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