bzero.c

/*
 * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
 *	The President and Fellows of Harvard College.
 *
 * 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.
 * 3. Neither the name of the University 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 UNIVERSITY 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 UNIVERSITY 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.
 */

/*
 * This file is shared between libc and the kernel, so don't put anything
 * in here that won't work in both contexts.
 */

#ifdef _KERNEL
#include <types.h>
#include <lib.h>
#else
#include <stdint.h>
#include <string.h>
#endif

/*
 * Standard (well, semi-standard) C string function - zero a block of
 * memory.
 */

void
bzero(void *vblock, size_t len)
{
	char *block = vblock;
	size_t i;

	/*
	 * For performance, optimize the common case where the pointer
	 * and the length are word-aligned, and write word-at-a-time
	 * instead of byte-at-a-time. Otherwise, write bytes.
	 *
	 * The alignment logic here should be portable. We rely on the
	 * compiler to be reasonably intelligent about optimizing the
	 * divides and moduli out. Fortunately, it is.
	 */

	if ((uintptr_t)block % sizeof(long) == 0 &&
	    len % sizeof(long) == 0) {
		long *lb = (long *)block;
		for (i=0; i<len/sizeof(long); i++) {
			lb[i] = 0;
		}
	}
	else {
		for (i=0; i<len; i++) {
			block[i] = 0;
		}
	}
}