firmware/libc/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" /* for _DEFUN */
  37 #include <string.h>
  38
  39 /* Nonzero if either X or Y is not aligned on a "long" boundary.  */
  40 #define UNALIGNED(X, Y) \
  41   (((long)X & (sizeof (long) - 1)) | ((long)Y & (sizeof (long) - 1)))
  42
  43 /* How many bytes are copied each iteration of the 4X unrolled loop.  */
  44 #define BIGBLOCKSIZE    (sizeof (long) << 2)
  45
  46 /* How many bytes are copied each iteration of the word copy loop.  */
  47 #define LITTLEBLOCKSIZE (sizeof (long))
  48
  49 /* Threshold for punting to the byte copier.  */
  50 #define TOO_SMALL(LEN)  ((LEN) < BIGBLOCKSIZE)
  51
  52 _PTR
  53 _DEFUN (memcpy, (dst0, src0, len0),
  54         _PTR dst0 _AND
  55         _CONST _PTR src0 _AND
  56         size_t len0) ICODE_ATTR;
  57
  58 _PTR
  59 _DEFUN (memcpy, (dst0, src0, len0),
  60         _PTR dst0 _AND
  61         _CONST _PTR src0 _AND
  62         size_t len0)
  63 {
  64 #if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
  65   char *dst = (char *) dst0;
  66   char *src = (char *) src0;
  67
  68   _PTR save = dst0;
  69
  70   while (len0--)
  71     {
  72       *dst++ = *src++;
  73     }
  74
  75   return save;
  76 #else
  77   char *dst = dst0;
  78   _CONST char *src = src0;
  79   long *aligned_dst;
  80   _CONST long *aligned_src;
  81   unsigned int   len =  len0;
  82
  83   /* If the size is small, or either SRC or DST is unaligned,
  84      then punt into the byte copy loop.  This should be rare.  */
  85   if (!TOO_SMALL(len) && !UNALIGNED (src, dst))
  86     {
  87       aligned_dst = (long*)dst;
  88       aligned_src = (long*)src;
  89
  90       /* Copy 4X long words at a time if possible.  */
  91       while (len >= BIGBLOCKSIZE)
  92         {
  93           *aligned_dst++ = *aligned_src++;
  94           *aligned_dst++ = *aligned_src++;
  95           *aligned_dst++ = *aligned_src++;
  96           *aligned_dst++ = *aligned_src++;
  97           len -= (unsigned int)BIGBLOCKSIZE;
  98         }
  99
 100       /* Copy one long word at a time if possible.  */
 101       while (len >= LITTLEBLOCKSIZE)
 102         {
 103           *aligned_dst++ = *aligned_src++;
 104           len -= LITTLEBLOCKSIZE;
 105         }
 106
 107        /* Pick up any residual with a byte copier.  */
 108       dst = (char*)aligned_dst;
 109       src = (char*)aligned_src;
 110     }
 111
 112   while (len--)
 113     *dst++ = *src++;
 114
 115   return dst0;
 116 #endif /* not PREFER_SIZE_OVER_SPEED */
 117 }