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
__weak_alias(heapsort,_heapsort)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