1/*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1991, 1993 5 * The Regents of the University of California. All rights reserved. 6 * Copyright (c) 2014 David T. Chisnall 7 * All rights reserved. 8 * 9 * This code is derived from software contributed to Berkeley by 10 * Ronnie Kon at Mindcraft Inc., Kevin Lew and Elmer Yglesias. 11 * 12 * Redistribution and use in source and binary forms, with or without 13 * modification, are permitted provided that the following conditions 14 * are met: 15 * 1. Redistributions of source code must retain the above copyright 16 * notice, this list of conditions and the following disclaimer. 17 * 2. Redistributions in binary form must reproduce the above copyright 18 * notice, this list of conditions and the following disclaimer in the 19 * documentation and/or other materials provided with the distribution. 20 * 3. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 */ 36 37#if defined(LIBC_SCCS) && !defined(lint) 38static char sccsid[] = "@(#)heapsort.c 8.1 (Berkeley) 6/4/93"; 39#endif /* LIBC_SCCS and not lint */ 40 41#include <errno.h> 42#include <stddef.h> 43#include <stdlib.h> 44 45#define COMPAR(x, y) compar(x, y) 46 47/* 48 * Swap two areas of size number of bytes. Although qsort(3) permits random 49 * blocks of memory to be sorted, sorting pointers is almost certainly the 50 * common case (and, were it not, could easily be made so). Regardless, it 51 * isn't worth optimizing; the SWAP's get sped up by the cache, and pointer 52 * arithmetic gets lost in the time required for comparison function calls. 53 */ 54#define SWAP(a, b, count, size, tmp) { \ 55 count = size; \ 56 do { \ 57 tmp = *a; \ 58 *a++ = *b; \ 59 *b++ = tmp; \ 60 } while (--count); \ 61} 62 63/* Copy one block of size size to another. */ 64#define COPY(a, b, count, size, tmp1, tmp2) { \ 65 count = size; \ 66 tmp1 = a; \ 67 tmp2 = b; \ 68 do { \ 69 *tmp1++ = *tmp2++; \ 70 } while (--count); \ 71} 72 73/* 74 * Build the list into a heap, where a heap is defined such that for 75 * the records K1 ... KN, Kj/2 >= Kj for 1 <= j/2 <= j <= N. 76 * 77 * There two cases. If j == nmemb, select largest of Ki and Kj. If 78 * j < nmemb, select largest of Ki, Kj and Kj+1. 79 */ 80#define CREATE(initval, nmemb, par_i, child_i, par, child, size, count, tmp) { \ 81 for (par_i = initval; (child_i = par_i * 2) <= nmemb; \ 82 par_i = child_i) { \ 83 child = base + child_i * size; \ 84 if (child_i < nmemb && COMPAR(child, child + size) < 0) { \ 85 child += size; \ 86 ++child_i; \ 87 } \ 88 par = base + par_i * size; \ 89 if (COMPAR(child, par) <= 0) \ 90 break; \ 91 SWAP(par, child, count, size, tmp); \ 92 } \ 93} 94 95/* 96 * Select the top of the heap and 'heapify'. Since by far the most expensive 97 * action is the call to the compar function, a considerable optimization 98 * in the average case can be achieved due to the fact that k, the displaced 99 * elememt, is usually quite small, so it would be preferable to first 100 * heapify, always maintaining the invariant that the larger child is copied 101 * over its parent's record. 102 * 103 * Then, starting from the *bottom* of the heap, finding k's correct place, 104 * again maintianing the invariant. As a result of the invariant no element 105 * is 'lost' when k is assigned its correct place in the heap. 106 * 107 * The time savings from this optimization are on the order of 15-20% for the 108 * average case. See Knuth, Vol. 3, page 158, problem 18. 109 * 110 * XXX Don't break the #define SELECT line, below. Reiser cpp gets upset. 111 */ 112#define SELECT(par_i, child_i, nmemb, par, child, size, k, count, tmp1, tmp2) { \ 113 for (par_i = 1; (child_i = par_i * 2) <= nmemb; par_i = child_i) { \ 114 child = base + child_i * size; \ 115 if (child_i < nmemb && COMPAR(child, child + size) < 0) { \ 116 child += size; \ 117 ++child_i; \ 118 } \ 119 par = base + par_i * size; \ 120 COPY(par, child, count, size, tmp1, tmp2); \ 121 } \ 122 for (;;) { \ 123 child_i = par_i; \ 124 par_i = child_i / 2; \ 125 child = base + child_i * size; \ 126 par = base + par_i * size; \ 127 if (child_i == 1 || COMPAR(k, par) < 0) { \ 128 COPY(child, k, count, size, tmp1, tmp2); \ 129 break; \ 130 } \ 131 COPY(child, par, count, size, tmp1, tmp2); \ 132 } \ 133} 134 135/* 136 * Heapsort -- Knuth, Vol. 3, page 145. Runs in O (N lg N), both average 137 * and worst. While heapsort is faster than the worst case of quicksort, 138 * the BSD quicksort does median selection so that the chance of finding 139 * a data set that will trigger the worst case is nonexistent. Heapsort's 140 * only advantage over quicksort is that it requires little additional memory. 141 */ 142int 143heapsort(void *vbase, size_t nmemb, size_t size, 144 int (*compar)(const void *, const void *)) 145{ 146 size_t cnt, i, j, l; 147 char tmp, *tmp1, *tmp2; 148 char *base, *k, *p, *t; 149 150 if (nmemb <= 1) 151 return (0); 152 153 if (!size) { 154 errno = EINVAL; 155 return (-1); 156 } 157 158 if ((k = malloc(size)) == NULL) 159 return (-1); 160 161 /* 162 * Items are numbered from 1 to nmemb, so offset from size bytes 163 * below the starting address. 164 */ 165 base = (char *)vbase - size; 166 167 for (l = nmemb / 2 + 1; --l;) 168 CREATE(l, nmemb, i, j, t, p, size, cnt, tmp); 169 170 /* 171 * For each element of the heap, save the largest element into its 172 * final slot, save the displaced element (k), then recreate the 173 * heap. 174 */ 175 while (nmemb > 1) { 176 COPY(k, base + nmemb * size, cnt, size, tmp1, tmp2); 177 COPY(base + nmemb * size, base + size, cnt, size, tmp1, tmp2); 178 --nmemb; 179 SELECT(i, j, nmemb, t, p, size, k, cnt, tmp1, tmp2); 180 } 181 free(k); 182 return (0); 183} 184