1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1991, 1993
5 * The Regents of the University of California. All rights reserved.
6 * Copyright (c) 2014 David T. Chisnall
7 * All rights reserved.
8 *
9 * This code is derived from software contributed to Berkeley by
10 * Ronnie Kon at Mindcraft Inc., Kevin Lew and Elmer Yglesias.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 3. 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 #include <sys/cdefs.h>
41 #include <errno.h>
42 #include <stddef.h>
43 #include <stdlib.h>
44
45 #ifdef I_AM_HEAPSORT_B
46 #include "block_abi.h"
47 #define COMPAR(x, y) CALL_BLOCK(compar, x, y)
48 typedef DECLARE_BLOCK(int, heapsort_block, const void *, const void *);
49 #else
50 #define COMPAR(x, y) compar(x, y)
51 #endif
52
53 /*
54 * Swap two areas of size number of bytes. Although qsort(3) permits random
55 * blocks of memory to be sorted, sorting pointers is almost certainly the
56 * common case (and, were it not, could easily be made so). Regardless, it
57 * isn't worth optimizing; the SWAP's get sped up by the cache, and pointer
58 * arithmetic gets lost in the time required for comparison function calls.
59 */
60 #define SWAP(a, b, count, size, tmp) { \
61 count = size; \
62 do { \
63 tmp = *a; \
64 *a++ = *b; \
65 *b++ = tmp; \
66 } while (--count); \
67 }
68
69 /* Copy one block of size size to another. */
70 #define COPY(a, b, count, size, tmp1, tmp2) { \
71 count = size; \
72 tmp1 = a; \
73 tmp2 = b; \
74 do { \
75 *tmp1++ = *tmp2++; \
76 } while (--count); \
77 }
78
79 /*
80 * Build the list into a heap, where a heap is defined such that for
81 * the records K1 ... KN, Kj/2 >= Kj for 1 <= j/2 <= j <= N.
82 *
83 * There two cases. If j == nmemb, select largest of Ki and Kj. If
84 * j < nmemb, select largest of Ki, Kj and Kj+1.
85 */
86 #define CREATE(initval, nmemb, par_i, child_i, par, child, size, count, tmp) { \
87 for (par_i = initval; (child_i = par_i * 2) <= nmemb; \
88 par_i = child_i) { \
89 child = base + child_i * size; \
90 if (child_i < nmemb && COMPAR(child, child + size) < 0) { \
91 child += size; \
92 ++child_i; \
93 } \
94 par = base + par_i * size; \
95 if (COMPAR(child, par) <= 0) \
96 break; \
97 SWAP(par, child, count, size, tmp); \
98 } \
99 }
100
101 /*
102 * Select the top of the heap and 'heapify'. Since by far the most expensive
103 * action is the call to the compar function, a considerable optimization
104 * in the average case can be achieved due to the fact that k, the displaced
105 * elememt, is usually quite small, so it would be preferable to first
106 * heapify, always maintaining the invariant that the larger child is copied
107 * over its parent's record.
108 *
109 * Then, starting from the *bottom* of the heap, finding k's correct place,
110 * again maintianing the invariant. As a result of the invariant no element
111 * is 'lost' when k is assigned its correct place in the heap.
112 *
113 * The time savings from this optimization are on the order of 15-20% for the
114 * average case. See Knuth, Vol. 3, page 158, problem 18.
115 *
116 * XXX Don't break the #define SELECT line, below. Reiser cpp gets upset.
117 */
118 #define SELECT(par_i, child_i, nmemb, par, child, size, k, count, tmp1, tmp2) { \
119 for (par_i = 1; (child_i = par_i * 2) <= nmemb; par_i = child_i) { \
120 child = base + child_i * size; \
121 if (child_i < nmemb && COMPAR(child, child + size) < 0) { \
122 child += size; \
123 ++child_i; \
124 } \
125 par = base + par_i * size; \
126 COPY(par, child, count, size, tmp1, tmp2); \
127 } \
128 for (;;) { \
129 child_i = par_i; \
130 par_i = child_i / 2; \
131 child = base + child_i * size; \
132 par = base + par_i * size; \
133 if (child_i == 1 || COMPAR(k, par) < 0) { \
134 COPY(child, k, count, size, tmp1, tmp2); \
135 break; \
136 } \
137 COPY(child, par, count, size, tmp1, tmp2); \
138 } \
139 }
140
141 #ifdef I_AM_HEAPSORT_B
142 int heapsort_b(void *, size_t, size_t, heapsort_block);
143 #else
144 int heapsort(void *, size_t, size_t,
145 int (*)(const void *, const void *));
146 #endif
147 /*
148 * Heapsort -- Knuth, Vol. 3, page 145. Runs in O (N lg N), both average
149 * and worst. While heapsort is faster than the worst case of quicksort,
150 * the BSD quicksort does median selection so that the chance of finding
151 * a data set that will trigger the worst case is nonexistent. Heapsort's
152 * only advantage over quicksort is that it requires little additional memory.
153 */
154 #ifdef I_AM_HEAPSORT_B
155 int
heapsort_b(void * vbase,size_t nmemb,size_t size,heapsort_block compar)156 heapsort_b(void *vbase, size_t nmemb, size_t size, heapsort_block compar)
157 #else
158 int
159 heapsort(void *vbase, size_t nmemb, size_t size,
160 int (*compar)(const void *, const void *))
161 #endif
162 {
163 size_t cnt, i, j, l;
164 char tmp, *tmp1, *tmp2;
165 char *base, *k, *p, *t;
166
167 if (nmemb <= 1)
168 return (0);
169
170 if (!size) {
171 errno = EINVAL;
172 return (-1);
173 }
174
175 if ((k = malloc(size)) == NULL)
176 return (-1);
177
178 /*
179 * Items are numbered from 1 to nmemb, so offset from size bytes
180 * below the starting address.
181 */
182 base = (char *)vbase - size;
183
184 for (l = nmemb / 2 + 1; --l;)
185 CREATE(l, nmemb, i, j, t, p, size, cnt, tmp);
186
187 /*
188 * For each element of the heap, save the largest element into its
189 * final slot, save the displaced element (k), then recreate the
190 * heap.
191 */
192 while (nmemb > 1) {
193 COPY(k, base + nmemb * size, cnt, size, tmp1, tmp2);
194 COPY(base + nmemb * size, base + size, cnt, size, tmp1, tmp2);
195 --nmemb;
196 SELECT(i, j, nmemb, t, p, size, k, cnt, tmp1, tmp2);
197 }
198 free(k);
199 return (0);
200 }
201