Commit | Line | Data |
---|---|---|
b5fffe6f WJ |
1 | /*- |
2 | * Copyright (c) 1991 The Regents of the University of California. | |
3 | * All rights reserved. | |
4 | * | |
5 | * Redistribution and use in source and binary forms, with or without | |
6 | * modification, are permitted provided that the following conditions | |
7 | * are met: | |
8 | * 1. Redistributions of source code must retain the above copyright | |
9 | * notice, this list of conditions and the following disclaimer. | |
10 | * 2. Redistributions in binary form must reproduce the above copyright | |
11 | * notice, this list of conditions and the following disclaimer in the | |
12 | * documentation and/or other materials provided with the distribution. | |
13 | * 3. All advertising materials mentioning features or use of this software | |
14 | * must display the following acknowledgement: | |
15 | * This product includes software developed by the University of | |
16 | * California, Berkeley and its contributors. | |
17 | * 4. Neither the name of the University nor the names of its contributors | |
18 | * may be used to endorse or promote products derived from this software | |
19 | * without specific prior written permission. | |
20 | * | |
21 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND | |
22 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
23 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |
24 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE | |
25 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
26 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS | |
27 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |
28 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | |
29 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY | |
30 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF | |
31 | * SUCH DAMAGE. | |
32 | */ | |
33 | ||
34 | #if defined(LIBC_SCCS) && !defined(lint) | |
35 | static char sccsid[] = "@(#)heapsort.c 5.1 (Berkeley) 6/4/91"; | |
36 | #endif /* LIBC_SCCS and not lint */ | |
37 | ||
38 | #include <sys/cdefs.h> | |
39 | #include <sys/types.h> | |
40 | #include <errno.h> | |
41 | #include <stdlib.h> | |
42 | ||
43 | /* | |
44 | * Swap two areas of size number of bytes. Although qsort(3) permits random | |
45 | * blocks of memory to be sorted, sorting pointers is almost certainly the | |
46 | * common case (and, were it not, could easily be made so). Regardless, it | |
47 | * isn't worth optimizing; the SWAP's get sped up by the cache, and pointer | |
48 | * arithmetic gets lost in the time required for comparison function calls. | |
49 | */ | |
50 | #define SWAP(a, b) { \ | |
51 | cnt = size; \ | |
52 | do { \ | |
53 | ch = *a; \ | |
54 | *a++ = *b; \ | |
55 | *b++ = ch; \ | |
56 | } while (--cnt); \ | |
57 | } | |
58 | ||
59 | /* | |
60 | * Build the list into a heap, where a heap is defined such that for | |
61 | * the records K1 ... KN, Kj/2 >= Kj for 1 <= j/2 <= j <= N. | |
62 | * | |
63 | * There two cases. If j == nmemb, select largest of Ki and Kj. If | |
64 | * j < nmemb, select largest of Ki, Kj and Kj+1. | |
65 | * | |
66 | * The initial value depends on if we're building the initial heap or | |
67 | * reconstructing it after saving a value. | |
68 | */ | |
69 | #define HEAP(initval) { \ | |
70 | for (i = initval; (j = i * 2) <= nmemb; i = j) { \ | |
71 | p = (char *)bot + j * size; \ | |
72 | if (j < nmemb && compar(p, p + size) < 0) { \ | |
73 | p += size; \ | |
74 | ++j; \ | |
75 | } \ | |
76 | t = (char *)bot + i * size; \ | |
77 | if (compar(p, t) <= 0) \ | |
78 | break; \ | |
79 | SWAP(t, p); \ | |
80 | } \ | |
81 | } | |
82 | ||
83 | /* | |
84 | * Heapsort -- Knuth, Vol. 3, page 145. Runs in O (N lg N), both average | |
85 | * and worst. While heapsort is faster than the worst case of quicksort, | |
86 | * the BSD quicksort does median selection so that the chance of finding | |
87 | * a data set that will trigger the worst case is nonexistent. Heapsort's | |
88 | * only advantage over quicksort is that it requires no additional memory. | |
89 | */ | |
90 | heapsort(bot, nmemb, size, compar) | |
91 | register void *bot; | |
92 | register size_t nmemb, size; | |
93 | int (*compar) __P((const void *, const void *)); | |
94 | { | |
95 | register char *p, *t, ch; | |
96 | register int cnt, i, j, l; | |
97 | ||
98 | if (nmemb <= 1) | |
99 | return (0); | |
100 | if (!size) { | |
101 | errno = EINVAL; | |
102 | return (-1); | |
103 | } | |
104 | /* | |
105 | * Items are numbered from 1 to nmemb, so offset from size bytes | |
106 | * below the starting address. | |
107 | */ | |
108 | bot -= size; | |
109 | ||
110 | for (l = nmemb / 2 + 1; --l;) | |
111 | HEAP(l); | |
112 | ||
113 | /* | |
114 | * For each element of the heap, save the largest element into its | |
115 | * final slot, then recreate the heap. | |
116 | */ | |
117 | while (nmemb > 1) { | |
118 | p = (char *)bot + size; | |
119 | t = (char *)bot + nmemb * size; | |
120 | SWAP(p, t); | |
121 | --nmemb; | |
122 | HEAP(1); | |
123 | } | |
124 | return (0); | |
125 | } |