1 /* $NetBSD: qsort.c,v 1.23 2017/05/19 19:48:19 christos 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 1.23 2017/05/19 19:48:19 christos 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 *));
48 static inline void swapfunc(char *, char *, size_t, int);
49
50 #define min(a, b) (a) < (b) ? a : b
51
52 /*
53 * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
54 */
55 #define swapcode(TYPE, parmi, parmj, n) { \
56 size_t i = (n) / sizeof (TYPE); \
57 TYPE *pi = (TYPE *)(void *)(parmi); \
58 TYPE *pj = (TYPE *)(void *)(parmj); \
59 do { \
60 TYPE t = *pi; \
61 *pi++ = *pj; \
62 *pj++ = t; \
63 } while (--i > 0); \
64 }
65
66 #define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
67 es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
68
69 static inline void
swapfunc(char * a,char * b,size_t n,int swaptype)70 swapfunc(char *a, char *b, size_t n, int swaptype)
71 {
72
73 if (swaptype <= 1)
74 swapcode(long, a, b, n)
75 else
76 swapcode(char, a, b, n)
77 }
78
79 #define swap(a, b) \
80 if (swaptype == 0) { \
81 long t = *(long *)(void *)(a); \
82 *(long *)(void *)(a) = *(long *)(void *)(b); \
83 *(long *)(void *)(b) = t; \
84 } else \
85 swapfunc(a, b, es, swaptype)
86
87 #define vecswap(a, b, n) if ((n) > 0) swapfunc((a), (b), (size_t)(n), swaptype)
88
89 static inline char *
med3(char * a,char * b,char * c,int (* cmp)(const void *,const void *))90 med3(char *a, char *b, char *c,
91 int (*cmp)(const void *, const void *))
92 {
93
94 return cmp(a, b) < 0 ?
95 (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a ))
96 :(cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c ));
97 }
98
99 void
qsort(void * a,size_t n,size_t es,int (* cmp)(const void *,const void *))100 qsort(void *a, size_t n, size_t es,
101 int (*cmp)(const void *, const void *))
102 {
103 char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
104 size_t d, r, s;
105 int swaptype, cmp_result;
106
107 _DIAGASSERT(a != NULL || n == 0 || es == 0);
108 _DIAGASSERT(cmp != NULL);
109
110 loop: SWAPINIT(a, es);
111 if (n < 7) {
112 for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
113 for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
114 pl -= es)
115 swap(pl, pl - es);
116 return;
117 }
118 pm = (char *) a + (n / 2) * es;
119 if (n > 7) {
120 pl = (char *) a;
121 pn = (char *) a + (n - 1) * es;
122 if (n > 40) {
123 d = (n / 8) * es;
124 pl = med3(pl, pl + d, pl + 2 * d, cmp);
125 pm = med3(pm - d, pm, pm + d, cmp);
126 pn = med3(pn - 2 * d, pn - d, pn, cmp);
127 }
128 pm = med3(pl, pm, pn, cmp);
129 }
130 swap(a, pm);
131 pa = pb = (char *) a + es;
132
133 pc = pd = (char *) a + (n - 1) * es;
134 for (;;) {
135 while (pb <= pc && (cmp_result = cmp(pb, a)) <= 0) {
136 if (cmp_result == 0) {
137 swap(pa, pb);
138 pa += es;
139 }
140 pb += es;
141 }
142 while (pb <= pc && (cmp_result = cmp(pc, a)) >= 0) {
143 if (cmp_result == 0) {
144 swap(pc, pd);
145 pd -= es;
146 }
147 pc -= es;
148 }
149 if (pb > pc)
150 break;
151 swap(pb, pc);
152 pb += es;
153 pc -= es;
154 }
155
156 pn = (char *) a + n * es;
157 r = min(pa - (char *) a, pb - pa);
158 vecswap(a, pb - r, r);
159 r = min((size_t)(pd - pc), pn - pd - es);
160 vecswap(pb, pn - r, r);
161 /*
162 * To save stack space we sort the smaller side of the partition first
163 * using recursion and eliminate tail recursion for the larger side.
164 */
165 r = pb - pa;
166 s = pd - pc;
167 if (r < s) {
168 /* Recurse for 1st side, iterate for 2nd side. */
169 if (s > es) {
170 if (r > es)
171 qsort(a, r / es, es, cmp);
172 a = pn - s;
173 n = s / es;
174 goto loop;
175 }
176 } else {
177 /* Recurse for 2nd side, iterate for 1st side. */
178 if (r > es) {
179 if (s > es)
180 qsort(pn - s, s / es, es, cmp);
181 n = r / es;
182 goto loop;
183 }
184 }
185 }
186