127 lines
4.3 KiB
C
127 lines
4.3 KiB
C
/*-
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* Copyright (c) 1991 The Regents of the University of California.
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* All rights reserved.
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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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#if defined(LIBC_SCCS) && !defined(lint)
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/*static char *sccsid = "from: @(#)heapsort.c 5.1 (Berkeley) 6/4/91";*/
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static char *rcsid = "$Id: heapsort.c,v 1.3 1993/08/26 00:48:00 jtc Exp $";
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#endif /* LIBC_SCCS and not lint */
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#include <sys/cdefs.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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/*
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* Swap two areas of size number of bytes. Although qsort(3) permits random
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* blocks of memory to be sorted, sorting pointers is almost certainly the
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* common case (and, were it not, could easily be made so). Regardless, it
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* isn't worth optimizing; the SWAP's get sped up by the cache, and pointer
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* arithmetic gets lost in the time required for comparison function calls.
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*/
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#define SWAP(a, b) { \
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cnt = size; \
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do { \
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ch = *a; \
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*a++ = *b; \
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*b++ = ch; \
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} while (--cnt); \
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}
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/*
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* Build the list into a heap, where a heap is defined such that for
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* the records K1 ... KN, Kj/2 >= Kj for 1 <= j/2 <= j <= N.
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*
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* There two cases. If j == nmemb, select largest of Ki and Kj. If
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* j < nmemb, select largest of Ki, Kj and Kj+1.
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*
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* The initial value depends on if we're building the initial heap or
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* reconstructing it after saving a value.
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*/
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#define HEAP(initval) { \
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for (i = initval; (j = i * 2) <= nmemb; i = j) { \
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p = (char *)bot + j * size; \
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if (j < nmemb && compar(p, p + size) < 0) { \
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p += size; \
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++j; \
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} \
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t = (char *)bot + i * size; \
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if (compar(p, t) <= 0) \
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break; \
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SWAP(t, p); \
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} \
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}
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/*
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* Heapsort -- Knuth, Vol. 3, page 145. Runs in O (N lg N), both average
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* and worst. While heapsort is faster than the worst case of quicksort,
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* the BSD quicksort does median selection so that the chance of finding
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* a data set that will trigger the worst case is nonexistent. Heapsort's
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* only advantage over quicksort is that it requires no additional memory.
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*/
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heapsort(bot, nmemb, size, compar)
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register void *bot;
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register size_t nmemb, size;
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int (*compar) __P((const void *, const void *));
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{
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register char *p, *t, ch;
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register int cnt, i, j, l;
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if (nmemb <= 1)
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return (0);
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if (!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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* Items are numbered from 1 to nmemb, so offset from size bytes
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* below the starting address.
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*/
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bot -= size;
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for (l = nmemb / 2 + 1; --l;)
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HEAP(l);
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/*
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* For each element of the heap, save the largest element into its
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* final slot, then recreate the heap.
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*/
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while (nmemb > 1) {
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p = (char *)bot + size;
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t = (char *)bot + nmemb * size;
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SWAP(p, t);
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--nmemb;
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HEAP(1);
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}
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return (0);
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}
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