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/*
FUNCTION
<<memmove>>---move possibly overlapping memory
INDEX
memmove
ANSI_SYNOPSIS
#include <string.h>
void *memmove(void *<[dst]>, const void *<[src]>, size_t <[length]>);
TRAD_SYNOPSIS
#include <string.h>
void *memmove(<[dst]>, <[src]>, <[length]>)
void *<[dst]>;
void *<[src]>;
size_t <[length]>;
DESCRIPTION
This function moves <[length]> characters from the block of
memory starting at <<*<[src]>>> to the memory starting at
<<*<[dst]>>>. <<memmove>> reproduces the characters correctly
at <<*<[dst]>>> even if the two areas overlap.
RETURNS
The function returns <[dst]> as passed.
PORTABILITY
<<memmove>> is ANSI C.
<<memmove>> requires no supporting OS subroutines.
QUICKREF
memmove ansi pure
*/
#include "config.h"
#include <_ansi.h>
#include <string.h>
/* Nonzero if either X or Y is not aligned on a "long" boundary. */
#define UNALIGNED(X, Y) \
(((long)X & (sizeof (long) - 1)) | ((long)Y & (sizeof (long) - 1)))
/* How many bytes are copied each iteration of the 4X unrolled loop. */
#define BIGBLOCKSIZE (sizeof (long) << 2)
/* How many bytes are copied each iteration of the word copy loop. */
#define LITTLEBLOCKSIZE (sizeof (long))
/* Threshhold for punting to the byte copier. */
#define TOO_SMALL(LEN) ((LEN) < BIGBLOCKSIZE)
_PTR
_DEFUN (memmove, (dst_void, src_void, length),
_PTR dst_void _AND
_CONST _PTR src_void _AND
size_t length) ICODE_ATTR;
_PTR
_DEFUN (memmove, (dst_void, src_void, length),
_PTR dst_void _AND
_CONST _PTR src_void _AND
size_t length)
{
#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
char *dst = dst_void;
_CONST char *src = src_void;
if (src < dst && dst < src + length)
{
/* Have to copy backwards */
src += length;
dst += length;
while (length--)
{
*--dst = *--src;
}
}
else
{
while (length--)
{
*dst++ = *src++;
}
}
return dst_void;
#else
char *dst = dst_void;
_CONST char *src = src_void;
long *aligned_dst;
_CONST long *aligned_src;
unsigned int len = length;
if (src < dst && dst < src + len)
{
/* Destructive overlap...have to copy backwards */
src += len;
dst += len;
while (len--)
{
*--dst = *--src;
}
}
else
{
/* Use optimizing algorithm for a non-destructive copy to closely
match memcpy. If the size is small or either SRC or DST is unaligned,
then punt into the byte copy loop. This should be rare. */
if (!TOO_SMALL(len) && !UNALIGNED (src, dst))
{
aligned_dst = (long*)dst;
aligned_src = (long*)src;
/* Copy 4X long words at a time if possible. */
while (len >= BIGBLOCKSIZE)
{
*aligned_dst++ = *aligned_src++;
*aligned_dst++ = *aligned_src++;
*aligned_dst++ = *aligned_src++;
*aligned_dst++ = *aligned_src++;
len -= BIGBLOCKSIZE;
}
/* Copy one long word at a time if possible. */
while (len >= LITTLEBLOCKSIZE)
{
*aligned_dst++ = *aligned_src++;
len -= LITTLEBLOCKSIZE;
}
/* Pick up any residual with a byte copier. */
dst = (char*)aligned_dst;
src = (char*)aligned_src;
}
while (len--)
{
*dst++ = *src++;
}
}
return dst_void;
#endif /* not PREFER_SIZE_OVER_SPEED */
}
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