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Annotation of pgp/src/memmove.c, revision 1.1

1.1     ! root        1: /*-
        !             2:  * Copyright (c) 1990, 1993
        !             3:  *     The Regents of the University of California.  All rights reserved.
        !             4:  *
        !             5:  * This code is derived from software contributed to Berkeley by
        !             6:  * Chris Torek.
        !             7:  *
        !             8:  * Redistribution and use in source and binary forms, with or without
        !             9:  * modification, are permitted provided that the following conditions
        !            10:  * are met:
        !            11:  * 1. Redistributions of source code must retain the above copyright
        !            12:  *    notice, this list of conditions and the following disclaimer.
        !            13:  * 2. Redistributions in binary form must reproduce the above copyright
        !            14:  *    notice, this list of conditions and the following disclaimer in the
        !            15:  *    documentation and/or other materials provided with the distribution.
        !            16:  * 3. All advertising materials mentioning features or use of this software
        !            17:  *    must display the following acknowledgement:
        !            18:  *     This product includes software developed by the University of
        !            19:  *     California, Berkeley and its contributors.
        !            20:  * 4. Neither the name of the University nor the names of its contributors
        !            21:  *    may be used to endorse or promote products derived from this software
        !            22:  *    without specific prior written permission.
        !            23:  *
        !            24:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
        !            25:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
        !            26:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
        !            27:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
        !            28:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
        !            29:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
        !            30:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
        !            31:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
        !            32:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
        !            33:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
        !            34:  * SUCH DAMAGE.
        !            35:  */
        !            36: 
        !            37: #if defined(LIBC_SCCS) && !defined(lint)
        !            38: static char sccsid[] = "@(#)bcopy.c    8.1 (Berkeley) 6/4/93";
        !            39: #endif /* LIBC_SCCS and not lint */
        !            40: 
        !            41: #include <sys/types.h>
        !            42: #include "cdefs.h"
        !            43: #include <string.h>
        !            44: 
        !            45: /*
        !            46:  * sizeof(word) MUST BE A POWER OF TWO
        !            47:  * SO THAT wmask BELOW IS ALL ONES
        !            48:  */
        !            49: typedef        int word;               /* "word" used for optimal copy speed */
        !            50: 
        !            51: #define        wsize   sizeof(word)
        !            52: #define        wmask   (wsize - 1)
        !            53: 
        !            54: /*
        !            55:  * Copy a block of memory, handling overlap.
        !            56:  * This is the routine that actually implements
        !            57:  * (the portable versions of) bcopy, memcpy, and memmove.
        !            58:  */
        !            59: void *
        !            60: memmove(dst0, src0, length)
        !            61:        void *dst0;
        !            62:        const void *src0;
        !            63:        register size_t length;
        !            64: {
        !            65:        register char *dst = dst0;
        !            66:        register const char *src = src0;
        !            67:        register size_t t;
        !            68: 
        !            69:        if (length == 0 || dst == src)          /* nothing to do */
        !            70:                goto done;
        !            71: 
        !            72:        /*
        !            73:         * Macros: loop-t-times; and loop-t-times, t>0
        !            74:         */
        !            75: #define        TLOOP(s) if (t) TLOOP1(s)
        !            76: #define        TLOOP1(s) do { s; } while (--t)
        !            77: 
        !            78:        if ((unsigned long)dst < (unsigned long)src) {
        !            79:                /*
        !            80:                 * Copy forward.
        !            81:                 */
        !            82:                t = (int)src;   /* only need low bits */
        !            83:                if ((t | (int)dst) & wmask) {
        !            84:                        /*
        !            85:                         * Try to align operands.  This cannot be done
        !            86:                         * unless the low bits match.
        !            87:                         */
        !            88:                        if ((t ^ (int)dst) & wmask || length < wsize)
        !            89:                                t = length;
        !            90:                        else
        !            91:                                t = wsize - (t & wmask);
        !            92:                        length -= t;
        !            93:                        TLOOP1(*dst++ = *src++);
        !            94:                }
        !            95:                /*
        !            96:                 * Copy whole words, then mop up any trailing bytes.
        !            97:                 */
        !            98:                t = length / wsize;
        !            99:                TLOOP(*(word *)dst = *(word *)src; src += wsize; dst += wsize);
        !           100:                t = length & wmask;
        !           101:                TLOOP(*dst++ = *src++);
        !           102:        } else {
        !           103:                /*
        !           104:                 * Copy backwards.  Otherwise essentially the same.
        !           105:                 * Alignment works as before, except that it takes
        !           106:                 * (t&wmask) bytes to align, not wsize-(t&wmask).
        !           107:                 */
        !           108:                src += length;
        !           109:                dst += length;
        !           110:                t = (int)src;
        !           111:                if ((t | (int)dst) & wmask) {
        !           112:                        if ((t ^ (int)dst) & wmask || length <= wsize)
        !           113:                                t = length;
        !           114:                        else
        !           115:                                t &= wmask;
        !           116:                        length -= t;
        !           117:                        TLOOP1(*--dst = *--src);
        !           118:                }
        !           119:                t = length / wsize;
        !           120:                TLOOP(src -= wsize; dst -= wsize; *(word *)dst = *(word *)src);
        !           121:                t = length & wmask;
        !           122:                TLOOP(*--dst = *--src);
        !           123:        }
        !           124: done:
        !           125:        return (dst0);
        !           126: }

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