gnu/lib/libmalloc/memalign.c

   1 /* Copyright (C) 1991, 1992 Free Software Foundation, Inc.
   2
   3 This library is free software; you can redistribute it and/or
   4 modify it under the terms of the GNU Library General Public License as
   5 published by the Free Software Foundation; either version 2 of the
   6 License, or (at your option) any later version.
   7
   8 This library is distributed in the hope that it will be useful,
   9 but WITHOUT ANY WARRANTY; without even the implied warranty of
  10 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11 Library General Public License for more details.
  12
  13 You should have received a copy of the GNU Library General Public
  14 License along with this library; see the file COPYING.LIB.  If
  15 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  16 Cambridge, MA 02139, USA.  */
  17
  18 #ifndef _MALLOC_INTERNAL
  19 #define _MALLOC_INTERNAL
  20 #include <malloc.h>
  21 #endif
  22
  23 __ptr_t
  24 memalign (alignment, size)
  25      size_t alignment;
  26      size_t size;
  27 {
  28   __ptr_t result;
  29   unsigned long int adj;
  30
  31   size = ((size + alignment - 1) / alignment) * alignment;
  32
  33   result = malloc (size);
  34   if (result == NULL)
  35     return NULL;
  36   adj = (unsigned long int) ((unsigned long int) ((char *) result -
  37                                                 (char *) NULL)) % alignment;
  38   if (adj != 0)
  39     {
  40       struct alignlist *l;
  41       for (l = _aligned_blocks; l != NULL; l = l->next)
  42         if (l->aligned == NULL)
  43           /* This slot is free.  Use it.  */
  44           break;
  45       if (l == NULL)
  46         {
  47           l = (struct alignlist *) malloc (sizeof (struct alignlist));
  48           if (l == NULL)
  49             {
  50               free (result);
  51               return NULL;
  52             }
  53         }
  54       l->exact = result;
  55       result = l->aligned = (char *) result + alignment - adj;
  56       l->next = _aligned_blocks;
  57       _aligned_blocks = l;
  58     }
  59
  60   return result;
  61 }