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Annotation of sys/lib/libkern/memset.c, Revision 1.1

1.1     ! nbrk        1: /*     $OpenBSD: memset.c,v 1.5 2004/08/07 00:38:32 deraadt Exp $      */
        !             2: /*     $NetBSD: memset.c,v 1.6 1998/03/27 05:35:47 cgd Exp $   */
        !             3:
        !             4: /*-
        !             5:  * Copyright (c) 1990, 1993
        !             6:  *     The Regents of the University of California.  All rights reserved.
        !             7:  *
        !             8:  * This code is derived from software contributed to Berkeley by
        !             9:  * Mike Hibler and Chris Torek.
        !            10:  *
        !            11:  * Redistribution and use in source and binary forms, with or without
        !            12:  * modification, are permitted provided that the following conditions
        !            13:  * are met:
        !            14:  * 1. Redistributions of source code must retain the above copyright
        !            15:  *    notice, this list of conditions and the following disclaimer.
        !            16:  * 2. Redistributions in binary form must reproduce the above copyright
        !            17:  *    notice, this list of conditions and the following disclaimer in the
        !            18:  *    documentation and/or other materials provided with the distribution.
        !            19:  * 3. Neither the name of the University nor the names of its contributors
        !            20:  *    may be used to endorse or promote products derived from this software
        !            21:  *    without specific prior written permission.
        !            22:  *
        !            23:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
        !            24:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
        !            25:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
        !            26:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
        !            27:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
        !            28:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
        !            29:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
        !            30:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
        !            31:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
        !            32:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
        !            33:  * SUCH DAMAGE.
        !            34:  */
        !            35:
        !            36: #include <sys/cdefs.h>
        !            37: #if defined(LIBC_SCCS) && !defined(lint)
        !            38: #if 0
        !            39: static char sccsid[] = "@(#)memset.c   8.1 (Berkeley) 6/4/93";
        !            40: #else
        !            41: __RCSID("$NetBSD: memset.c,v 1.6 1998/03/27 05:35:47 cgd Exp $");
        !            42: #endif
        !            43: #endif /* LIBC_SCCS and not lint */
        !            44:
        !            45: #include <sys/types.h>
        !            46:
        !            47: #if !defined(_KERNEL) && !defined(_STANDALONE)
        !            48: #include <string.h>
        !            49: #include <limits.h>
        !            50: #else
        !            51: #include <sys/limits.h>
        !            52: #include <sys/systm.h>
        !            53: #include <lib/libkern/libkern.h>
        !            54: #endif
        !            55:
        !            56: #define        wsize   sizeof(u_int)
        !            57: #define        wmask   (wsize - 1)
        !            58:
        !            59: #ifdef BZERO
        !            60: #define        RETURN  return
        !            61: #define        VAL     0
        !            62: #define        WIDEVAL 0
        !            63:
        !            64: void
        !            65: bzero(void *dst0, size_t length)
        !            66: #else
        !            67: #define        RETURN  return (dst0)
        !            68: #define        VAL     c0
        !            69: #define        WIDEVAL c
        !            70:
        !            71: void *
        !            72: memset(void *dst0, int c0, size_t length)
        !            73: #endif
        !            74: {
        !            75:        size_t t;
        !            76: #ifndef BZERO
        !            77:        u_int c;
        !            78: #endif
        !            79:        u_char *dst;
        !            80:
        !            81:        dst = dst0;
        !            82:        /*
        !            83:         * If not enough words, just fill bytes.  A length >= 2 words
        !            84:         * guarantees that at least one of them is `complete' after
        !            85:         * any necessary alignment.  For instance:
        !            86:         *
        !            87:         *      |-----------|-----------|-----------|
        !            88:         *      |00|01|02|03|04|05|06|07|08|09|0A|00|
        !            89:         *                ^---------------------^
        !            90:         *               dst             dst+length-1
        !            91:         *
        !            92:         * but we use a minimum of 3 here since the overhead of the code
        !            93:         * to do word writes is substantial.
        !            94:         */
        !            95:        if (length < 3 * wsize) {
        !            96:                while (length != 0) {
        !            97:                        *dst++ = VAL;
        !            98:                        --length;
        !            99:                }
        !           100:                RETURN;
        !           101:        }
        !           102:
        !           103: #ifndef BZERO
        !           104:        if ((c = (u_char)c0) != 0) {    /* Fill the word. */
        !           105:                c = (c << 8) | c;       /* u_int is 16 bits. */
        !           106: #if UINT_MAX > 0xffff
        !           107:                c = (c << 16) | c;      /* u_int is 32 bits. */
        !           108: #endif
        !           109: #if UINT_MAX > 0xffffffff
        !           110:                c = (c << 32) | c;      /* u_int is 64 bits. */
        !           111: #endif
        !           112:        }
        !           113: #endif
        !           114:        /* Align destination by filling in bytes. */
        !           115:        if ((t = (u_long)dst & wmask) != 0) {
        !           116:                t = wsize - t;
        !           117:                length -= t;
        !           118:                do {
        !           119:                        *dst++ = VAL;
        !           120:                } while (--t != 0);
        !           121:        }
        !           122:
        !           123:        /* Fill words.  Length was >= 2*words so we know t >= 1 here. */
        !           124:        t = length / wsize;
        !           125:        do {
        !           126:                *(u_int *)dst = WIDEVAL;
        !           127:                dst += wsize;
        !           128:        } while (--t != 0);
        !           129:
        !           130:        /* Mop up trailing bytes, if any. */
        !           131:        t = length & wmask;
        !           132:        if (t != 0)
        !           133:                do {
        !           134:                        *dst++ = VAL;
        !           135:                } while (--t != 0);
        !           136:        RETURN;
        !           137: }