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Annotation of embedaddon/ntp/libntp/memmove.c, revision 1.1.1.1

1.1       misho       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: #ifdef HAVE_CONFIG_H
                     42: # include <config.h>
                     43: #endif
                     44: 
                     45: #ifndef HAVE_MEMMOVE
                     46: #ifdef HAVE_SYS_TYPES_H
                     47: #include <sys/types.h>
                     48: #endif
                     49: #include <string.h>
                     50: 
                     51: #include "l_stdlib.h"
                     52: 
                     53: /*
                     54:  * sizeof(word) MUST BE A POWER OF TWO
                     55:  * SO THAT wmask BELOW IS ALL ONES
                     56:  */
                     57: typedef        int word;               /* "word" used for optimal copy speed */
                     58: 
                     59: #define        wsize   sizeof(word)
                     60: #define        wmask   (wsize - 1)
                     61: 
                     62: /*
                     63:  * Copy a block of memory, handling overlap.
                     64:  * This is the routine that actually implements
                     65:  * (the portable versions of) bcopy, memcpy, and memmove.
                     66:  */
                     67: void *
                     68: memmove(
                     69:        void *dst0,
                     70:        const void *src0,
                     71:        register size_t length
                     72:        )
                     73: {
                     74:        register char *dst = dst0;
                     75:        register const char *src = src0;
                     76:        register size_t t;
                     77: 
                     78:        if (length == 0 || dst == src)          /* nothing to do */
                     79:            goto done;
                     80: 
                     81:        /*
                     82:         * Macros: loop-t-times; and loop-t-times, t>0
                     83:         */
                     84: #define        TLOOP(s) if (t) TLOOP1(s)
                     85: #define        TLOOP1(s) do { s; } while (--t)
                     86: 
                     87:        if ((unsigned long)dst < (unsigned long)src) {
                     88:                /*
                     89:                 * Copy forward.
                     90:                 */
                     91:                t = (int)src;   /* only need low bits */
                     92:                if ((t | (int)dst) & wmask) {
                     93:                        /*
                     94:                         * Try to align operands.  This cannot be done
                     95:                         * unless the low bits match.
                     96:                         */
                     97:                        if ((t ^ (int)dst) & wmask || length < wsize)
                     98:                            t = length;
                     99:                        else
                    100:                            t = wsize - (t & wmask);
                    101:                        length -= t;
                    102:                        TLOOP1(*dst++ = *src++);
                    103:                }
                    104:                /*
                    105:                 * Copy whole words, then mop up any trailing bytes.
                    106:                 */
                    107:                t = length / wsize;
                    108:                TLOOP(*(word *)dst = *(const word *)src; src += wsize;
                    109:                    dst += wsize);
                    110:                t = length & wmask;
                    111:                TLOOP(*dst++ = *src++);
                    112:        } else {
                    113:                /*
                    114:                 * Copy backwards.  Otherwise essentially the same.
                    115:                 * Alignment works as before, except that it takes
                    116:                 * (t&wmask) bytes to align, not wsize-(t&wmask).
                    117:                 */
                    118:                src += length;
                    119:                dst += length;
                    120:                t = (int)src;
                    121:                if ((t | (int)dst) & wmask) {
                    122:                        if ((t ^ (int)dst) & wmask || length <= wsize)
                    123:                            t = length;
                    124:                        else
                    125:                            t &= wmask;
                    126:                        length -= t;
                    127:                        TLOOP1(*--dst = *--src);
                    128:                }
                    129:                t = length / wsize;
                    130:                TLOOP(src -= wsize; dst -= wsize;
                    131:                    *(word *)dst = *(const word *)src);
                    132:                t = length & wmask;
                    133:                TLOOP(*--dst = *--src);
                    134:        }
                    135:     done:
                    136:        return (dst0);
                    137: }
                    138: #else
                    139: int memmove_bs;
                    140: #endif