toolchain/gcc/newlib/libc/string/mempcpy.c

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