1 /* $NetBSD: qsort.c,v 1.24 2025/03/02 16:35:41 riastradh Exp $ */
2 /*-
3 * Copyright (c) 1992, 1993
4 * The Regents of the University of California. All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 * 3. Neither the name of the University nor the names of its contributors
15 * may be used to endorse or promote products derived from this software
16 * without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGE.
29 */
30
31 #include <sys/cdefs.h>
32 #if defined(LIBC_SCCS) && !defined(lint)
33 #if 0
34 static char sccsid[] = "@(#)qsort.c 8.1 (Berkeley) 6/4/93";
35 #else
36 __RCSID("$NetBSD: qsort.c,v 1.24 2025/03/02 16:35:41 riastradh Exp $");
37 #endif
38 #endif /* LIBC_SCCS and not lint */
39
40 #include <sys/types.h>
41
42 #include <assert.h>
43 #include <errno.h>
44 #include <stdlib.h>
45
46 static inline char *med3(char *, char *, char *,
47 int (*)(const void *, const void *, void *),
48 void *);
49 static inline void swapfunc(char *, char *, size_t, int);
50
51 #define min(a, b) (a) < (b) ? a : b
52
53 /*
54 * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
55 */
56 #define swapcode(TYPE, parmi, parmj, n) { \
57 size_t i = (n) / sizeof (TYPE); \
58 TYPE *pi = (TYPE *)(void *)(parmi); \
59 TYPE *pj = (TYPE *)(void *)(parmj); \
60 do { \
61 TYPE t = *pi; \
62 *pi++ = *pj; \
63 *pj++ = t; \
64 } while (--i > 0); \
65 }
66
67 #define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
68 es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
69
70 static inline void
swapfunc(char * a,char * b,size_t n,int swaptype)71 swapfunc(char *a, char *b, size_t n, int swaptype)
72 {
73
74 if (swaptype <= 1)
75 swapcode(long, a, b, n)
76 else
77 swapcode(char, a, b, n)
78 }
79
80 #define swap(a, b) \
81 if (swaptype == 0) { \
82 long t = *(long *)(void *)(a); \
83 *(long *)(void *)(a) = *(long *)(void *)(b); \
84 *(long *)(void *)(b) = t; \
85 } else \
86 swapfunc(a, b, es, swaptype)
87
88 #define vecswap(a, b, n) if ((n) > 0) swapfunc((a), (b), (size_t)(n), swaptype)
89
90 static inline char *
med3(char * a,char * b,char * c,int (* cmp)(const void *,const void *,void *),void * cookie)91 med3(char *a, char *b, char *c,
92 int (*cmp)(const void *, const void *, void *), void *cookie)
93 {
94
95 return cmp(a, b, cookie) < 0 ?
96 (cmp(b, c, cookie) < 0 ? b : (cmp(a, c, cookie) < 0 ? c : a ))
97 :(cmp(b, c, cookie) > 0 ? b : (cmp(a, c, cookie) < 0 ? a : c ));
98 }
99
100 void
qsort_r(void * a,size_t n,size_t es,int (* cmp)(const void *,const void *,void *),void * cookie)101 qsort_r(void *a, size_t n, size_t es,
102 int (*cmp)(const void *, const void *, void *), void *cookie)
103 {
104 char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
105 size_t d, r, s;
106 int swaptype, cmp_result;
107
108 _DIAGASSERT(a != NULL || n == 0 || es == 0);
109 _DIAGASSERT(cmp != NULL);
110
111 loop: SWAPINIT(a, es);
112 if (n < 7) {
113 for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
114 for (pl = pm;
115 pl > (char *) a && cmp(pl - es, pl, cookie) > 0;
116 pl -= es)
117 swap(pl, pl - es);
118 return;
119 }
120 pm = (char *) a + (n / 2) * es;
121 if (n > 7) {
122 pl = (char *) a;
123 pn = (char *) a + (n - 1) * es;
124 if (n > 40) {
125 d = (n / 8) * es;
126 pl = med3(pl, pl + d, pl + 2 * d, cmp, cookie);
127 pm = med3(pm - d, pm, pm + d, cmp, cookie);
128 pn = med3(pn - 2 * d, pn - d, pn, cmp, cookie);
129 }
130 pm = med3(pl, pm, pn, cmp, cookie);
131 }
132 swap(a, pm);
133 pa = pb = (char *) a + es;
134
135 pc = pd = (char *) a + (n - 1) * es;
136 for (;;) {
137 while (pb <= pc && (cmp_result = cmp(pb, a, cookie)) <= 0) {
138 if (cmp_result == 0) {
139 swap(pa, pb);
140 pa += es;
141 }
142 pb += es;
143 }
144 while (pb <= pc && (cmp_result = cmp(pc, a, cookie)) >= 0) {
145 if (cmp_result == 0) {
146 swap(pc, pd);
147 pd -= es;
148 }
149 pc -= es;
150 }
151 if (pb > pc)
152 break;
153 swap(pb, pc);
154 pb += es;
155 pc -= es;
156 }
157
158 pn = (char *) a + n * es;
159 r = min(pa - (char *) a, pb - pa);
160 vecswap(a, pb - r, r);
161 r = min((size_t)(pd - pc), pn - pd - es);
162 vecswap(pb, pn - r, r);
163 /*
164 * To save stack space we sort the smaller side of the partition first
165 * using recursion and eliminate tail recursion for the larger side.
166 */
167 r = pb - pa;
168 s = pd - pc;
169 if (r < s) {
170 /* Recurse for 1st side, iterate for 2nd side. */
171 if (s > es) {
172 if (r > es)
173 qsort_r(a, r / es, es, cmp, cookie);
174 a = pn - s;
175 n = s / es;
176 goto loop;
177 }
178 } else {
179 /* Recurse for 2nd side, iterate for 1st side. */
180 if (r > es) {
181 if (s > es)
182 qsort_r(pn - s, s / es, es, cmp, cookie);
183 n = r / es;
184 goto loop;
185 }
186 }
187 }
188
189 static int
cmpnocookie(const void * a,const void * b,void * cookie)190 cmpnocookie(const void *a, const void *b, void *cookie)
191 {
192 int (*cmp)(const void *, const void *) = cookie;
193
194 return cmp(a, b);
195 }
196
197 void
qsort(void * a,size_t n,size_t es,int (* cmp)(const void *,const void *))198 qsort(void *a, size_t n, size_t es,
199 int (*cmp)(const void *, const void *))
200 {
201
202 qsort_r(a, n, es, cmpnocookie, cmp);
203 }
204