1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
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 #if defined(LIBC_SCCS) && !defined(lint)
33 static char sccsid[] = "@(#)qsort.c 8.1 (Berkeley) 6/4/93";
34 #endif /* LIBC_SCCS and not lint */
35 #include <sys/cdefs.h>
36 __FBSDID("$FreeBSD: head/lib/libc/stdlib/qsort.c 334928 2018-06-10 17:54:44Z kib $");
37
38 #include <stdlib.h>
39
40 #ifdef I_AM_QSORT_R
41 typedef int cmp_t(void *, const void *, const void *);
42 #else
43 typedef int cmp_t(const void *, const void *);
44 #endif
45 static inline char *med3(char *, char *, char *, cmp_t *, void *);
46
47 #define MIN(a, b) ((a) < (b) ? a : b)
48
49 /*
50 * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
51 */
52
53 static inline void
swapfunc(char * a,char * b,size_t es)54 swapfunc(char *a, char *b, size_t es)
55 {
56 char t;
57
58 do {
59 t = *a;
60 *a++ = *b;
61 *b++ = t;
62 } while (--es > 0);
63 }
64
65 #define vecswap(a, b, n) \
66 if ((n) > 0) swapfunc(a, b, n)
67
68 #ifdef I_AM_QSORT_R
69 #define CMP(t, x, y) (cmp((t), (x), (y)))
70 #else
71 #define CMP(t, x, y) (cmp((x), (y)))
72 #endif
73
74 static inline char *
med3(char * a,char * b,char * c,cmp_t * cmp,void * thunk __unused)75 med3(char *a, char *b, char *c, cmp_t *cmp, void *thunk
76 #ifndef I_AM_QSORT_R
77 __unused
78 #endif
79 )
80 {
81 return CMP(thunk, a, b) < 0 ?
82 (CMP(thunk, b, c) < 0 ? b : (CMP(thunk, a, c) < 0 ? c : a ))
83 :(CMP(thunk, b, c) > 0 ? b : (CMP(thunk, a, c) < 0 ? a : c ));
84 }
85
86 #ifdef I_AM_QSORT_R
87 void
qsort_r(void * a,size_t n,size_t es,void * thunk,cmp_t * cmp)88 qsort_r(void *a, size_t n, size_t es, void *thunk, cmp_t *cmp)
89 #else
90 #define thunk NULL
91 void
92 qsort(void *a, size_t n, size_t es, cmp_t *cmp)
93 #endif
94 {
95 char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
96 size_t d1, d2;
97 int cmp_result;
98 int swap_cnt;
99
100 loop:
101 swap_cnt = 0;
102 if (n < 7) {
103 for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
104 for (pl = pm;
105 pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
106 pl -= es)
107 swapfunc(pl, pl - es, es);
108 return;
109 }
110 pm = (char *)a + (n / 2) * es;
111 if (n > 7) {
112 pl = a;
113 pn = (char *)a + (n - 1) * es;
114 if (n > 40) {
115 size_t d = (n / 8) * es;
116
117 pl = med3(pl, pl + d, pl + 2 * d, cmp, thunk);
118 pm = med3(pm - d, pm, pm + d, cmp, thunk);
119 pn = med3(pn - 2 * d, pn - d, pn, cmp, thunk);
120 }
121 pm = med3(pl, pm, pn, cmp, thunk);
122 }
123 swapfunc(a, pm, es);
124 pa = pb = (char *)a + es;
125
126 pc = pd = (char *)a + (n - 1) * es;
127 for (;;) {
128 while (pb <= pc && (cmp_result = CMP(thunk, pb, a)) <= 0) {
129 if (cmp_result == 0) {
130 swap_cnt = 1;
131 swapfunc(pa, pb, es);
132 pa += es;
133 }
134 pb += es;
135 }
136 while (pb <= pc && (cmp_result = CMP(thunk, pc, a)) >= 0) {
137 if (cmp_result == 0) {
138 swap_cnt = 1;
139 swapfunc(pc, pd, es);
140 pd -= es;
141 }
142 pc -= es;
143 }
144 if (pb > pc)
145 break;
146 swapfunc(pb, pc, es);
147 swap_cnt = 1;
148 pb += es;
149 pc -= es;
150 }
151 if (swap_cnt == 0) { /* Switch to insertion sort */
152 for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
153 for (pl = pm;
154 pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
155 pl -= es)
156 swapfunc(pl, pl - es, es);
157 return;
158 }
159
160 pn = (char *)a + n * es;
161 d1 = MIN(pa - (char *)a, pb - pa);
162 vecswap(a, pb - d1, d1);
163 d1 = MIN(pd - pc, pn - pd - es);
164 vecswap(pb, pn - d1, d1);
165
166 d1 = pb - pa;
167 d2 = pd - pc;
168 if (d1 <= d2) {
169 /* Recurse on left partition, then iterate on right partition */
170 if (d1 > es) {
171 #ifdef I_AM_QSORT_R
172 qsort_r(a, d1 / es, es, thunk, cmp);
173 #else
174 qsort(a, d1 / es, es, cmp);
175 #endif
176 }
177 if (d2 > es) {
178 /* Iterate rather than recurse to save stack space */
179 /* qsort(pn - d2, d2 / es, es, cmp); */
180 a = pn - d2;
181 n = d2 / es;
182 goto loop;
183 }
184 } else {
185 /* Recurse on right partition, then iterate on left partition */
186 if (d2 > es) {
187 #ifdef I_AM_QSORT_R
188 qsort_r(pn - d2, d2 / es, es, thunk, cmp);
189 #else
190 qsort(pn - d2, d2 / es, es, cmp);
191 #endif
192 }
193 if (d1 > es) {
194 /* Iterate rather than recurse to save stack space */
195 /* qsort(a, d1 / es, es, cmp); */
196 n = d1 / es;
197 goto loop;
198 }
199 }
200 }
201