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