1 /* $NetBSD: heapsort.c,v 1.4 2025/03/02 16:35:40 riastradh 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 #undef heapsort_r
43 #endif
44
45 #include <sys/cdefs.h>
46 #if defined(LIBC_SCCS) && !defined(lint)
47 #if 0
48 static char sccsid[] = "from: @(#)heapsort.c 8.1 (Berkeley) 6/4/93";
49 #else
50 __RCSID("$NetBSD: heapsort.c,v 1.4 2025/03/02 16:35:40 riastradh Exp $");
51 #endif
52 #endif /* LIBC_SCCS and not lint */
53
54 #if defined(_KERNEL) || defined(_STANDALONE)
55 #include <sys/types.h>
56
57 #include <lib/libkern/libkern.h>
58 #else /* _KERNEL || _STANDALONE */
59 #include "namespace.h"
60 #include <sys/types.h>
61
62 #include <assert.h>
63 #include <errno.h>
64 #include <stdlib.h>
65
66 #if HAVE_NBTOOL_CONFIG_H
67 /* XXX Now, re-apply the renaming that we undid above. */
68 #define heapsort __nbcompat_heapsort
69 #define heapsort_r __nbcompat_heapsort_r
70 #endif
71
72 #ifdef __weak_alias
__weak_alias(heapsort,_heapsort)73 __weak_alias(heapsort,_heapsort)
74 __weak_alias(heapsort_r,_heapsort_r)
75 #endif
76 #endif /* _KERNEL || _STANDALONE */
77
78 /*
79 * Swap two areas of size number of bytes. Although qsort(3) permits random
80 * blocks of memory to be sorted, sorting pointers is almost certainly the
81 * common case (and, were it not, could easily be made so). Regardless, it
82 * isn't worth optimizing; the SWAP's get sped up by the cache, and pointer
83 * arithmetic gets lost in the time required for comparison function calls.
84 */
85 #define SWAP(a, b, count, size, tmp) { \
86 count = size; \
87 do { \
88 tmp = *a; \
89 *a++ = *b; \
90 *b++ = tmp; \
91 } while (--count); \
92 }
93
94 /* Copy one block of size size to another. */
95 #define COPY(a, b, count, size, tmp1, tmp2) { \
96 count = size; \
97 tmp1 = a; \
98 tmp2 = b; \
99 do { \
100 *tmp1++ = *tmp2++; \
101 } while (--count); \
102 }
103
104 /*
105 * Build the list into a heap, where a heap is defined such that for
106 * the records K1 ... KN, Kj/2 >= Kj for 1 <= j/2 <= j <= N.
107 *
108 * There are two cases. If j == nmemb, select largest of Ki and Kj. If
109 * j < nmemb, select largest of Ki, Kj and Kj+1.
110 */
111 #define CREATE(initval, nmemb, par_i, child_i, par, child, size, count, tmp) { \
112 for (par_i = initval; (child_i = par_i * 2) <= nmemb; \
113 par_i = child_i) { \
114 child = base + child_i * size; \
115 if (child_i < nmemb && \
116 compar(child, child + size, cookie) < 0) { \
117 child += size; \
118 ++child_i; \
119 } \
120 par = base + par_i * size; \
121 if (compar(child, par, cookie) <= 0) \
122 break; \
123 SWAP(par, child, count, size, tmp); \
124 } \
125 }
126
127 /*
128 * Select the top of the heap and 'heapify'. Since by far the most expensive
129 * action is the call to the compar function, a considerable optimization
130 * in the average case can be achieved due to the fact that k, the displaced
131 * element, is usually quite small, so it would be preferable to first
132 * heapify, always maintaining the invariant that the larger child is copied
133 * over its parent's record.
134 *
135 * Then, starting from the *bottom* of the heap, finding k's correct place,
136 * again maintaining the invariant. As a result of the invariant no element
137 * is 'lost' when k is assigned its correct place in the heap.
138 *
139 * The time savings from this optimization are on the order of 15-20% for the
140 * average case. See Knuth, Vol. 3, page 158, problem 18.
141 *
142 * XXX Don't break the #define SELECT line, below. Reiser cpp gets upset.
143 */
144 #define SELECT(par_i, child_i, nmemb, par, child, size, k, count, tmp1, tmp2) { \
145 for (par_i = 1; (child_i = par_i * 2) <= nmemb; par_i = child_i) { \
146 child = base + child_i * size; \
147 if (child_i < nmemb && \
148 compar(child, child + size, cookie) < 0) { \
149 child += size; \
150 ++child_i; \
151 } \
152 par = base + par_i * size; \
153 COPY(par, child, count, size, tmp1, tmp2); \
154 } \
155 for (;;) { \
156 child_i = par_i; \
157 par_i = child_i / 2; \
158 child = base + child_i * size; \
159 par = base + par_i * size; \
160 if (child_i == 1 || compar(k, par, cookie) < 0) { \
161 COPY(child, k, count, size, tmp1, tmp2); \
162 break; \
163 } \
164 COPY(child, par, count, size, tmp1, tmp2); \
165 } \
166 }
167
168 /*
169 * Heapsort -- Knuth, Vol. 3, page 145. Runs in O (N lg N), both average
170 * and worst. While heapsort is faster than the worst case of quicksort,
171 * the BSD quicksort does median selection so that the chance of finding
172 * a data set that will trigger the worst case is nonexistent. Heapsort's
173 * only advantage over quicksort is that it requires little additional memory.
174 */
175 #if defined(_KERNEL) || defined(_STANDALONE)
176 int
177 kheapsort_r(void *vbase, size_t nmemb, size_t size,
178 int (*compar)(const void *, const void *, void *), void *cookie,
179 void *k)
180 #else
181 int
182 heapsort_r(void *vbase, size_t nmemb, size_t size,
183 int (*compar)(const void *, const void *, void *), void *cookie)
184 #endif
185 {
186 size_t cnt, i, j, l;
187 char tmp, *tmp1, *tmp2;
188 char *base, *p, *t;
189 #if !defined(_KERNEL) && !defined(_STANDALONE)
190 char *k;
191 #endif
192
193 _DIAGASSERT(vbase != NULL);
194 _DIAGASSERT(compar != NULL);
195
196 if (nmemb <= 1)
197 return (0);
198
199 if (!size) {
200 #if !defined(_KERNEL) && !defined(_STANDALONE)
201 errno = EINVAL;
202 #endif
203 return (-1);
204 }
205
206 #if !defined(_KERNEL) && !defined(_STANDALONE)
207 if ((k = malloc(size)) == NULL)
208 return (-1);
209 #endif
210
211 /*
212 * Items are numbered from 1 to nmemb, so offset from size bytes
213 * below the starting address.
214 */
215 base = (char *)vbase - size;
216
217 for (l = nmemb / 2 + 1; --l;)
218 CREATE(l, nmemb, i, j, t, p, size, cnt, tmp);
219
220 /*
221 * For each element of the heap, save the largest element into its
222 * final slot, save the displaced element (k), then recreate the
223 * heap.
224 */
225 while (nmemb > 1) {
226 COPY(k, base + nmemb * size, cnt, size, tmp1, tmp2);
227 COPY(base + nmemb * size, base + size, cnt, size, tmp1, tmp2);
228 --nmemb;
229 SELECT(i, j, nmemb, t, p, size, k, cnt, tmp1, tmp2);
230 }
231 #if !defined(_KERNEL) && !defined(_STANDALONE)
232 free(k);
233 #endif
234 return (0);
235 }
236
237 static int
cmpnocookie(const void * a,const void * b,void * cookie)238 cmpnocookie(const void *a, const void *b, void *cookie)
239 {
240 int (*cmp)(const void *, const void *) = cookie;
241
242 return cmp(a, b);
243 }
244
245 int
246 #if defined(_KERNEL) || defined(_STANDALONE)
kheapsort(void * a,size_t n,size_t es,int (* cmp)(const void *,const void *),void * k)247 kheapsort(void *a, size_t n, size_t es,
248 int (*cmp)(const void *, const void *),
249 void *k)
250 #else
251 heapsort(void *a, size_t n, size_t es,
252 int (*cmp)(const void *, const void *))
253 #endif
254 {
255
256 #if defined(_KERNEL) || defined(_STANDALONE)
257 return kheapsort_r(a, n, es, cmpnocookie, cmp, k);
258 #else
259 return heapsort_r(a, n, es, cmpnocookie, cmp);
260 #endif
261 }
262