1 /* rev 1.15 of lib/libc/stdlib/qsort.c */
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 <sys/systm.h>
33
34 static __inline char *med3(char *, char *, char *, int (*)(const void *, const void *));
35 static __inline void swapfunc(char *, char *, size_t, 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 size_t 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,size_t n,int swaptype)57 swapfunc(char *a, char *b, size_t n, int swaptype)
58 {
59 if (swaptype <= 1)
60 swapcode(long, a, b, n)
61 else
62 swapcode(char, a, b, n)
63 }
64
65 #define swap(a, b) \
66 if (swaptype == 0) { \
67 long t = *(long *)(a); \
68 *(long *)(a) = *(long *)(b); \
69 *(long *)(b) = t; \
70 } else \
71 swapfunc(a, b, es, swaptype)
72
73 #define vecswap(a, b, n) if ((n) > 0) swapfunc(a, b, n, swaptype)
74
75 static __inline char *
med3(char * a,char * b,char * c,int (* cmp)(const void *,const void *))76 med3(char *a, char *b, char *c, int (*cmp)(const void *, const void *))
77 {
78 return cmp(a, b) < 0 ?
79 (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a ))
80 :(cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c ));
81 }
82
83 static void
qsort(void * aa,size_t n,size_t es,int (* cmp)(const void *,const void *))84 qsort(void *aa, size_t n, size_t es, int (*cmp)(const void *, const void *))
85 {
86 char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
87 int cmp_result, swaptype;
88 size_t d, r, s;
89 char *a = aa;
90
91 loop: SWAPINIT(a, es);
92 if (n < 7) {
93 for (pm = a + es; pm < a + n * es; pm += es)
94 for (pl = pm; pl > a && cmp(pl - es, pl) > 0;
95 pl -= es)
96 swap(pl, pl - es);
97 return;
98 }
99 pm = a + (n / 2) * es;
100 if (n > 7) {
101 pl = a;
102 pn = a + (n - 1) * es;
103 if (n > 40) {
104 d = (n / 8) * es;
105 pl = med3(pl, pl + d, pl + 2 * d, cmp);
106 pm = med3(pm - d, pm, pm + d, cmp);
107 pn = med3(pn - 2 * d, pn - d, pn, cmp);
108 }
109 pm = med3(pl, pm, pn, cmp);
110 }
111 swap(a, pm);
112 pa = pb = a + es;
113
114 pc = pd = a + (n - 1) * es;
115 for (;;) {
116 while (pb <= pc && (cmp_result = cmp(pb, a)) <= 0) {
117 if (cmp_result == 0) {
118 swap(pa, pb);
119 pa += es;
120 }
121 pb += es;
122 }
123 while (pb <= pc && (cmp_result = cmp(pc, a)) >= 0) {
124 if (cmp_result == 0) {
125 swap(pc, pd);
126 pd -= es;
127 }
128 pc -= es;
129 }
130 if (pb > pc)
131 break;
132 swap(pb, pc);
133 pb += es;
134 pc -= es;
135 }
136
137 pn = a + n * es;
138 r = min(pa - a, pb - pa);
139 vecswap(a, pb - r, r);
140 r = min(pd - pc, pn - pd - es);
141 vecswap(pb, pn - r, r);
142 /*
143 * To save stack space we sort the smaller side of the partition first
144 * using recursion and eliminate tail recursion for the larger side.
145 */
146 r = pb - pa;
147 s = pd - pc;
148 if (r < s) {
149 /* Recurse for 1st side, iterate for 2nd side. */
150 if (s > es) {
151 if (r > es)
152 qsort(a, r / es, es, cmp);
153 a = pn - s;
154 n = s / es;
155 goto loop;
156 }
157 } else {
158 /* Recurse for 2nd side, iterate for 1st side. */
159 if (r > es) {
160 if (s > es)
161 qsort(pn - s, s / es, es, cmp);
162 n = r / es;
163 goto loop;
164 }
165 }
166 }
167
168 void
sort(void * a,size_t n,size_t es,int (* cmp)(const void *,const void *),void * x)169 sort(void *a, size_t n, size_t es, int (*cmp)(const void *, const void *),
170 void *x)
171 {
172 KASSERT(x == NULL);
173 qsort(a, n, es, cmp);
174 }
175