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//
// detail/object_pool.hpp
// ~~~~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2016 Christopher M. Kohlhoff (chris at kohlhoff dot com)
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
#ifndef BOOST_ASIO_DETAIL_OBJECT_POOL_HPP
#define BOOST_ASIO_DETAIL_OBJECT_POOL_HPP
#if defined(_MSC_VER) && (_MSC_VER >= 1200)
# pragma once
#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
#include <boost/asio/detail/noncopyable.hpp>
#include <boost/asio/detail/push_options.hpp>
namespace boost {
namespace asio {
namespace detail {
template <typename Object>
class object_pool;
class object_pool_access
{
public:
template <typename Object>
static Object* create()
{
return new Object;
}
template <typename Object>
static void destroy(Object* o)
{
delete o;
}
template <typename Object>
static Object*& next(Object* o)
{
return o->next_;
}
template <typename Object>
static Object*& prev(Object* o)
{
return o->prev_;
}
};
template <typename Object>
class object_pool
: private noncopyable
{
public:
// Constructor.
object_pool()
: live_list_(0),
free_list_(0)
{
}
// Destructor destroys all objects.
~object_pool()
{
destroy_list(live_list_);
destroy_list(free_list_);
}
// Get the object at the start of the live list.
Object* first()
{
return live_list_;
}
// Allocate a new object.
Object* alloc()
{
Object* o = free_list_;
if (o)
free_list_ = object_pool_access::next(free_list_);
else
o = object_pool_access::create<Object>();
object_pool_access::next(o) = live_list_;
object_pool_access::prev(o) = 0;
if (live_list_)
object_pool_access::prev(live_list_) = o;
live_list_ = o;
return o;
}
// Free an object. Moves it to the free list. No destructors are run.
void free(Object* o)
{
if (live_list_ == o)
live_list_ = object_pool_access::next(o);
if (object_pool_access::prev(o))
{
object_pool_access::next(object_pool_access::prev(o))
= object_pool_access::next(o);
}
if (object_pool_access::next(o))
{
object_pool_access::prev(object_pool_access::next(o))
= object_pool_access::prev(o);
}
object_pool_access::next(o) = free_list_;
object_pool_access::prev(o) = 0;
free_list_ = o;
}
private:
// Helper function to destroy all elements in a list.
void destroy_list(Object* list)
{
while (list)
{
Object* o = list;
list = object_pool_access::next(o);
object_pool_access::destroy(o);
}
}
// The list of live objects.
Object* live_list_;
// The free list.
Object* free_list_;
};
} // namespace detail
} // namespace asio
} // namespace boost
#include <boost/asio/detail/pop_options.hpp>
#endif // BOOST_ASIO_DETAIL_OBJECT_POOL_HPP
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