compiler/clib/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 <sys/types.h>
  15 #include <stdlib.h>
  16
  17         void * realloc (
  18
  19 /*  SYNOPSIS */
  20         void * oldmem,
  21         size_t size)
  22
  23 /*  FUNCTION
  24         Change the size of an allocated part of memory. The memory must
  25         have been allocated by malloc() or calloc(). If you reduce the
  26         size, the old contents will be lost. If you enlarge the size,
  27         the new contents will be undefined.
  28
  29     INPUTS
  30         oldmem - What you got from malloc() or calloc().
  31         size - The new size.
  32
  33     RESULT
  34         A pointer to the allocated memory or NULL. If you don't need the
  35         memory anymore, you can pass this pointer to free(). If you don't,
  36         the memory will be freed for you when the application exits.
  37
  38     NOTES
  39         If you get NULL, the memory at oldmem will not have been freed and
  40         can still be used.
  41
  42         This function must not be used in a shared library or
  43         in a threaded application.
  44
  45
  46     EXAMPLE
  47
  48     BUGS
  49
  50     SEE ALSO
  51         free(), malloc(), calloc()
  52
  53     INTERNALS
  54
  55 ******************************************************************************/
  56 {
  57     UBYTE * mem, * newmem;
  58     size_t oldsize;
  59
  60     if (!oldmem)
  61         return malloc (size);
  62
  63     mem = (UBYTE *)oldmem - AROS_ALIGN(sizeof(size_t));
  64     oldsize = *((size_t *)mem);
  65
  66     /* Reduce or enlarge the memory ? */
  67     if (size < oldsize)
  68     {
  69         /* Don't change anything for small changes */
  70         if ((oldsize - size) < 4096)
  71             newmem = oldmem;
  72         else
  73             goto copy;
  74     }
  75     else if (size == oldsize) /* Keep the size ? */
  76         newmem = oldmem;
  77     else
  78     {
  79 copy:
  80         newmem = malloc (size);
  81
  82         if (newmem)
  83         {
  84             if (size > oldsize)
  85                 size = oldsize;
  86             CopyMem (oldmem, newmem, size);
  87             free (oldmem);
  88         }
  89     }
  90
  91     return newmem;
  92 } /* realloc */
  93