138 lines
3.2 KiB
C
138 lines
3.2 KiB
C
/*
|
|
FUNCTION
|
|
<<memmove>>---move possibly overlapping memory
|
|
|
|
INDEX
|
|
memmove
|
|
|
|
SYNOPSIS
|
|
#include <string.h>
|
|
void *memmove(void *<[dst]>, const 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 <string.h>
|
|
#include <_ansi.h>
|
|
#include <stddef.h>
|
|
#include <limits.h>
|
|
#include "local.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)
|
|
|
|
/*SUPPRESS 20*/
|
|
_PTR
|
|
__inhibit_loop_to_libcall
|
|
_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;
|
|
|
|
if (src < dst && dst < src + length)
|
|
{
|
|
/* Destructive overlap...have to copy backwards */
|
|
src += length;
|
|
dst += length;
|
|
while (length--)
|
|
{
|
|
*--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(length) && !UNALIGNED (src, dst))
|
|
{
|
|
aligned_dst = (long*)dst;
|
|
aligned_src = (long*)src;
|
|
|
|
/* Copy 4X long words at a time if possible. */
|
|
while (length >= BIGBLOCKSIZE)
|
|
{
|
|
*aligned_dst++ = *aligned_src++;
|
|
*aligned_dst++ = *aligned_src++;
|
|
*aligned_dst++ = *aligned_src++;
|
|
*aligned_dst++ = *aligned_src++;
|
|
length -= BIGBLOCKSIZE;
|
|
}
|
|
|
|
/* Copy one long word at a time if possible. */
|
|
while (length >= LITTLEBLOCKSIZE)
|
|
{
|
|
*aligned_dst++ = *aligned_src++;
|
|
length -= LITTLEBLOCKSIZE;
|
|
}
|
|
|
|
/* Pick up any residual with a byte copier. */
|
|
dst = (char*)aligned_dst;
|
|
src = (char*)aligned_src;
|
|
}
|
|
|
|
while (length--)
|
|
{
|
|
*dst++ = *src++;
|
|
}
|
|
}
|
|
|
|
return dst_void;
|
|
#endif /* not PREFER_SIZE_OVER_SPEED */
|
|
}
|