rom/exec/copymemquick.c

   1 /*
   2     Copyright © 1995-2001, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: Copy aligned memory.
   6     Lang: english
   7 */
   8 #include <aros/libcall.h>
   9 #include <exec/types.h>
  10
  11 /*****************************************************************************
  12
  13     NAME */
  14
  15         AROS_LH3I(void, CopyMemQuick,
  16
  17 /*  SYNOPSIS */
  18         AROS_LHA(CONST_APTR,  source, A0),
  19         AROS_LHA(APTR,  dest,   A1),
  20         AROS_LHA(ULONG, size,   D0),
  21
  22 /*  LOCATION */
  23         struct ExecBase *, SysBase, 105, Exec)
  24
  25 /*  FUNCTION
  26         Copy some longwords from one destination in memory to another using
  27         a fast copying method.
  28
  29     INPUTS
  30         source - Pointer to source area (must be ULONG aligned)
  31         dest   - Pointer to destination (must be ULONG aligned)
  32         size   - number of bytes to copy (must be a multiple of sizeof(ULONG))
  33
  34     RESULT
  35
  36     NOTES
  37         The source and destination area are not allowed to overlap.
  38
  39     EXAMPLE
  40
  41     BUGS
  42
  43     SEE ALSO
  44         CopyMem()
  45
  46     INTERNALS
  47
  48 ******************************************************************************/
  49 {
  50     AROS_LIBFUNC_INIT
  51
  52     ULONG low,high;
  53     const ULONG *src = source;
  54     ULONG *dst = dest;
  55
  56     /* Calculate number of ULONGs to copy */
  57     size/=sizeof(ULONG);
  58
  59     /*
  60         To minimize the loop overhead I copy more than one (eight) ULONG per
  61         iteration. Therefore I need to split size into size/8 and the rest.
  62     */
  63     low =size&7;
  64     high=size/8;
  65
  66     /* Then copy for both parts */
  67     if(low)
  68         do
  69             *dst++=*src++;
  70         while(--low);
  71
  72     /*
  73         Partly unrolled copying loop. The predecrement helps the compiler to
  74         find the best possible loop. The if is necessary to do this.
  75     */
  76     if(high)
  77         do
  78         {
  79             *dst++=*src++;
  80             *dst++=*src++;
  81             *dst++=*src++;
  82             *dst++=*src++;
  83             *dst++=*src++;
  84             *dst++=*src++;
  85             *dst++=*src++;
  86             *dst++=*src++;
  87         }while(--high);
  88     AROS_LIBFUNC_EXIT
  89 } /* CopyMemQuick */
  90