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394d998315
At least in neovim, `│vi:` is not recognized as a modeline because it has no preceding whitespace. After fixing this, opening a file yields an error because `net` is not an option. (`noet`, however, is.)
198 lines
7.7 KiB
C
198 lines
7.7 KiB
C
/*-*- mode:c;indent-tabs-mode:t;c-basic-offset:8;tab-width:8;coding:utf-8 -*-│
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│ vi: set et ft=c ts=8 tw=8 fenc=utf-8 :vi │
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright (c) 1991, 1993 │
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│ The Regents of the University of California. 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. 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 "libc/mem/alg.h"
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#include "libc/mem/mem.h"
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#include "libc/sysv/errfuns.h"
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// clang-format off
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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, count, size, tmp) { \
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count = size; \
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do { \
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tmp = *a; \
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*a++ = *b; \
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*b++ = tmp; \
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} while (--count); \
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}
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/* Copy one block of size size to another. */
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#define COPY(a, b, count, size, tmp1, tmp2) { \
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count = size; \
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tmp1 = a; \
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tmp2 = b; \
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do { \
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*tmp1++ = *tmp2++; \
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} while (--count); \
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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 are 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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#define CREATE(initval, nmemb, par_i, child_i, par, child, size, count, tmp) { \
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for (par_i = initval; (child_i = par_i * 2) <= nmemb; \
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par_i = child_i) { \
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child = base + child_i * size; \
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if (child_i < nmemb && compar(child, child + size, z) < 0) { \
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child += size; \
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++child_i; \
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} \
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par = base + par_i * size; \
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if (compar(child, par, z) <= 0) \
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break; \
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SWAP(par, child, count, size, tmp); \
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} \
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}
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/*
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* Select the top of the heap and 'heapify'. Since by far the most expensive
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* action is the call to the compar function, a considerable optimization
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* in the average case can be achieved due to the fact that k, the displaced
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* element, is usually quite small, so it would be preferable to first
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* heapify, always maintaining the invariant that the larger child is copied
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* over its parent's record.
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*
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* Then, starting from the *bottom* of the heap, finding k's correct place,
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* again maintaining the invariant. As a result of the invariant no element
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* is 'lost' when k is assigned its correct place in the heap.
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*
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* The time savings from this optimization are on the order of 15-20% for the
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* average case. See Knuth, Vol. 3, page 158, problem 18.
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*
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* XXX Don't break the #define SELECT line, below. Reiser cpp gets upset.
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*/
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#define SELECT(par_i, child_i, nmemb, par, child, size, k, count, tmp1, tmp2) { \
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for (par_i = 1; (child_i = par_i * 2) <= nmemb; par_i = child_i) { \
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child = base + child_i * size; \
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if (child_i < nmemb && compar(child, child + size, z) < 0) { \
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child += size; \
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++child_i; \
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} \
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par = base + par_i * size; \
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COPY(par, child, count, size, tmp1, tmp2); \
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} \
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for (;;) { \
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child_i = par_i; \
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par_i = child_i / 2; \
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child = base + child_i * size; \
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par = base + par_i * size; \
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if (child_i == 1 || compar(k, par, z) < 0) { \
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COPY(child, k, count, size, tmp1, tmp2); \
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break; \
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} \
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COPY(child, par, count, size, tmp1, tmp2); \
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} \
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}
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/**
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* Sorts array w/ optional callback argument.
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*
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* @param vbase is base of array
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* @param nmemb is item count
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* @param size is item width
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* @param compar is a callback returning <0, 0, or >0
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* @param z will optionally be passed as the third argument to cmp
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* @see heapsort()
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*/
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int
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heapsort_r(void *vbase, size_t nmemb, size_t size,
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int (*compar)(const void *, const void *, void *), void *z)
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{
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size_t cnt, i, j, l;
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char tmp, *tmp1, *tmp2;
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char *base, *k, *p, *t;
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if (nmemb <= 1)
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return (0);
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if (!size)
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return (einval());
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if ((k = malloc(size)) == NULL)
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return (-1);
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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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base = (char *)vbase - size;
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for (l = nmemb / 2 + 1; --l;)
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CREATE(l, nmemb, i, j, t, p, size, cnt, tmp);
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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, save the displaced element (k), then recreate the
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* heap.
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*/
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while (nmemb > 1) {
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COPY(k, base + nmemb * size, cnt, size, tmp1, tmp2);
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COPY(base + nmemb * size, base + size, cnt, size, tmp1, tmp2);
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--nmemb;
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SELECT(i, j, nmemb, t, p, size, k, cnt, tmp1, tmp2);
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}
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free(k);
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return (0);
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}
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/**
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* Sorts array.
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*
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* Runs in O (N lg N), both average and worst. While heapsort is faster
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* than the worst case of quicksort, the BSD quicksort does median
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* selection so that the chance of finding a data set that will trigger
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* the worst case is nonexistent. Heapsort's only advantage over
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* quicksort is that it requires little additional memory.
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*
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* @param vbase is base of array
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* @param nmemb is item count
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* @param size is item width
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* @param compar is a callback returning <0, 0, or >0
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* @see Knuth, Vol. 3, page 145.
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* @see heapsort_r()
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* @see mergesort()
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* @see qsort()
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*/
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int
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heapsort(void *vbase, size_t nmemb, size_t size,
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int (*compar)(const void *, const void *))
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{
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return heapsort_r(vbase, nmemb, size, (void *)compar, 0);
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}
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