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) 38 static char sccsid[] = "@(#)heapsort.c 8.1 (Berkeley) 6/4/93"; 39 #endif /* LIBC_SCCS and not lint */ 40 #include <sys/cdefs.h> 41 __FBSDID("$FreeBSD$"); 42 43 #include <errno.h> 44 #include <stddef.h> 45 #include <stdlib.h> 46 47 #ifdef I_AM_HEAPSORT_B 48 #include "block_abi.h" 49 #define COMPAR(x, y) CALL_BLOCK(compar, x, y) 50 typedef DECLARE_BLOCK(int, heapsort_block, const void *, const void *); 51 #else 52 #define COMPAR(x, y) compar(x, y) 53 #endif 54 55 /* 56 * Swap two areas of size number of bytes. Although qsort(3) permits random 57 * blocks of memory to be sorted, sorting pointers is almost certainly the 58 * common case (and, were it not, could easily be made so). Regardless, it 59 * isn't worth optimizing; the SWAP's get sped up by the cache, and pointer 60 * arithmetic gets lost in the time required for comparison function calls. 61 */ 62 #define SWAP(a, b, count, size, tmp) { \ 63 count = size; \ 64 do { \ 65 tmp = *a; \ 66 *a++ = *b; \ 67 *b++ = tmp; \ 68 } while (--count); \ 69 } 70 71 /* Copy one block of size size to another. */ 72 #define COPY(a, b, count, size, tmp1, tmp2) { \ 73 count = size; \ 74 tmp1 = a; \ 75 tmp2 = b; \ 76 do { \ 77 *tmp1++ = *tmp2++; \ 78 } while (--count); \ 79 } 80 81 /* 82 * Build the list into a heap, where a heap is defined such that for 83 * the records K1 ... KN, Kj/2 >= Kj for 1 <= j/2 <= j <= N. 84 * 85 * There two cases. If j == nmemb, select largest of Ki and Kj. If 86 * j < nmemb, select largest of Ki, Kj and Kj+1. 87 */ 88 #define CREATE(initval, nmemb, par_i, child_i, par, child, size, count, tmp) { \ 89 for (par_i = initval; (child_i = par_i * 2) <= nmemb; \ 90 par_i = child_i) { \ 91 child = base + child_i * size; \ 92 if (child_i < nmemb && COMPAR(child, child + size) < 0) { \ 93 child += size; \ 94 ++child_i; \ 95 } \ 96 par = base + par_i * size; \ 97 if (COMPAR(child, par) <= 0) \ 98 break; \ 99 SWAP(par, child, count, size, tmp); \ 100 } \ 101 } 102 103 /* 104 * Select the top of the heap and 'heapify'. Since by far the most expensive 105 * action is the call to the compar function, a considerable optimization 106 * in the average case can be achieved due to the fact that k, the displaced 107 * elememt, is usually quite small, so it would be preferable to first 108 * heapify, always maintaining the invariant that the larger child is copied 109 * over its parent's record. 110 * 111 * Then, starting from the *bottom* of the heap, finding k's correct place, 112 * again maintianing the invariant. As a result of the invariant no element 113 * is 'lost' when k is assigned its correct place in the heap. 114 * 115 * The time savings from this optimization are on the order of 15-20% for the 116 * average case. See Knuth, Vol. 3, page 158, problem 18. 117 * 118 * XXX Don't break the #define SELECT line, below. Reiser cpp gets upset. 119 */ 120 #define SELECT(par_i, child_i, nmemb, par, child, size, k, count, tmp1, tmp2) { \ 121 for (par_i = 1; (child_i = par_i * 2) <= nmemb; par_i = child_i) { \ 122 child = base + child_i * size; \ 123 if (child_i < nmemb && COMPAR(child, child + size) < 0) { \ 124 child += size; \ 125 ++child_i; \ 126 } \ 127 par = base + par_i * size; \ 128 COPY(par, child, count, size, tmp1, tmp2); \ 129 } \ 130 for (;;) { \ 131 child_i = par_i; \ 132 par_i = child_i / 2; \ 133 child = base + child_i * size; \ 134 par = base + par_i * size; \ 135 if (child_i == 1 || COMPAR(k, par) < 0) { \ 136 COPY(child, k, count, size, tmp1, tmp2); \ 137 break; \ 138 } \ 139 COPY(child, par, count, size, tmp1, tmp2); \ 140 } \ 141 } 142 143 #ifdef I_AM_HEAPSORT_B 144 int heapsort_b(void *, size_t, size_t, heapsort_block); 145 #else 146 int heapsort(void *, size_t, size_t, 147 int (*)(const void *, const void *)); 148 #endif 149 /* 150 * Heapsort -- Knuth, Vol. 3, page 145. Runs in O (N lg N), both average 151 * and worst. While heapsort is faster than the worst case of quicksort, 152 * the BSD quicksort does median selection so that the chance of finding 153 * a data set that will trigger the worst case is nonexistent. Heapsort's 154 * only advantage over quicksort is that it requires little additional memory. 155 */ 156 #ifdef I_AM_HEAPSORT_B 157 int 158 heapsort_b(void *vbase, size_t nmemb, size_t size, heapsort_block compar) 159 #else 160 int 161 heapsort(void *vbase, size_t nmemb, size_t size, 162 int (*compar)(const void *, const void *)) 163 #endif 164 { 165 size_t cnt, i, j, l; 166 char tmp, *tmp1, *tmp2; 167 char *base, *k, *p, *t; 168 169 if (nmemb <= 1) 170 return (0); 171 172 if (!size) { 173 errno = EINVAL; 174 return (-1); 175 } 176 177 if ((k = malloc(size)) == NULL) 178 return (-1); 179 180 /* 181 * Items are numbered from 1 to nmemb, so offset from size bytes 182 * below the starting address. 183 */ 184 base = (char *)vbase - size; 185 186 for (l = nmemb / 2 + 1; --l;) 187 CREATE(l, nmemb, i, j, t, p, size, cnt, tmp); 188 189 /* 190 * For each element of the heap, save the largest element into its 191 * final slot, save the displaced element (k), then recreate the 192 * heap. 193 */ 194 while (nmemb > 1) { 195 COPY(k, base + nmemb * size, cnt, size, tmp1, tmp2); 196 COPY(base + nmemb * size, base + size, cnt, size, tmp1, tmp2); 197 --nmemb; 198 SELECT(i, j, nmemb, t, p, size, k, cnt, tmp1, tmp2); 199 } 200 free(k); 201 return (0); 202 } 203