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 * $DragonFly: src/lib/libc/stdlib/heapsort.c,v 1.4 2003/09/06 08:19:16 asmodai Exp $ 37 * 38 * @(#)heapsort.c 8.1 (Berkeley) 6/4/93 39 */ 40 41 #include <errno.h> 42 #include <stddef.h> 43 #include <stdlib.h> 44 45 /* 46 * Swap two areas of size number of bytes. Although qsort(3) permits random 47 * blocks of memory to be sorted, sorting pointers is almost certainly the 48 * common case (and, were it not, could easily be made so). Regardless, it 49 * isn't worth optimizing; the SWAP's get sped up by the cache, and pointer 50 * arithmetic gets lost in the time required for comparison function calls. 51 */ 52 #define SWAP(a, b, count, size, tmp) { \ 53 count = size; \ 54 do { \ 55 tmp = *a; \ 56 *a++ = *b; \ 57 *b++ = tmp; \ 58 } while (--count); \ 59 } 60 61 /* Copy one block of size size to another. */ 62 #define COPY(a, b, count, size, tmp1, tmp2) { \ 63 count = size; \ 64 tmp1 = a; \ 65 tmp2 = b; \ 66 do { \ 67 *tmp1++ = *tmp2++; \ 68 } while (--count); \ 69 } 70 71 /* 72 * Build the list into a heap, where a heap is defined such that for 73 * the records K1 ... KN, Kj/2 >= Kj for 1 <= j/2 <= j <= N. 74 * 75 * There two cases. If j == nmemb, select largest of Ki and Kj. If 76 * j < nmemb, select largest of Ki, Kj and Kj+1. 77 */ 78 #define CREATE(initval, nmemb, par_i, child_i, par, child, size, count, tmp) { \ 79 for (par_i = initval; (child_i = par_i * 2) <= nmemb; \ 80 par_i = child_i) { \ 81 child = base + child_i * size; \ 82 if (child_i < nmemb && compar(child, child + size) < 0) { \ 83 child += size; \ 84 ++child_i; \ 85 } \ 86 par = base + par_i * size; \ 87 if (compar(child, par) <= 0) \ 88 break; \ 89 SWAP(par, child, count, size, tmp); \ 90 } \ 91 } 92 93 /* 94 * Select the top of the heap and 'heapify'. Since by far the most expensive 95 * action is the call to the compar function, a considerable optimization 96 * in the average case can be achieved due to the fact that k, the displaced 97 * elememt, is ususally quite small, so it would be preferable to first 98 * heapify, always maintaining the invariant that the larger child is copied 99 * over its parent's record. 100 * 101 * Then, starting from the *bottom* of the heap, finding k's correct place, 102 * again maintianing the invariant. As a result of the invariant no element 103 * is 'lost' when k is assigned its correct place in the heap. 104 * 105 * The time savings from this optimization are on the order of 15-20% for the 106 * average case. See Knuth, Vol. 3, page 158, problem 18. 107 * 108 * XXX Don't break the #define SELECT line, below. Reiser cpp gets upset. 109 */ 110 #define SELECT(par_i, child_i, nmemb, par, child, size, k, count, tmp1, tmp2) { \ 111 for (par_i = 1; (child_i = par_i * 2) <= nmemb; par_i = child_i) { \ 112 child = base + child_i * size; \ 113 if (child_i < nmemb && compar(child, child + size) < 0) { \ 114 child += size; \ 115 ++child_i; \ 116 } \ 117 par = base + par_i * size; \ 118 COPY(par, child, count, size, tmp1, tmp2); \ 119 } \ 120 for (;;) { \ 121 child_i = par_i; \ 122 par_i = child_i / 2; \ 123 child = base + child_i * size; \ 124 par = base + par_i * size; \ 125 if (child_i == 1 || compar(k, par) < 0) { \ 126 COPY(child, k, count, size, tmp1, tmp2); \ 127 break; \ 128 } \ 129 COPY(child, par, count, size, tmp1, tmp2); \ 130 } \ 131 } 132 133 /* 134 * Heapsort -- Knuth, Vol. 3, page 145. Runs in O (N lg N), both average 135 * and worst. While heapsort is faster than the worst case of quicksort, 136 * the BSD quicksort does median selection so that the chance of finding 137 * a data set that will trigger the worst case is nonexistent. Heapsort's 138 * only advantage over quicksort is that it requires little additional memory. 139 */ 140 int 141 heapsort(vbase, nmemb, size, compar) 142 void *vbase; 143 size_t nmemb, size; 144 int (*compar) (const void *, const void *); 145 { 146 int 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