FreeBSD/Linux Kernel Cross Reference
sys/libkern/qsort.c
1 /*-
2 * Copyright (c) 1992, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 4. Neither the name of the University nor the names of its contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30 #include <sys/cdefs.h>
31 __FBSDID("$FreeBSD: src/sys/libkern/qsort.c,v 1.15 2004/07/15 23:58:23 glebius Exp $");
32
33 #include <sys/param.h>
34 #include <sys/libkern.h>
35
36 #ifdef I_AM_QSORT_R
37 typedef int cmp_t(void *, const void *, const void *);
38 #else
39 typedef int cmp_t(const void *, const void *);
40 #endif
41 static __inline char *med3(char *, char *, char *, cmp_t *, void *);
42 static __inline void swapfunc(char *, char *, int, int);
43
44 #define min(a, b) (a) < (b) ? (a) : (b)
45
46 /*
47 * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
48 */
49 #define swapcode(TYPE, parmi, parmj, n) { \
50 long i = (n) / sizeof (TYPE); \
51 register TYPE *pi = (TYPE *) (parmi); \
52 register TYPE *pj = (TYPE *) (parmj); \
53 do { \
54 register TYPE t = *pi; \
55 *pi++ = *pj; \
56 *pj++ = t; \
57 } while (--i > 0); \
58 }
59
60 #define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
61 es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
62
63 static __inline void
64 swapfunc(char *a, char *b, int n, int swaptype)
65 {
66 if(swaptype <= 1)
67 swapcode(long, a, b, n)
68 else
69 swapcode(char, a, b, n)
70 }
71
72 #define swap(a, b) \
73 if (swaptype == 0) { \
74 long t = *(long *)(a); \
75 *(long *)(a) = *(long *)(b); \
76 *(long *)(b) = t; \
77 } else \
78 swapfunc(a, b, es, swaptype)
79
80 #define vecswap(a, b, n) if ((n) > 0) swapfunc(a, b, n, swaptype)
81
82 #ifdef I_AM_QSORT_R
83 #define CMP(t, x, y) (cmp((t), (x), (y)))
84 #else
85 #define CMP(t, x, y) (cmp((x), (y)))
86 #endif
87
88 static __inline char *
89 med3(char *a, char *b, char *c, cmp_t *cmp, void *thunk
90 #ifndef I_AM_QSORT_R
91 __unused
92 #endif
93 )
94 {
95 return CMP(thunk, a, b) < 0 ?
96 (CMP(thunk, b, c) < 0 ? b : (CMP(thunk, a, c) < 0 ? c : a ))
97 :(CMP(thunk, b, c) > 0 ? b : (CMP(thunk, a, c) < 0 ? a : c ));
98 }
99
100 #ifdef I_AM_QSORT_R
101 void
102 qsort_r(void *a, size_t n, size_t es, void *thunk, cmp_t *cmp)
103 #else
104 #define thunk NULL
105 void
106 qsort(void *a, size_t n, size_t es, cmp_t *cmp)
107 #endif
108 {
109 char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
110 int d, r, swaptype, swap_cnt;
111
112 loop: SWAPINIT(a, es);
113 swap_cnt = 0;
114 if (n < 7) {
115 for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
116 for (pl = pm; pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
117 pl -= es)
118 swap(pl, pl - es);
119 return;
120 }
121 pm = (char *)a + (n / 2) * es;
122 if (n > 7) {
123 pl = a;
124 pn = (char *)a + (n - 1) * es;
125 if (n > 40) {
126 d = (n / 8) * es;
127 pl = med3(pl, pl + d, pl + 2 * d, cmp, thunk);
128 pm = med3(pm - d, pm, pm + d, cmp, thunk);
129 pn = med3(pn - 2 * d, pn - d, pn, cmp, thunk);
130 }
131 pm = med3(pl, pm, pn, cmp, thunk);
132 }
133 swap(a, pm);
134 pa = pb = (char *)a + es;
135
136 pc = pd = (char *)a + (n - 1) * es;
137 for (;;) {
138 while (pb <= pc && (r = CMP(thunk, pb, a)) <= 0) {
139 if (r == 0) {
140 swap_cnt = 1;
141 swap(pa, pb);
142 pa += es;
143 }
144 pb += es;
145 }
146 while (pb <= pc && (r = CMP(thunk, pc, a)) >= 0) {
147 if (r == 0) {
148 swap_cnt = 1;
149 swap(pc, pd);
150 pd -= es;
151 }
152 pc -= es;
153 }
154 if (pb > pc)
155 break;
156 swap(pb, pc);
157 swap_cnt = 1;
158 pb += es;
159 pc -= es;
160 }
161 if (swap_cnt == 0) { /* Switch to insertion sort */
162 for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
163 for (pl = pm; pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
164 pl -= es)
165 swap(pl, pl - es);
166 return;
167 }
168
169 pn = (char *)a + n * es;
170 r = min(pa - (char *)a, pb - pa);
171 vecswap(a, pb - r, r);
172 r = min(pd - pc, pn - pd - es);
173 vecswap(pb, pn - r, r);
174 if ((r = pb - pa) > es)
175 #ifdef I_AM_QSORT_R
176 qsort_r(a, r / es, es, thunk, cmp);
177 #else
178 qsort(a, r / es, es, cmp);
179 #endif
180 if ((r = pd - pc) > es) {
181 /* Iterate rather than recurse to save stack space */
182 a = pn - r;
183 n = r / es;
184 goto loop;
185 }
186 }
187
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