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Annotation of 43BSDReno/lib/libc/string/bcopy.c, revision 1.1.1.1

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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