compiler/stdc/realloc_nocopy.c

   1 /*
   2     Copyright © 1995-2014, 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 <stdlib.h>
  13
  14         void * realloc_nocopy (
  15
  16 /*  SYNOPSIS */
  17         void * oldmem,
  18         size_t size)
  19
  20 /*  FUNCTION
  21         Change the size of an allocated part of memory. The memory must
  22         have been allocated by malloc(), calloc(), realloc() or realloc_nocopy().
  23
  24         The reallocated buffer, unlike with realloc(), is not guaranteed to hold
  25         a copy of the old one.
  26
  27     INPUTS
  28         oldmem - What you got from malloc(), calloc(), realloc() or realloc_nocopy().
  29                  If NULL, the function will behave exactly like malloc().
  30         size   - The new size. If 0, the buffer will be freed.
  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         This function is AROS specific.
  42
  43     EXAMPLE
  44
  45     BUGS
  46
  47     SEE ALSO
  48         free(), malloc(), calloc(), realloc()
  49
  50     INTERNALS
  51
  52 ******************************************************************************/
  53 {
  54     UBYTE * mem, * newmem;
  55     size_t oldsize;
  56
  57     if (!oldmem)
  58         return malloc (size);
  59
  60     mem = (UBYTE *)oldmem - AROS_ALIGN(sizeof(size_t));
  61     oldsize = *((size_t *)mem);
  62
  63     /* Reduce or enlarge the memory ? */
  64     if (size < oldsize)
  65     {
  66         /* Don't change anything for small changes */
  67         if ((oldsize - size) < 4096)
  68             newmem = oldmem;
  69         else
  70             goto alloc;
  71     }
  72     else if (size == oldsize) /* Keep the size ? */
  73         newmem = oldmem;
  74     else
  75     {
  76 alloc:
  77         newmem = malloc (size);
  78
  79         if (newmem)
  80             free (oldmem);
  81     }
  82
  83     return newmem;
  84 } /* realloc */
  85