lib/libc/memmove.c

/*
 * Copyright (c) 2013-2018, Arm Limited and Contributors. All rights reserved.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

#include <string.h>

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;
}