</span></code>
 773             to stream <code class="computeroutput"><span class="identifier">os</span></code>.
 774           </p></dd>
 775 <dt><span class="term">Returns:</span></dt>
 776 <dd><p>
 777             <code class="computeroutput"><span class="identifier">os</span></code>
 778           </p></dd>
 779 </dl>
 780 </div>
 781 </div>
 782 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 783 <td align="left"></td>
 784 <td align="right"><div class="copyright-footer">Copyright &#169; 2014 Oliver Kowalke<p>
 785         Distributed under the Boost Software License, Version 1.0. (See accompanying
 786         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>)
 787       </p>
 788 </div></td>
 789 </tr></table>
 790 <hr>
 791 <div class="spirit-nav">
 792 <a accesskey="p" href="econtext.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><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="stack.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
 793 </div>
 794 </body>
 795 </html>