memalign_allocator.h

// Allocator that wraps "C" malloc -*- 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.

/** @file ext/malloc_allocator.h
 *  This file is a GNU extension to the Standard C++ Library.
 */

#ifndef _MALLOC_ALLOCATOR_H
#define _MALLOC_ALLOCATOR_H 1

#include <stdlib.h>
#include <new>
#include <bits/functexcept.h>

int posix_memalign(void **, size_t, size_t);

namespace __gnu_cxx
{
  /**
   *  @brief  An allocator that uses malloc.
   *
   *  This is precisely the allocator defined in the C++ Standard. 
   *    - all allocation calls malloc
   *    - all deallocation calls free
   */
  template<typename _Tp, int Ialign>
    class malloc_allocator
    {
      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 malloc_allocator<_Tp1, Ialign> other; };

        malloc_allocator() throw() { }

        malloc_allocator(const malloc_allocator&) throw() { }

        template<typename _Tp1>
          malloc_allocator(const malloc_allocator<_Tp1, Ialign>&) throw() { }

        ~malloc_allocator() throw() { }

        pointer
          address(reference __x) const { return &__x; }

        const_pointer
          address(const_reference __x) const { return &__x; }

        // NB: __n is permitted to be 0.  The C++ standard says nothing
        // about what the return value is when __n == 0.
        pointer
          allocate(size_type __n, const void* = 0)
          {
            if (__builtin_expect(__n > this->max_size(), false))
              std::__throw_bad_alloc();

#ifdef __MACOSX__
            pointer __ret = static_cast<_Tp*>(valloc(__n * sizeof(_Tp)));
#else
            void *ptr;
            int err = posix_memalign(&ptr, Ialign, __n * sizeof(_Tp));
            assert(err == 0);
            pointer __ret = static_cast<_Tp*>(ptr);
#endif
            if (!__ret)
              std::__throw_bad_alloc();
            return __ret;
          }

        // __p is not permitted to be a null pointer.
        void
          deallocate(pointer __p, size_type)
          { free(static_cast<void*>(__p)); }

        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) value_type(__val); }

        void 
          destroy(pointer __p) { __p->~_Tp(); }
    };

  template<typename _Tp, int Ialign>
    inline bool
    operator==(const malloc_allocator<_Tp, Ialign>&, const malloc_allocator<_Tp, Ialign>&)
    { return true; }

  template<typename _Tp, int Ialign>
    inline bool
    operator!=(const malloc_allocator<_Tp, Ialign>&, const malloc_allocator<_Tp, Ialign>&)
    { return false; }
} // namespace __gnu_cxx

#endif