1 /* $NetBSD: qsort.c,v 1.22 2012/05/26 21:47:05 christos Exp $ */
2
3 /*-
4 * Copyright (c) 1992, 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its contributors
16 * may be used to endorse or promote products derived from this software
17 * without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32 #include <sys/cdefs.h>
33 #if defined(LIBC_SCCS) && !defined(lint)
34 #if 0
35 static char sccsid[] = "@(#)qsort.c 8.1 (Berkeley) 6/4/93";
36 #else
37 __RCSID("$NetBSD: qsort.c,v 1.22 2012/05/26 21:47:05 christos Exp $");
38 #endif
39 #endif /* LIBC_SCCS and not lint */
40
41 #include <sys/types.h>
42
43 #include <assert.h>
44 #include <errno.h>
45 #include <stdlib.h>
46
47 static inline char *med3(char *, char *, char *,
48 int (*)(const void *, const 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 *))91 med3(char *a, char *b, char *c,
92 int (*cmp)(const void *, const void *))
93 {
94
95 return cmp(a, b) < 0 ?
96 (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a ))
97 :(cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c ));
98 }
99
100 void
qsort(void * a,size_t n,size_t es,int (* cmp)(const void *,const void *))101 qsort(void *a, size_t n, size_t es,
102 int (*cmp)(const void *, const void *))
103 {
104 char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
105 size_t d, r;
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; pl > (char *) a && cmp(pl - es, pl) > 0;
115 pl -= es)
116 swap(pl, pl - es);
117 return;
118 }
119 pm = (char *) a + (n / 2) * es;
120 if (n > 7) {
121 pl = (char *) a;
122 pn = (char *) a + (n - 1) * es;
123 if (n > 40) {
124 d = (n / 8) * es;
125 pl = med3(pl, pl + d, pl + 2 * d, cmp);
126 pm = med3(pm - d, pm, pm + d, cmp);
127 pn = med3(pn - 2 * d, pn - d, pn, cmp);
128 }
129 pm = med3(pl, pm, pn, cmp);
130 }
131 swap(a, pm);
132 pa = pb = (char *) a + es;
133
134 pc = pd = (char *) a + (n - 1) * es;
135 for (;;) {
136 while (pb <= pc && (cmp_result = cmp(pb, a)) <= 0) {
137 if (cmp_result == 0) {
138 swap(pa, pb);
139 pa += es;
140 }
141 pb += es;
142 }
143 while (pb <= pc && (cmp_result = cmp(pc, a)) >= 0) {
144 if (cmp_result == 0) {
145 swap(pc, pd);
146 pd -= es;
147 }
148 pc -= es;
149 }
150 if (pb > pc)
151 break;
152 swap(pb, pc);
153 pb += es;
154 pc -= es;
155 }
156
157 pn = (char *) a + n * es;
158 r = min(pa - (char *) a, pb - pa);
159 vecswap(a, pb - r, r);
160 r = min((size_t)(pd - pc), pn - pd - es);
161 vecswap(pb, pn - r, r);
162 if ((r = pb - pa) > es)
163 qsort(a, r / es, es, cmp);
164 if ((r = pd - pc) > es) {
165 /* Iterate rather than recurse to save stack space */
166 a = pn - r;
167 n = r / es;
168 goto loop;
169 }
170 /* qsort(pn - r, r / es, es, cmp);*/
171 }
172