firmware/common/memcpy.c

   1 /*
   2 FUNCTION
   3         <<memcpy>>---copy memory regions
   4
   5 ANSI_SYNOPSIS
   6         #include <string.h>
   7         void* memcpy(void *<[out]>, const void *<[in]>, size_t <[n]>);
   8
   9 TRAD_SYNOPSIS
  10         void *memcpy(<[out]>, <[in]>, <[n]>
  11         void *<[out]>;
  12         void *<[in]>;
  13         size_t <[n]>;
  14
  15 DESCRIPTION
  16         This function copies <[n]> bytes from the memory region
  17         pointed to by <[in]> to the memory region pointed to by
  18         <[out]>.
  19
  20         If the regions overlap, the behavior is undefined.
  21
  22 RETURNS
  23         <<memcpy>> returns a pointer to the first byte of the <[out]>
  24         region.
  25
  26 PORTABILITY
  27 <<memcpy>> is ANSI C.
  28
  29 <<memcpy>> requires no supporting OS subroutines.
  30
  31 QUICKREF
  32         memcpy ansi pure
  33         */
  34
  35 #include "config.h"
  36 #include <_ansi.h>
  37 #include <stddef.h>
  38 #include <limits.h>
  39
  40 /* Nonzero if either X or Y is not aligned on a "long" boundary.  */
  41 #define UNALIGNED(X, Y) \
  42   (((long)X & (sizeof (long) - 1)) | ((long)Y & (sizeof (long) - 1)))
  43
  44 /* How many bytes are copied each iteration of the 4X unrolled loop.  */
  45 #define BIGBLOCKSIZE    (sizeof (long) << 2)
  46
  47 /* How many bytes are copied each iteration of the word copy loop.  */
  48 #define LITTLEBLOCKSIZE (sizeof (long))
  49
  50 /* Threshhold for punting to the byte copier.  */
  51 #define TOO_SMALL(LEN)  ((LEN) < BIGBLOCKSIZE)
  52
  53 _PTR
  54 _DEFUN (memcpy, (dst0, src0, len0),
  55         _PTR dst0 _AND
  56         _CONST _PTR src0 _AND
  57         size_t len0) ICODE_ATTR;
  58
  59 _PTR
  60 _DEFUN (memcpy, (dst0, src0, len0),
  61         _PTR dst0 _AND
  62         _CONST _PTR src0 _AND
  63         size_t len0)
  64 {
  65 #if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
  66   char *dst = (char *) dst0;
  67   char *src = (char *) src0;
  68
  69   _PTR save = dst0;
  70
  71   while (len0--)
  72     {
  73       *dst++ = *src++;
  74     }
  75
  76   return save;
  77 #else
  78   char *dst = dst0;
  79   _CONST char *src = src0;
  80   long *aligned_dst;
  81   _CONST long *aligned_src;
  82   unsigned int   len =  len0;
  83
  84   /* If the size is small, or either SRC or DST is unaligned,
  85      then punt into the byte copy loop.  This should be rare.  */
  86   if (!TOO_SMALL(len) && !UNALIGNED (src, dst))
  87     {
  88       aligned_dst = (long*)dst;
  89       aligned_src = (long*)src;
  90
  91       /* Copy 4X long words at a time if possible.  */
  92       while (len >= BIGBLOCKSIZE)
  93         {
  94           *aligned_dst++ = *aligned_src++;
  95           *aligned_dst++ = *aligned_src++;
  96           *aligned_dst++ = *aligned_src++;
  97           *aligned_dst++ = *aligned_src++;
  98           len -= (unsigned int)BIGBLOCKSIZE;
  99         }
 100
 101       /* Copy one long word at a time if possible.  */
 102       while (len >= LITTLEBLOCKSIZE)
 103         {
 104           *aligned_dst++ = *aligned_src++;
 105           len -= LITTLEBLOCKSIZE;
 106         }
 107
 108        /* Pick up any residual with a byte copier.  */
 109       dst = (char*)aligned_dst;
 110       src = (char*)aligned_src;
 111     }
 112
 113   while (len--)
 114     *dst++ = *src++;
 115
 116   return dst0;
 117 #endif /* not PREFER_SIZE_OVER_SPEED */
 118 }