1 /* $OpenBSD: qsort.c,v 1.10 2005/08/08 08:05:37 espie 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/types.h>
32 #include <stdlib.h>
33
34 static __inline char *med3(char *, char *, char *, int ( *)(const void *, const void *));
35 static __inline void swapfunc(char *, char *, int, int);
36
37 #define min(a, b) (a) < (b) ? a : b
38
39 /*
40 * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
41 */
42 #define swapcode(TYPE, parmi, parmj, n) { \
43 long i = (n) / sizeof (TYPE); \
44 TYPE *pi = (TYPE *) (parmi); \
45 TYPE *pj = (TYPE *) (parmj); \
46 do { \
47 TYPE t = *pi; \
48 *pi++ = *pj; \
49 *pj++ = t; \
50 } while (--i > 0); \
51 }
52
53 #define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
54 es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
55
56 static __inline void
swapfunc(char * a,char * b,int n,int swaptype)57 swapfunc(char *a, char *b, int n, int swaptype) {
58 if (swaptype <= 1)
59 swapcode(long, a, b, n)
60 else
61 swapcode(char, a, b, n)
62 }
63
64 #define swap(a, b) \
65 if (swaptype == 0) { \
66 long t = *(long *)(a); \
67 *(long *)(a) = *(long *)(b); \
68 *(long *)(b) = t; \
69 } else \
70 swapfunc(a, b, es, swaptype)
71
72 #define vecswap(a, b, n) if ((n) > 0) swapfunc(a, b, n, swaptype)
73
74 static __inline char *
med3(char * a,char * b,char * c,int (* cmp)(const void *,const void *))75 med3(char *a, char *b, char *c, int (*cmp)(const void *, const void *)) {
76 return cmp(a, b) < 0 ?
77 (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a ))
78 :(cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c ));
79 }
80
81 void
qsort(void * aa,size_t n,size_t es,int (* cmp)(const void *,const void *))82 qsort(void *aa, size_t n, size_t es, int (*cmp)(const void *, const void *)) {
83 char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
84 int d, r, swaptype, swap_cnt;
85 char *a = aa;
86
87 loop:
88 SWAPINIT(a, es);
89 swap_cnt = 0;
90 if (n < 7) {
91 for (pm = (char *)a + es; pm < (char *) a + n * es; pm += es)
92 for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
93 pl -= es)
94 swap(pl, pl - es);
95 return;
96 }
97 pm = (char *)a + (n / 2) * es;
98 if (n > 7) {
99 pl = (char *)a;
100 pn = (char *)a + (n - 1) * es;
101 if (n > 40) {
102 d = (n / 8) * es;
103 pl = med3(pl, pl + d, pl + 2 * d, cmp);
104 pm = med3(pm - d, pm, pm + d, cmp);
105 pn = med3(pn - 2 * d, pn - d, pn, cmp);
106 }
107 pm = med3(pl, pm, pn, cmp);
108 }
109 swap(a, pm);
110 pa = pb = (char *)a + es;
111
112 pc = pd = (char *)a + (n - 1) * es;
113 for (;;) {
114 while (pb <= pc && (r = cmp(pb, a)) <= 0) {
115 if (r == 0) {
116 swap_cnt = 1;
117 swap(pa, pb);
118 pa += es;
119 }
120 pb += es;
121 }
122 while (pb <= pc && (r = cmp(pc, a)) >= 0) {
123 if (r == 0) {
124 swap_cnt = 1;
125 swap(pc, pd);
126 pd -= es;
127 }
128 pc -= es;
129 }
130 if (pb > pc)
131 break;
132 swap(pb, pc);
133 swap_cnt = 1;
134 pb += es;
135 pc -= es;
136 }
137 if (swap_cnt == 0) { /* Switch to insertion sort */
138 for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
139 for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
140 pl -= es)
141 swap(pl, pl - es);
142 return;
143 }
144
145 pn = (char *)a + n * es;
146 r = min(pa - (char *)a, pb - pa);
147 vecswap(a, pb - r, r);
148 r = min(pd - pc, pn - pd - (int)es);
149 vecswap(pb, pn - r, r);
150 if ((r = pb - pa) > (int)es)
151 qsort(a, r / es, es, cmp);
152 if ((r = pd - pc) > (int)es) {
153 /* Iterate rather than recurse to save stack space */
154 a = pn - r;
155 n = r / es;
156 goto loop;
157 }
158 /* qsort(pn - r, r / es, es, cmp); */
159 }
160