| 1 | /* $NetBSD: heapsort.c,v 1.3 2008/11/17 10:21:30 jnemeth Exp $ */ |
| 2 | |
| 3 | /*- |
| 4 | * Copyright (c) 1991, 1993 |
| 5 | * The Regents of the University of California. All rights reserved. |
| 6 | * |
| 7 | * This code is derived from software contributed to Berkeley by |
| 8 | * Ronnie Kon at Mindcraft Inc., Kevin Lew and Elmer Yglesias. |
| 9 | * |
| 10 | * Redistribution and use in source and binary forms, with or without |
| 11 | * modification, are permitted provided that the following conditions |
| 12 | * are met: |
| 13 | * 1. Redistributions of source code must retain the above copyright |
| 14 | * notice, this list of conditions and the following disclaimer. |
| 15 | * 2. Redistributions in binary form must reproduce the above copyright |
| 16 | * notice, this list of conditions and the following disclaimer in the |
| 17 | * documentation and/or other materials provided with the distribution. |
| 18 | * 3. Neither the name of the University nor the names of its contributors |
| 19 | * may be used to endorse or promote products derived from this software |
| 20 | * without specific prior written permission. |
| 21 | * |
| 22 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND |
| 23 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| 24 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| 25 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE |
| 26 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| 27 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| 28 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| 29 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| 30 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| 31 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| 32 | * SUCH DAMAGE. |
| 33 | */ |
| 34 | |
| 35 | #if HAVE_NBTOOL_CONFIG_H |
| 36 | #include "nbtool_config.h" |
| 37 | /* |
| 38 | * XXX Undefine the renames of these functions so that we don't |
| 39 | * XXX rename the versions found in the host's headers by mistake! |
| 40 | */ |
| 41 | #undef heapsort |
| 42 | #endif |
| 43 | |
| 44 | #include <sys/cdefs.h> |
| 45 | #if defined(LIBC_SCCS) && !defined(lint) |
| 46 | #if 0 |
| 47 | static char sccsid[] = "from: @(#)heapsort.c 8.1 (Berkeley) 6/4/93" ; |
| 48 | #else |
| 49 | __RCSID("$NetBSD: heapsort.c,v 1.3 2008/11/17 10:21:30 jnemeth Exp $" ); |
| 50 | #endif |
| 51 | #endif /* LIBC_SCCS and not lint */ |
| 52 | |
| 53 | #if defined(_KERNEL) || defined(_STANDALONE) |
| 54 | #include <sys/types.h> |
| 55 | |
| 56 | #include <lib/libkern/libkern.h> |
| 57 | #else /* _KERNEL || _STANDALONE */ |
| 58 | #include "namespace.h" |
| 59 | #include <sys/types.h> |
| 60 | |
| 61 | #include <assert.h> |
| 62 | #include <errno.h> |
| 63 | #include <stdlib.h> |
| 64 | |
| 65 | #if HAVE_NBTOOL_CONFIG_H |
| 66 | /* XXX Now, re-apply the renaming that we undid above. */ |
| 67 | #define heapsort __nbcompat_heapsort |
| 68 | #endif |
| 69 | |
| 70 | #ifdef __weak_alias |
| 71 | __weak_alias(heapsort,_heapsort) |
| 72 | #endif |
| 73 | #endif /* _KERNEL || _STANDALONE */ |
| 74 | |
| 75 | /* |
| 76 | * Swap two areas of size number of bytes. Although qsort(3) permits random |
| 77 | * blocks of memory to be sorted, sorting pointers is almost certainly the |
| 78 | * common case (and, were it not, could easily be made so). Regardless, it |
| 79 | * isn't worth optimizing; the SWAP's get sped up by the cache, and pointer |
| 80 | * arithmetic gets lost in the time required for comparison function calls. |
| 81 | */ |
| 82 | #define SWAP(a, b, count, size, tmp) { \ |
| 83 | count = size; \ |
| 84 | do { \ |
| 85 | tmp = *a; \ |
| 86 | *a++ = *b; \ |
| 87 | *b++ = tmp; \ |
| 88 | } while (--count); \ |
| 89 | } |
| 90 | |
| 91 | /* Copy one block of size size to another. */ |
| 92 | #define COPY(a, b, count, size, tmp1, tmp2) { \ |
| 93 | count = size; \ |
| 94 | tmp1 = a; \ |
| 95 | tmp2 = b; \ |
| 96 | do { \ |
| 97 | *tmp1++ = *tmp2++; \ |
| 98 | } while (--count); \ |
| 99 | } |
| 100 | |
| 101 | /* |
| 102 | * Build the list into a heap, where a heap is defined such that for |
| 103 | * the records K1 ... KN, Kj/2 >= Kj for 1 <= j/2 <= j <= N. |
| 104 | * |
| 105 | * There are two cases. If j == nmemb, select largest of Ki and Kj. If |
| 106 | * j < nmemb, select largest of Ki, Kj and Kj+1. |
| 107 | */ |
| 108 | #define CREATE(initval, nmemb, par_i, child_i, par, child, size, count, tmp) { \ |
| 109 | for (par_i = initval; (child_i = par_i * 2) <= nmemb; \ |
| 110 | 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 | if (compar(child, par) <= 0) \ |
| 118 | break; \ |
| 119 | SWAP(par, child, count, size, tmp); \ |
| 120 | } \ |
| 121 | } |
| 122 | |
| 123 | /* |
| 124 | * Select the top of the heap and 'heapify'. Since by far the most expensive |
| 125 | * action is the call to the compar function, a considerable optimization |
| 126 | * in the average case can be achieved due to the fact that k, the displaced |
| 127 | * element, is usually quite small, so it would be preferable to first |
| 128 | * heapify, always maintaining the invariant that the larger child is copied |
| 129 | * over its parent's record. |
| 130 | * |
| 131 | * Then, starting from the *bottom* of the heap, finding k's correct place, |
| 132 | * again maintaining the invariant. As a result of the invariant no element |
| 133 | * is 'lost' when k is assigned its correct place in the heap. |
| 134 | * |
| 135 | * The time savings from this optimization are on the order of 15-20% for the |
| 136 | * average case. See Knuth, Vol. 3, page 158, problem 18. |
| 137 | * |
| 138 | * XXX Don't break the #define SELECT line, below. Reiser cpp gets upset. |
| 139 | */ |
| 140 | #define SELECT(par_i, child_i, nmemb, par, child, size, k, count, tmp1, tmp2) { \ |
| 141 | for (par_i = 1; (child_i = par_i * 2) <= nmemb; par_i = child_i) { \ |
| 142 | child = base + child_i * size; \ |
| 143 | if (child_i < nmemb && compar(child, child + size) < 0) { \ |
| 144 | child += size; \ |
| 145 | ++child_i; \ |
| 146 | } \ |
| 147 | par = base + par_i * size; \ |
| 148 | COPY(par, child, count, size, tmp1, tmp2); \ |
| 149 | } \ |
| 150 | for (;;) { \ |
| 151 | child_i = par_i; \ |
| 152 | par_i = child_i / 2; \ |
| 153 | child = base + child_i * size; \ |
| 154 | par = base + par_i * size; \ |
| 155 | if (child_i == 1 || compar(k, par) < 0) { \ |
| 156 | COPY(child, k, count, size, tmp1, tmp2); \ |
| 157 | break; \ |
| 158 | } \ |
| 159 | COPY(child, par, count, size, tmp1, tmp2); \ |
| 160 | } \ |
| 161 | } |
| 162 | |
| 163 | /* |
| 164 | * Heapsort -- Knuth, Vol. 3, page 145. Runs in O (N lg N), both average |
| 165 | * and worst. While heapsort is faster than the worst case of quicksort, |
| 166 | * the BSD quicksort does median selection so that the chance of finding |
| 167 | * a data set that will trigger the worst case is nonexistent. Heapsort's |
| 168 | * only advantage over quicksort is that it requires little additional memory. |
| 169 | */ |
| 170 | #if defined(_KERNEL) || defined(_STANDALONE) |
| 171 | int |
| 172 | kheapsort(void *vbase, size_t nmemb, size_t size, |
| 173 | int (*compar)(const void *, const void *), void *k) |
| 174 | #else |
| 175 | int |
| 176 | heapsort(void *vbase, size_t nmemb, size_t size, |
| 177 | int (*compar)(const void *, const void *)) |
| 178 | #endif |
| 179 | { |
| 180 | size_t cnt, i, j, l; |
| 181 | char tmp, *tmp1, *tmp2; |
| 182 | char *base, *p, *t; |
| 183 | #if !defined(_KERNEL) && !defined(_STANDALONE) |
| 184 | char *k; |
| 185 | #endif |
| 186 | |
| 187 | _DIAGASSERT(vbase != NULL); |
| 188 | _DIAGASSERT(compar != NULL); |
| 189 | |
| 190 | if (nmemb <= 1) |
| 191 | return (0); |
| 192 | |
| 193 | if (!size) { |
| 194 | #if !defined(_KERNEL) && !defined(_STANDALONE) |
| 195 | errno = EINVAL; |
| 196 | #endif |
| 197 | return (-1); |
| 198 | } |
| 199 | |
| 200 | #if !defined(_KERNEL) && !defined(_STANDALONE) |
| 201 | if ((k = malloc(size)) == NULL) |
| 202 | return (-1); |
| 203 | #endif |
| 204 | |
| 205 | /* |
| 206 | * Items are numbered from 1 to nmemb, so offset from size bytes |
| 207 | * below the starting address. |
| 208 | */ |
| 209 | base = (char *)vbase - size; |
| 210 | |
| 211 | for (l = nmemb / 2 + 1; --l;) |
| 212 | CREATE(l, nmemb, i, j, t, p, size, cnt, tmp); |
| 213 | |
| 214 | /* |
| 215 | * For each element of the heap, save the largest element into its |
| 216 | * final slot, save the displaced element (k), then recreate the |
| 217 | * heap. |
| 218 | */ |
| 219 | while (nmemb > 1) { |
| 220 | COPY(k, base + nmemb * size, cnt, size, tmp1, tmp2); |
| 221 | COPY(base + nmemb * size, base + size, cnt, size, tmp1, tmp2); |
| 222 | --nmemb; |
| 223 | SELECT(i, j, nmemb, t, p, size, k, cnt, tmp1, tmp2); |
| 224 | } |
| 225 | #if !defined(_KERNEL) && !defined(_STANDALONE) |
| 226 | free(k); |
| 227 | #endif |
| 228 | return (0); |
| 229 | } |
| 230 | |