ceph/src/boost/libs/fiber/doc/html/fiber/when_any/when_all_functionality/when_all_until_first_exception.html

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  26 <div class="titlepage"><div><div><h4 class="title">
  27 <a name="fiber.when_any.when_all_functionality.when_all_until_first_exception"></a><a class="link" href="when_all_until_first_exception.html" title="when_all until first exception">when_all
  28         until first exception</a>
  29 </h4></div></div></div>
  30 <p>
  31           Naturally, just as with <a class="link" href="../when_any/when_any__produce_first_outcome__whether_result_or_exception.html#wait_first_outcome"><code class="computeroutput"><span class="identifier">wait_first_outcome</span><span class="special">()</span></code></a>,
  32           we can elaborate <a class="link" href="when_all__return_values.html#wait_all_values"><code class="computeroutput"><span class="identifier">wait_all_values</span><span class="special">()</span></code></a> and <a class="link" href="when_all__return_values.html#wait_all_values_source"><code class="computeroutput"><span class="identifier">wait_all_values_source</span><span class="special">()</span></code></a>
  33           by passing <code class="computeroutput"><span class="identifier">future</span><span class="special">&lt;</span>
  34           <span class="identifier">T</span> <span class="special">&gt;</span></code>
  35           instead of plain <code class="computeroutput"><span class="identifier">T</span></code>.
  36         </p>
  37 <p>
  38           <a name="wait_all_until_error"></a><code class="computeroutput"><span class="identifier">wait_all_until_error</span><span class="special">()</span></code> pops that <code class="computeroutput"><span class="identifier">future</span><span class="special">&lt;</span> <span class="identifier">T</span> <span class="special">&gt;</span></code> and calls its <a class="link" href="../../synchronization/futures/future.html#future_get"><code class="computeroutput">future::get()</code></a>:
  39         </p>
  40 <p>
  41 </p>
  42 <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">Fns</span> <span class="special">&gt;</span>
  43 <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">result_of</span><span class="special">&lt;</span> <span class="identifier">Fn</span><span class="special">()</span> <span class="special">&gt;::</span><span class="identifier">type</span> <span class="special">&gt;</span>
  44 <span class="identifier">wait_all_until_error</span><span class="special">(</span> <span class="identifier">Fn</span> <span class="special">&amp;&amp;</span> <span class="identifier">function</span><span class="special">,</span> <span class="identifier">Fns</span> <span class="special">&amp;&amp;</span> <span class="special">...</span> <span class="identifier">functions</span><span class="special">)</span> <span class="special">{</span>
  45     <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">count</span><span class="special">(</span> <span class="number">1</span> <span class="special">+</span> <span class="keyword">sizeof</span> <span class="special">...</span> <span class="special">(</span> <span class="identifier">functions</span><span class="special">)</span> <span class="special">);</span>
  46     <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">result_of</span><span class="special">&lt;</span> <span class="identifier">Fn</span><span class="special">()</span> <span class="special">&gt;::</span><span class="identifier">type</span> <span class="identifier">return_t</span><span class="special">;</span>
  47     <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">fibers</span><span class="special">::</span><span class="identifier">future</span><span class="special">&lt;</span> <span class="identifier">return_t</span> <span class="special">&gt;</span> <span class="identifier">future_t</span><span class="special">;</span>
  48     <span class="keyword">typedef</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special">&lt;</span> <span class="identifier">return_t</span> <span class="special">&gt;</span> <span class="identifier">vector_t</span><span class="special">;</span>
  49     <span class="identifier">vector_t</span> <span class="identifier">results</span><span class="special">;</span>
  50     <span class="identifier">results</span><span class="special">.</span><span class="identifier">reserve</span><span class="special">(</span> <span class="identifier">count</span><span class="special">);</span>
  51
  52     <span class="comment">// get channel</span>
  53     <span class="identifier">std</span><span class="special">::</span><span class="identifier">shared_ptr</span><span class="special">&lt;</span>
  54         <span class="identifier">boost</span><span class="special">::</span><span class="identifier">fibers</span><span class="special">::</span><span class="identifier">unbounded_channel</span><span class="special">&lt;</span> <span class="identifier">future_t</span> <span class="special">&gt;</span> <span class="special">&gt;</span> <span class="identifier">channel</span><span class="special">(</span>
  55             <span class="identifier">wait_all_until_error_source</span><span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special">&lt;</span> <span class="identifier">Fn</span> <span class="special">&gt;(</span> <span class="identifier">function</span><span class="special">),</span>
  56                                          <span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special">&lt;</span> <span class="identifier">Fns</span> <span class="special">&gt;(</span> <span class="identifier">functions</span><span class="special">)</span> <span class="special">...</span> <span class="special">)</span> <span class="special">);</span>
  57     <span class="comment">// fill results vector</span>
  58     <span class="identifier">future_t</span> <span class="identifier">future</span><span class="special">;</span>
  59     <span class="keyword">while</span> <span class="special">(</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">fibers</span><span class="special">::</span><span class="identifier">channel_op_status</span><span class="special">::</span><span class="identifier">success</span> <span class="special">==</span> <span class="identifier">channel</span><span class="special">-&gt;</span><span class="identifier">pop</span><span class="special">(</span> <span class="identifier">future</span><span class="special">)</span> <span class="special">)</span> <span class="special">{</span>
  60         <span class="identifier">results</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span> <span class="identifier">future</span><span class="special">.</span><span class="identifier">get</span><span class="special">()</span> <span class="special">);</span>
  61     <span class="special">}</span>
  62     <span class="comment">// return vector to caller</span>
  63     <span class="keyword">return</span> <span class="identifier">results</span><span class="special">;</span>
  64 <span class="special">}</span>
  65 </pre>
  66 <p>
  67         </p>
  68 <p>
  69           For example:
  70         </p>
  71 <p>
  72 </p>
  73 <pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">thrown</span><span class="special">;</span>
  74 <span class="keyword">try</span> <span class="special">{</span>
  75     <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</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">values</span> <span class="special">=</span> <span class="identifier">wait_all_until_error</span><span class="special">(</span>
  76             <span class="special">[](){</span> <span class="keyword">return</span> <span class="identifier">sleeper</span><span class="special">(</span><span class="string">"waue_late"</span><span class="special">,</span>   <span class="number">150</span><span class="special">);</span> <span class="special">},</span>
  77             <span class="special">[](){</span> <span class="keyword">return</span> <span class="identifier">sleeper</span><span class="special">(</span><span class="string">"waue_middle"</span><span class="special">,</span> <span class="number">100</span><span class="special">,</span> <span class="keyword">true</span><span class="special">);</span> <span class="special">},</span>
  78             <span class="special">[](){</span> <span class="keyword">return</span> <span class="identifier">sleeper</span><span class="special">(</span><span class="string">"waue_early"</span><span class="special">,</span>   <span class="number">50</span><span class="special">);</span> <span class="special">});</span>
  79 <span class="special">}</span> <span class="keyword">catch</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">exception</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">e</span><span class="special">)</span> <span class="special">{</span>
  80     <span class="identifier">thrown</span> <span class="special">=</span> <span class="identifier">e</span><span class="special">.</span><span class="identifier">what</span><span class="special">();</span>
  81 <span class="special">}</span>
  82 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"wait_all_until_error(fail) threw '"</span> <span class="special">&lt;&lt;</span> <span class="identifier">thrown</span>
  83           <span class="special">&lt;&lt;</span> <span class="string">"'"</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>
  84 </pre>
  85 <p>
  86         </p>
  87 <p>
  88           <a name="wait_all_until_error_source"></a>Naturally this complicates the
  89           API for <code class="computeroutput"><span class="identifier">wait_all_until_error_source</span><span class="special">()</span></code>. The caller must both retrieve a <code class="computeroutput"><span class="identifier">future</span><span class="special">&lt;</span>
  90           <span class="identifier">T</span> <span class="special">&gt;</span></code>
  91           and call its <code class="computeroutput"><span class="identifier">get</span><span class="special">()</span></code>
  92           method. It would, of course, be possible to return a fa&#231;ade over the consumer
  93           end of the channel that would implicitly perform the <code class="computeroutput"><span class="identifier">get</span><span class="special">()</span></code> and return a simple <code class="computeroutput"><span class="identifier">T</span></code>
  94           (or throw).
  95         </p>
  96 <p>
  97           The implementation is just as you would expect. Notice, however, that we
  98           can reuse <a class="link" href="../when_any/when_any__produce_first_outcome__whether_result_or_exception.html#wait_first_outcome_impl"><code class="computeroutput"><span class="identifier">wait_first_outcome_impl</span><span class="special">()</span></code></a>, passing the <code class="computeroutput"><span class="identifier">nchannel</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> rather than <code class="computeroutput"><span class="identifier">unbounded_channel</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code>.
  99         </p>
 100 <p>
 101 </p>
 102 <pre class="programlisting"><span class="comment">// Return a shared_ptr&lt;unbounded_channel&lt;future&lt;T&gt;&gt;&gt; from which the caller can</span>
 103 <span class="comment">// get() each new result as it arrives, until 'closed'.</span>
 104 <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">Fns</span> <span class="special">&gt;</span>
 105 <span class="identifier">std</span><span class="special">::</span><span class="identifier">shared_ptr</span><span class="special">&lt;</span>
 106     <span class="identifier">boost</span><span class="special">::</span><span class="identifier">fibers</span><span class="special">::</span><span class="identifier">unbounded_channel</span><span class="special">&lt;</span>
 107         <span class="identifier">boost</span><span class="special">::</span><span class="identifier">fibers</span><span class="special">::</span><span class="identifier">future</span><span class="special">&lt;</span>
 108             <span class="keyword">typename</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">result_of</span><span class="special">&lt;</span> <span class="identifier">Fn</span><span class="special">()</span> <span class="special">&gt;::</span><span class="identifier">type</span> <span class="special">&gt;</span> <span class="special">&gt;</span> <span class="special">&gt;</span>
 109 <span class="identifier">wait_all_until_error_source</span><span class="special">(</span> <span class="identifier">Fn</span> <span class="special">&amp;&amp;</span> <span class="identifier">function</span><span class="special">,</span> <span class="identifier">Fns</span> <span class="special">&amp;&amp;</span> <span class="special">...</span> <span class="identifier">functions</span><span class="special">)</span> <span class="special">{</span>
 110     <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">count</span><span class="special">(</span> <span class="number">1</span> <span class="special">+</span> <span class="keyword">sizeof</span> <span class="special">...</span> <span class="special">(</span> <span class="identifier">functions</span><span class="special">)</span> <span class="special">);</span>
 111     <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">result_of</span><span class="special">&lt;</span> <span class="identifier">Fn</span><span class="special">()</span> <span class="special">&gt;::</span><span class="identifier">type</span> <span class="identifier">return_t</span><span class="special">;</span>
 112     <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">fibers</span><span class="special">::</span><span class="identifier">future</span><span class="special">&lt;</span> <span class="identifier">return_t</span> <span class="special">&gt;</span> <span class="identifier">future_t</span><span class="special">;</span>
 113     <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">fibers</span><span class="special">::</span><span class="identifier">unbounded_channel</span><span class="special">&lt;</span> <span class="identifier">future_t</span> <span class="special">&gt;</span> <span class="identifier">channel_t</span><span class="special">;</span>
 114     <span class="comment">// make the channel</span>
 115     <span class="keyword">auto</span> <span class="identifier">channelp</span><span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">make_shared</span><span class="special">&lt;</span> <span class="identifier">channel_t</span> <span class="special">&gt;()</span> <span class="special">);</span>
 116     <span class="comment">// and make an nchannel facade to close it after 'count' items</span>
 117     <span class="keyword">auto</span> <span class="identifier">ncp</span><span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">make_shared</span><span class="special">&lt;</span> <span class="identifier">nchannel</span><span class="special">&lt;</span> <span class="identifier">future_t</span> <span class="special">&gt;</span> <span class="special">&gt;(</span> <span class="identifier">channelp</span><span class="special">,</span> <span class="identifier">count</span><span class="special">)</span> <span class="special">);</span>
 118     <span class="comment">// pass that nchannel facade to all the relevant fibers</span>
 119     <span class="identifier">wait_first_outcome_impl</span><span class="special">&lt;</span> <span class="identifier">return_t</span> <span class="special">&gt;(</span> <span class="identifier">ncp</span><span class="special">,</span>
 120                                          <span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special">&lt;</span> <span class="identifier">Fn</span> <span class="special">&gt;(</span> <span class="identifier">function</span><span class="special">),</span>
 121                                          <span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special">&lt;</span> <span class="identifier">Fns</span> <span class="special">&gt;(</span> <span class="identifier">functions</span><span class="special">)</span> <span class="special">...</span> <span class="special">);</span>
 122     <span class="comment">// then return the channel for consumer</span>
 123     <span class="keyword">return</span> <span class="identifier">channelp</span><span class="special">;</span>
 124 <span class="special">}</span>
 125 </pre>
 126 <p>
 127         </p>
 128 <p>
 129           For example:
 130         </p>
 131 <p>
 132 </p>
 133 <pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">fibers</span><span class="special">::</span><span class="identifier">future</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">future_t</span><span class="special">;</span>
 134 <span class="identifier">std</span><span class="special">::</span><span class="identifier">shared_ptr</span><span class="special">&lt;</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">fibers</span><span class="special">::</span><span class="identifier">unbounded_channel</span><span class="special">&lt;</span> <span class="identifier">future_t</span> <span class="special">&gt;</span> <span class="special">&gt;</span> <span class="identifier">channel</span> <span class="special">=</span>
 135     <span class="identifier">wait_all_until_error_source</span><span class="special">(</span>
 136             <span class="special">[](){</span> <span class="keyword">return</span> <span class="identifier">sleeper</span><span class="special">(</span><span class="string">"wauess_third"</span><span class="special">,</span>  <span class="number">150</span><span class="special">);</span> <span class="special">},</span>
 137             <span class="special">[](){</span> <span class="keyword">return</span> <span class="identifier">sleeper</span><span class="special">(</span><span class="string">"wauess_second"</span><span class="special">,</span> <span class="number">100</span><span class="special">);</span> <span class="special">},</span>
 138             <span class="special">[](){</span> <span class="keyword">return</span> <span class="identifier">sleeper</span><span class="special">(</span><span class="string">"wauess_first"</span><span class="special">,</span>   <span class="number">50</span><span class="special">);</span> <span class="special">});</span>
 139 <span class="identifier">future_t</span> <span class="identifier">future</span><span class="special">;</span>
 140 <span class="keyword">while</span> <span class="special">(</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">fibers</span><span class="special">::</span><span class="identifier">channel_op_status</span><span class="special">::</span><span class="identifier">success</span> <span class="special">==</span> <span class="identifier">channel</span><span class="special">-&gt;</span><span class="identifier">pop</span><span class="special">(</span> <span class="identifier">future</span><span class="special">)</span> <span class="special">)</span> <span class="special">{</span>
 141     <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">value</span><span class="special">(</span> <span class="identifier">future</span><span class="special">.</span><span class="identifier">get</span><span class="special">()</span> <span class="special">);</span>
 142     <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"wait_all_until_error_source(success) =&gt; '"</span> <span class="special">&lt;&lt;</span> <span class="identifier">value</span>
 143               <span class="special">&lt;&lt;</span> <span class="string">"'"</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>
 144 <span class="special">}</span>
 145 </pre>
 146 <p>
 147         </p>
 148 </div>
 149 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 150 <td align="left"></td>
 151 <td align="right"><div class="copyright-footer">Copyright &#169; 2013 Oliver Kowalke<p>
 152         Distributed under the Boost Software License, Version 1.0. (See accompanying
 153         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>)
 154       </p>
 155 </div></td>
 156 </tr></table>
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