1 /*- 2 * Copyright (c) 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Ronnie Kon at Mindcraft Inc., Kevin Lew and Elmer Yglesias. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. 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 41 #include <errno.h> 42 #include <stdlib.h> 43 44 /* 45 * Swap two areas of size number of bytes. Although qsort(3) permits random 46 * blocks of memory to be sorted, sorting pointers is almost certainly the 47 * common case (and, were it not, could easily be made so). Regardless, it 48 * isn't worth optimizing; the SWAP's get sped up by the cache, and pointer 49 * arithmetic gets lost in the time required for comparison function calls. 50 */ 51 #define SWAP(a, b, count, size, tmp) { \ 52 count = size; \ 53 do { \ 54 tmp = *a; \ 55 *a++ = *b; \ 56 *b++ = tmp; \ 57 } while (--count); \ 58 } 59 60 /* Copy one block of size size to another. */ 61 #define COPY(a, b, count, size, tmp1, tmp2) { \ 62 count = size; \ 63 tmp1 = a; \ 64 tmp2 = b; \ 65 do { \ 66 *tmp1++ = *tmp2++; \ 67 } while (--count); \ 68 } 69 70 /* 71 * Build the list into a heap, where a heap is defined such that for 72 * the records K1 ... KN, Kj/2 >= Kj for 1 <= j/2 <= j <= N. 73 * 74 * There two cases. If j == nmemb, select largest of Ki and Kj. If 75 * j < nmemb, select largest of Ki, Kj and Kj+1. 76 */ 77 #define CREATE(initval, nmemb, par_i, child_i, par, child, size, count, tmp) { \ 78 for (par_i = initval; (child_i = par_i * 2) <= nmemb; \ 79 par_i = child_i) { \ 80 child = base + child_i * size; \ 81 if (child_i < nmemb && compar(child, child + size) < 0) { \ 82 child += size; \ 83 ++child_i; \ 84 } \ 85 par = base + par_i * size; \ 86 if (compar(child, par) <= 0) \ 87 break; \ 88 SWAP(par, child, count, size, tmp); \ 89 } \ 90 } 91 92 /* 93 * Select the top of the heap and 'heapify'. Since by far the most expensive 94 * action is the call to the compar function, a considerable optimization 95 * in the average case can be achieved due to the fact that k, the displaced 96 * elememt, is ususally quite small, so it would be preferable to first 97 * heapify, always maintaining the invariant that the larger child is copied 98 * over its parent's record. 99 * 100 * Then, starting from the *bottom* of the heap, finding k's correct place, 101 * again maintianing the invariant. As a result of the invariant no element 102 * is 'lost' when k is assigned its correct place in the heap. 103 * 104 * The time savings from this optimization are on the order of 15-20% for the 105 * average case. See Knuth, Vol. 3, page 158, problem 18. 106 * 107 * XXX Don't break the #define SELECT line, below. Reiser cpp gets upset. 108 */ 109 #define SELECT(par_i, child_i, nmemb, par, child, size, k, count, tmp1, tmp2) { \ 110 for (par_i = 1; (child_i = par_i * 2) <= nmemb; par_i = child_i) { \ 111 child = base + child_i * size; \ 112 if (child_i < nmemb && compar(child, child + size) < 0) { \ 113 child += size; \ 114 ++child_i; \ 115 } \ 116 par = base + par_i * size; \ 117 COPY(par, child, count, size, tmp1, tmp2); \ 118 } \ 119 for (;;) { \ 120 child_i = par_i; \ 121 par_i = child_i / 2; \ 122 child = base + child_i * size; \ 123 par = base + par_i * size; \ 124 if (child_i == 1 || compar(k, par) < 0) { \ 125 COPY(child, k, count, size, tmp1, tmp2); \ 126 break; \ 127 } \ 128 COPY(child, par, count, size, tmp1, tmp2); \ 129 } \ 130 } 131 132 /* 133 * Heapsort -- Knuth, Vol. 3, page 145. Runs in O (N lg N), both average 134 * and worst. While heapsort is faster than the worst case of quicksort, 135 * the BSD quicksort does median selection so that the chance of finding 136 * a data set that will trigger the worst case is nonexistent. Heapsort's 137 * only advantage over quicksort is that it requires little additional memory. 138 */ 139 int 140 heapsort(void *vbase, size_t nmemb, size_t size, int (*compar)(void const *, void const *)) 141 { 142 size_t cnt; 143 size_t i; 144 size_t j; 145 size_t l; 146 char tmp; 147 char *tmp1; 148 char *tmp2; 149 char *base; 150 char *k; 151 char *p; 152 char *t; 153 154 if (nmemb <= 1) { 155 return (0); 156 } 157 158 if (!size) { 159 // errno = EINVAL; 160 return (-1); 161 } 162 163 if ((k = malloc(size)) == NULL) { 164 return (-1); 165 } 166 167 /* 168 * Items are numbered from 1 to nmemb, so offset from size bytes 169 * below the starting address. 170 */ 171 base = (char *)vbase - size; 172 173 for (l = nmemb / 2 + 1; --l;) 174 CREATE(l, nmemb, i, j, t, p, size, cnt, tmp); 175 176 /* 177 * For each element of the heap, save the largest element into its 178 * final slot, save the displaced element (k), then recreate the 179 * heap. 180 */ 181 while (nmemb > 1) { 182 COPY(k, base + nmemb * size, cnt, size, tmp1, tmp2); 183 COPY(base + nmemb * size, base + size, cnt, size, tmp1, tmp2); 184 --nmemb; 185 SELECT(i, j, nmemb, t, p, size, k, cnt, tmp1, tmp2); 186 } 187 free(k); 188 return (0); 189 } 190