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| <div class="section"> |
| <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
| <a name="intrusive.recursive"></a><a class="link" href="recursive.html" title="Recursive Boost.Intrusive containers">Recursive Boost.Intrusive containers</a> |
| </h2></div></div></div> |
| <p> |
| <span class="bold"><strong>Boost.Intrusive</strong></span> containers can be used to |
| define recursive structures very easily, allowing complex data structures with |
| very low overhead. Let's see an example: |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">intrusive</span><span class="special">/</span><span class="identifier">list</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">cassert</span><span class="special">></span> |
| |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">intrusive</span><span class="special">;</span> |
| |
| <span class="keyword">typedef</span> <span class="identifier">list_base_hook</span><span class="special"><></span> <span class="identifier">BaseHook</span><span class="special">;</span> |
| |
| <span class="comment">//A recursive class |
| </span><span class="keyword">class</span> <span class="identifier">Recursive</span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">BaseHook</span> |
| <span class="special">{</span> |
| <span class="keyword">private</span><span class="special">:</span> |
| <span class="identifier">Recursive</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">Recursive</span><span class="special">&);</span> |
| <span class="identifier">Recursive</span> <span class="special">&</span> <span class="keyword">operator</span><span class="special">=(</span><span class="keyword">const</span> <span class="identifier">Recursive</span><span class="special">&);</span> |
| |
| <span class="keyword">public</span><span class="special">:</span> |
| <span class="identifier">Recursive</span><span class="special">()</span> <span class="special">:</span> <span class="identifier">BaseHook</span><span class="special">(),</span> <span class="identifier">children</span><span class="special">(){}</span> |
| <span class="identifier">list</span><span class="special"><</span> <span class="identifier">Recursive</span><span class="special">,</span> <span class="identifier">base_hook</span><span class="special"><</span><span class="identifier">BaseHook</span><span class="special">></span> <span class="special">></span> <span class="identifier">children</span><span class="special">;</span> |
| <span class="special">};</span> |
| |
| <span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="identifier">Recursive</span> <span class="identifier">f</span><span class="special">,</span> <span class="identifier">f2</span><span class="special">;</span> |
| <span class="comment">//A recursive list of Recursive |
| </span> <span class="identifier">list</span><span class="special"><</span> <span class="identifier">Recursive</span><span class="special">,</span> <span class="identifier">base_hook</span><span class="special"><</span><span class="identifier">BaseHook</span><span class="special">></span> <span class="special">></span> <span class="identifier">l</span><span class="special">;</span> |
| |
| <span class="comment">//Insert a node in parent list |
| </span> <span class="identifier">l</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span><span class="identifier">l</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">f</span><span class="special">);</span> |
| |
| <span class="comment">//Insert a node in child list |
| </span> <span class="identifier">l</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()-></span><span class="identifier">children</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span><span class="identifier">l</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()-></span><span class="identifier">children</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">f2</span><span class="special">);</span> |
| |
| <span class="comment">//Objects properly inserted |
| </span> <span class="identifier">assert</span><span class="special">(</span><span class="identifier">l</span><span class="special">.</span><span class="identifier">size</span><span class="special">()</span> <span class="special">==</span> <span class="identifier">l</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()-></span><span class="identifier">children</span><span class="special">.</span><span class="identifier">size</span><span class="special">());</span> |
| <span class="identifier">assert</span><span class="special">(</span><span class="identifier">l</span><span class="special">.</span><span class="identifier">size</span><span class="special">()</span> <span class="special">==</span> <span class="number">1</span><span class="special">);</span> |
| |
| <span class="comment">//Clear both lists |
| </span> <span class="identifier">l</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()-></span><span class="identifier">children</span><span class="special">.</span><span class="identifier">clear</span><span class="special">();</span> |
| <span class="identifier">l</span><span class="special">.</span><span class="identifier">clear</span><span class="special">();</span> |
| <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| Recursive data structures using <span class="bold"><strong>Boost.Intrusive</strong></span> |
| containers must avoid using hook deduction to avoid early type instantiation: |
| </p> |
| <pre class="programlisting"><span class="comment">//This leads to compilation error (Recursive is instantiated by |
| </span><span class="comment">//'list' to deduce hook properties (pointer type, tag, safe-mode...) |
| </span><span class="keyword">class</span> <span class="identifier">Recursive</span> |
| <span class="special">{</span> <span class="comment">//... |
| </span> |
| <span class="identifier">list</span><span class="special"><</span> <span class="identifier">Recursive</span> <span class="special">></span> <span class="identifier">l</span><span class="special">;</span> |
| <span class="comment">//... |
| </span><span class="special">};</span> |
| |
| <span class="comment">//Ok, programmer must specify the hook type to avoid early Recursive instantiation |
| </span><span class="keyword">class</span> <span class="identifier">Recursive</span> |
| <span class="special">{</span> <span class="comment">//... |
| </span> <span class="identifier">list</span><span class="special"><</span> <span class="identifier">Recursive</span><span class="special">,</span> <span class="identifier">base_hook</span><span class="special"><</span><span class="identifier">BaseHook</span><span class="special">></span> <span class="special">></span> <span class="identifier">l</span><span class="special">;</span> |
| <span class="comment">//... |
| </span><span class="special">};</span> |
| </pre> |
| <p> |
| Member hooks are not suitable for recursive structures: |
| </p> |
| <pre class="programlisting"><span class="keyword">class</span> <span class="identifier">Recursive</span> |
| <span class="special">{</span> |
| <span class="keyword">private</span><span class="special">:</span> |
| <span class="identifier">Recursive</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">Recursive</span><span class="special">&);</span> |
| <span class="identifier">Recursive</span> <span class="special">&</span> <span class="keyword">operator</span><span class="special">=(</span><span class="keyword">const</span> <span class="identifier">Recursive</span><span class="special">&);</span> |
| |
| <span class="keyword">public</span><span class="special">:</span> |
| <span class="identifier">list_member_hook</span><span class="special"><></span> <span class="identifier">memhook</span><span class="special">;</span> |
| <span class="identifier">list</span><span class="special"><</span> <span class="identifier">Recursive</span><span class="special">,</span> <span class="identifier">member_hook</span><span class="special"><</span><span class="identifier">Recursive</span><span class="special">,</span> <span class="identifier">list_member_hook</span><span class="special"><>,</span> <span class="special">&</span><span class="identifier">Recursive</span><span class="special">::</span><span class="identifier">memhook</span><span class="special">></span> <span class="special">></span> <span class="identifier">children</span><span class="special">;</span> |
| <span class="special">};</span> |
| </pre> |
| <p> |
| Specifying <code class="computeroutput"><span class="special">&</span><span class="identifier">Recursive</span><span class="special">::</span><span class="identifier">memhook</span></code> |
| (that is, the offset between memhook and Recursive) provokes an early instantiation |
| of <code class="computeroutput"><span class="identifier">Recursive</span></code>. To define recursive |
| structures using member hooks, a programmer should use <code class="computeroutput">function_hook</code>: |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">intrusive</span><span class="special">/</span><span class="identifier">list</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">intrusive</span><span class="special">/</span><span class="identifier">parent_from_member</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">intrusive</span><span class="special">;</span> |
| |
| <span class="keyword">class</span> <span class="identifier">Recursive</span><span class="special">;</span> |
| |
| <span class="comment">//Declaration of the functor that converts betwen the Recursive |
| </span><span class="comment">//class and the hook |
| </span><span class="keyword">struct</span> <span class="identifier">Functor</span> |
| <span class="special">{</span> |
| <span class="comment">//Required types |
| </span> <span class="keyword">typedef</span> <span class="identifier">list_member_hook</span><span class="special"><></span> <span class="identifier">hook_type</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">hook_type</span><span class="special">*</span> <span class="identifier">hook_ptr</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="keyword">const</span> <span class="identifier">hook_type</span><span class="special">*</span> <span class="identifier">const_hook_ptr</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">Recursive</span> <span class="identifier">value_type</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">value_type</span><span class="special">*</span> <span class="identifier">pointer</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="keyword">const</span> <span class="identifier">value_type</span><span class="special">*</span> <span class="identifier">const_pointer</span><span class="special">;</span> |
| |
| <span class="comment">//Required static functions |
| </span> <span class="keyword">static</span> <span class="identifier">hook_ptr</span> <span class="identifier">to_hook_ptr</span> <span class="special">(</span><span class="identifier">value_type</span> <span class="special">&</span><span class="identifier">value</span><span class="special">);</span> |
| <span class="keyword">static</span> <span class="identifier">const_hook_ptr</span> <span class="identifier">to_hook_ptr</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">value_type</span> <span class="special">&</span><span class="identifier">value</span><span class="special">);</span> |
| <span class="keyword">static</span> <span class="identifier">pointer</span> <span class="identifier">to_value_ptr</span><span class="special">(</span><span class="identifier">hook_ptr</span> <span class="identifier">n</span><span class="special">);</span> |
| <span class="keyword">static</span> <span class="identifier">const_pointer</span> <span class="identifier">to_value_ptr</span><span class="special">(</span><span class="identifier">const_hook_ptr</span> <span class="identifier">n</span><span class="special">);</span> |
| <span class="special">};</span> |
| |
| <span class="comment">//Define the recursive class |
| </span><span class="keyword">class</span> <span class="identifier">Recursive</span> |
| <span class="special">{</span> |
| <span class="keyword">private</span><span class="special">:</span> |
| <span class="identifier">Recursive</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">Recursive</span><span class="special">&);</span> |
| <span class="identifier">Recursive</span> <span class="special">&</span> <span class="keyword">operator</span><span class="special">=(</span><span class="keyword">const</span> <span class="identifier">Recursive</span><span class="special">&);</span> |
| |
| <span class="keyword">public</span><span class="special">:</span> |
| <span class="identifier">Recursive</span><span class="special">()</span> <span class="special">:</span> <span class="identifier">hook</span><span class="special">(),</span> <span class="identifier">children</span><span class="special">()</span> <span class="special">{}</span> |
| <span class="identifier">list_member_hook</span><span class="special"><></span> <span class="identifier">hook</span><span class="special">;</span> |
| <span class="identifier">list</span><span class="special"><</span> <span class="identifier">Recursive</span><span class="special">,</span> <span class="identifier">function_hook</span><span class="special"><</span> <span class="identifier">Functor</span><span class="special">></span> <span class="special">></span> <span class="identifier">children</span><span class="special">;</span> |
| <span class="special">};</span> |
| |
| <span class="comment">//Definition of Functor functions |
| </span><span class="keyword">inline</span> <span class="identifier">Functor</span><span class="special">::</span><span class="identifier">hook_ptr</span> <span class="identifier">Functor</span><span class="special">::</span><span class="identifier">to_hook_ptr</span> <span class="special">(</span><span class="identifier">Functor</span><span class="special">::</span><span class="identifier">value_type</span> <span class="special">&</span><span class="identifier">value</span><span class="special">)</span> |
| <span class="special">{</span> <span class="keyword">return</span> <span class="special">&</span><span class="identifier">value</span><span class="special">.</span><span class="identifier">hook</span><span class="special">;</span> <span class="special">}</span> |
| <span class="keyword">inline</span> <span class="identifier">Functor</span><span class="special">::</span><span class="identifier">const_hook_ptr</span> <span class="identifier">Functor</span><span class="special">::</span><span class="identifier">to_hook_ptr</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">Functor</span><span class="special">::</span><span class="identifier">value_type</span> <span class="special">&</span><span class="identifier">value</span><span class="special">)</span> |
| <span class="special">{</span> <span class="keyword">return</span> <span class="special">&</span><span class="identifier">value</span><span class="special">.</span><span class="identifier">hook</span><span class="special">;</span> <span class="special">}</span> |
| <span class="keyword">inline</span> <span class="identifier">Functor</span><span class="special">::</span><span class="identifier">pointer</span> <span class="identifier">Functor</span><span class="special">::</span><span class="identifier">to_value_ptr</span><span class="special">(</span><span class="identifier">Functor</span><span class="special">::</span><span class="identifier">hook_ptr</span> <span class="identifier">n</span><span class="special">)</span> |
| <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">get_parent_from_member</span><span class="special"><</span><span class="identifier">Recursive</span><span class="special">>(</span><span class="identifier">n</span><span class="special">,</span> <span class="special">&</span><span class="identifier">Recursive</span><span class="special">::</span><span class="identifier">hook</span><span class="special">);</span> <span class="special">}</span> |
| <span class="keyword">inline</span> <span class="identifier">Functor</span><span class="special">::</span><span class="identifier">const_pointer</span> <span class="identifier">Functor</span><span class="special">::</span><span class="identifier">to_value_ptr</span><span class="special">(</span><span class="identifier">Functor</span><span class="special">::</span><span class="identifier">const_hook_ptr</span> <span class="identifier">n</span><span class="special">)</span> |
| <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">get_parent_from_member</span><span class="special"><</span><span class="identifier">Recursive</span><span class="special">>(</span><span class="identifier">n</span><span class="special">,</span> <span class="special">&</span><span class="identifier">Recursive</span><span class="special">::</span><span class="identifier">hook</span><span class="special">);</span> <span class="special">}</span> |
| |
| <span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="identifier">Recursive</span> <span class="identifier">f</span><span class="special">,</span> <span class="identifier">f2</span><span class="special">;</span> |
| <span class="comment">//A recursive list of Recursive |
| </span> <span class="identifier">list</span><span class="special"><</span> <span class="identifier">Recursive</span><span class="special">,</span> <span class="identifier">function_hook</span><span class="special"><</span> <span class="identifier">Functor</span><span class="special">></span> <span class="special">></span> <span class="identifier">l</span><span class="special">;</span> |
| |
| <span class="comment">//Insert a node in parent list |
| </span> <span class="identifier">l</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span><span class="identifier">l</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">f</span><span class="special">);</span> |
| |
| <span class="comment">//Insert a node in child list |
| </span> <span class="identifier">l</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()-></span><span class="identifier">children</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span><span class="identifier">l</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()-></span><span class="identifier">children</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">f2</span><span class="special">);</span> |
| |
| <span class="comment">//Objects properly inserted |
| </span> <span class="identifier">assert</span><span class="special">(</span><span class="identifier">l</span><span class="special">.</span><span class="identifier">size</span><span class="special">()</span> <span class="special">==</span> <span class="identifier">l</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()-></span><span class="identifier">children</span><span class="special">.</span><span class="identifier">size</span><span class="special">());</span> |
| <span class="identifier">assert</span><span class="special">(</span><span class="identifier">l</span><span class="special">.</span><span class="identifier">size</span><span class="special">()</span> <span class="special">==</span> <span class="number">1</span><span class="special">);</span> |
| |
| <span class="comment">//Clear both lists |
| </span> <span class="identifier">l</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()-></span><span class="identifier">children</span><span class="special">.</span><span class="identifier">clear</span><span class="special">();</span> |
| <span class="identifier">l</span><span class="special">.</span><span class="identifier">clear</span><span class="special">();</span> |
| <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| </p> |
| </div> |
| <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> |
| <td align="left"></td> |
| <td align="right"><div class="copyright-footer">Copyright © 2005 Olaf Krzikalla, 2006-2010 Ion Gaztanaga<p> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| 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>) |
| </p> |
| </div></td> |
| </tr></table> |
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