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// Allocators -*- C++ -*-
// Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006
// Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 2, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING. If not, write to the Free
// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
// USA.
// As a special exception, you may use this file as part of a free software
// library without restriction. Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License. This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.
/*
* Copyright (c) 1996-1997
* Silicon Graphics Computer Systems, Inc.
*
* Permission to use, copy, modify, distribute and sell this software
* and its documentation for any purpose is hereby granted without fee,
* provided that the above copyright notice appear in all copies and
* that both that copyright notice and this permission notice appear
* in supporting documentation. Silicon Graphics makes no
* representations about the suitability of this software for any
* purpose. It is provided "as is" without express or implied warranty.
*/
/** @file ext/pool_allocator.h
* This file is a GNU extension to the Standard C++ Library.
*/
#ifndef _POOL_ALLOCATOR_H
#define _POOL_ALLOCATOR_H 1
#include <bits/c++config.h>
#include <cstdlib>
#include <new>
#include <bits/functexcept.h>
#include <ext/atomicity.h>
#include <ext/concurrence.h>
_GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
using std::size_t;
using std::ptrdiff_t;
/**
* @brief Base class for __pool_alloc.
*
* @if maint
* Uses various allocators to fulfill underlying requests (and makes as
* few requests as possible when in default high-speed pool mode).
*
* Important implementation properties:
* 0. If globally mandated, then allocate objects from new
* 1. If the clients request an object of size > _S_max_bytes, the resulting
* object will be obtained directly from new
* 2. In all other cases, we allocate an object of size exactly
* _S_round_up(requested_size). Thus the client has enough size
* information that we can return the object to the proper free list
* without permanently losing part of the object.
*
* @endif
*/
class __pool_alloc_base
{
protected:
enum { _S_align = 8 };
enum { _S_max_bytes = 128 };
enum { _S_free_list_size = (size_t)_S_max_bytes / (size_t)_S_align };
union _Obj
{
union _Obj* _M_free_list_link;
char _M_client_data[1]; // The client sees this.
};
static _Obj* volatile _S_free_list[_S_free_list_size];
// Chunk allocation state.
static char* _S_start_free;
static char* _S_end_free;
static size_t _S_heap_size;
size_t
_M_round_up(size_t __bytes)
{ return ((__bytes + (size_t)_S_align - 1) & ~((size_t)_S_align - 1)); }
_Obj* volatile*
_M_get_free_list(size_t __bytes);
__mutex&
_M_get_mutex();
// Returns an object of size __n, and optionally adds to size __n
// free list.
void*
_M_refill(size_t __n);
// Allocates a chunk for nobjs of size size. nobjs may be reduced
// if it is inconvenient to allocate the requested number.
char*
_M_allocate_chunk(size_t __n, int& __nobjs);
};
/// @brief class __pool_alloc.
template<typename _Tp>
class __pool_alloc : private __pool_alloc_base
{
private:
static _Atomic_word _S_force_new;
public:
typedef size_t size_type;
typedef ptrdiff_t difference_type;
typedef _Tp* pointer;
typedef const _Tp* const_pointer;
typedef _Tp& reference;
typedef const _Tp& const_reference;
typedef _Tp value_type;
template<typename _Tp1>
struct rebind
{ typedef __pool_alloc<_Tp1> other; };
__pool_alloc() throw() { }
__pool_alloc(const __pool_alloc&) throw() { }
template<typename _Tp1>
__pool_alloc(const __pool_alloc<_Tp1>&) throw() { }
~__pool_alloc() throw() { }
pointer
address(reference __x) const { return &__x; }
const_pointer
address(const_reference __x) const { return &__x; }
size_type
max_size() const throw()
{ return size_t(-1) / sizeof(_Tp); }
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 402. wrong new expression in [some_] allocator::construct
void
construct(pointer __p, const _Tp& __val)
{ ::new(__p) _Tp(__val); }
void
destroy(pointer __p) { __p->~_Tp(); }
pointer
allocate(size_type __n, const void* = 0);
void
deallocate(pointer __p, size_type __n);
};
template<typename _Tp>
inline bool
operator==(const __pool_alloc<_Tp>&, const __pool_alloc<_Tp>&)
{ return true; }
template<typename _Tp>
inline bool
operator!=(const __pool_alloc<_Tp>&, const __pool_alloc<_Tp>&)
{ return false; }
template<typename _Tp>
_Atomic_word
__pool_alloc<_Tp>::_S_force_new;
template<typename _Tp>
_Tp*
__pool_alloc<_Tp>::allocate(size_type __n, const void*)
{
pointer __ret = 0;
if (__builtin_expect(__n != 0, true))
{
if (__builtin_expect(__n > this->max_size(), false))
std::__throw_bad_alloc();
// If there is a race through here, assume answer from getenv
// will resolve in same direction. Inspired by techniques
// to efficiently support threading found in basic_string.h.
if (_S_force_new == 0)
{
if (std::getenv("GLIBCXX_FORCE_NEW"))
__atomic_add_dispatch(&_S_force_new, 1);
else
__atomic_add_dispatch(&_S_force_new, -1);
}
const size_t __bytes = __n * sizeof(_Tp);
if (__bytes > size_t(_S_max_bytes) || _S_force_new == 1)
__ret = static_cast<_Tp*>(::operator new(__bytes));
else
{
_Obj* volatile* __free_list = _M_get_free_list(__bytes);
__scoped_lock sentry(_M_get_mutex());
_Obj* __restrict__ __result = *__free_list;
if (__builtin_expect(__result == 0, 0))
__ret = static_cast<_Tp*>(_M_refill(_M_round_up(__bytes)));
else
{
*__free_list = __result->_M_free_list_link;
__ret = reinterpret_cast<_Tp*>(__result);
}
if (__builtin_expect(__ret == 0, 0))
std::__throw_bad_alloc();
}
}
return __ret;
}
template<typename _Tp>
void
__pool_alloc<_Tp>::deallocate(pointer __p, size_type __n)
{
if (__builtin_expect(__n != 0 && __p != 0, true))
{
const size_t __bytes = __n * sizeof(_Tp);
if (__bytes > static_cast<size_t>(_S_max_bytes) || _S_force_new == 1)
::operator delete(__p);
else
{
_Obj* volatile* __free_list = _M_get_free_list(__bytes);
_Obj* __q = reinterpret_cast<_Obj*>(__p);
__scoped_lock sentry(_M_get_mutex());
__q ->_M_free_list_link = *__free_list;
*__free_list = __q;
}
}
}
_GLIBCXX_END_NAMESPACE
#endif
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