BLI_allocator.hh

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/*
 * This program 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
 * of the License, or (at your option) any later version.
 *
 * This program 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 program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */
#pragma once
 
#include <algorithm>
#include <stdlib.h>
 
#include "MEM_guardedalloc.h"
 
#include "BLI_math_base.h"
#include "BLI_utildefines.h"
 
namespace blender {
 
class GuardedAllocator {
 public:
  void *allocate(size_t size, size_t alignment, const char *name)
  {
    /* Should we use MEM_mallocN, when alignment is small? If yes, how small must alignment be? */
    return MEM_mallocN_aligned(size, alignment, name);
  }
 
  void deallocate(void *ptr)
  {
    MEM_freeN(ptr);
  }
};
 
class RawAllocator {
 private:
  struct MemHead {
    int offset;
  };
 
 public:
  void *allocate(size_t size, size_t alignment, const char *UNUSED(name))
  {
    BLI_assert(is_power_of_2_i(static_cast<int>(alignment)));
    void *ptr = malloc(size + alignment + sizeof(MemHead));
    void *used_ptr = reinterpret_cast<void *>(
        reinterpret_cast<uintptr_t>(POINTER_OFFSET(ptr, alignment + sizeof(MemHead))) &
        ~(static_cast<uintptr_t>(alignment) - 1));
    int offset = static_cast<int>((intptr_t)used_ptr - (intptr_t)ptr);
    BLI_assert(offset >= static_cast<int>(sizeof(MemHead)));
    (static_cast<MemHead *>(used_ptr) - 1)->offset = offset;
    return used_ptr;
  }
 
  void deallocate(void *ptr)
  {
    MemHead *head = static_cast<MemHead *>(ptr) - 1;
    int offset = -head->offset;
    void *actual_pointer = POINTER_OFFSET(ptr, offset);
    free(actual_pointer);
  }
};
 
}  // namespace blender