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/* $NetBSD: memcpy.c,v 1.1 2014/09/03 19:34:25 matt Exp $ */
/*-
* Copyright (c) 2014 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Matt Thomas of 3am Software Foundry.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__RCSID("$NetBSD: memcpy.c,v 1.1 2014/09/03 19:34:25 matt Exp $");
#include <stddef.h>
#include <stdint.h>
#include <string.h>
static inline unsigned long
combine_words(unsigned long w1, unsigned long w2, int shift1, int shift2)
{
#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
return (w1 << shift1) | (w2 >> shift2);
#else
return (w1 >> shift1) | (w2 << shift2);
#endif
}
void *
memcpy(void * restrict a, const void * restrict b, size_t len)
{
const unsigned char *cb = b;
unsigned char *ca = a;
if (len == 0)
return a;
/*
* Make sure the destination is long aligned.
*/
while ((uintptr_t)ca & (sizeof(long) - 1)) {
*ca++ = *cb++;
if (--len == 0)
return a;
}
unsigned long *la = (long *)ca;
const int offset = (uintptr_t)cb & (sizeof(*la) - 1);
const unsigned long *lb = (const unsigned long *) (cb - offset);
unsigned long * const ea = la + len / sizeof(*la);
if (offset == 0) {
/*
* a & b are now both long alignment.
* First try to copy 4 longs at a time,
*/
for (; la + 4 <= ea; la += 4, lb += 4) {
la[0] = lb[0];
la[1] = lb[1];
la[2] = lb[2];
la[3] = lb[3];
}
/*
* Now try to copy one long at a time.
*/
while (la <= ea) {
*la++ = *lb++;
}
} else {
const int shift1 = offset * 8;
const int shift2 = sizeof(*la) * 8 - shift1;
unsigned long w1 = *lb++;
/*
* We try to write 4 words per loop.
*/
for (; la + 4 <= ea; la += 4, lb += 4) {
unsigned long w2 = lb[0];
la[0] = combine_words(w1, w2, shift1, shift2);
w1 = lb[1];
la[1] = combine_words(w2, w1, shift1, shift2);
w2 = lb[2];
la[2] = combine_words(w1, w2, shift1, shift2);
w1 = lb[3];
la[3] = combine_words(w2, w1, shift1, shift2);
}
/*
* Now try to copy one long at a time.
*/
while (la <= ea) {
unsigned long w2 = *lb++;
*la++ = combine_words(w1, w2, shift1, shift2);
w1 = w2;
}
}
len &= sizeof(*la) - 1;
if (len) {
cb = (const unsigned char *)lb + offset;
ca = (unsigned char *)la;
while (len-- > 0) {
*ca++ = *cb++;
}
}
return a;
}
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