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 #include <errno.h>
38 #include <stddef.h>
39 #include <stdlib.h>
40
41 #ifdef I_AM_HEAPSORT_B
42 #include "block_abi.h"
43 #define COMPAR(x, y) CALL_BLOCK(compar, x, y)
44 typedef DECLARE_BLOCK(int, heapsort_block, const void *, const void *);
45 #else
46 #define COMPAR(x, y) compar(x, y)
47 #endif
48
49 /*
50 * Swap two areas of size number of bytes. Although qsort(3) permits random
51 * blocks of memory to be sorted, sorting pointers is almost certainly the
52 * common case (and, were it not, could easily be made so). Regardless, it
53 * isn't worth optimizing; the SWAP's get sped up by the cache, and pointer
54 * arithmetic gets lost in the time required for comparison function calls.
55 */
56 #define SWAP(a, b, count, size, tmp) { \
57 count = size; \
58 do { \
59 tmp = *a; \
60 *a++ = *b; \
61 *b++ = tmp; \
62 } while (--count); \
63 }
64
65 /* Copy one block of size size to another. */
66 #define COPY(a, b, count, size, tmp1, tmp2) { \
67 count = size; \
68 tmp1 = a; \
69 tmp2 = b; \
70 do { \
71 *tmp1++ = *tmp2++; \
72 } while (--count); \
73 }
74
75 /*
76 * Build the list into a heap, where a heap is defined such that for
77 * the records K1 ... KN, Kj/2 >= Kj for 1 <= j/2 <= j <= N.
78 *
79 * There two cases. If j == nmemb, select largest of Ki and Kj. If
80 * j < nmemb, select largest of Ki, Kj and Kj+1.
81 */
82 #define CREATE(initval, nmemb, par_i, child_i, par, child, size, count, tmp) { \
83 for (par_i = initval; (child_i = par_i * 2) <= nmemb; \
84 par_i = child_i) { \
85 child = base + child_i * size; \
86 if (child_i < nmemb && COMPAR(child, child + size) < 0) { \
87 child += size; \
88 ++child_i; \
89 } \
90 par = base + par_i * size; \
91 if (COMPAR(child, par) <= 0) \
92 break; \
93 SWAP(par, child, count, size, tmp); \
94 } \
95 }
96
97 /*
98 * Select the top of the heap and 'heapify'. Since by far the most expensive
99 * action is the call to the compar function, a considerable optimization
100 * in the average case can be achieved due to the fact that k, the displaced
101 * elememt, is usually quite small, so it would be preferable to first
102 * heapify, always maintaining the invariant that the larger child is copied
103 * over its parent's record.
104 *
105 * Then, starting from the *bottom* of the heap, finding k's correct place,
106 * again maintianing the invariant. As a result of the invariant no element
107 * is 'lost' when k is assigned its correct place in the heap.
108 *
109 * The time savings from this optimization are on the order of 15-20% for the
110 * average case. See Knuth, Vol. 3, page 158, problem 18.
111 *
112 * XXX Don't break the #define SELECT line, below. Reiser cpp gets upset.
113 */
114 #define SELECT(par_i, child_i, nmemb, par, child, size, k, count, tmp1, tmp2) { \
115 for (par_i = 1; (child_i = par_i * 2) <= nmemb; par_i = child_i) { \
116 child = base + child_i * size; \
117 if (child_i < nmemb && COMPAR(child, child + size) < 0) { \
118 child += size; \
119 ++child_i; \
120 } \
121 par = base + par_i * size; \
122 COPY(par, child, count, size, tmp1, tmp2); \
123 } \
124 for (;;) { \
125 child_i = par_i; \
126 par_i = child_i / 2; \
127 child = base + child_i * size; \
128 par = base + par_i * size; \
129 if (child_i == 1 || COMPAR(k, par) < 0) { \
130 COPY(child, k, count, size, tmp1, tmp2); \
131 break; \
132 } \
133 COPY(child, par, count, size, tmp1, tmp2); \
134 } \
135 }
136
137 #ifdef I_AM_HEAPSORT_B
138 int heapsort_b(void *, size_t, size_t, heapsort_block);
139 #else
140 int heapsort(void *, size_t, size_t,
141 int (*)(const void *, const void *));
142 #endif
143 /*
144 * Heapsort -- Knuth, Vol. 3, page 145. Runs in O (N lg N), both average
145 * and worst. While heapsort is faster than the worst case of quicksort,
146 * the BSD quicksort does median selection so that the chance of finding
147 * a data set that will trigger the worst case is nonexistent. Heapsort's
148 * only advantage over quicksort is that it requires little additional memory.
149 */
150 #ifdef I_AM_HEAPSORT_B
151 int
heapsort_b(void * vbase,size_t nmemb,size_t size,heapsort_block compar)152 heapsort_b(void *vbase, size_t nmemb, size_t size, heapsort_block compar)
153 #else
154 int
155 heapsort(void *vbase, size_t nmemb, size_t size,
156 int (*compar)(const void *, const void *))
157 #endif
158 {
159 size_t cnt, i, j, l;
160 char tmp, *tmp1, *tmp2;
161 char *base, *k, *p, *t;
162
163 if (nmemb <= 1)
164 return (0);
165
166 if (!size) {
167 errno = EINVAL;
168 return (-1);
169 }
170
171 if ((k = malloc(size)) == NULL)
172 return (-1);
173
174 /*
175 * Items are numbered from 1 to nmemb, so offset from size bytes
176 * below the starting address.
177 */
178 base = (char *)vbase - size;
179
180 for (l = nmemb / 2 + 1; --l;)
181 CREATE(l, nmemb, i, j, t, p, size, cnt, tmp);
182
183 /*
184 * For each element of the heap, save the largest element into its
185 * final slot, save the displaced element (k), then recreate the
186 * heap.
187 */
188 while (nmemb > 1) {
189 COPY(k, base + nmemb * size, cnt, size, tmp1, tmp2);
190 COPY(base + nmemb * size, base + size, cnt, size, tmp1, tmp2);
191 --nmemb;
192 SELECT(i, j, nmemb, t, p, size, k, cnt, tmp1, tmp2);
193 }
194 free(k);
195 return (0);
196 }
197