compiler/stdc/realloc.c

   1 /*
   2     Copyright © 1995-2012, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     C99 function realloc().
   6 */
   7
   8 #include <aros/cpu.h>
   9 #include <proto/exec.h>
  10
  11 /*****************************************************************************
  12
  13     NAME */
  14 #include <stdlib.h>
  15
  16         void * realloc (
  17
  18 /*  SYNOPSIS */
  19         void * oldmem,
  20         size_t size)
  21
  22 /*  FUNCTION
  23         Change the size of an allocated part of memory. The memory must
  24         have been allocated by malloc() or calloc(). If you reduce the
  25         size, the old contents will be lost. If you enlarge the size,
  26         the new contents will be undefined.
  27
  28     INPUTS
  29         oldmem - What you got from malloc() or calloc().
  30         size - The new size.
  31
  32     RESULT
  33         A pointer to the allocated memory or NULL. If you don't need the
  34         memory anymore, you can pass this pointer to free(). If you don't,
  35         the memory will be freed for you when the application exits.
  36
  37     NOTES
  38         If you get NULL, the memory at oldmem will not have been freed and
  39         can still be used.
  40
  41     EXAMPLE
  42
  43     BUGS
  44
  45     SEE ALSO
  46         calloc(), free(), malloc()
  47
  48     INTERNALS
  49
  50 ******************************************************************************/
  51 {
  52     UBYTE * mem, * newmem;
  53     size_t oldsize;
  54
  55     if (!oldmem)
  56         return malloc (size);
  57
  58     mem = (UBYTE *)oldmem - AROS_ALIGN(sizeof(size_t));
  59     oldsize = *((size_t *)mem);
  60
  61     /* Reduce or enlarge the memory ? */
  62     if (size < oldsize)
  63     {
  64         /* Don't change anything for small changes */
  65         if ((oldsize - size) < 4096)
  66             newmem = oldmem;
  67         else
  68             goto copy;
  69     }
  70     else if (size == oldsize) /* Keep the size ? */
  71         newmem = oldmem;
  72     else
  73     {
  74 copy:
  75         newmem = malloc (size);
  76
  77         if (newmem)
  78         {
  79             if (size > oldsize)
  80                 size = oldsize;
  81             CopyMem (oldmem, newmem, size);
  82             free (oldmem);
  83         }
  84     }
  85
  86     return newmem;
  87 } /* realloc */
  88