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: releng/11.1/sys/libkern/qsort.c 319285 2017-05-31 05:52:32Z delphij $");
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 *, size_t, int, int);
43
44 /*
45 * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
46 */
47 #define swapcode(TYPE, parmi, parmj, n) { \
48 size_t i = (n) / sizeof (TYPE); \
49 TYPE *pi = (TYPE *) (parmi); \
50 TYPE *pj = (TYPE *) (parmj); \
51 do { \
52 TYPE t = *pi; \
53 *pi++ = *pj; \
54 *pj++ = t; \
55 } while (--i > 0); \
56 }
57
58 #define SWAPINIT(TYPE, a, es) swaptype_ ## TYPE = \
59 ((char *)a - (char *)0) % sizeof(TYPE) || \
60 es % sizeof(TYPE) ? 2 : es == sizeof(TYPE) ? 0 : 1;
61
62 static inline void
63 swapfunc(char *a, char *b, size_t n, int swaptype_long, int swaptype_int)
64 {
65 if (swaptype_long <= 1)
66 swapcode(long, a, b, n)
67 else if (swaptype_int <= 1)
68 swapcode(int, a, b, n)
69 else
70 swapcode(char, a, b, n)
71 }
72
73 #define swap(a, b) \
74 if (swaptype_long == 0) { \
75 long t = *(long *)(a); \
76 *(long *)(a) = *(long *)(b); \
77 *(long *)(b) = t; \
78 } else if (swaptype_int == 0) { \
79 int t = *(int *)(a); \
80 *(int *)(a) = *(int *)(b); \
81 *(int *)(b) = t; \
82 } else \
83 swapfunc(a, b, es, swaptype_long, swaptype_int)
84
85 #define vecswap(a, b, n) \
86 if ((n) > 0) swapfunc(a, b, n, swaptype_long, swaptype_int)
87
88 #ifdef I_AM_QSORT_R
89 #define CMP(t, x, y) (cmp((t), (x), (y)))
90 #else
91 #define CMP(t, x, y) (cmp((x), (y)))
92 #endif
93
94 static inline char *
95 med3(char *a, char *b, char *c, cmp_t *cmp, void *thunk
96 #ifndef I_AM_QSORT_R
97 __unused
98 #endif
99 )
100 {
101 return CMP(thunk, a, b) < 0 ?
102 (CMP(thunk, b, c) < 0 ? b : (CMP(thunk, a, c) < 0 ? c : a ))
103 :(CMP(thunk, b, c) > 0 ? b : (CMP(thunk, a, c) < 0 ? a : c ));
104 }
105
106 #ifdef I_AM_QSORT_R
107 void
108 qsort_r(void *a, size_t n, size_t es, void *thunk, cmp_t *cmp)
109 #else
110 #define thunk NULL
111 void
112 qsort(void *a, size_t n, size_t es, cmp_t *cmp)
113 #endif
114 {
115 char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
116 size_t d1, d2;
117 int cmp_result;
118 int swaptype_long, swaptype_int, swap_cnt;
119
120 loop: SWAPINIT(long, a, es);
121 SWAPINIT(int, a, es);
122 swap_cnt = 0;
123 if (n < 7) {
124 for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
125 for (pl = pm;
126 pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
127 pl -= es)
128 swap(pl, pl - es);
129 return;
130 }
131 pm = (char *)a + (n / 2) * es;
132 if (n > 7) {
133 pl = a;
134 pn = (char *)a + (n - 1) * es;
135 if (n > 40) {
136 size_t d = (n / 8) * es;
137
138 pl = med3(pl, pl + d, pl + 2 * d, cmp, thunk);
139 pm = med3(pm - d, pm, pm + d, cmp, thunk);
140 pn = med3(pn - 2 * d, pn - d, pn, cmp, thunk);
141 }
142 pm = med3(pl, pm, pn, cmp, thunk);
143 }
144 swap(a, pm);
145 pa = pb = (char *)a + es;
146
147 pc = pd = (char *)a + (n - 1) * es;
148 for (;;) {
149 while (pb <= pc && (cmp_result = CMP(thunk, pb, a)) <= 0) {
150 if (cmp_result == 0) {
151 swap_cnt = 1;
152 swap(pa, pb);
153 pa += es;
154 }
155 pb += es;
156 }
157 while (pb <= pc && (cmp_result = CMP(thunk, pc, a)) >= 0) {
158 if (cmp_result == 0) {
159 swap_cnt = 1;
160 swap(pc, pd);
161 pd -= es;
162 }
163 pc -= es;
164 }
165 if (pb > pc)
166 break;
167 swap(pb, pc);
168 swap_cnt = 1;
169 pb += es;
170 pc -= es;
171 }
172 if (swap_cnt == 0) { /* Switch to insertion sort */
173 for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
174 for (pl = pm;
175 pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
176 pl -= es)
177 swap(pl, pl - es);
178 return;
179 }
180
181 pn = (char *)a + n * es;
182 d1 = MIN(pa - (char *)a, pb - pa);
183 vecswap(a, pb - d1, d1);
184 d1 = MIN(pd - pc, pn - pd - es);
185 vecswap(pb, pn - d1, d1);
186
187 d1 = pb - pa;
188 d2 = pd - pc;
189 if (d1 <= d2) {
190 /* Recurse on left partition, then iterate on right partition */
191 if (d1 > es) {
192 #ifdef I_AM_QSORT_R
193 qsort_r(a, d1 / es, es, thunk, cmp);
194 #else
195 qsort(a, d1 / es, es, cmp);
196 #endif
197 }
198 if (d2 > es) {
199 /* Iterate rather than recurse to save stack space */
200 /* qsort(pn - d2, d2 / es, es, cmp); */
201 a = pn - d2;
202 n = d2 / es;
203 goto loop;
204 }
205 } else {
206 /* Recurse on right partition, then iterate on left partition */
207 if (d2 > es) {
208 #ifdef I_AM_QSORT_R
209 qsort_r(pn - d2, d2 / es, es, thunk, cmp);
210 #else
211 qsort(pn - d2, d2 / es, es, cmp);
212 #endif
213 }
214 if (d1 > es) {
215 /* Iterate rather than recurse to save stack space */
216 /* qsort(a, d1 / es, es, cmp); */
217 n = d1 / es;
218 goto loop;
219 }
220 }
221 }
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