compiler/alib/liballocaligned.c

   1 /*
   2  * Copyright (C) 2012-2015, The AROS Development Team
   3  * All right reserved.
   4  * Author: Jason S. McMullan <jason.mcmullan@gmail.com>
   5  *
   6  * Licensed under the AROS PUBLIC LICENSE (APL) Version 1.1
   7  */
   8
   9 #include <proto/exec.h>
  10
  11 /*****************************************************************************
  12
  13     NAME */
  14 #include <proto/alib.h>
  15
  16         APTR LibAllocAligned (
  17
  18 /*  SYNOPSIS */
  19         IPTR memSize,
  20         ULONG requirements,
  21         IPTR  alignBytes)
  22
  23 /*  FUNCTION
  24         Allocate a memory block with a start address and size that are
  25         multiples of a power-of-two. The returned memory must be freed using
  26         FreeMem().
  27
  28     INPUTS
  29         memSize      - Size in bytes of the aligned area
  30         requirements - Memory requirements (same as AllocMem())
  31         alignBytes   - Required alignment, in bytes.
  32                        This must be a power of 2!
  33
  34     RESULT
  35         Pointer to the newly allocated area, or NULL if no satisfying memory
  36         can be found.
  37
  38     NOTES
  39         If alignBytes is not a power of two, NULL is returned.
  40
  41         If memSize is not a multiple of alignBytes, NULL is returned.
  42
  43     EXAMPLE
  44
  45     BUGS
  46
  47     SEE ALSO
  48         exec.library/AllocMem, exec.library/FreeMem().
  49
  50     INTERNALS
  51
  52 ******************************************************************************/
  53 {
  54     APTR ptr;
  55     IPTR alignMask;
  56
  57     /* Verify that alignBytes is a power of two */
  58     if ((alignBytes & (alignBytes-1)) != 0)
  59         return NULL;
  60
  61     /* Verify that memSize is modulo alignBytes */
  62     if ((memSize & (alignBytes - 1)) != 0)
  63         return NULL;
  64
  65     alignMask = alignBytes - 1;
  66
  67     if ((ptr = AllocMem(memSize + alignMask, requirements)))
  68     {
  69         APTR aptr = (APTR)((((IPTR)ptr) + alignMask) & ~alignMask);
  70         Forbid();
  71         FreeMem(ptr, memSize + alignMask);
  72         ptr = AllocAbs(memSize, aptr);
  73         Permit();
  74     }
  75
  76     return ptr;
  77 }