compiler/alib/liballocaligned.c

   1 /*
   2  * Copyright (C) 2012, 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         ULONG memSize,
  20         ULONG requirements,
  21         IPTR  alignBytes)
  22
  23 /*  FUNCTION
  24
  25     INPUTS
  26         memSize      - Size in bytes of the aligned area
  27         requirements - Memory requirements (same as AllocMem())
  28         alignBytes   - Required alignment, in bytes.
  29                        This must be a power of 2!
  30
  31     RESULT
  32
  33         Pointer to the newly alloctated area, or
  34         NULL if no saisfying memory can be found.
  35
  36         Free this pointer using FreeMem(..., memSize)
  37
  38     NOTES
  39
  40         If alignBytes is not a power of two, NULL is returned.
  41
  42         If memSize is not a multiple of alignBytes, NULL is returned.
  43
  44     EXAMPLE
  45
  46     BUGS
  47
  48     SEE ALSO
  49
  50     INTERNALS
  51
  52     HISTORY
  53
  54 ******************************************************************************/
  55 {
  56     APTR ptr;
  57     IPTR alignMask;
  58
  59     /* Verify that alignBytes is a power of two */
  60     if ((alignBytes & (alignBytes-1)) != 0)
  61         return NULL;
  62
  63     /* Verify that memSize is modulo alignBytes */
  64     if ((memSize & (alignBytes - 1)) != 0)
  65         return NULL;
  66
  67     alignMask = alignBytes - 1;
  68
  69     if ((ptr = AllocMem(memSize + alignMask, requirements))) {
  70         APTR aptr = (APTR)((((IPTR)ptr) + alignMask) & ~alignMask);
  71         if (aptr != ptr) {
  72             Forbid();
  73             FreeMem(ptr, memSize + alignMask);
  74             ptr = AllocAbs(memSize, aptr);
  75             Permit();
  76         }
  77     }
  78
  79     return ptr;
  80 }