compiler/clib/realloc_nocopy.c

   1 /*
   2     Copyright © 1995-2003, The AROS Development Team. All rights reserved.
   3     $Id$
   4 */
   5
   6 #include <aros/cpu.h>
   7 #include <proto/exec.h>
   8
   9 /*****************************************************************************
  10
  11     NAME */
  12 #include <sys/types.h>
  13 #include <stdlib.h>
  14
  15         void * realloc_nocopy (
  16
  17 /*  SYNOPSIS */
  18         void * oldmem,
  19         size_t size)
  20
  21 /*  FUNCTION
  22         Change the size of an allocated part of memory. The memory must
  23         have been allocated by malloc(), calloc(), realloc() or realloc_nocopy().
  24
  25         The reallocated buffer, unlike with realloc(), is not guaranteed to hold
  26         a copy of the old one.
  27
  28     INPUTS
  29         oldmen - What you got from malloc(), calloc(), realloc() or realloc_nocopy().
  30                  If NULL, the function will behave exactly like malloc().
  31         size   - The new size. If 0, the buffer will be freed.
  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         This function is AROS specific.
  46
  47     EXAMPLE
  48
  49     BUGS
  50
  51     SEE ALSO
  52         free(), malloc(), calloc(), realloc()
  53
  54     INTERNALS
  55
  56 ******************************************************************************/
  57 {
  58     UBYTE * mem, * newmem;
  59     size_t oldsize;
  60
  61     if (!oldmem)
  62         return malloc (size);
  63
  64     mem = (UBYTE *)oldmem - AROS_ALIGN(sizeof(size_t));
  65     oldsize = *((size_t *)mem);
  66
  67     /* Reduce or enlarge the memory ? */
  68     if (size < oldsize)
  69     {
  70         /* Don't change anything for small changes */
  71         if ((oldsize - size) < 4096)
  72             newmem = oldmem;
  73         else
  74             goto alloc;
  75     }
  76     else if (size == oldsize) /* Keep the size ? */
  77         newmem = oldmem;
  78     else
  79     {
  80 alloc:
  81         newmem = malloc (size);
  82
  83         if (newmem)
  84             free (oldmem);
  85     }
  86
  87     return newmem;
  88 } /* realloc */
  89