1 // SPDX-License-Identifier: BSD-3-Clause
2 /* $OpenBSD: qsort.c,v 1.10 2005/08/08 08:05:37 espie Exp $ */
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 #include <sys/types.h>
32 #include <stdlib.h>
33 static __inline char
34 *med3(char *, char *, char *, int (*)(const void *, const void *));
35 static __inline void swapfunc(char *, char *, int, int);
36 #define min(a, b) (a) < (b) ? a : b
37 /*
38 * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
39 */
40 #define swapcode(TYPE, parmi, parmj, n) { \
41 long i = (n) / sizeof (TYPE); \
42 TYPE *pi = (TYPE *) (parmi); \
43 TYPE *pj = (TYPE *) (parmj); \
44 do { \
45 TYPE t = *pi; \
46 *pi++ = *pj; \
47 *pj++ = t; \
48 } while (--i > 0); \
49 }
50 #define SWAPINIT(a, es) swaptype = (uintptr_t)a % sizeof(long) || \
51 es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
52 static __inline void
swapfunc(char * a,char * b,int n,int swaptype)53 swapfunc(char *a, char *b, int n, int swaptype)
54 {
55 if (swaptype <= 1)
56 swapcode(long, a, b, n)
57 else
58 swapcode(char, a, b, n)
59 }
60 #define swap(a, b) \
61 if (swaptype == 0) { \
62 long t = *(long *)(a); \
63 *(long *)(a) = *(long *)(b); \
64 *(long *)(b) = t; \
65 } else \
66 swapfunc(a, b, es, swaptype)
67 #define vecswap(a, b, n) if ((n) > 0) swapfunc(a, b, n, swaptype)
68 static __inline char *
med3(char * a,char * b,char * c,int (* cmp)(const void *,const void *))69 med3(char *a, char *b, char *c, int (*cmp)(const void *, const void *))
70 {
71 return cmp(a, b) < 0 ?
72 (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a ))
73 :(cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c ));
74 }
75 void
qsort(void * aa,size_t n,size_t es,int (* cmp)(const void *,const void *))76 qsort(void *aa, size_t n, size_t es, int (*cmp)(const void *, const void *))
77 {
78 char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
79 int d, r, swaptype, swap_cnt;
80 char *a = aa;
81 loop: SWAPINIT(a, es);
82 swap_cnt = 0;
83 if (n < 7) {
84 for (pm = (char *)a + es; pm < (char *) a + n * es; pm += es)
85 for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
86 pl -= es)
87 swap(pl, pl - es);
88 return;
89 }
90 pm = (char *)a + (n / 2) * es;
91 if (n > 7) {
92 pl = (char *)a;
93 pn = (char *)a + (n - 1) * es;
94 if (n > 40) {
95 d = (n / 8) * es;
96 pl = med3(pl, pl + d, pl + 2 * d, cmp);
97 pm = med3(pm - d, pm, pm + d, cmp);
98 pn = med3(pn - 2 * d, pn - d, pn, cmp);
99 }
100 pm = med3(pl, pm, pn, cmp);
101 }
102 swap(a, pm);
103 pa = pb = (char *)a + es;
104
105 pc = pd = (char *)a + (n - 1) * es;
106 for (;;) {
107 while (pb <= pc && (r = cmp(pb, a)) <= 0) {
108 if (r == 0) {
109 swap_cnt = 1;
110 swap(pa, pb);
111 pa += es;
112 }
113 pb += es;
114 }
115 while (pb <= pc && (r = cmp(pc, a)) >= 0) {
116 if (r == 0) {
117 swap_cnt = 1;
118 swap(pc, pd);
119 pd -= es;
120 }
121 pc -= es;
122 }
123 if (pb > pc)
124 break;
125 swap(pb, pc);
126 swap_cnt = 1;
127 pb += es;
128 pc -= es;
129 }
130 if (swap_cnt == 0) { /* Switch to insertion sort */
131 for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
132 for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
133 pl -= es)
134 swap(pl, pl - es);
135 return;
136 }
137 pn = (char *)a + n * es;
138 r = min(pa - (char *)a, pb - pa);
139 vecswap(a, pb - r, r);
140 r = min(pd - pc, pn - pd - (int)es);
141 vecswap(pb, pn - r, r);
142 if ((r = pb - pa) > (int)es)
143 qsort(a, r / es, es, cmp);
144 if ((r = pd - pc) > (int)es) {
145 /* Iterate rather than recurse to save stack space */
146 a = pn - r;
147 n = r / es;
148 goto loop;
149 }
150 /* qsort(pn - r, r / es, es, cmp);*/
151 }
152