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Annotation of 43BSDReno/lib/libc/string/bcopy.c, revision 1.1

1.1     ! root        1: /*-
        !             2:  * Copyright (c) 1990 The Regents of the University of California.
        !             3:  * 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 are permitted provided
        !             9:  * that: (1) source distributions retain this entire copyright notice and
        !            10:  * comment, and (2) distributions including binaries display the following
        !            11:  * acknowledgement:  ``This product includes software developed by the
        !            12:  * University of California, Berkeley and its contributors'' in the
        !            13:  * documentation or other materials provided with the distribution and in
        !            14:  * all advertising materials mentioning features or use of this software.
        !            15:  * Neither the name of the University nor the names of its contributors may
        !            16:  * be used to endorse or promote products derived from this software without
        !            17:  * specific prior written permission.
        !            18:  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
        !            19:  * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
        !            20:  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
        !            21:  */
        !            22: 
        !            23: #if defined(LIBC_SCCS) && !defined(lint)
        !            24: static char sccsid[] = "@(#)bcopy.c    5.8 (Berkeley) 6/23/90";
        !            25: #endif /* LIBC_SCCS and not lint */
        !            26: 
        !            27: #include <sys/stdc.h>
        !            28: #include <string.h>
        !            29: 
        !            30: /*
        !            31:  * sizeof(word) MUST BE A POWER OF TWO
        !            32:  * SO THAT wmask BELOW IS ALL ONES
        !            33:  */
        !            34: typedef        int word;               /* "word" used for optimal copy speed */
        !            35: 
        !            36: #define        wsize   sizeof(word)
        !            37: #define        wmask   (wsize - 1)
        !            38: 
        !            39: /*
        !            40:  * Copy a block of memory, handling overlap.
        !            41:  * This is the routine that actually implements
        !            42:  * (the portable versions of) bcopy, memcpy, and memmove.
        !            43:  */
        !            44: #ifdef MEMCOPY
        !            45: void *
        !            46: memcpy(dst0, src0, length)
        !            47: #else
        !            48: #ifdef MEMMOVE
        !            49: void *
        !            50: memmove(dst0, src0, length)
        !            51: #else
        !            52: void
        !            53: bcopy(src0, dst0, length)
        !            54: #endif
        !            55: #endif
        !            56:        char *dst0;
        !            57:        const char *src0;
        !            58:        register size_t length;
        !            59: {
        !            60:        register char *dst = dst0;
        !            61:        register const char *src = src0;
        !            62:        register size_t t;
        !            63: 
        !            64:        if (length == 0 || dst == src)          /* nothing to do */
        !            65:                return;
        !            66: 
        !            67:        /*
        !            68:         * Macros: loop-t-times; and loop-t-times, t>0
        !            69:         */
        !            70: #define        TLOOP(s) if (t) TLOOP1(s)
        !            71: #define        TLOOP1(s) do { s; } while (--t)
        !            72: 
        !            73:        if ((unsigned long)dst < (unsigned long)src) {
        !            74:                /*
        !            75:                 * Copy forward.
        !            76:                 */
        !            77:                t = (int)src;   /* only need low bits */
        !            78:                if ((t | (int)dst) & wmask) {
        !            79:                        /*
        !            80:                         * Try to align operands.  This cannot be done
        !            81:                         * unless the low bits match.
        !            82:                         */
        !            83:                        if ((t ^ (int)dst) & wmask || length < wsize)
        !            84:                                t = length;
        !            85:                        else
        !            86:                                t = wsize - (t & wmask);
        !            87:                        length -= t;
        !            88:                        TLOOP1(*dst++ = *src++);
        !            89:                }
        !            90:                /*
        !            91:                 * Copy whole words, then mop up any trailing bytes.
        !            92:                 */
        !            93:                t = length / wsize;
        !            94:                TLOOP(*(word *)dst = *(word *)src; src += wsize; dst += wsize);
        !            95:                t = length & wmask;
        !            96:                TLOOP(*dst++ = *src++);
        !            97:        } else {
        !            98:                /*
        !            99:                 * Copy backwards.  Otherwise essentially the same.
        !           100:                 * Alignment works as before, except that it takes
        !           101:                 * (t&wmask) bytes to align, not wsize-(t&wmask).
        !           102:                 */
        !           103:                src += length;
        !           104:                dst += length;
        !           105:                t = (int)src;
        !           106:                if ((t | (int)dst) & wmask) {
        !           107:                        if ((t ^ (int)dst) & wmask || length <= wsize)
        !           108:                                t = length;
        !           109:                        else
        !           110:                                t &= wmask;
        !           111:                        length -= t;
        !           112:                        TLOOP1(*--dst = *--src);
        !           113:                }
        !           114:                t = length / wsize;
        !           115:                TLOOP(src -= wsize; dst -= wsize; *(word *)dst = *(word *)src);
        !           116:                t = length & wmask;
        !           117:                TLOOP(*--dst = *--src);
        !           118:        }
        !           119: #ifdef MEMCOPY
        !           120:        return(dst0);
        !           121: #else
        !           122: #ifdef MEMMOVE
        !           123:        return(dst0);
        !           124: #else
        !           125:        return;
        !           126: #endif
        !           127: #endif
        !           128: }

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