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<img src="../../../../boost.png" width="276" height="86" alt="C++ Boost">
<h1 align="center">Pool</h1>
<h2>Introduction</h2>
<p><span class="code">pool</span> is a fast memory allocator, and
guarantees proper alignment of all allocated chunks.</p>
<p>pool.hpp provides two <a href="user_allocator.html">UserAllocator</a>
classes and a template class <span class="code">pool</span>, which extends
and generalizes the framework provided by the <a href=
"simple_segregated_storage.html">simple segregated storage</a> solution.
For information on other pool-based interfaces, see <a href=
"../interfaces.html">the other pool interfaces</a>.</p>
<h2>Synopsis</h2>
<pre class="code">
struct default_user_allocator_new_delete; // see <a href=
"user_allocator.html">User Allocators</a>
struct default_user_allocator_malloc_free; // see <a href=
"user_allocator.html">User Allocators</a>
template <typename UserAllocator = default_user_allocator_new_delete>
class pool
{
private:
pool(const pool &);
void operator=(const pool &);
public:
typedef UserAllocator user_allocator;
typedef typename UserAllocator::size_type size_type;
typedef typename UserAllocator::difference_type difference_type;
explicit pool(size_type requested_size);
~pool();
bool release_memory();
bool purge_memory();
bool is_from(void * chunk) const;
size_type get_requested_size() const;
void * malloc();
void * ordered_malloc();
void * ordered_malloc(size_type n);
void free(void * chunk);
void ordered_free(void * chunk);
void free(void * chunks, size_type n);
void ordered_free(void * chunks, size_type n);
};
</pre>
<h2>Template Parameters</h2>
<h3>UserAllocator</h3>
<p>Defines the method that the Pool will use to allocate memory from the
system. See <a href="user_allocator.html">User Allocators</a> for
details.</p>
<h2>Semantics</h2>
<table border align="center" summary="">
<caption>
<em>Symbol Table</em>
</caption>
<tr>
<th>Symbol</th>
<th>Meaning</th>
</tr>
<tr>
<td class="code">Pool</td>
<td class="code">pool<UserAllocator></td>
</tr>
<tr>
<td class="code">t</td>
<td>value of type <span class="code">Pool</span></td>
</tr>
<tr>
<td class="code">u</td>
<td>value of type <span class="code">const Pool</span></td>
</tr>
<tr>
<td class="code">chunk</td>
<td>value of type <span class="code">void *</span></td>
</tr>
<tr>
<td class="code">n</td>
<td>value of type <span class="code">size_type</span></td>
</tr>
<tr>
<td class="code">RequestedSize</td>
<td>value of type <span class="code">Pool::size_type</span>; must be
greater than 0</td>
</tr>
</table><br>
<table border align="center" summary="">
<caption>
<em>Typedefs</em>
</caption>
<tr>
<th>Expression</th>
<th>Type</th>
</tr>
<tr>
<td class="code">Pool::user_allocator</td>
<td class="code">UserAllocator</td>
</tr>
<tr>
<td class="code">Pool::size_type</td>
<td class="code">UserAllocator::size_type</td>
</tr>
<tr>
<td class="code">Pool::difference_type</td>
<td class="code">UserAllocator::difference_type</td>
</tr>
</table><br>
<table border align="center" summary="">
<caption>
<em>Constructors, Destructors, and Testing</em>
</caption>
<tr>
<th>Expression</th>
<th>Return Type</th>
<th>Notes</th>
</tr>
<tr>
<td class="code">Pool(RequestedSize)</td>
<td>not used</td>
<td>Constructs a new empty <span class="code">Pool</span> that can be
used to allocate chunks of size <span class=
"code">RequestedSize</span></td>
</tr>
<tr>
<td class="code">(&t)->~Pool()</td>
<td>not used</td>
<td>Destructs the <span class="code">Pool</span>, freeing its list of
memory blocks</td>
</tr>
<tr>
<td class="code">u.is_from(chunk)</td>
<td class="code">bool</td>
<td>Returns <span class="code">true</span> if <span class=
"code">chunk</span> was allocated from <span class="code">u</span> or
may be returned as the result of a future allocation from <span class=
"code">u</span>. Returns <span class="code">false</span> if
<span class="code">chunk</span> was allocated from some other pool or
may be returned as the result of a future allocation from some other
pool. Otherwise, the return value is meaningless; note that this
function may <strong>not</strong> be used to reliably test random
pointer values.</td>
</tr>
<tr>
<td class="code">u.get_requested_size()</td>
<td class="code">size_type</td>
<td>Returns the value passed into the constructor. This value will not
change during the lifetime of a <span class="code">Pool</span>
object.</td>
</tr>
</table><br>
<table border align="center" summary="">
<caption>
<em>Allocation and Deallocation</em>
</caption>
<tr>
<th>Expression</th>
<th>Return Type</th>
<th>Pre-Condition</th>
<th>Notes</th>
</tr>
<tr>
<td class="code">t.malloc()</td>
<td class="code">void *</td>
<td></td>
<td>Allocates a chunk of memory. Searches in the list of memory blocks
for a block that has a free chunk, and returns that free chunk if
found. Otherwise, creates a new memory block, adds its free list to
<span class="code">t</span>'s free list, and returns a free chunk from
that block. If a new memory block cannot be allocated, returns
<span class="code">0</span>. Amortized O(1).</td>
</tr>
<tr>
<td class="code">t.ordered_malloc()</td>
<td class="code">void *</td>
<td></td>
<td>Same as above, only merges the free lists, to preserve order.
Amortized O(1).</td>
</tr>
<tr>
<td class="code">t.ordered_malloc(n)</td>
<td class="code">void *</td>
<td></td>
<td>Same as above, only allocates enough contiguous chunks to cover
<span class="code">n * requested_size</span> bytes. Amortized
O(n).</td>
</tr>
<tr>
<td class="code">t.free(chunk)</td>
<td class="code">void</td>
<td><span class="code">chunk</span> must have been previously returned
by <span class="code">t.malloc()</span> or <span class=
"code">t.ordered_malloc()</span>.</td>
<td>Deallocates a chunk of memory. Note that <span class=
"code">chunk</span> may not be <span class="code">0</span>. O(1).</td>
</tr>
<tr>
<td class="code">t.ordered_free(chunk)</td>
<td class="code">void</td>
<td>Same as above</td>
<td>Same as above, but is order-preserving. Note that <span class=
"code">chunk</span> may not be <span class="code">0</span>. O(N) with
respect to the size of the free list</td>
</tr>
<tr>
<td class="code">t.free(chunk, n)</td>
<td class="code">void</td>
<td><span class="code">chunk</span> must have been previously returned
by <span class="code">t.ordered_malloc(n)</span>.</td>
<td>Assumes that <span class="code">chunk</span> actually refers to a
block of chunks spanning <span class="code">n * partition_sz</span>
bytes; deallocates each chunk in that block. Note that <span class=
"code">chunk</span> may not be <span class="code">0</span>. O(n).</td>
</tr>
<tr>
<td class="code">t.ordered_free(chunk, n)</td>
<td class="code">void</td>
<td><span class="code">chunk</span> must have been previously returned
by <span class="code">t.ordered_malloc(n)</span>.</td>
<td>Assumes that <span class="code">chunk</span> actually refers to a
block of chunks spanning <span class="code">n * partition_sz</span>
bytes; deallocates each chunk in that block. Note that <span class=
"code">chunk</span> may not be <span class="code">0</span>.
Order-preserving. O(N + n) where N is the size of the free list.</td>
</tr>
<tr>
<td class="code">t.release_memory()</td>
<td class="code">bool</td>
<td><span class="code">t</span> must be ordered.</td>
<td>Frees every memory block that doesn't have any allocated chunks.
Returns <span class="code">true</span> if at least one memory block was
freed.</td>
</tr>
<tr>
<td class="code">t.purge_memory()</td>
<td class="code">bool</td>
<td></td>
<td>Frees every memory block. This function invalidates any pointers
previously returned by allocation functions of <span class=
"code">t</span>. Returns <span class="code">true</span> if at least one
memory block was freed.</td>
</tr>
</table>
<h2>Symbols</h2>
<ul>
<li>boost::default_user_allocator_new_delete</li>
<li>boost::default_user_allocator_malloc_new</li>
<li>boost::pool</li>
</ul>
<h2><a href="../implementation/pool.html">Implementation Details</a></h2>
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<p>Revised
<!--webbot bot="Timestamp" s-type="EDITED" s-format="%d %B, %Y" startspan -->05
December, 2006<!--webbot bot="Timestamp" endspan i-checksum="38516" --></p>
<p><i>Copyright © 2000, 2001 Stephen Cleary (scleary AT jerviswebb DOT
com)</i></p>
<p><i>Distributed under the Boost Software License, Version 1.0. (See
accompanying file <a href="../../../../LICENSE_1_0.txt">LICENSE_1_0.txt</a>
or copy at <a href=
"http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</a>)</i></p>
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