1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
|
/*-
* Copyright (c) 1991, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Ronnie Kon at Mindcraft Inc., Kevin Lew and Elmer Yglesias.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/types.h>
#include <errno.h>
#include <stdlib.h>
/*
* Swap two areas of size number of bytes. Although qsort(3) permits random
* blocks of memory to be sorted, sorting pointers is almost certainly the
* common case (and, were it not, could easily be made so). Regardless, it
* isn't worth optimizing; the SWAP's get sped up by the cache, and pointer
* arithmetic gets lost in the time required for comparison function calls.
*/
#define SWAP(a, b, count, size, tmp) { \
count = size; \
do { \
tmp = *a; \
*a++ = *b; \
*b++ = tmp; \
} while (--count); \
}
/* Copy one block of size size to another. */
#define COPY(a, b, count, size, tmp1, tmp2) { \
count = size; \
tmp1 = a; \
tmp2 = b; \
do { \
*tmp1++ = *tmp2++; \
} while (--count); \
}
/*
* Build the list into a heap, where a heap is defined such that for
* the records K1 ... KN, Kj/2 >= Kj for 1 <= j/2 <= j <= N.
*
* There are two cases. If j == nmemb, select largest of Ki and Kj. If
* j < nmemb, select largest of Ki, Kj and Kj+1.
*/
#define CREATE(initval, nmemb, par_i, child_i, par, child, size, count, tmp) { \
for (par_i = initval; (child_i = par_i * 2) <= nmemb; \
par_i = child_i) { \
child = base + child_i * size; \
if (child_i < nmemb && compar(child, child + size) < 0) { \
child += size; \
++child_i; \
} \
par = base + par_i * size; \
if (compar(child, par) <= 0) \
break; \
SWAP(par, child, count, size, tmp); \
} \
}
/*
* Select the top of the heap and 'heapify'. Since by far the most expensive
* action is the call to the compar function, a considerable optimization
* in the average case can be achieved due to the fact that k, the displaced
* element, is usually quite small, so it would be preferable to first
* heapify, always maintaining the invariant that the larger child is copied
* over its parent's record.
*
* Then, starting from the *bottom* of the heap, finding k's correct place,
* again maintaining the invariant. As a result of the invariant no element
* is 'lost' when k is assigned its correct place in the heap.
*
* The time savings from this optimization are on the order of 15-20% for the
* average case. See Knuth, Vol. 3, page 158, problem 18.
*
* XXX Don't break the #define SELECT line, below. Reiser cpp gets upset.
*/
#define SELECT(par_i, child_i, nmemb, par, child, size, k, count, tmp1, tmp2) { \
for (par_i = 1; (child_i = par_i * 2) <= nmemb; par_i = child_i) { \
child = base + child_i * size; \
if (child_i < nmemb && compar(child, child + size) < 0) { \
child += size; \
++child_i; \
} \
par = base + par_i * size; \
COPY(par, child, count, size, tmp1, tmp2); \
} \
for (;;) { \
child_i = par_i; \
par_i = child_i / 2; \
child = base + child_i * size; \
par = base + par_i * size; \
if (child_i == 1 || compar(k, par) < 0) { \
COPY(child, k, count, size, tmp1, tmp2); \
break; \
} \
COPY(child, par, count, size, tmp1, tmp2); \
} \
}
/*
* Heapsort -- Knuth, Vol. 3, page 145. Runs in O (N lg N), both average
* and worst. While heapsort is faster than the worst case of quicksort,
* the BSD quicksort does median selection so that the chance of finding
* a data set that will trigger the worst case is nonexistent. Heapsort's
* only advantage over quicksort is that it requires little additional memory.
*/
int
heapsort(void *vbase, size_t nmemb, size_t size,
int (*compar)(const void *, const void *))
{
int cnt, i, j, l;
char tmp, *tmp1, *tmp2;
char *base, *k, *p, *t;
if (nmemb <= 1)
return (0);
if (!size) {
errno = EINVAL;
return (-1);
}
if ((k = malloc(size)) == NULL)
return (-1);
/*
* Items are numbered from 1 to nmemb, so offset from size bytes
* below the starting address.
*/
base = (char *)vbase - size;
for (l = nmemb / 2 + 1; --l;)
CREATE(l, nmemb, i, j, t, p, size, cnt, tmp);
/*
* For each element of the heap, save the largest element into its
* final slot, save the displaced element (k), then recreate the
* heap.
*/
while (nmemb > 1) {
COPY(k, base + nmemb * size, cnt, size, tmp1, tmp2);
COPY(base + nmemb * size, base + size, cnt, size, tmp1, tmp2);
--nmemb;
SELECT(i, j, nmemb, t, p, size, k, cnt, tmp1, tmp2);
}
free(k);
return (0);
}
|
