lib/stdlib/mem.c

/*
 * Copyright (c) 2013-2014, ARM Limited and Contributors. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * 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.
 *
 * Neither the name of ARM nor the names of its contributors may be used
 * to endorse or promote products derived from this software without specific
 * prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT HOLDER 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 <stddef.h> /* size_t */

/*
 * Fill @count bytes of memory pointed to by @dst with @val
 */
void *memset(void *dst, int val, size_t count)
{
	char *ptr = dst;

	while (count--)
		*ptr++ = val;

	return dst;
}

/*
 * Compare @len bytes of @s1 and @s2
 */
int memcmp(const void *s1, const void *s2, size_t len)
{
	const unsigned char *s = s1;
	const unsigned char *d = s2;
	unsigned char sc;
	unsigned char dc;

	while (len--) {
		sc = *s++;
		dc = *d++;
		if (sc - dc)
			return (sc - dc);
	}

	return 0;
}

/*
 * Copy @len bytes from @src to @dst
 */
void *memcpy(void *dst, const void *src, size_t len)
{
	const char *s = src;
	char *d = dst;

	while (len--)
		*d++ = *s++;

	return dst;
}

/*
 * Move @len bytes from @src to @dst
 */
void *memmove(void *dst, const void *src, size_t len)
{
	/*
	 * The following test makes use of unsigned arithmetic overflow to
	 * more efficiently test the condition !(src <= dst && dst < str+len).
	 * It also avoids the situation where the more explicit test would give
	 * incorrect results were the calculation str+len to overflow (though
	 * that issue is probably moot as such usage is probably undefined
	 * behaviour and a bug anyway.
	 */
	if ((size_t)dst - (size_t)src >= len) {
		/* destination not in source data, so can safely use memcpy */
		return memcpy(dst, src, len);
	} else {
		/* copy backwards... */
		const char *end = dst;
		const char *s = (const char *)src + len;
		char *d = (char *)dst + len;
		while (d != end)
			*--d = *--s;
	}
	return dst;
}

/*
 * Scan @len bytes of @src for value @c
 */
void *memchr(const void *src, int c, size_t len)
{
	const char *s = src;

	while (len--) {
		if (*s == c)
			return (void *) s;
		s++;
	}

	return NULL;
}