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/*
FUNCTION
<<mempcpy>>---copy memory regions and return end pointer
SYNOPSIS
#include <string.h>
void* mempcpy(void *<[out]>, const void *<[in]>, size_t <[n]>);
DESCRIPTION
This function copies <[n]> bytes from the memory region
pointed to by <[in]> to the memory region pointed to by
<[out]>.
If the regions overlap, the behavior is undefined.
RETURNS
<<mempcpy>> returns a pointer to the byte following the
last byte copied to the <[out]> region.
PORTABILITY
<<mempcpy>> is a GNU extension.
<<mempcpy>> requires no supporting OS subroutines.
*/
#include <_ansi.h>
#include <stddef.h>
#include <limits.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 (mempcpy, (dst0, src0, len0),
_PTR dst0,
_CONST _PTR src0,
size_t len0)
{
#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
char *dst = (char *) dst0;
char *src = (char *) src0;
while (len0--)
{
*dst++ = *src++;
}
return dst;
#else
char *dst = dst0;
_CONST char *src = src0;
long *aligned_dst;
_CONST long *aligned_src;
/* 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(len0) && !UNALIGNED (src, dst))
{
aligned_dst = (long*)dst;
aligned_src = (long*)src;
/* Copy 4X long words at a time if possible. */
while (len0 >= BIGBLOCKSIZE)
{
*aligned_dst++ = *aligned_src++;
*aligned_dst++ = *aligned_src++;
*aligned_dst++ = *aligned_src++;
*aligned_dst++ = *aligned_src++;
len0 -= BIGBLOCKSIZE;
}
/* Copy one long word at a time if possible. */
while (len0 >= LITTLEBLOCKSIZE)
{
*aligned_dst++ = *aligned_src++;
len0 -= LITTLEBLOCKSIZE;
}
/* Pick up any residual with a byte copier. */
dst = (char*)aligned_dst;
src = (char*)aligned_src;
}
while (len0--)
*dst++ = *src++;
return dst;
#endif /* not PREFER_SIZE_OVER_SPEED */
}
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