rom/exec/copymemquick.c

   1 /*
   2     Copyright © 1995-2012, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: Copy aligned memory.
   6     Lang: english
   7 */
   8 #include <aros/debug.h>
   9 #include <aros/libcall.h>
  10 #include <exec/types.h>
  11
  12 /*****************************************************************************
  13
  14     NAME */
  15
  16         AROS_LH3I(void, CopyMemQuick,
  17
  18 /*  SYNOPSIS */
  19         AROS_LHA(CONST_APTR,  source, A0),
  20         AROS_LHA(APTR,  dest,   A1),
  21         AROS_LHA(IPTR, size,   D0),
  22
  23 /*  LOCATION */
  24         struct ExecBase *, SysBase, 105, Exec)
  25
  26 /*  FUNCTION
  27         Copy some longwords from one destination in memory to another using
  28         a fast copying method.
  29
  30     INPUTS
  31         source - Pointer to source area (must be ULONG aligned)
  32         dest   - Pointer to destination (must be ULONG aligned)
  33         size   - number of bytes to copy (must be a multiple of sizeof(ULONG)).
  34                  May be zero.
  35
  36     RESULT
  37
  38     NOTES
  39         The source and destination areas are not allowed to overlap.
  40
  41     EXAMPLE
  42
  43     BUGS
  44
  45     SEE ALSO
  46         CopyMem()
  47
  48     INTERNALS
  49         64-bit sizes are not handled yet.
  50
  51 ******************************************************************************/
  52 {
  53     AROS_LIBFUNC_INIT
  54
  55     ULONG low,high;
  56     const ULONG *src = source;
  57     ULONG *dst = dest;
  58
  59     /* Calculate number of ULONGs to copy */
  60     size/=sizeof(ULONG);
  61
  62     /*
  63     To minimize the loop overhead I copy more than one (eight) ULONG per
  64     iteration. Therefore I need to split size into size/8 and the rest.
  65     */
  66     low =size&7;
  67     high=size/8;
  68
  69     /* Then copy for both parts */
  70     if(low)
  71         do
  72             *dst++=*src++;
  73         while(--low);
  74
  75     /*
  76     Partly unrolled copying loop. The predecrement helps the compiler to
  77     find the best possible loop. The if is necessary to do this.
  78     */
  79     if(high)
  80         do
  81         {
  82             *dst++=*src++;
  83             *dst++=*src++;
  84             *dst++=*src++;
  85             *dst++=*src++;
  86             *dst++=*src++;
  87             *dst++=*src++;
  88             *dst++=*src++;
  89             *dst++=*src++;
  90         }while(--high);
  91     AROS_LIBFUNC_EXIT
  92 } /* CopyMemQuick */
  93