Subversion Repositories scarts

// Allocators -*- C++ -*-

// Copyright (C) 2001, 2002, 2003, 2004 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 <bits/atomicity.h>

#include <bits/concurrence.h>

namespace __gnu_cxx

{

  /**

   *  @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_type&

      _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 (getenv("GLIBCXX_FORCE_NEW"))

                __atomic_add(&_S_force_new, 1);

              else

                __atomic_add(&_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);

              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);

              lock sentry(_M_get_mutex());

              __q ->_M_free_list_link = *__free_list;

              *__free_list = __q;

            }

        }

    }

} // namespace __gnu_cxx

#endif