xref: /freebsd/lib/libc/stdlib/qsort.c (revision 1e413cf93298b5b97441a21d9a50fdcd0ee9945e)
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 #if defined(LIBC_SCCS) && !defined(lint)
31 static char sccsid[] = "@(#)qsort.c	8.1 (Berkeley) 6/4/93";
32 #endif /* LIBC_SCCS and not lint */
33 #include <sys/cdefs.h>
34 __FBSDID("$FreeBSD$");
35 
36 #include <stdlib.h>
37 
38 #ifdef I_AM_QSORT_R
39 typedef int		 cmp_t(void *, const void *, const void *);
40 #else
41 typedef int		 cmp_t(const void *, const void *);
42 #endif
43 static inline char	*med3(char *, char *, char *, cmp_t *, void *);
44 static inline void	 swapfunc(char *, char *, int, int);
45 
46 #define min(a, b)	(a) < (b) ? a : b
47 
48 /*
49  * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
50  */
51 #define swapcode(TYPE, parmi, parmj, n) { 		\
52 	long i = (n) / sizeof (TYPE); 			\
53 	TYPE *pi = (TYPE *) (parmi); 		\
54 	TYPE *pj = (TYPE *) (parmj); 		\
55 	do { 						\
56 		TYPE	t = *pi;		\
57 		*pi++ = *pj;				\
58 		*pj++ = t;				\
59         } while (--i > 0);				\
60 }
61 
62 #define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
63 	es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
64 
65 static inline void
66 swapfunc(a, b, n, swaptype)
67 	char *a, *b;
68 	int n, swaptype;
69 {
70 	if(swaptype <= 1)
71 		swapcode(long, a, b, n)
72 	else
73 		swapcode(char, a, b, n)
74 }
75 
76 #define swap(a, b)					\
77 	if (swaptype == 0) {				\
78 		long t = *(long *)(a);			\
79 		*(long *)(a) = *(long *)(b);		\
80 		*(long *)(b) = t;			\
81 	} else						\
82 		swapfunc(a, b, es, swaptype)
83 
84 #define vecswap(a, b, n) 	if ((n) > 0) swapfunc(a, b, n, swaptype)
85 
86 #ifdef I_AM_QSORT_R
87 #define	CMP(t, x, y) (cmp((t), (x), (y)))
88 #else
89 #define	CMP(t, x, y) (cmp((x), (y)))
90 #endif
91 
92 static inline char *
93 med3(char *a, char *b, char *c, cmp_t *cmp, void *thunk
94 #ifndef I_AM_QSORT_R
95 __unused
96 #endif
97 )
98 {
99 	return CMP(thunk, a, b) < 0 ?
100 	       (CMP(thunk, b, c) < 0 ? b : (CMP(thunk, a, c) < 0 ? c : a ))
101               :(CMP(thunk, b, c) > 0 ? b : (CMP(thunk, a, c) < 0 ? a : c ));
102 }
103 
104 #ifdef I_AM_QSORT_R
105 void
106 qsort_r(void *a, size_t n, size_t es, void *thunk, cmp_t *cmp)
107 #else
108 #define thunk NULL
109 void
110 qsort(void *a, size_t n, size_t es, cmp_t *cmp)
111 #endif
112 {
113 	char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
114 	size_t d, r;
115 	int cmp_result;
116 	int swaptype, swap_cnt;
117 
118 loop:	SWAPINIT(a, es);
119 	swap_cnt = 0;
120 	if (n < 7) {
121 		for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
122 			for (pl = pm;
123 			     pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
124 			     pl -= es)
125 				swap(pl, pl - es);
126 		return;
127 	}
128 	pm = (char *)a + (n / 2) * es;
129 	if (n > 7) {
130 		pl = a;
131 		pn = (char *)a + (n - 1) * es;
132 		if (n > 40) {
133 			d = (n / 8) * es;
134 			pl = med3(pl, pl + d, pl + 2 * d, cmp, thunk);
135 			pm = med3(pm - d, pm, pm + d, cmp, thunk);
136 			pn = med3(pn - 2 * d, pn - d, pn, cmp, thunk);
137 		}
138 		pm = med3(pl, pm, pn, cmp, thunk);
139 	}
140 	swap(a, pm);
141 	pa = pb = (char *)a + es;
142 
143 	pc = pd = (char *)a + (n - 1) * es;
144 	for (;;) {
145 		while (pb <= pc && (cmp_result = CMP(thunk, pb, a)) <= 0) {
146 			if (cmp_result == 0) {
147 				swap_cnt = 1;
148 				swap(pa, pb);
149 				pa += es;
150 			}
151 			pb += es;
152 		}
153 		while (pb <= pc && (cmp_result = CMP(thunk, pc, a)) >= 0) {
154 			if (cmp_result == 0) {
155 				swap_cnt = 1;
156 				swap(pc, pd);
157 				pd -= es;
158 			}
159 			pc -= es;
160 		}
161 		if (pb > pc)
162 			break;
163 		swap(pb, pc);
164 		swap_cnt = 1;
165 		pb += es;
166 		pc -= es;
167 	}
168 	if (swap_cnt == 0) {  /* Switch to insertion sort */
169 		for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
170 			for (pl = pm;
171 			     pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
172 			     pl -= es)
173 				swap(pl, pl - es);
174 		return;
175 	}
176 
177 	pn = (char *)a + n * es;
178 	r = min(pa - (char *)a, pb - pa);
179 	vecswap(a, pb - r, r);
180 	r = min(pd - pc, pn - pd - es);
181 	vecswap(pb, pn - r, r);
182 	if ((r = pb - pa) > es)
183 #ifdef I_AM_QSORT_R
184 		qsort_r(a, r / es, es, thunk, cmp);
185 #else
186 		qsort(a, r / es, es, cmp);
187 #endif
188 	if ((r = pd - pc) > es) {
189 		/* Iterate rather than recurse to save stack space */
190 		a = pn - r;
191 		n = r / es;
192 		goto loop;
193 	}
194 /*		qsort(pn - r, r / es, es, cmp);*/
195 }
196