rom/exec/copymem.c

   1 /*
   2     Copyright © 1995-2012, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: Copy memory.
   6     Lang: english
   7 */
   8 #include <aros/libcall.h>
   9 #include <proto/exec.h>
  10
  11 /*****************************************************************************
  12
  13     NAME */
  14
  15         AROS_LH3I(void, CopyMem,
  16
  17 /*  SYNOPSIS */
  18         AROS_LHA(CONST_APTR,  source, A0),
  19         AROS_LHA(APTR,  dest,   A1),
  20         AROS_LHA(IPTR,  size,   D0),
  21
  22 /*  LOCATION */
  23         struct ExecBase *, SysBase, 104, Exec)
  24
  25 /*  FUNCTION
  26         Copy some memory from one destination in memory to another using
  27         a fast copying method.
  28
  29     INPUTS
  30         source - Pointer to source area
  31         dest   - Pointer to destination
  32         size   - number of bytes to copy (may be zero)
  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         CopyMemQuick()
  45
  46     INTERNALS
  47         64-bit sizes are not handled yet.
  48
  49 ******************************************************************************/
  50 {
  51     AROS_LIBFUNC_INIT
  52
  53     UBYTE *src,*dst;
  54     ULONG mis,low,high;
  55
  56     /*
  57     I try to fall back to copying LONGs if possible. To do this I copy
  58     the misaligned leading bytes of the source first. I use sizeof(LONG)
  59     instead of LONGALIGN because it is sometimes faster.
  60     */
  61
  62     if (!size) return;
  63
  64     src = (UBYTE *)source;
  65     dst = (UBYTE *)dest;
  66
  67 #if 0 /* stegerg: this is the wrong way round??? */
  68     mis =(IPTR)src&(sizeof(LONG)-1);
  69 #else
  70     mis = (sizeof(LONG) - 1) - (((IPTR)src - 1) & (sizeof(LONG) - 1));
  71 #endif
  72     if(mis>size)
  73     mis=size;
  74     size-=mis;
  75
  76     if(mis)
  77         do
  78             *dst++=*src++;
  79         while(--mis);
  80
  81     /*
  82     The source has the right alignment now. All I need to do is to
  83     check if this is true for the destination, too.
  84     */
  85     if(!((IPTR)dst&(AROS_LONGALIGN-1)))
  86     {
  87         /* Yes. I may copy LONGs. */
  88         LONG *s=(LONG *)src,*d=(LONG *)dst;
  89         ULONG longs;
  90
  91         /* How many of them? */
  92         longs=size/sizeof(LONG);
  93
  94         /*
  95             To minimize the loop overhead I copy more than one (eight) LONG per
  96             iteration. Therefore I need to split size into size/8 and the rest.
  97         */
  98         low =longs&7;
  99         high=longs/8;
 100
 101         /* Then copy for both parts */
 102         if(low)
 103             do
 104                 *d++=*s++;
 105             while(--low);
 106
 107         if(high)
 108             do
 109             {
 110                 *d++=*s++;
 111                 *d++=*s++;
 112                 *d++=*s++;
 113                 *d++=*s++;
 114                 *d++=*s++;
 115                 *d++=*s++;
 116                 *d++=*s++;
 117                 *d++=*s++;
 118             }while(--high);
 119
 120         /* Get the rest. */
 121
 122         size&=sizeof(LONG)-1;
 123
 124         src=(UBYTE *)s;
 125         dst=(UBYTE *)d;
 126     }
 127
 128     /* The remaining job can only be done by copying single bytes. */
 129     low =size&7;
 130     high=size/8;
 131
 132     /* Copy for both parts */
 133     if(low)
 134         do
 135             *dst++=*src++;
 136         while(--low);
 137
 138     /*
 139     Partly unrolled copying loop. The predecrement helps the compiler to
 140     find the best possible loop. The if is necessary to do this.
 141     */
 142     if(high)
 143         do
 144         {
 145             *dst++=*src++;
 146             *dst++=*src++;
 147             *dst++=*src++;
 148             *dst++=*src++;
 149             *dst++=*src++;
 150             *dst++=*src++;
 151             *dst++=*src++;
 152             *dst++=*src++;
 153         }while(--high);
 154     AROS_LIBFUNC_EXIT
 155 } /* CopyMem */
 156