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| <div class="section"> |
| <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
| <a name="intrusive.unordered_set_unordered_multiset"></a><a class="link" href="unordered_set_unordered_multiset.html" title="Semi-Intrusive unordered associative containers: unordered_set, unordered_multiset">Semi-Intrusive |
| unordered associative containers: unordered_set, unordered_multiset</a> |
| </h2></div></div></div> |
| <div class="toc"><dl> |
| <dt><span class="section"><a href="unordered_set_unordered_multiset.html#intrusive.unordered_set_unordered_multiset.unordered_set_unordered_multiset_performance">unordered_set |
| and unordered_multiset performance notes</a></span></dt> |
| <dt><span class="section"><a href="unordered_set_unordered_multiset.html#intrusive.unordered_set_unordered_multiset.unordered_set_unordered_multiset_hooks">unordered_set |
| and unordered_multiset hooks</a></span></dt> |
| <dt><span class="section"><a href="unordered_set_unordered_multiset.html#intrusive.unordered_set_unordered_multiset.unordered_set_unordered_multiset_containers">unordered_set |
| and unordered_multiset containers</a></span></dt> |
| <dt><span class="section"><a href="unordered_set_unordered_multiset.html#intrusive.unordered_set_unordered_multiset.unordered_set_unordered_multiset_example">Example</a></span></dt> |
| <dt><span class="section"><a href="unordered_set_unordered_multiset.html#intrusive.unordered_set_unordered_multiset.custom_bucket_traits">Custom |
| bucket traits</a></span></dt> |
| </dl></div> |
| <p> |
| <span class="bold"><strong>Boost.Intrusive</strong></span> also offers hashed containers |
| that can be very useful to implement fast-lookup containers. These containers |
| (<code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_set.html" title="Class template unordered_set">unordered_set</a></code> |
| and <code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_multiset.html" title="Class template unordered_multiset">unordered_multiset</a></code>) |
| are semi-intrusive containers: they need additional memory apart from the hook |
| stored in the <code class="computeroutput"><span class="identifier">value_type</span></code>. This |
| additional memory must be passed in the constructor of the container. |
| </p> |
| <p> |
| Unlike C++ TR1 unordered associative containers (which are also hashed containers), |
| the contents of these semi-intrusive containers are not rehashed to maintain |
| a load factor: that would require memory management and intrusive containers |
| don't implement any memory management at all. However, the user can request |
| an explicit rehashing passing a new bucket array. This also offers an additional |
| guarantee over TR1 unordered associative containers: <span class="bold"><strong>iterators |
| are not invalidated when inserting an element</strong></span> in the container. |
| </p> |
| <p> |
| As with TR1 unordered associative containers, rehashing invalidates iterators, |
| changes ordering between elements and changes which buckets elements appear |
| in, but does not invalidate pointers or references to elements. |
| </p> |
| <p> |
| Apart from expected hash and equality function objects, <span class="bold"><strong>Boost.Intrusive</strong></span> |
| unordered associative containers' constructors take an argument specifying |
| an auxiliary bucket vector to be used by the container. |
| </p> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="intrusive.unordered_set_unordered_multiset.unordered_set_unordered_multiset_performance"></a><a class="link" href="unordered_set_unordered_multiset.html#intrusive.unordered_set_unordered_multiset.unordered_set_unordered_multiset_performance" title="unordered_set and unordered_multiset performance notes">unordered_set |
| and unordered_multiset performance notes</a> |
| </h3></div></div></div> |
| <p> |
| The size overhead for a hashed container is moderate: 1 pointer per value |
| plus a bucket array per container. The size of an element of the bucket array |
| is usually one pointer. To obtain a good performance hashed container, the |
| bucket length is usually the same as the number of elements that the container |
| contains, so a well-balanced hashed container (<code class="computeroutput"><span class="identifier">bucket_count</span><span class="special">()</span></code> is equal to <code class="computeroutput"><span class="identifier">size</span><span class="special">()</span></code> ) will have an equivalent overhead of two |
| pointers per element. |
| </p> |
| <p> |
| An empty, non constant-time size <code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_set.html" title="Class template unordered_set">unordered_set</a></code> |
| or <code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_multiset.html" title="Class template unordered_multiset">unordered_multiset</a></code> |
| has also the size of <code class="computeroutput"><span class="identifier">bucket_count</span><span class="special">()</span></code> pointers. |
| </p> |
| <p> |
| Insertions, erasures, and searches, have amortized constant-time complexity |
| in hashed containers. However, some worst-case guarantees are linear. See |
| <code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_set.html" title="Class template unordered_set">unordered_set</a></code> |
| or <code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_multiset.html" title="Class template unordered_multiset">unordered_multiset</a></code> |
| for complexity guarantees of each operation. |
| </p> |
| <p> |
| <span class="bold"><strong>Be careful with non constant-time size hashed containers</strong></span>: |
| some operations, like <code class="computeroutput"><span class="identifier">empty</span><span class="special">()</span></code>, have linear complexity, unlike other |
| <span class="bold"><strong>Boost.Intrusive</strong></span> containers. |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="intrusive.unordered_set_unordered_multiset.unordered_set_unordered_multiset_hooks"></a><a class="link" href="unordered_set_unordered_multiset.html#intrusive.unordered_set_unordered_multiset.unordered_set_unordered_multiset_hooks" title="unordered_set and unordered_multiset hooks">unordered_set |
| and unordered_multiset hooks</a> |
| </h3></div></div></div> |
| <p> |
| <code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_set.html" title="Class template unordered_set">unordered_set</a></code> |
| and <code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_multiset.html" title="Class template unordered_multiset">unordered_multiset</a></code> |
| share the same hooks. This is an advantage, because the same user type can |
| be inserted first in a <code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_multiset.html" title="Class template unordered_multiset">unordered_multiset</a></code> |
| and after that in <code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_set.html" title="Class template unordered_set">unordered_set</a></code> |
| without changing the definition of the user class. |
| </p> |
| <pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="special">...</span><span class="identifier">Options</span><span class="special">></span> |
| <span class="keyword">class</span> <span class="identifier">unordered_set_base_hook</span><span class="special">;</span> |
| </pre> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"> |
| <code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_set_base_hook.html" title="Class template unordered_set_base_hook">unordered_set_base_hook</a></code>: |
| the user class derives publicly from <code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_set_base_hook.html" title="Class template unordered_set_base_hook">unordered_set_base_hook</a></code> |
| to make it <code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_set.html" title="Class template unordered_set">unordered_set</a></code>/<code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_multiset.html" title="Class template unordered_multiset">unordered_multiset</a></code>-compatible. |
| </li></ul></div> |
| <pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="special">...</span><span class="identifier">Options</span><span class="special">></span> |
| <span class="keyword">class</span> <span class="identifier">unordered_set_member_hook</span><span class="special">;</span> |
| </pre> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"> |
| <code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_set_member_hook.html" title="Class template unordered_set_member_hook">unordered_set_member_hook</a></code>: |
| the user class contains a public <code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_set_member_hook.html" title="Class template unordered_set_member_hook">unordered_set_member_hook</a></code> |
| to make it <code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_set.html" title="Class template unordered_set">unordered_set</a></code>/<code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_multiset.html" title="Class template unordered_multiset">unordered_multiset</a></code>-compatible. |
| </li></ul></div> |
| <p> |
| <code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_set_base_hook.html" title="Class template unordered_set_base_hook">unordered_set_base_hook</a></code> |
| and <code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_set_member_hook.html" title="Class template unordered_set_member_hook">unordered_set_member_hook</a></code> |
| receive the same options explained in the section <a class="link" href="usage.html" title="How to use Boost.Intrusive">How |
| to use Boost.Intrusive</a>: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| <span class="bold"><strong><code class="computeroutput"><span class="identifier">tag</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Tag</span><span class="special">></span></code></strong></span> |
| (for base hooks only): This argument serves as a tag, so you can derive |
| from more than one base hook. Default: <code class="computeroutput"><span class="identifier">tag</span><span class="special"><</span><span class="identifier">default_tag</span><span class="special">></span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong><code class="computeroutput"><span class="identifier">link_mode</span><span class="special"><</span><span class="identifier">link_mode_type</span> |
| <span class="identifier">LinkMode</span><span class="special">></span></code></strong></span>: |
| The linking policy. Default: <code class="computeroutput"><span class="identifier">link_mode</span><span class="special"><</span><span class="identifier">safe_link</span><span class="special">></span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong><code class="computeroutput"><span class="identifier">void_pointer</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">VoidPointer</span><span class="special">></span></code></strong></span>: |
| The pointer type to be used internally in the hook and propagated to |
| the container. Default: <code class="computeroutput"><span class="identifier">void_pointer</span><span class="special"><</span><span class="keyword">void</span><span class="special">*></span></code>. |
| </li> |
| </ul></div> |
| <p> |
| Apart from them, these hooks offer additional options: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| <span class="bold"><strong><code class="computeroutput"><span class="identifier">store_hash</span><span class="special"><</span><span class="keyword">bool</span> <span class="identifier">Enabled</span><span class="special">></span></code></strong></span>: |
| This option reserves additional space in the hook to store the hash value |
| of the object once it's introduced in the container. When this option |
| is used, the unordered container will store the calculated hash value |
| in the hook and rehashing operations won't need to recalculate the hash |
| of the value. This option will improve the performance of unordered containers |
| when rehashing is frequent or hashing the value is a slow operation. |
| Default: <code class="computeroutput"><span class="identifier">store_hash</span><span class="special"><</span><span class="keyword">false</span><span class="special">></span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong><code class="computeroutput"><span class="identifier">optimize_multikey</span><span class="special"><</span><span class="keyword">bool</span> <span class="identifier">Enabled</span><span class="special">></span></code></strong></span>: |
| This option reserves additional space in the hook that will be used to |
| group equal elements in unordered multisets, improving significantly |
| the performance when many equal values are inserted in these containers. |
| Default: <code class="computeroutput"><span class="identifier">optimize_multikey</span><span class="special"><</span><span class="keyword">false</span><span class="special">></span></code>. |
| </li> |
| </ul></div> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="intrusive.unordered_set_unordered_multiset.unordered_set_unordered_multiset_containers"></a><a class="link" href="unordered_set_unordered_multiset.html#intrusive.unordered_set_unordered_multiset.unordered_set_unordered_multiset_containers" title="unordered_set and unordered_multiset containers">unordered_set |
| and unordered_multiset containers</a> |
| </h3></div></div></div> |
| <pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">,</span> <span class="keyword">class</span> <span class="special">...</span><span class="identifier">Options</span><span class="special">></span> |
| <span class="keyword">class</span> <span class="identifier">unordered_set</span><span class="special">;</span> |
| |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">,</span> <span class="keyword">class</span> <span class="special">...</span><span class="identifier">Options</span><span class="special">></span> |
| <span class="keyword">class</span> <span class="identifier">unordered_multiset</span><span class="special">;</span> |
| </pre> |
| <p> |
| As mentioned, unordered containers need an auxiliary array to work. <span class="bold"><strong>Boost.Intrusive</strong></span> unordered containers receive this |
| auxiliary array packed in a type called <code class="computeroutput"><span class="identifier">bucket_traits</span></code> |
| (which can be also customized by a container option). All unordered containers |
| receive a <code class="computeroutput"><span class="identifier">bucket_traits</span></code> object |
| in their constructors. The default <code class="computeroutput"><span class="identifier">bucket_traits</span></code> |
| class is initialized with a pointer to an array of buckets and its size: |
| </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">unordered_set</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">struct</span> <span class="identifier">MyClass</span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">unordered_set_base_hook</span><span class="special"><></span> |
| <span class="special">{};</span> |
| |
| <span class="keyword">typedef</span> <span class="identifier">unordered_set</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">>::</span><span class="identifier">bucket_type</span> <span class="identifier">bucket_type</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">unordered_set</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">>::</span><span class="identifier">bucket_traits</span> <span class="identifier">bucket_traits</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">bucket_type</span> <span class="identifier">buckets</span><span class="special">[</span><span class="number">100</span><span class="special">];</span> |
| <span class="identifier">unordered_set</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">></span> <span class="identifier">uset</span><span class="special">(</span><span class="identifier">bucket_traits</span><span class="special">(</span><span class="identifier">buckets</span><span class="special">,</span> <span class="number">100</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> |
| Each hashed container needs <span class="bold"><strong>its own bucket traits</strong></span>, |
| that is, <span class="bold"><strong>its own bucket vector</strong></span>. Two hashed |
| containers <span class="bold"><strong>can't</strong></span> share the same <code class="computeroutput"><span class="identifier">bucket_type</span></code> elements. The bucket array |
| <span class="bold"><strong>must</strong></span> be destroyed <span class="bold"><strong>after</strong></span> |
| the container using it is destroyed, otherwise, the result is undefined. |
| </p> |
| <p> |
| <code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_set.html" title="Class template unordered_set">unordered_set</a></code> |
| and <code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_multiset.html" title="Class template unordered_multiset">unordered_multiset</a></code> |
| receive the same options explained in the section <a class="link" href="usage.html" title="How to use Boost.Intrusive">How |
| to use Boost.Intrusive</a>: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| <span class="bold"><strong><code class="computeroutput"><span class="identifier">base_hook</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Hook</span><span class="special">></span></code></strong></span> |
| / <span class="bold"><strong><code class="computeroutput"><span class="identifier">member_hook</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Hook</span><span class="special">,</span> <span class="identifier">Hook</span> <span class="identifier">T</span><span class="special">::*</span> <span class="identifier">PtrToMember</span><span class="special">></span></code></strong></span> |
| / <span class="bold"><strong><code class="computeroutput"><span class="identifier">value_traits</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">ValueTraits</span><span class="special">></span></code></strong></span>: |
| To specify the hook type or value traits used to configure the container. |
| (To learn about value traits go to the section <a class="link" href="value_traits.html" title="Containers with custom ValueTraits">Containers |
| with custom ValueTraits</a>.) |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong><code class="computeroutput"><span class="identifier">constant_time_size</span><span class="special"><</span><span class="keyword">bool</span> <span class="identifier">Enabled</span><span class="special">></span></code></strong></span>: |
| To activate the constant-time <code class="computeroutput"><span class="identifier">size</span><span class="special">()</span></code> operation. Default: <code class="computeroutput"><span class="identifier">constant_time_size</span><span class="special"><</span><span class="keyword">true</span><span class="special">></span></code> |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong><code class="computeroutput"><span class="identifier">size_type</span><span class="special"><</span><span class="keyword">bool</span> <span class="identifier">Enabled</span><span class="special">></span></code></strong></span>: |
| To specify the type that will be used to store the size of the container. |
| Default: <code class="computeroutput"><span class="identifier">size_type</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span><span class="special">></span></code> |
| </li> |
| </ul></div> |
| <p> |
| And they also can receive additional options: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| <span class="bold"><strong><code class="computeroutput"><span class="identifier">equal</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Equal</span><span class="special">></span></code></strong></span>: |
| Equality function for the objects to be inserted in containers. Default: |
| <code class="computeroutput"><span class="identifier">equal</span><span class="special"><</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">equal_to</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="special">></span></code> |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong><code class="computeroutput"><span class="identifier">hash</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Hash</span><span class="special">></span></code></strong></span>: |
| Hash function to be used in the container. Default: <code class="computeroutput"><span class="identifier">hash</span><span class="special"><</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">hash</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="special">></span></code> |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong><code class="computeroutput"><span class="identifier">bucket_traits</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">BucketTraits</span><span class="special">></span></code></strong></span>: |
| A type that wraps the bucket vector to be used by the unordered container. |
| Default: a type initialized by the address and size of a bucket array |
| and stores both variables internally. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong><code class="computeroutput"><span class="identifier">power_2_buckets</span><span class="special"><</span><span class="keyword">bool</span> <span class="identifier">Enabled</span><span class="special">></span></code></strong></span>: |
| The user guarantees that only bucket arrays with power of two length |
| will be used. The container will then use masks instead of modulo operations |
| to obtain the bucket number from the hash value. Masks are faster than |
| modulo operations and for some applications modulo operations can impose |
| a considerable overhead. In debug mode an assertion will be raised if |
| the user provides a bucket length that is not power of two. Default: |
| <code class="computeroutput"><span class="identifier">power_2_buckets</span><span class="special"><</span><span class="keyword">false</span><span class="special">></span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong><code class="computeroutput"><span class="identifier">cache_begin</span><span class="special"><</span><span class="keyword">bool</span> <span class="identifier">Enabled</span><span class="special">></span></code></strong></span>: |
| <span class="bold"><strong>Note: this option is not compatible with <code class="computeroutput"><span class="identifier">auto_unlink</span></code> hooks</strong></span>. Due to |
| its internal structure, finding the first element of an unordered container |
| (<code class="computeroutput"><span class="identifier">begin</span><span class="special">()</span></code> |
| operation) is amortized constant-time. It's possible to speed up <code class="computeroutput"><span class="identifier">begin</span><span class="special">()</span></code> |
| and other operations related to it (like <code class="computeroutput"><span class="identifier">clear</span><span class="special">()</span></code>) if the container caches internally |
| the position of the first element. This imposes the overhead of one pointer |
| to the size of the container. Default: <code class="computeroutput"><span class="identifier">cache_begin</span><span class="special"><</span><span class="keyword">false</span><span class="special">></span></code>. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong><code class="computeroutput"><span class="identifier">compare_hash</span><span class="special"><</span><span class="keyword">bool</span> <span class="identifier">Enabled</span><span class="special">></span></code></strong></span>: |
| <span class="bold"><strong>Note: this option requires <code class="computeroutput"><span class="identifier">store_hash</span><span class="special"><</span><span class="keyword">true</span><span class="special">></span></code> option in the hook</strong></span>. When |
| the comparison function is expensive, (e.g. strings with a long common |
| predicate) sometimes (specially when the load factor is high or we have |
| many equivalent elements in an <code class="computeroutput"><a class="link" href="../boost/intrusive/unordered_multiset.html" title="Class template unordered_multiset">unordered_multiset</a></code> |
| and no <code class="computeroutput"><span class="identifier">optimize_multikey</span><span class="special"><></span></code> is activated in the hook) the |
| equality function is a performance problem. Two equal values must have |
| equal hashes, so comparing the hash values of two elements before using |
| the comparison functor can speed up some implementations. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong><code class="computeroutput"><span class="identifier">incremental</span><span class="special"><</span><span class="keyword">bool</span> <span class="identifier">Enabled</span><span class="special">></span></code></strong></span>: |
| Activates incremental hashing (also known as Linear Hashing). This option |
| implies <code class="computeroutput"><span class="identifier">power_2_buckets</span><span class="special"><</span><span class="keyword">true</span><span class="special">></span></code> and the container will require power |
| of two buckets. For more information on incremental hashing, see <a href="http://en.wikipedia.org/wiki/Linear_hashing" target="_top"><code class="computeroutput"><span class="identifier">Linear</span> |
| <span class="identifier">hash</span></code> on Wikipedia</a> Default: |
| <code class="computeroutput"><span class="identifier">incremental</span><span class="special"><</span><span class="keyword">false</span><span class="special">></span></code> |
| </li> |
| </ul></div> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="intrusive.unordered_set_unordered_multiset.unordered_set_unordered_multiset_example"></a><a class="link" href="unordered_set_unordered_multiset.html#intrusive.unordered_set_unordered_multiset.unordered_set_unordered_multiset_example" title="Example">Example</a> |
| </h3></div></div></div> |
| <p> |
| Now let's see a small example using both hooks and both containers: |
| </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">unordered_set</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">vector</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">algorithm</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">functional</span><span class="special">/</span><span class="identifier">hash</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">MyClass</span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">unordered_set_base_hook</span><span class="special"><></span> |
| <span class="special">{</span> <span class="comment">//This is a derivation hook |
| </span> <span class="keyword">int</span> <span class="identifier">int_</span><span class="special">;</span> |
| |
| <span class="keyword">public</span><span class="special">:</span> |
| <span class="identifier">unordered_set_member_hook</span><span class="special"><></span> <span class="identifier">member_hook_</span><span class="special">;</span> <span class="comment">//This is a member hook |
| </span> |
| <span class="identifier">MyClass</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">i</span><span class="special">)</span> |
| <span class="special">:</span> <span class="identifier">int_</span><span class="special">(</span><span class="identifier">i</span><span class="special">)</span> |
| <span class="special">{}</span> |
| |
| <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">==</span> <span class="special">(</span><span class="keyword">const</span> <span class="identifier">MyClass</span> <span class="special">&</span><span class="identifier">a</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">MyClass</span> <span class="special">&</span><span class="identifier">b</span><span class="special">)</span> |
| <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">a</span><span class="special">.</span><span class="identifier">int_</span> <span class="special">==</span> <span class="identifier">b</span><span class="special">.</span><span class="identifier">int_</span><span class="special">;</span> <span class="special">}</span> |
| |
| <span class="keyword">friend</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">hash_value</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">MyClass</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="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span><span class="special">(</span><span class="identifier">value</span><span class="special">.</span><span class="identifier">int_</span><span class="special">);</span> <span class="special">}</span> |
| <span class="special">};</span> |
| |
| <span class="comment">//Define an unordered_set that will store MyClass objects using the base hook |
| </span><span class="keyword">typedef</span> <span class="identifier">unordered_set</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">></span> <span class="identifier">BaseSet</span><span class="special">;</span> |
| |
| <span class="comment">//Define an unordered_multiset that will store MyClass using the member hook |
| </span><span class="keyword">typedef</span> <span class="identifier">member_hook</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">,</span> <span class="identifier">unordered_set_member_hook</span><span class="special"><>,</span> <span class="special">&</span><span class="identifier">MyClass</span><span class="special">::</span><span class="identifier">member_hook_</span><span class="special">></span> |
| <span class="identifier">MemberOption</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">unordered_multiset</span><span class="special"><</span> <span class="identifier">MyClass</span><span class="special">,</span> <span class="identifier">MemberOption</span><span class="special">></span> <span class="identifier">MemberMultiSet</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="keyword">typedef</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">>::</span><span class="identifier">iterator</span> <span class="identifier">VectIt</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">>::</span><span class="identifier">reverse_iterator</span> <span class="identifier">VectRit</span><span class="special">;</span> |
| |
| <span class="comment">//Create a vector with 100 different MyClass objects |
| </span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">></span> <span class="identifier">values</span><span class="special">;</span> |
| <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"><</span> <span class="number">100</span><span class="special">;</span> <span class="special">++</span><span class="identifier">i</span><span class="special">)</span> <span class="identifier">values</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="identifier">MyClass</span><span class="special">(</span><span class="identifier">i</span><span class="special">));</span> |
| |
| <span class="comment">//Create a copy of the vector |
| </span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">></span> <span class="identifier">values2</span><span class="special">(</span><span class="identifier">values</span><span class="special">);</span> |
| |
| <span class="comment">//Create a bucket array for base_set |
| </span> <span class="identifier">BaseSet</span><span class="special">::</span><span class="identifier">bucket_type</span> <span class="identifier">base_buckets</span><span class="special">[</span><span class="number">100</span><span class="special">];</span> |
| |
| <span class="comment">//Create a bucket array for member_multi_set |
| </span> <span class="identifier">MemberMultiSet</span><span class="special">::</span><span class="identifier">bucket_type</span> <span class="identifier">member_buckets</span><span class="special">[</span><span class="number">200</span><span class="special">];</span> |
| |
| <span class="comment">//Create unordered containers taking buckets as arguments |
| </span> <span class="identifier">BaseSet</span> <span class="identifier">base_set</span><span class="special">(</span><span class="identifier">BaseSet</span><span class="special">::</span><span class="identifier">bucket_traits</span><span class="special">(</span><span class="identifier">base_buckets</span><span class="special">,</span> <span class="number">100</span><span class="special">));</span> |
| <span class="identifier">MemberMultiSet</span> <span class="identifier">member_multi_set</span> |
| <span class="special">(</span><span class="identifier">MemberMultiSet</span><span class="special">::</span><span class="identifier">bucket_traits</span><span class="special">(</span><span class="identifier">member_buckets</span><span class="special">,</span> <span class="number">200</span><span class="special">));</span> |
| |
| <span class="comment">//Now insert values's elements in the unordered_set |
| </span> <span class="keyword">for</span><span class="special">(</span><span class="identifier">VectIt</span> <span class="identifier">it</span><span class="special">(</span><span class="identifier">values</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()),</span> <span class="identifier">itend</span><span class="special">(</span><span class="identifier">values</span><span class="special">.</span><span class="identifier">end</span><span class="special">());</span> <span class="identifier">it</span> <span class="special">!=</span> <span class="identifier">itend</span><span class="special">;</span> <span class="special">++</span><span class="identifier">it</span><span class="special">)</span> |
| <span class="identifier">base_set</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(*</span><span class="identifier">it</span><span class="special">);</span> |
| |
| <span class="comment">//Now insert values's and values2's elements in the unordered_multiset |
| </span> <span class="keyword">for</span><span class="special">(</span><span class="identifier">VectIt</span> <span class="identifier">it</span><span class="special">(</span><span class="identifier">values</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()),</span> <span class="identifier">itend</span><span class="special">(</span><span class="identifier">values</span><span class="special">.</span><span class="identifier">end</span><span class="special">()),</span> |
| <span class="identifier">it2</span><span class="special">(</span><span class="identifier">values2</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()),</span><span class="identifier">itend2</span><span class="special">(</span><span class="identifier">values2</span><span class="special">.</span><span class="identifier">end</span><span class="special">())</span> |
| <span class="special">;</span> <span class="identifier">it</span> <span class="special">!=</span> <span class="identifier">itend</span><span class="special">;</span> <span class="special">++</span><span class="identifier">it</span><span class="special">,</span> <span class="special">++</span><span class="identifier">it2</span><span class="special">){</span> |
| <span class="identifier">member_multi_set</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(*</span><span class="identifier">it</span><span class="special">);</span> |
| <span class="identifier">member_multi_set</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(*</span><span class="identifier">it2</span><span class="special">);</span> |
| <span class="special">}</span> |
| |
| <span class="comment">//Now find every element |
| </span> <span class="special">{</span> |
| <span class="identifier">VectIt</span> <span class="identifier">it</span><span class="special">(</span><span class="identifier">values</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()),</span> <span class="identifier">itend</span><span class="special">(</span><span class="identifier">values</span><span class="special">.</span><span class="identifier">end</span><span class="special">());</span> |
| |
| <span class="keyword">for</span><span class="special">(;</span> <span class="identifier">it</span> <span class="special">!=</span> <span class="identifier">itend</span><span class="special">;</span> <span class="special">++</span><span class="identifier">it</span><span class="special">){</span> |
| <span class="comment">//base_set should contain one element for each key |
| </span> <span class="keyword">if</span><span class="special">(</span><span class="identifier">base_set</span><span class="special">.</span><span class="identifier">count</span><span class="special">(*</span><span class="identifier">it</span><span class="special">)</span> <span class="special">!=</span> <span class="number">1</span><span class="special">)</span> <span class="keyword">return</span> <span class="number">1</span><span class="special">;</span> |
| <span class="comment">//member_multi_set should contain two elements for each key |
| </span> <span class="keyword">if</span><span class="special">(</span><span class="identifier">member_multi_set</span><span class="special">.</span><span class="identifier">count</span><span class="special">(*</span><span class="identifier">it</span><span class="special">)</span> <span class="special">!=</span> <span class="number">2</span><span class="special">)</span> <span class="keyword">return</span> <span class="number">1</span><span class="special">;</span> |
| <span class="special">}</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> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="intrusive.unordered_set_unordered_multiset.custom_bucket_traits"></a><a class="link" href="unordered_set_unordered_multiset.html#intrusive.unordered_set_unordered_multiset.custom_bucket_traits" title="Custom bucket traits">Custom |
| bucket traits</a> |
| </h3></div></div></div> |
| <p> |
| Instead of using the default <code class="computeroutput"><span class="identifier">bucket_traits</span></code> |
| class to store the bucket array, a user can define his own class to store |
| the bucket array using the <span class="bold"><strong><span class="emphasis"><em>bucket_traits<></em></span></strong></span> |
| option. A user-defined bucket-traits must fulfill the following interface: |
| </p> |
| <pre class="programlisting"><span class="keyword">class</span> <span class="identifier">my_bucket_traits</span> |
| <span class="special">{</span> |
| <span class="identifier">bucket_ptr</span> <span class="identifier">bucket_begin</span><span class="special">();</span> |
| <span class="identifier">const_bucket_ptr</span> <span class="identifier">bucket_begin</span><span class="special">()</span> <span class="keyword">const</span><span class="special">;</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">bucket_count</span><span class="special">()</span> <span class="keyword">const</span><span class="special">;</span> |
| <span class="special">};</span> |
| </pre> |
| <p> |
| The following bucket traits just stores a pointer to the bucket array but |
| the size is a compile-time constant. Note the use of the auxiliary <code class="computeroutput">unordered_bucket</code> and |
| <code class="computeroutput">unordered_bucket_ptr</code> |
| utilities to obtain the type of the bucket and its pointer before defining |
| the unordered container: |
| </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">unordered_set</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">functional</span><span class="special">/</span><span class="identifier">hash</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">vector</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="comment">//A class to be inserted in an unordered_set |
| </span><span class="keyword">class</span> <span class="identifier">MyClass</span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">unordered_set_base_hook</span><span class="special"><></span> |
| <span class="special">{</span> |
| <span class="keyword">int</span> <span class="identifier">int_</span><span class="special">;</span> |
| |
| <span class="keyword">public</span><span class="special">:</span> |
| <span class="identifier">MyClass</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="special">:</span> <span class="identifier">int_</span><span class="special">(</span><span class="identifier">i</span><span class="special">)</span> |
| <span class="special">{}</span> |
| |
| <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">==(</span><span class="keyword">const</span> <span class="identifier">MyClass</span> <span class="special">&</span><span class="identifier">l</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">MyClass</span> <span class="special">&</span><span class="identifier">r</span><span class="special">)</span> |
| <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">l</span><span class="special">.</span><span class="identifier">int_</span> <span class="special">==</span> <span class="identifier">r</span><span class="special">.</span><span class="identifier">int_</span><span class="special">;</span> <span class="special">}</span> |
| <span class="keyword">friend</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">hash_value</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">MyClass</span> <span class="special">&</span><span class="identifier">v</span><span class="special">)</span> |
| <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">hash_value</span><span class="special">(</span><span class="identifier">v</span><span class="special">.</span><span class="identifier">int_</span><span class="special">);</span> <span class="special">}</span> |
| <span class="special">};</span> |
| |
| <span class="comment">//Define the base hook option |
| </span><span class="keyword">typedef</span> <span class="identifier">base_hook</span><span class="special"><</span> <span class="identifier">unordered_set_base_hook</span><span class="special"><></span> <span class="special">></span> <span class="identifier">BaseHookOption</span><span class="special">;</span> |
| |
| <span class="comment">//Obtain the types of the bucket and the bucket pointer |
| </span><span class="keyword">typedef</span> <span class="identifier">unordered_bucket</span><span class="special"><</span><span class="identifier">BaseHookOption</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">BucketType</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">unordered_bucket_ptr</span><span class="special"><</span><span class="identifier">BaseHookOption</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">BucketPtr</span><span class="special">;</span> |
| |
| <span class="comment">//The custom bucket traits. |
| </span><span class="keyword">class</span> <span class="identifier">custom_bucket_traits</span> |
| <span class="special">{</span> |
| <span class="keyword">public</span><span class="special">:</span> |
| <span class="keyword">static</span> <span class="keyword">const</span> <span class="keyword">int</span> <span class="identifier">NumBuckets</span> <span class="special">=</span> <span class="number">100</span><span class="special">;</span> |
| |
| <span class="identifier">custom_bucket_traits</span><span class="special">(</span><span class="identifier">BucketPtr</span> <span class="identifier">buckets</span><span class="special">)</span> |
| <span class="special">:</span> <span class="identifier">buckets_</span><span class="special">(</span><span class="identifier">buckets</span><span class="special">)</span> |
| <span class="special">{}</span> |
| |
| <span class="comment">//Functions to be implemented by custom bucket traits |
| </span> <span class="identifier">BucketPtr</span> <span class="identifier">bucket_begin</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">buckets_</span><span class="special">;</span> <span class="special">}</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">bucket_count</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">NumBuckets</span><span class="special">;}</span> |
| |
| <span class="keyword">private</span><span class="special">:</span> |
| <span class="identifier">BucketPtr</span> <span class="identifier">buckets_</span><span class="special">;</span> |
| <span class="special">};</span> |
| |
| <span class="comment">//Define the container using the custom bucket traits |
| </span><span class="keyword">typedef</span> <span class="identifier">unordered_set</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">,</span> <span class="identifier">bucket_traits</span><span class="special"><</span><span class="identifier">custom_bucket_traits</span><span class="special">></span> <span class="special">></span> <span class="identifier">BucketTraitsUset</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="keyword">typedef</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">>::</span><span class="identifier">iterator</span> <span class="identifier">VectIt</span><span class="special">;</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">></span> <span class="identifier">values</span><span class="special">;</span> |
| |
| <span class="comment">//Fill values |
| </span> <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"><</span> <span class="number">100</span><span class="special">;</span> <span class="special">++</span><span class="identifier">i</span><span class="special">)</span> <span class="identifier">values</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="identifier">MyClass</span><span class="special">(</span><span class="identifier">i</span><span class="special">));</span> |
| |
| <span class="comment">//Now create the bucket array and the custom bucket traits object |
| </span> <span class="identifier">BucketType</span> <span class="identifier">buckets</span><span class="special">[</span><span class="identifier">custom_bucket_traits</span><span class="special">::</span><span class="identifier">NumBuckets</span><span class="special">];</span> |
| <span class="identifier">custom_bucket_traits</span> <span class="identifier">btraits</span><span class="special">(</span><span class="identifier">buckets</span><span class="special">);</span> |
| |
| <span class="comment">//Now create the unordered set |
| </span> <span class="identifier">BucketTraitsUset</span> <span class="identifier">uset</span><span class="special">(</span><span class="identifier">btraits</span><span class="special">);</span> |
| |
| <span class="comment">//Insert the values in the unordered set |
| </span> <span class="keyword">for</span><span class="special">(</span><span class="identifier">VectIt</span> <span class="identifier">it</span><span class="special">(</span><span class="identifier">values</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()),</span> <span class="identifier">itend</span><span class="special">(</span><span class="identifier">values</span><span class="special">.</span><span class="identifier">end</span><span class="special">());</span> <span class="identifier">it</span> <span class="special">!=</span> <span class="identifier">itend</span><span class="special">;</span> <span class="special">++</span><span class="identifier">it</span><span class="special">)</span> |
| <span class="identifier">uset</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(*</span><span class="identifier">it</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> |
| </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> |
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