vfs: check userland buffers before reading them.
[haiku.git] / src / system / libroot / posix / stdlib / heapsort.c
blob7b39361497b536586593c959cb20d9f1165c07dc
1 /*-
2 * Copyright (c) 1991, 1993
3 * The Regents of the University of California. All rights reserved.
5 * This code is derived from software contributed to Berkeley by
6 * Ronnie Kon at Mindcraft Inc., Kevin Lew and Elmer Yglesias.
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. All advertising materials mentioning features or use of this software
17 * must display the following acknowledgement:
18 * This product includes software developed by the University of
19 * California, Berkeley and its contributors.
20 * 4. 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.
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.
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 */
41 #include <errno.h>
42 #include <stdlib.h>
44 #include <errno_private.h>
47 * Swap two areas of size number of bytes. Although qsort(3) permits random
48 * blocks of memory to be sorted, sorting pointers is almost certainly the
49 * common case (and, were it not, could easily be made so). Regardless, it
50 * isn't worth optimizing; the SWAP's get sped up by the cache, and pointer
51 * arithmetic gets lost in the time required for comparison function calls.
53 #define SWAP(a, b, count, size, tmp) { \
54 count = size; \
55 do { \
56 tmp = *a; \
57 *a++ = *b; \
58 *b++ = tmp; \
59 } while (--count); \
62 /* Copy one block of size size to another. */
63 #define COPY(a, b, count, size, tmp1, tmp2) { \
64 count = size; \
65 tmp1 = a; \
66 tmp2 = b; \
67 do { \
68 *tmp1++ = *tmp2++; \
69 } while (--count); \
73 * Build the list into a heap, where a heap is defined such that for
74 * the records K1 ... KN, Kj/2 >= Kj for 1 <= j/2 <= j <= N.
76 * There two cases. If j == nmemb, select largest of Ki and Kj. If
77 * j < nmemb, select largest of Ki, Kj and Kj+1.
79 #define CREATE(initval, nmemb, par_i, child_i, par, child, size, count, tmp) { \
80 for (par_i = initval; (child_i = par_i * 2) <= nmemb; \
81 par_i = child_i) { \
82 child = base + child_i * size; \
83 if (child_i < nmemb && compar(child, child + size) < 0) { \
84 child += size; \
85 ++child_i; \
86 } \
87 par = base + par_i * size; \
88 if (compar(child, par) <= 0) \
89 break; \
90 SWAP(par, child, count, size, tmp); \
91 } \
95 * Select the top of the heap and 'heapify'. Since by far the most expensive
96 * action is the call to the compar function, a considerable optimization
97 * in the average case can be achieved due to the fact that k, the displaced
98 * elememt, is ususally quite small, so it would be preferable to first
99 * heapify, always maintaining the invariant that the larger child is copied
100 * over its parent's record.
102 * Then, starting from the *bottom* of the heap, finding k's correct place,
103 * again maintianing the invariant. As a result of the invariant no element
104 * is 'lost' when k is assigned its correct place in the heap.
106 * The time savings from this optimization are on the order of 15-20% for the
107 * average case. See Knuth, Vol. 3, page 158, problem 18.
109 * XXX Don't break the #define SELECT line, below. Reiser cpp gets upset.
111 #define SELECT(par_i, child_i, nmemb, par, child, size, k, count, tmp1, tmp2) { \
112 for (par_i = 1; (child_i = par_i * 2) <= nmemb; par_i = child_i) { \
113 child = base + child_i * size; \
114 if (child_i < nmemb && compar(child, child + size) < 0) { \
115 child += size; \
116 ++child_i; \
118 par = base + par_i * size; \
119 COPY(par, child, count, size, tmp1, tmp2); \
121 for (;;) { \
122 child_i = par_i; \
123 par_i = child_i / 2; \
124 child = base + child_i * size; \
125 par = base + par_i * size; \
126 if (child_i == 1 || compar(k, par) < 0) { \
127 COPY(child, k, count, size, tmp1, tmp2); \
128 break; \
130 COPY(child, par, count, size, tmp1, tmp2); \
135 * Heapsort -- Knuth, Vol. 3, page 145. Runs in O (N lg N), both average
136 * and worst. While heapsort is faster than the worst case of quicksort,
137 * the BSD quicksort does median selection so that the chance of finding
138 * a data set that will trigger the worst case is nonexistent. Heapsort's
139 * only advantage over quicksort is that it requires little additional memory.
142 heapsort(void *vbase, size_t nmemb, size_t size, int (*compar)(void const *, void const *))
144 size_t cnt;
145 size_t i;
146 size_t j;
147 size_t l;
148 char tmp;
149 char *tmp1;
150 char *tmp2;
151 char *base;
152 char *k;
153 char *p;
154 char *t;
156 if (nmemb <= 1) {
157 return (0);
160 if (!size) {
161 // __set_errno(EINVAL);
162 return (-1);
165 if ((k = malloc(size)) == NULL) {
166 return (-1);
170 * Items are numbered from 1 to nmemb, so offset from size bytes
171 * below the starting address.
173 base = (char *)vbase - size;
175 for (l = nmemb / 2 + 1; --l;)
176 CREATE(l, nmemb, i, j, t, p, size, cnt, tmp);
179 * For each element of the heap, save the largest element into its
180 * final slot, save the displaced element (k), then recreate the
181 * heap.
183 while (nmemb > 1) {
184 COPY(k, base + nmemb * size, cnt, size, tmp1, tmp2);
185 COPY(base + nmemb * size, base + size, cnt, size, tmp1, tmp2);
186 --nmemb;
187 SELECT(i, j, nmemb, t, p, size, k, cnt, tmp1, tmp2);
189 free(k);
190 return (0);