os161-1.99
 All Data Structures
bzero.c
00001 /*
00002  * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
00003  *      The President and Fellows of Harvard College.
00004  *
00005  * Redistribution and use in source and binary forms, with or without
00006  * modification, are permitted provided that the following conditions
00007  * are met:
00008  * 1. Redistributions of source code must retain the above copyright
00009  *    notice, this list of conditions and the following disclaimer.
00010  * 2. Redistributions in binary form must reproduce the above copyright
00011  *    notice, this list of conditions and the following disclaimer in the
00012  *    documentation and/or other materials provided with the distribution.
00013  * 3. Neither the name of the University nor the names of its contributors
00014  *    may be used to endorse or promote products derived from this software
00015  *    without specific prior written permission.
00016  *
00017  * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
00018  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
00019  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
00020  * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
00021  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
00022  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
00023  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
00024  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
00025  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
00026  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
00027  * SUCH DAMAGE.
00028  */
00029 
00030 /*
00031  * This file is shared between libc and the kernel, so don't put anything
00032  * in here that won't work in both contexts.
00033  */
00034 
00035 #ifdef _KERNEL
00036 #include <types.h>
00037 #include <lib.h>
00038 #else
00039 #include <stdint.h>
00040 #include <string.h>
00041 #endif
00042 
00043 /*
00044  * Standard (well, semi-standard) C string function - zero a block of
00045  * memory.
00046  */
00047 
00048 void
00049 bzero(void *vblock, size_t len)
00050 {
00051         char *block = vblock;
00052         size_t i;
00053 
00054         /*
00055          * For performance, optimize the common case where the pointer
00056          * and the length are word-aligned, and write word-at-a-time
00057          * instead of byte-at-a-time. Otherwise, write bytes.
00058          *
00059          * The alignment logic here should be portable. We rely on the
00060          * compiler to be reasonably intelligent about optimizing the
00061          * divides and moduli out. Fortunately, it is.
00062          */
00063 
00064         if ((uintptr_t)block % sizeof(long) == 0 &&
00065             len % sizeof(long) == 0) {
00066                 long *lb = (long *)block;
00067                 for (i=0; i<len/sizeof(long); i++) {
00068                         lb[i] = 0;
00069                 }
00070         }
00071         else {
00072                 for (i=0; i<len; i++) {
00073                         block[i] = 0;
00074                 }
00075         }
00076 }
 All Data Structures