toolchain/gcc/newlib/libc/string/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 <_ansi.h>
  36 #include <stddef.h>
  37 #include <limits.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 /* Threshhold 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)
  57 {
  58 #if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
  59   char *dst = (char *) dst0;
  60   char *src = (char *) src0;
  61
  62   _PTR save = dst0;
  63
  64   while (len0--)
  65     {
  66       *dst++ = *src++;
  67     }
  68
  69   return save;
  70 #else
  71   char *dst = dst0;
  72   _CONST char *src = src0;
  73   long *aligned_dst;
  74   _CONST long *aligned_src;
  75   int   len =  len0;
  76
  77   /* If the size is small, or either SRC or DST is unaligned,
  78      then punt into the byte copy loop.  This should be rare.  */
  79   if (!TOO_SMALL(len) && !UNALIGNED (src, dst))
  80     {
  81       aligned_dst = (long*)dst;
  82       aligned_src = (long*)src;
  83
  84       /* Copy 4X long words at a time if possible.  */
  85       while (len >= BIGBLOCKSIZE)
  86         {
  87           *aligned_dst++ = *aligned_src++;
  88           *aligned_dst++ = *aligned_src++;
  89           *aligned_dst++ = *aligned_src++;
  90           *aligned_dst++ = *aligned_src++;
  91           len -= BIGBLOCKSIZE;
  92         }
  93
  94       /* Copy one long word at a time if possible.  */
  95       while (len >= LITTLEBLOCKSIZE)
  96         {
  97           *aligned_dst++ = *aligned_src++;
  98           len -= LITTLEBLOCKSIZE;
  99         }
 100
 101        /* Pick up any residual with a byte copier.  */
 102       dst = (char*)aligned_dst;
 103       src = (char*)aligned_src;
 104     }
 105
 106   while (len--)
 107     *dst++ = *src++;
 108
 109   return dst0;
 110 #endif /* not PREFER_SIZE_OVER_SPEED */
 111 }