memmove.c
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上传日期:2022-05-23
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文件大小:4k
- /*-
- * See the file LICENSE for redistribution information.
- *
- * Copyright (c) 1996-2002
- * Sleepycat Software. All rights reserved.
- */
- /*
- * Copyright (c) 1990, 1993
- * The Regents of the University of California. All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in the
- * documentation and/or other materials provided with the distribution.
- * 3. Neither the name of the University nor the names of its contributors
- * may be used to endorse or promote products derived from this software
- * without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
- * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
- * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
- * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
- * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
- * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- */
- #include "db_config.h"
- #ifndef lint
- static const char revid[] = "$Id: memmove.c,v 11.6 2002/01/11 15:51:28 bostic Exp $";
- #endif /* not lint */
- #ifndef NO_SYSTEM_INCLUDES
- #include <sys/types.h>
- #endif
- /*
- * sizeof(word) MUST BE A POWER OF TWO
- * SO THAT wmask BELOW IS ALL ONES
- */
- typedef int word; /* "word" used for optimal copy speed */
- #undef wsize
- #define wsize sizeof(word)
- #undef wmask
- #define wmask (wsize - 1)
- /*
- * Copy a block of memory, handling overlap.
- * This is the routine that actually implements
- * (the portable versions of) bcopy, memcpy, and memmove.
- */
- #ifdef MEMCOPY
- /*
- * PUBLIC: #ifndef HAVE_MEMCPY
- * PUBLIC: void *memcpy __P((void *, const void *, size_t));
- * PUBLIC: #endif
- */
- void *
- memcpy(dst0, src0, length)
- #else
- #ifdef MEMMOVE
- /*
- * PUBLIC: #ifndef HAVE_MEMMOVE
- * PUBLIC: void *memmove __P((void *, const void *, size_t));
- * PUBLIC: #endif
- */
- void *
- memmove(dst0, src0, length)
- #else
- void
- bcopy(src0, dst0, length)
- #endif
- #endif
- void *dst0;
- const void *src0;
- register size_t length;
- {
- register char *dst = dst0;
- register const char *src = src0;
- register size_t t;
- if (length == 0 || dst == src) /* nothing to do */
- goto done;
- /*
- * Macros: loop-t-times; and loop-t-times, t>0
- */
- #undef TLOOP
- #define TLOOP(s) if (t) TLOOP1(s)
- #undef TLOOP1
- #define TLOOP1(s) do { s; } while (--t)
- if ((unsigned long)dst < (unsigned long)src) {
- /*
- * Copy forward.
- */
- t = (int)src; /* only need low bits */
- if ((t | (int)dst) & wmask) {
- /*
- * Try to align operands. This cannot be done
- * unless the low bits match.
- */
- if ((t ^ (int)dst) & wmask || length < wsize)
- t = length;
- else
- t = wsize - (t & wmask);
- length -= t;
- TLOOP1(*dst++ = *src++);
- }
- /*
- * Copy whole words, then mop up any trailing bytes.
- */
- t = length / wsize;
- TLOOP(*(word *)dst = *(word *)src; src += wsize; dst += wsize);
- t = length & wmask;
- TLOOP(*dst++ = *src++);
- } else {
- /*
- * Copy backwards. Otherwise essentially the same.
- * Alignment works as before, except that it takes
- * (t&wmask) bytes to align, not wsize-(t&wmask).
- */
- src += length;
- dst += length;
- t = (int)src;
- if ((t | (int)dst) & wmask) {
- if ((t ^ (int)dst) & wmask || length <= wsize)
- t = length;
- else
- t &= wmask;
- length -= t;
- TLOOP1(*--dst = *--src);
- }
- t = length / wsize;
- TLOOP(src -= wsize; dst -= wsize; *(word *)dst = *(word *)src);
- t = length & wmask;
- TLOOP(*--dst = *--src);
- }
- done:
- #if defined(MEMCOPY) || defined(MEMMOVE)
- return (dst0);
- #else
- return;
- #endif
- }