368 lines
9.5 KiB
C
368 lines
9.5 KiB
C
/* $NetBSD: merge.c,v 1.5 1997/07/21 14:08:56 jtc Exp $ */
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/*-
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* Copyright (c) 1992, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Peter McIlroy.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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#if defined(LIBC_SCCS) && !defined(lint)
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#if 0
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static char sccsid[] = "from: @(#)merge.c 8.2 (Berkeley) 2/14/94";
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#else
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__RCSID("$NetBSD: merge.c,v 1.5 1997/07/21 14:08:56 jtc Exp $");
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#endif
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#endif /* LIBC_SCCS and not lint */
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/*
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* Hybrid exponential search/linear search merge sort with hybrid
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* natural/pairwise first pass. Requires about .3% more comparisons
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* for random data than LSMS with pairwise first pass alone.
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* It works for objects as small as two bytes.
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*/
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#define NATURAL
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#define THRESHOLD 16 /* Best choice for natural merge cut-off. */
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/* #define NATURAL to get hybrid natural merge.
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* (The default is pairwise merging.)
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*/
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#include "namespace.h"
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#include <sys/types.h>
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#include <errno.h>
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#include <stdlib.h>
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#include <string.h>
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#ifdef __weak_alias
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__weak_alias(mergesort,_mergesort);
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#endif
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static void setup __P((u_char *, u_char *, size_t, size_t,
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int (*)(const void *, const void *)));
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static void insertionsort __P((u_char *, size_t, size_t,
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int (*)(const void *, const void *)));
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#define ISIZE sizeof(int)
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#define PSIZE sizeof(u_char *)
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#define ICOPY_LIST(src, dst, last) \
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do \
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*(int*)dst = *(int*)src, src += ISIZE, dst += ISIZE; \
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while(src < last)
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#define ICOPY_ELT(src, dst, i) \
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do \
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*(int*) dst = *(int*) src, src += ISIZE, dst += ISIZE; \
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while (i -= ISIZE)
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#define CCOPY_LIST(src, dst, last) \
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do \
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*dst++ = *src++; \
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while (src < last)
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#define CCOPY_ELT(src, dst, i) \
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do \
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*dst++ = *src++; \
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while (i -= 1)
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/*
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* Find the next possible pointer head. (Trickery for forcing an array
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* to do double duty as a linked list when objects do not align with word
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* boundaries.
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*/
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/* Assumption: PSIZE is a power of 2. */
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#define EVAL(p) (u_char **) \
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((u_char *)0 + \
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(((u_char *)p + PSIZE - 1 - (u_char *) 0) & ~(PSIZE - 1)))
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/*
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* Arguments are as for qsort.
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*/
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int
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mergesort(base, nmemb, size, cmp)
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void *base;
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size_t nmemb;
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register size_t size;
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int (*cmp) __P((const void *, const void *));
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{
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register int i, sense;
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int big, iflag;
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register u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2;
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u_char *list2, *list1, *p2, *p, *last, **p1;
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if (size < PSIZE / 2) { /* Pointers must fit into 2 * size. */
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errno = EINVAL;
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return (-1);
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}
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/*
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* XXX
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* Stupid subtraction for the Cray.
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*/
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iflag = 0;
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if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE))
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iflag = 1;
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if ((list2 = malloc(nmemb * size + PSIZE)) == NULL)
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return (-1);
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list1 = base;
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setup(list1, list2, nmemb, size, cmp);
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last = list2 + nmemb * size;
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i = big = 0;
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while (*EVAL(list2) != last) {
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l2 = list1;
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p1 = EVAL(list1);
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for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) {
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p2 = *EVAL(p2);
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f1 = l2;
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f2 = l1 = list1 + (p2 - list2);
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if (p2 != last)
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p2 = *EVAL(p2);
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l2 = list1 + (p2 - list2);
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while (f1 < l1 && f2 < l2) {
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if ((*cmp)(f1, f2) <= 0) {
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q = f2;
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b = f1, t = l1;
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sense = -1;
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} else {
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q = f1;
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b = f2, t = l2;
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sense = 0;
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}
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if (!big) { /* here i = 0 */
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#if 0
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LINEAR:
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#endif
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while ((b += size) < t && cmp(q, b) >sense)
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if (++i == 6) {
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big = 1;
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goto EXPONENTIAL;
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}
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} else {
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EXPONENTIAL: for (i = size; ; i <<= 1)
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if ((p = (b + i)) >= t) {
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if ((p = t - size) > b &&
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(*cmp)(q, p) <= sense)
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t = p;
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else
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b = p;
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break;
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} else if ((*cmp)(q, p) <= sense) {
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t = p;
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if (i == size)
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big = 0;
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goto FASTCASE;
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} else
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b = p;
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#if 0
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SLOWCASE:
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#endif
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while (t > b+size) {
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i = (((t - b) / size) >> 1) * size;
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if ((*cmp)(q, p = b + i) <= sense)
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t = p;
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else
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b = p;
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}
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goto COPY;
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FASTCASE: while (i > size)
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if ((*cmp)(q,
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p = b + (i >>= 1)) <= sense)
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t = p;
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else
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b = p;
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COPY: b = t;
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}
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i = size;
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if (q == f1) {
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if (iflag) {
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ICOPY_LIST(f2, tp2, b);
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ICOPY_ELT(f1, tp2, i);
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} else {
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CCOPY_LIST(f2, tp2, b);
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CCOPY_ELT(f1, tp2, i);
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}
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} else {
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if (iflag) {
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ICOPY_LIST(f1, tp2, b);
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ICOPY_ELT(f2, tp2, i);
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} else {
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CCOPY_LIST(f1, tp2, b);
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CCOPY_ELT(f2, tp2, i);
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}
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}
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}
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if (f2 < l2) {
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if (iflag)
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ICOPY_LIST(f2, tp2, l2);
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else
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CCOPY_LIST(f2, tp2, l2);
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} else if (f1 < l1) {
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if (iflag)
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ICOPY_LIST(f1, tp2, l1);
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else
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CCOPY_LIST(f1, tp2, l1);
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}
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*p1 = l2;
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}
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tp2 = list1; /* swap list1, list2 */
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list1 = list2;
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list2 = tp2;
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last = list2 + nmemb*size;
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}
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if (base == list2) {
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memmove(list2, list1, nmemb*size);
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list2 = list1;
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}
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free(list2);
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return (0);
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}
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#define swap(a, b) { \
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s = b; \
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i = size; \
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do { \
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tmp = *a; *a++ = *s; *s++ = tmp; \
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} while (--i); \
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a -= size; \
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}
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#define reverse(bot, top) { \
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s = top; \
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do { \
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i = size; \
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do { \
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tmp = *bot; *bot++ = *s; *s++ = tmp; \
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} while (--i); \
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s -= size2; \
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} while(bot < s); \
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}
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/*
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* Optional hybrid natural/pairwise first pass. Eats up list1 in runs of
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* increasing order, list2 in a corresponding linked list. Checks for runs
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* when THRESHOLD/2 pairs compare with same sense. (Only used when NATURAL
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* is defined. Otherwise simple pairwise merging is used.)
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*/
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void
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setup(list1, list2, n, size, cmp)
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size_t n, size;
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int (*cmp) __P((const void *, const void *));
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u_char *list1, *list2;
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{
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int i, length, size2, tmp, sense;
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u_char *f1, *f2, *s, *l2, *last, *p2;
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size2 = size*2;
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if (n <= 5) {
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insertionsort(list1, n, size, cmp);
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*EVAL(list2) = (u_char*) list2 + n*size;
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return;
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}
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/*
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* Avoid running pointers out of bounds; limit n to evens
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* for simplicity.
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*/
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i = 4 + (n & 1);
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insertionsort(list1 + (n - i) * size, i, size, cmp);
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last = list1 + size * (n - i);
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*EVAL(list2 + (last - list1)) = list2 + n * size;
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#ifdef NATURAL
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p2 = list2;
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f1 = list1;
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sense = (cmp(f1, f1 + size) > 0);
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for (; f1 < last; sense = !sense) {
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length = 2;
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/* Find pairs with same sense. */
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for (f2 = f1 + size2; f2 < last; f2 += size2) {
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if ((cmp(f2, f2+ size) > 0) != sense)
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break;
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length += 2;
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}
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if (length < THRESHOLD) { /* Pairwise merge */
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do {
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p2 = *EVAL(p2) = f1 + size2 - list1 + list2;
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if (sense > 0)
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swap (f1, f1 + size);
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} while ((f1 += size2) < f2);
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} else { /* Natural merge */
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l2 = f2;
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for (f2 = f1 + size2; f2 < l2; f2 += size2) {
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if ((cmp(f2-size, f2) > 0) != sense) {
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p2 = *EVAL(p2) = f2 - list1 + list2;
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if (sense > 0)
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reverse(f1, f2-size);
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f1 = f2;
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}
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}
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if (sense > 0)
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reverse (f1, f2-size);
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f1 = f2;
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if (f2 < last || cmp(f2 - size, f2) > 0)
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p2 = *EVAL(p2) = f2 - list1 + list2;
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else
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p2 = *EVAL(p2) = list2 + n*size;
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}
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}
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#else /* pairwise merge only. */
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for (f1 = list1, p2 = list2; f1 < last; f1 += size2) {
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p2 = *EVAL(p2) = p2 + size2;
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if (cmp (f1, f1 + size) > 0)
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swap(f1, f1 + size);
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}
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#endif /* NATURAL */
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}
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/*
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* This is to avoid out-of-bounds addresses in sorting the
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* last 4 elements.
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*/
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static void
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insertionsort(a, n, size, cmp)
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u_char *a;
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size_t n, size;
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int (*cmp) __P((const void *, const void *));
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{
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u_char *ai, *s, *t, *u, tmp;
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int i;
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for (ai = a+size; --n >= 1; ai += size)
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for (t = ai; t > a; t -= size) {
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u = t - size;
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if (cmp(u, t) <= 0)
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break;
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swap(u, t);
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}
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}
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