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[/] [or1k/] [trunk/] [newlib-1.10.0/] [newlib/] [libc/] [string/] [memcpy.c] - Blame information for rev 1773

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1 1010 ivang
/*
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FUNCTION
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        <<memcpy>>---copy memory regions
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ANSI_SYNOPSIS
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        #include <string.h>
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        void* memcpy(void *<[out]>, const void *<[in]>, size_t <[n]>);
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TRAD_SYNOPSIS
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        void *memcpy(<[out]>, <[in]>, <[n]>
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        void *<[out]>;
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        void *<[in]>;
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        size_t <[n]>;
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DESCRIPTION
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        This function copies <[n]> bytes from the memory region
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        pointed to by <[in]> to the memory region pointed to by
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        <[out]>.
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        If the regions overlap, the behavior is undefined.
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RETURNS
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        <<memcpy>> returns a pointer to the first byte of the <[out]>
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        region.
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PORTABILITY
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<<memcpy>> is ANSI C.
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<<memcpy>> requires no supporting OS subroutines.
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QUICKREF
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        memcpy ansi pure
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        */
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#include <_ansi.h>
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#include <stddef.h>
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#include <limits.h>
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/* Nonzero if either X or Y is not aligned on a "long" boundary.  */
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#define UNALIGNED(X, Y) \
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  (((long)X & (sizeof (long) - 1)) | ((long)Y & (sizeof (long) - 1)))
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/* How many bytes are copied each iteration of the 4X unrolled loop.  */
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#define BIGBLOCKSIZE    (sizeof (long) << 2)
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/* How many bytes are copied each iteration of the word copy loop.  */
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#define LITTLEBLOCKSIZE (sizeof (long))
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/* Threshhold for punting to the byte copier.  */
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#define TOO_SMALL(LEN)  ((LEN) < BIGBLOCKSIZE)
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_PTR
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_DEFUN (memcpy, (dst0, src0, len0),
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        _PTR dst0 _AND
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        _CONST _PTR src0 _AND
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        size_t len0)
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{
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#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
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  char *dst = (char *) dst0;
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  char *src = (char *) src0;
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  _PTR save = dst0;
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  while (len0--)
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    {
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      *dst++ = *src++;
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    }
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  return save;
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#else
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  char *dst = dst0;
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  _CONST char *src = src0;
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  long *aligned_dst;
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  _CONST long *aligned_src;
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  int   len =  len0;
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  /* If the size is small, or either SRC or DST is unaligned,
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     then punt into the byte copy loop.  This should be rare.  */
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  if (!TOO_SMALL(len) && !UNALIGNED (src, dst))
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    {
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      aligned_dst = (long*)dst;
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      aligned_src = (long*)src;
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      /* Copy 4X long words at a time if possible.  */
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      while (len >= BIGBLOCKSIZE)
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        {
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          *aligned_dst++ = *aligned_src++;
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          *aligned_dst++ = *aligned_src++;
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          *aligned_dst++ = *aligned_src++;
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          *aligned_dst++ = *aligned_src++;
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          len -= BIGBLOCKSIZE;
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        }
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      /* Copy one long word at a time if possible.  */
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      while (len >= LITTLEBLOCKSIZE)
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        {
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          *aligned_dst++ = *aligned_src++;
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          len -= LITTLEBLOCKSIZE;
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        }
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       /* Pick up any residual with a byte copier.  */
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      dst = (char*)aligned_dst;
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      src = (char*)aligned_src;
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    }
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  while (len--)
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    *dst++ = *src++;
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  return dst0;
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#endif /* not PREFER_SIZE_OVER_SPEED */
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}

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