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| <div class="section"> |
| <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
| <a name="interprocess.customizing_interprocess"></a><a class="link" href="customizing_interprocess.html" title="Customizing Boost.Interprocess">Customizing Boost.Interprocess</a> |
| </h2></div></div></div> |
| <div class="toc"><dl class="toc"> |
| <dt><span class="section"><a href="customizing_interprocess.html#interprocess.customizing_interprocess.custom_interprocess_alloc">Writing |
| a new shared memory allocation algorithm</a></span></dt> |
| <dt><span class="section"><a href="customizing_interprocess.html#interprocess.customizing_interprocess.custom_allocators">Building |
| custom STL compatible allocators for Boost.Interprocess</a></span></dt> |
| <dt><span class="section"><a href="customizing_interprocess.html#interprocess.customizing_interprocess.custom_indexes">Building |
| custom indexes</a></span></dt> |
| </dl></div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="interprocess.customizing_interprocess.custom_interprocess_alloc"></a><a class="link" href="customizing_interprocess.html#interprocess.customizing_interprocess.custom_interprocess_alloc" title="Writing a new shared memory allocation algorithm">Writing |
| a new shared memory allocation algorithm</a> |
| </h3></div></div></div> |
| <p> |
| If the default algorithm does not satisfy user requirements, it's easy to |
| provide different algorithms like bitmapping or more advanced segregated |
| lists to meet requirements. The class implementing the algorithm must be |
| compatible with shared memory, so it shouldn't have any virtual function |
| or virtual inheritance or any indirect base class with virtual function or |
| inheritance. |
| </p> |
| <p> |
| This is the interface to be implemented: |
| </p> |
| <pre class="programlisting"><span class="keyword">class</span> <span class="identifier">my_algorithm</span> |
| <span class="special">{</span> |
| <span class="keyword">public</span><span class="special">:</span> |
| |
| <span class="comment">//!The mutex type to be used by the rest of Interprocess framework</span> |
| <span class="keyword">typedef</span> <span class="identifier">implementation_defined</span> <span class="identifier">mutex_family</span><span class="special">;</span> |
| |
| <span class="comment">//!The pointer type to be used by the rest of Interprocess framework</span> |
| <span class="keyword">typedef</span> <span class="identifier">implementation_defined</span> <span class="identifier">void_pointer</span><span class="special">;</span> |
| |
| <span class="comment">//!Constructor. "size" is the total size of the managed memory segment,</span> |
| <span class="comment">//!"extra_hdr_bytes" indicates the extra bytes after the sizeof(my_algorithm)</span> |
| <span class="comment">//!that the allocator should not use at all.</span> |
| <span class="identifier">my_algorithm</span> <span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">size</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">extra_hdr_bytes</span><span class="special">);</span> |
| |
| <span class="comment">//!Obtains the minimum size needed by the algorithm</span> |
| <span class="keyword">static</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">get_min_size</span> <span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">extra_hdr_bytes</span><span class="special">);</span> |
| |
| <span class="comment">//!Allocates bytes, returns 0 if there is not more memory</span> |
| <span class="keyword">void</span><span class="special">*</span> <span class="identifier">allocate</span> <span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">nbytes</span><span class="special">);</span> |
| |
| <span class="comment">//!Deallocates previously allocated bytes</span> |
| <span class="keyword">void</span> <span class="identifier">deallocate</span> <span class="special">(</span><span class="keyword">void</span> <span class="special">*</span><span class="identifier">adr</span><span class="special">);</span> |
| |
| <span class="comment">//!Returns the size of the memory segment</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">get_size</span><span class="special">()</span> <span class="keyword">const</span><span class="special">;</span> |
| |
| <span class="comment">//!Increases managed memory in extra_size bytes more</span> |
| <span class="keyword">void</span> <span class="identifier">grow</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">extra_size</span><span class="special">);</span> |
| <span class="comment">/*...*/</span> |
| <span class="special">};</span> |
| </pre> |
| <p> |
| Let's see the public typedefs to define: |
| </p> |
| <pre class="programlisting"><span class="keyword">typedef</span> <span class="comment">/* . . . */</span> <span class="identifier">void_pointer</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="comment">/* . . . */</span> <span class="identifier">mutex_family</span><span class="special">;</span> |
| </pre> |
| <p> |
| The <code class="computeroutput"><span class="identifier">void_pointer</span></code> typedef |
| specifies the pointer type to be used in the <span class="bold"><strong>Boost.Interprocess</strong></span> |
| framework that uses the algorithm. For example, if we define |
| </p> |
| <pre class="programlisting"><span class="keyword">typedef</span> <span class="keyword">void</span> <span class="special">*</span> <span class="identifier">void_pointer</span><span class="special">;</span> |
| </pre> |
| <p> |
| all <span class="bold"><strong>Boost.Interprocess</strong></span> framework using this |
| algorithm will use raw pointers as members. But if we define: |
| </p> |
| <pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">offset_ptr</span><span class="special"><</span><span class="keyword">void</span><span class="special">></span> <span class="identifier">void_pointer</span><span class="special">;</span> |
| </pre> |
| <p> |
| then all <span class="bold"><strong>Boost.Interprocess</strong></span> framework will |
| use relative pointers. |
| </p> |
| <p> |
| The <code class="computeroutput"><span class="identifier">mutex_family</span></code> is a structure |
| containing typedefs for different interprocess_mutex types to be used in |
| the <span class="bold"><strong>Boost.Interprocess</strong></span> framework. For example |
| the defined |
| </p> |
| <pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">mutex_family</span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">interprocess</span><span class="special">::</span><span class="identifier">interprocess_mutex</span> <span class="identifier">mutex_type</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">interprocess</span><span class="special">::</span><span class="identifier">interprocess_recursive_mutex</span> <span class="identifier">recursive_mutex_type</span><span class="special">;</span> |
| <span class="special">};</span> |
| </pre> |
| <p> |
| defines all interprocess_mutex types using boost::interprocess interprocess_mutex |
| types. The user can specify the desired mutex family. |
| </p> |
| <pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">mutex_family</span> <span class="identifier">mutex_family</span><span class="special">;</span> |
| </pre> |
| <p> |
| The new algorithm (let's call it <span class="bold"><strong>my_algorithm</strong></span>) |
| must implement all the functions that boost::interprocess::rbtree_best_fit |
| class offers: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>my_algorithm</strong></span>'s constructor must take |
| 2 arguments: |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "> |
| <li class="listitem"> |
| <span class="bold"><strong>size</strong></span> indicates the total size |
| of the managed memory segment, and <span class="bold"><strong>my_algorithm</strong></span> |
| object will be always constructed a at offset 0 of the memory segment. |
| </li> |
| <li class="listitem"> |
| The <span class="bold"><strong>extra_hdr_bytes</strong></span> parameter |
| indicates the number of bytes after the offset <code class="computeroutput"><span class="keyword">sizeof</span><span class="special">(</span><span class="identifier">my_algorithm</span><span class="special">)</span></code> that <span class="bold"><strong>my_algorithm</strong></span> |
| can't use at all. This extra bytes will be used to store additional |
| data that should not be overwritten. So, <span class="bold"><strong>my_algorithm</strong></span> |
| will be placed at address XXX of the memory segment, and will manage |
| the <span class="bold"><strong>[XXX + sizeof(my_algorithm) + extra_hdr_bytes, |
| XXX + size)</strong></span> range of the segment. |
| </li> |
| </ul></div> |
| </li> |
| <li class="listitem"> |
| The <span class="bold"><strong>get_min_size()</strong></span> function should return |
| the minimum space the algorithm needs to be valid with the passed <span class="bold"><strong>extra_hdr_bytes</strong></span> parameter. This function will |
| be used to check if the memory segment is big enough to place the algorithm |
| there. |
| </li> |
| <li class="listitem"> |
| The <span class="bold"><strong>allocate()</strong></span> function must return |
| 0 if there is no more available memory. The memory returned by <span class="bold"><strong>my_algorithm</strong></span> must be aligned to the most restrictive |
| memory alignment of the system. This function should be executed with |
| the synchronization capabilities offered by <code class="computeroutput"><span class="keyword">typename</span> |
| <span class="identifier">mutex_family</span><span class="special">::</span><span class="identifier">mutex_type</span></code> interprocess_mutex. That |
| means, that if we define <code class="computeroutput"><span class="keyword">typedef</span> |
| <span class="identifier">mutex_family</span> <span class="identifier">mutex_family</span><span class="special">;</span></code> then this function should offer the |
| same synchronization as if it was surrounded by an interprocess_mutex |
| lock/unlock. Normally, this is implemented using a member of type <code class="computeroutput"><span class="identifier">mutex_family</span><span class="special">::</span><span class="identifier">mutex_type</span></code>, but it could be done using |
| atomic instructions or lock free algorithms. |
| </li> |
| <li class="listitem"> |
| The <span class="bold"><strong>deallocate()</strong></span> function must make |
| the returned buffer available for new allocations. This function should |
| offer the same synchronization as <code class="computeroutput"><span class="identifier">allocate</span><span class="special">()</span></code>. |
| </li> |
| <li class="listitem"> |
| The <span class="bold"><strong>size()</strong></span> function will return the |
| passed <span class="bold"><strong>size</strong></span> parameter in the constructor. |
| So, <span class="bold"><strong>my_algorithm</strong></span> should store the size |
| internally. |
| </li> |
| <li class="listitem"> |
| The <span class="bold"><strong>grow()</strong></span> function will expand the |
| managed memory by <span class="bold"><strong>my_algorithm</strong></span> in <span class="bold"><strong>extra_size</strong></span> bytes. So <span class="bold"><strong>size()</strong></span> |
| function should return the updated size, and the new managed memory range |
| will be (if the address where the algorithm is constructed is XXX): |
| <span class="bold"><strong>[XXX + sizeof(my_algorithm) + extra_hdr_bytes, |
| XXX + old_size + extra_size)</strong></span>. This function should offer the |
| same synchronization as <code class="computeroutput"><span class="identifier">allocate</span><span class="special">()</span></code>. |
| </li> |
| </ul></div> |
| <p> |
| That's it. Now we can create new managed shared memory that uses our new |
| algorithm: |
| </p> |
| <pre class="programlisting"><span class="comment">//Managed memory segment to allocate named (c-string) objects</span> |
| <span class="comment">//using a user-defined memory allocation algorithm</span> |
| <span class="identifier">basic_managed_shared_memory</span><span class="special"><</span><span class="keyword">char</span><span class="special">,</span> |
| <span class="special">,</span><span class="identifier">my_algorithm</span> |
| <span class="special">,</span><span class="identifier">flat_map_index</span><span class="special">></span> |
| <span class="identifier">my_managed_shared_memory</span><span class="special">;</span> |
| </pre> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="interprocess.customizing_interprocess.custom_allocators"></a><a class="link" href="customizing_interprocess.html#interprocess.customizing_interprocess.custom_allocators" title="Building custom STL compatible allocators for Boost.Interprocess">Building |
| custom STL compatible allocators for Boost.Interprocess</a> |
| </h3></div></div></div> |
| <p> |
| If provided STL-like allocators don't satisfy user needs, the user can implement |
| another STL compatible allocator using raw memory allocation and named object |
| construction functions. The user can this way implement more suitable allocation |
| schemes on top of basic shared memory allocation schemes, just like more |
| complex allocators are built on top of new/delete functions. |
| </p> |
| <p> |
| When using a managed memory segment, <span class="bold"><strong>get_segment_manager()</strong></span> |
| function returns a pointer to the segment manager. With this pointer, the |
| raw memory allocation and named object construction functions can be called |
| directly: |
| </p> |
| <pre class="programlisting"><span class="comment">//Create the managed shared memory and initialize resources</span> |
| <span class="identifier">managed_shared_memory</span> <span class="identifier">segment</span> |
| <span class="special">(</span><span class="identifier">create_only</span> |
| <span class="special">,</span><span class="string">"/MySharedMemory"</span> <span class="comment">//segment name</span> |
| <span class="special">,</span><span class="number">65536</span><span class="special">);</span> <span class="comment">//segment size in bytes</span> |
| |
| <span class="comment">//Obtain the segment manager</span> |
| <span class="identifier">managed_shared_memory</span><span class="special">::</span><span class="identifier">segment_manager</span> <span class="special">*</span><span class="identifier">segment_mngr</span> |
| <span class="special">=</span> <span class="identifier">segment</span><span class="special">.</span><span class="identifier">get_segment_manager</span><span class="special">();</span> |
| |
| <span class="comment">//With the segment manager, now we have access to all allocation functions</span> |
| <span class="identifier">segment_mngr</span><span class="special">-></span><span class="identifier">deallocate</span><span class="special">(</span><span class="identifier">segment_mngr</span><span class="special">-></span><span class="identifier">allocate</span><span class="special">(</span><span class="number">32</span><span class="special">));</span> |
| <span class="identifier">segment_mngr</span><span class="special">-></span><span class="identifier">construct</span><span class="special"><</span><span class="keyword">int</span><span class="special">>(</span><span class="string">"My_Int"</span><span class="special">)[</span><span class="number">32</span><span class="special">](</span><span class="number">0</span><span class="special">);</span> |
| <span class="identifier">segment_mngr</span><span class="special">-></span><span class="identifier">destroy</span><span class="special"><</span><span class="keyword">int</span><span class="special">>(</span><span class="string">"My_Int"</span><span class="special">);</span> |
| |
| <span class="comment">//Initialize the custom, managed memory segment compatible</span> |
| <span class="comment">//allocator with the segment manager.</span> |
| <span class="comment">//</span> |
| <span class="comment">//MySTLAllocator uses segment_mngr->xxx functions to</span> |
| <span class="comment">//implement its allocation scheme</span> |
| <span class="identifier">MySTLAllocator</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">stl_alloc</span><span class="special">(</span><span class="identifier">segment_mngr</span><span class="special">);</span> |
| |
| <span class="comment">//Alias a new vector type that uses the custom STL compatible allocator</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="keyword">int</span><span class="special">,</span> <span class="identifier">MySTLAllocator</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="special">></span> <span class="identifier">MyVect</span><span class="special">;</span> |
| |
| <span class="comment">//Construct the vector in shared memory with the allocator as constructor parameter</span> |
| <span class="identifier">segment</span><span class="special">.</span><span class="identifier">construct</span><span class="special"><</span><span class="identifier">MyVect</span><span class="special">>(</span><span class="string">"MyVect_instance"</span><span class="special">)(</span><span class="identifier">stl_alloc</span><span class="special">);</span> |
| </pre> |
| <p> |
| The user can create new STL compatible allocators that use the segment manager |
| to access to all memory management/object construction functions. All <span class="bold"><strong>Boost.Interprocess</strong></span>' STL compatible allocators are |
| based on this approach. <span class="bold"><strong>Remember</strong></span> that to |
| be compatible with managed memory segments, allocators should define their |
| <span class="bold"><strong>pointer</strong></span> typedef as the same pointer family |
| as <code class="computeroutput"><span class="identifier">segment_manager</span><span class="special">::</span><span class="identifier">void_pointer</span></code> typedef. This means that if |
| <code class="computeroutput"><span class="identifier">segment_manager</span><span class="special">::</span><span class="identifier">void_pointer</span></code> is <code class="computeroutput"><span class="identifier">offset_ptr</span><span class="special"><</span><span class="keyword">void</span><span class="special">></span></code>, |
| <code class="computeroutput"><span class="identifier">MySTLAllocator</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span></code> should |
| define <code class="computeroutput"><span class="identifier">pointer</span></code> as <code class="computeroutput"><span class="identifier">offset_ptr</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span></code>. The |
| reason for this is that allocators are members of containers, and if we want |
| to put the container in a managed memory segment, the allocator should be |
| ready for that. |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="interprocess.customizing_interprocess.custom_indexes"></a><a class="link" href="customizing_interprocess.html#interprocess.customizing_interprocess.custom_indexes" title="Building custom indexes">Building |
| custom indexes</a> |
| </h3></div></div></div> |
| <p> |
| The managed memory segment uses a name/object index to speed up object searching |
| and creation. Default specializations of managed memory segments (<code class="computeroutput"><span class="identifier">managed_shared_memory</span></code> for example), use |
| <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">interprocess</span><span class="special">::</span><span class="identifier">flat_map</span></code> as index. |
| </p> |
| <p> |
| However, the index type can be chosen via template parameter, so that the |
| user can define its own index type if he needs that. To construct a new index |
| type, the user must create a class with the following guidelines: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> |
| The interface of the index must follow the common public interface of |
| std::map and std::tr1::unordered_map including public typedefs. The |
| <code class="computeroutput"><span class="identifier">value_type</span></code> typedef can |
| be of type: |
| </li></ul></div> |
| <pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span><span class="identifier">key_type</span><span class="special">,</span> <span class="identifier">mapped_type</span><span class="special">></span> |
| </pre> |
| <p> |
| or |
| </p> |
| <pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span><span class="keyword">const</span> <span class="identifier">key_type</span><span class="special">,</span> <span class="identifier">mapped_type</span><span class="special">></span> |
| </pre> |
| <p> |
| so that ordered arrays or deques can be used as index types. Some known classes |
| following this basic interface are <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">unordered_map</span></code>, |
| <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">interprocess</span><span class="special">::</span><span class="identifier">flat_map</span></code> and <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">interprocess</span><span class="special">::</span><span class="identifier">map</span></code>. |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> |
| The class must be a class template taking only a traits struct of this |
| type: |
| </li></ul></div> |
| <pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">index_traits</span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="comment">/*...*/</span> <span class="identifier">key_type</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="comment">/*...*/</span> <span class="identifier">mapped_type</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="comment">/*...*/</span> <span class="identifier">segment_manager</span><span class="special">;</span> |
| <span class="special">};</span> |
| </pre> |
| <pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">IndexTraits</span><span class="special">></span> |
| <span class="keyword">class</span> <span class="identifier">my_index_type</span><span class="special">;</span> |
| </pre> |
| <p> |
| The <code class="computeroutput"><span class="identifier">key_type</span></code> typedef of the |
| passed <code class="computeroutput"><span class="identifier">index_traits</span></code> will |
| be a specialization of the following class: |
| </p> |
| <pre class="programlisting"><span class="comment">//!The key of the named allocation information index. Stores a to</span> |
| <span class="comment">//!a null string and the length of the string to speed up sorting</span> |
| <span class="keyword">template</span><span class="special"><...></span> |
| <span class="keyword">struct</span> <span class="identifier">index_key</span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="comment">/*...*/</span> <span class="identifier">char_type</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="comment">/*...*/</span> <span class="identifier">const_char_ptr_t</span><span class="special">;</span> |
| |
| <span class="comment">//Pointer to the object's name (null terminated)</span> |
| <span class="identifier">const_char_ptr_t</span> <span class="identifier">mp_str</span><span class="special">;</span> |
| |
| <span class="comment">//Length of the name buffer (null NOT included)</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">m_len</span><span class="special">;</span> |
| |
| <span class="comment">//!Constructor of the key</span> |
| <span class="identifier">index_key</span> <span class="special">(</span><span class="keyword">const</span> <span class="identifier">CharT</span> <span class="special">*</span><span class="identifier">name</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">length</span><span class="special">);</span> |
| |
| <span class="comment">//!Less than function for index ordering</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">index_key</span> <span class="special">&</span> <span class="identifier">right</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span> |
| |
| <span class="comment">//!Equal to function for index ordering</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">index_key</span> <span class="special">&</span> <span class="identifier">right</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span> |
| <span class="special">};</span> |
| </pre> |
| <p> |
| The <code class="computeroutput"><span class="identifier">mapped_type</span></code> is not directly |
| modified by the customized index but it is needed to define the index type. |
| The <span class="bold"><strong>segment_manager</strong></span> will be the type of |
| the segment manager that will manage the index. <code class="computeroutput"><span class="identifier">segment_manager</span></code> |
| will define interesting internal types like <code class="computeroutput"><span class="identifier">void_pointer</span></code> |
| or <code class="computeroutput"><span class="identifier">mutex_family</span></code>. |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> |
| The constructor of the customized index type must take a pointer to segment_manager |
| as constructor argument: |
| </li></ul></div> |
| <pre class="programlisting"><span class="identifier">constructor</span><span class="special">(</span><span class="identifier">segment_manager</span> <span class="special">*</span><span class="identifier">segment_mngr</span><span class="special">);</span> |
| </pre> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> |
| The index must provide a memory reservation function, that optimizes |
| the index if the user knows the number of elements to be inserted in |
| the index: |
| </li></ul></div> |
| <pre class="programlisting"><span class="keyword">void</span> <span class="identifier">reserve</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">n</span><span class="special">);</span> |
| </pre> |
| <p> |
| For example, the index type <code class="computeroutput"><span class="identifier">flat_map_index</span></code> |
| based in <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">interprocess</span><span class="special">::</span><span class="identifier">flat_map</span></code> is just defined as: |
| </p> |
| <p> |
| </p> |
| <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">interprocess</span> <span class="special">{</span> |
| |
| <span class="preprocessor">#ifndef</span> <span class="identifier">BOOST_INTERPROCESS_DOXYGEN_INVOKED</span> |
| |
| <span class="comment">//!Helper class to define typedefs from IndexTraits</span> |
| <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">MapConfig</span><span class="special">></span> |
| <span class="keyword">struct</span> <span class="identifier">flat_map_index_aux</span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">MapConfig</span><span class="special">::</span><span class="identifier">key_type</span> <span class="identifier">key_type</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">MapConfig</span><span class="special">::</span><span class="identifier">mapped_type</span> <span class="identifier">mapped_type</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">MapConfig</span><span class="special">::</span> |
| <span class="identifier">segment_manager_base</span> <span class="identifier">segment_manager_base</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">less</span><span class="special"><</span><span class="identifier">key_type</span><span class="special">></span> <span class="identifier">key_less</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span><span class="identifier">key_type</span><span class="special">,</span> <span class="identifier">mapped_type</span><span class="special">></span> <span class="identifier">value_type</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">allocator</span><span class="special"><</span><span class="identifier">value_type</span> |
| <span class="special">,</span><span class="identifier">segment_manager_base</span><span class="special">></span> <span class="identifier">allocator_type</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">flat_map</span><span class="special"><</span><span class="identifier">key_type</span><span class="special">,</span> <span class="identifier">mapped_type</span><span class="special">,</span> |
| <span class="identifier">key_less</span><span class="special">,</span> <span class="identifier">allocator_type</span><span class="special">></span> <span class="identifier">index_t</span><span class="special">;</span> |
| <span class="special">};</span> |
| |
| <span class="preprocessor">#endif</span> <span class="comment">//#ifndef BOOST_INTERPROCESS_DOXYGEN_INVOKED</span> |
| |
| <span class="comment">//!Index type based in flat_map. Just derives from flat_map and</span> |
| <span class="comment">//!defines the interface needed by managed memory segments.</span> |
| <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">MapConfig</span><span class="special">></span> |
| <span class="keyword">class</span> <span class="identifier">flat_map_index</span> |
| <span class="comment">//Derive class from flat_map specialization</span> |
| <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">flat_map_index_aux</span><span class="special"><</span><span class="identifier">MapConfig</span><span class="special">>::</span><span class="identifier">index_t</span> |
| <span class="special">{</span> |
| <span class="preprocessor">#if</span> <span class="special">!</span><span class="identifier">defined</span><span class="special">(</span><span class="identifier">BOOST_INTERPROCESS_DOXYGEN_INVOKED</span><span class="special">)</span> |
| <span class="keyword">typedef</span> <span class="identifier">flat_map_index_aux</span><span class="special"><</span><span class="identifier">MapConfig</span><span class="special">></span> <span class="identifier">index_aux</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">index_aux</span><span class="special">::</span><span class="identifier">index_t</span> <span class="identifier">base_type</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">index_aux</span><span class="special">::</span> |
| <span class="identifier">segment_manager_base</span> <span class="identifier">segment_manager_base</span><span class="special">;</span> |
| <span class="preprocessor">#endif</span> <span class="comment">//#ifndef BOOST_INTERPROCESS_DOXYGEN_INVOKED</span> |
| |
| <span class="keyword">public</span><span class="special">:</span> |
| <span class="comment">//!Constructor. Takes a pointer to the segment manager. Can throw</span> |
| <span class="identifier">flat_map_index</span><span class="special">(</span><span class="identifier">segment_manager_base</span> <span class="special">*</span><span class="identifier">segment_mngr</span><span class="special">)</span> |
| <span class="special">:</span> <span class="identifier">base_type</span><span class="special">(</span><span class="keyword">typename</span> <span class="identifier">index_aux</span><span class="special">::</span><span class="identifier">key_less</span><span class="special">(),</span> |
| <span class="keyword">typename</span> <span class="identifier">index_aux</span><span class="special">::</span><span class="identifier">allocator_type</span><span class="special">(</span><span class="identifier">segment_mngr</span><span class="special">))</span> |
| <span class="special">{}</span> |
| |
| <span class="comment">//!This reserves memory to optimize the insertion of n elements in the index</span> |
| <span class="keyword">void</span> <span class="identifier">reserve</span><span class="special">(</span><span class="keyword">typename</span> <span class="identifier">segment_manager_base</span><span class="special">::</span><span class="identifier">size_type</span> <span class="identifier">n</span><span class="special">)</span> |
| <span class="special">{</span> <span class="identifier">base_type</span><span class="special">::</span><span class="identifier">reserve</span><span class="special">(</span><span class="identifier">n</span><span class="special">);</span> <span class="special">}</span> |
| |
| <span class="comment">//!This frees all unnecessary memory</span> |
| <span class="keyword">void</span> <span class="identifier">shrink_to_fit</span><span class="special">()</span> |
| <span class="special">{</span> <span class="identifier">base_type</span><span class="special">::</span><span class="identifier">shrink_to_fit</span><span class="special">();</span> <span class="special">}</span> |
| <span class="special">};</span> |
| |
| <span class="special">}}</span> <span class="comment">//namespace boost { namespace interprocess</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| If the user is defining a node container based index (a container whose iterators |
| are not invalidated when inserting or erasing other elements), <span class="bold"><strong>Boost.Interprocess</strong></span> can optimize named object destruction |
| when destructing via pointer. <span class="bold"><strong>Boost.Interprocess</strong></span> |
| can store an iterator next to the object and instead of using the name of |
| the object to erase the index entry, it uses the iterator, which is a faster |
| operation. So if you are creating a new node container based index (for example, |
| a tree), you should define an specialization of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">interprocess</span><span class="special">::</span><span class="identifier">is_node_index</span><span class="special"><...></span></code> defined in <code class="computeroutput"><span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">interprocess</span><span class="special">/</span><span class="identifier">detail</span><span class="special">/</span><span class="identifier">utilities</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span></code>: |
| </p> |
| <pre class="programlisting"><span class="comment">//!Trait classes to detect if an index is a node</span> |
| <span class="comment">//!index. This allows more efficient operations</span> |
| <span class="comment">//!when deallocating named objects.</span> |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">MapConfig</span><span class="special">></span> |
| <span class="keyword">struct</span> <span class="identifier">is_node_index</span> |
| <span class="special"><</span><span class="identifier">my_index</span><span class="special"><</span><span class="identifier">MapConfig</span><span class="special">></span> <span class="special">></span> |
| <span class="special">{</span> |
| <span class="keyword">static</span> <span class="keyword">const</span> <span class="keyword">bool</span> <span class="identifier">value</span> <span class="special">=</span> <span class="keyword">true</span><span class="special">;</span> |
| <span class="special">};</span> |
| </pre> |
| <p> |
| Interprocess also defines other index types: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <span class="bold"><strong>boost::map_index</strong></span> uses <span class="bold"><strong>boost::interprocess::map</strong></span> |
| as index type. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>boost::null_index</strong></span> that uses an dummy |
| index type if the user just needs anonymous allocations and wants to |
| save some space and class instantations. |
| </li> |
| </ul></div> |
| <p> |
| Defining a new managed memory segment that uses the new index is easy. For |
| example, a new managed shared memory that uses the new index: |
| </p> |
| <pre class="programlisting"><span class="comment">//!Defines a managed shared memory with a c-strings as</span> |
| <span class="comment">//!a keys, the red-black tree best fit algorithm (with process-shared mutexes</span> |
| <span class="comment">//!and offset_ptr pointers) as raw shared memory management algorithm</span> |
| <span class="comment">//!and a custom index</span> |
| <span class="keyword">typedef</span> |
| <span class="identifier">basic_managed_shared_memory</span> <span class="special"><</span> |
| <span class="keyword">char</span><span class="special">,</span> |
| <span class="identifier">rbtree_best_fit</span><span class="special"><</span><span class="identifier">mutex_family</span><span class="special">>,</span> |
| <span class="identifier">my_index_type</span> |
| <span class="special">></span> |
| <span class="identifier">my_managed_shared_memory</span><span class="special">;</span> |
| </pre> |
| </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 © 2005-2012 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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