105 lines
2.5 KiB
C
105 lines
2.5 KiB
C
/*
|
|
FUNCTION
|
|
<<memcpy>>---copy memory regions
|
|
|
|
SYNOPSIS
|
|
#include <string.h>
|
|
void* memcpy(void *restrict <[out]>, const void *restrict <[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
|
|
<<memcpy>> returns a pointer to the first byte of the <[out]>
|
|
region.
|
|
|
|
PORTABILITY
|
|
<<memcpy>> is ANSI C.
|
|
|
|
<<memcpy>> requires no supporting OS subroutines.
|
|
|
|
QUICKREF
|
|
memcpy ansi pure
|
|
*/
|
|
|
|
#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)
|
|
|
|
void *
|
|
_DEFUN (memcpy, (dst0, src0, len0),
|
|
void *__restrict dst0,
|
|
const void *__restrict src0,
|
|
size_t len0)
|
|
{
|
|
#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
|
|
char *dst = (char *) dst0;
|
|
char *src = (char *) src0;
|
|
|
|
void *save = dst0;
|
|
|
|
while (len0--)
|
|
{
|
|
*dst++ = *src++;
|
|
}
|
|
|
|
return save;
|
|
#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 dst0;
|
|
#endif /* not PREFER_SIZE_OVER_SPEED */
|
|
}
|