/*- * Copyright (c) 1991, 1993 * The Regents of the University of California. All rights reserved. * * This code is derived from software contributed to Berkeley by * Ronnie Kon at Mindcraft Inc., Kevin Lew and Elmer Yglesias. * * 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. * 4. 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. */ #if defined(LIBC_SCCS) && !defined(lint) static char sccsid[] = "@(#)heapsort.c 8.1 (Berkeley) 6/4/93"; #endif /* LIBC_SCCS and not lint */ #include <sys/cdefs.h> __FBSDID("$FreeBSD: src/lib/libc/stdlib/heapsort.c,v 1.6 2008/01/13 02:11:10 das Exp $"); #include <errno.h> #include <stddef.h> #include <stdlib.h> /* * Swap two areas of size number of bytes. Although qsort(3) permits random * blocks of memory to be sorted, sorting pointers is almost certainly the * common case (and, were it not, could easily be made so). Regardless, it * isn't worth optimizing; the SWAP's get sped up by the cache, and pointer * arithmetic gets lost in the time required for comparison function calls. */ #define SWAP(a, b, count, size, tmp) { \ count = size; \ do { \ tmp = *a; \ *a++ = *b; \ *b++ = tmp; \ } while (--count); \ } /* Copy one block of size size to another. */ #define COPY(a, b, count, size, tmp1, tmp2) { \ count = size; \ tmp1 = a; \ tmp2 = b; \ do { \ *tmp1++ = *tmp2++; \ } while (--count); \ } /* * Build the list into a heap, where a heap is defined such that for * the records K1 ... KN, Kj/2 >= Kj for 1 <= j/2 <= j <= N. * * There two cases. If j == nmemb, select largest of Ki and Kj. If * j < nmemb, select largest of Ki, Kj and Kj+1. */ #define CREATE(initval, nmemb, par_i, child_i, par, child, size, count, tmp) { \ for (par_i = initval; (child_i = par_i * 2) <= nmemb; \ par_i = child_i) { \ child = base + child_i * size; \ if (child_i < nmemb && compar(child, child + size) < 0) { \ child += size; \ ++child_i; \ } \ par = base + par_i * size; \ if (compar(child, par) <= 0) \ break; \ SWAP(par, child, count, size, tmp); \ } \ } /* * Select the top of the heap and 'heapify'. Since by far the most expensive * action is the call to the compar function, a considerable optimization * in the average case can be achieved due to the fact that k, the displaced * elememt, is ususally quite small, so it would be preferable to first * heapify, always maintaining the invariant that the larger child is copied * over its parent's record. * * Then, starting from the *bottom* of the heap, finding k's correct place, * again maintianing the invariant. As a result of the invariant no element * is 'lost' when k is assigned its correct place in the heap. * * The time savings from this optimization are on the order of 15-20% for the * average case. See Knuth, Vol. 3, page 158, problem 18. * * XXX Don't break the #define SELECT line, below. Reiser cpp gets upset. */ #define SELECT(par_i, child_i, nmemb, par, child, size, k, count, tmp1, tmp2) { \ for (par_i = 1; (child_i = par_i * 2) <= nmemb; par_i = child_i) { \ child = base + child_i * size; \ if (child_i < nmemb && compar(child, child + size) < 0) { \ child += size; \ ++child_i; \ } \ par = base + par_i * size; \ COPY(par, child, count, size, tmp1, tmp2); \ } \ for (;;) { \ child_i = par_i; \ par_i = child_i / 2; \ child = base + child_i * size; \ par = base + par_i * size; \ if (child_i == 1 || compar(k, par) < 0) { \ COPY(child, k, count, size, tmp1, tmp2); \ break; \ } \ COPY(child, par, count, size, tmp1, tmp2); \ } \ } /* * Heapsort -- Knuth, Vol. 3, page 145. Runs in O (N lg N), both average * and worst. While heapsort is faster than the worst case of quicksort, * the BSD quicksort does median selection so that the chance of finding * a data set that will trigger the worst case is nonexistent. Heapsort's * only advantage over quicksort is that it requires little additional memory. */ int heapsort(vbase, nmemb, size, compar) void *vbase; size_t nmemb, size; int (*compar)(const void *, const void *); { size_t cnt, i, j, l; char tmp, *tmp1, *tmp2; char *base, *k, *p, *t; if (nmemb <= 1) return (0); if (!size) { errno = EINVAL; return (-1); } if ((k = malloc(size)) == NULL) return (-1); /* * Items are numbered from 1 to nmemb, so offset from size bytes * below the starting address. */ base = (char *)vbase - size; for (l = nmemb / 2 + 1; --l;) CREATE(l, nmemb, i, j, t, p, size, cnt, tmp); /* * For each element of the heap, save the largest element into its * final slot, save the displaced element (k), then recreate the * heap. */ while (nmemb > 1) { COPY(k, base + nmemb * size, cnt, size, tmp1, tmp2); COPY(base + nmemb * size, base + size, cnt, size, tmp1, tmp2); --nmemb; SELECT(i, j, nmemb, t, p, size, k, cnt, tmp1, tmp2); } free(k); return (0); }