qsort.c revision 319285 
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 * 3. 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)
31static 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: stable/11/lib/libc/stdlib/qsort.c 319285 2017-05-31 05:52:32Z delphij $");
35
36#include <stdlib.h>
37
38#ifdef I_AM_QSORT_R
39typedef int		 cmp_t(void *, const void *, const void *);
40#else
41typedef int		 cmp_t(const void *, const void *);
42#endif
43static inline char	*med3(char *, char *, char *, cmp_t *, void *);
44static inline void	 swapfunc(char *, char *, size_t, 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	size_t 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(TYPE, a, es) swaptype_ ## TYPE =	\
63	((char *)a - (char *)0) % sizeof(TYPE) ||	\
64	es % sizeof(TYPE) ? 2 : es == sizeof(TYPE) ? 0 : 1;
65
66static inline void
67swapfunc(char *a, char *b, size_t n, int swaptype_long, int swaptype_int)
68{
69	if (swaptype_long <= 1)
70		swapcode(long, a, b, n)
71	else if (swaptype_int <= 1)
72		swapcode(int, a, b, n)
73	else
74		swapcode(char, a, b, n)
75}
76
77#define	swap(a, b)					\
78	if (swaptype_long == 0) {			\
79		long t = *(long *)(a);			\
80		*(long *)(a) = *(long *)(b);		\
81		*(long *)(b) = t;			\
82	} else if (swaptype_int == 0) {			\
83		int t = *(int *)(a);			\
84		*(int *)(a) = *(int *)(b);		\
85		*(int *)(b) = t;			\
86	} else						\
87		swapfunc(a, b, es, swaptype_long, swaptype_int)
88
89#define	vecswap(a, b, n)				\
90	if ((n) > 0) swapfunc(a, b, n, swaptype_long, swaptype_int)
91
92#ifdef I_AM_QSORT_R
93#define	CMP(t, x, y) (cmp((t), (x), (y)))
94#else
95#define	CMP(t, x, y) (cmp((x), (y)))
96#endif
97
98static inline char *
99med3(char *a, char *b, char *c, cmp_t *cmp, void *thunk
100#ifndef I_AM_QSORT_R
101__unused
102#endif
103)
104{
105	return CMP(thunk, a, b) < 0 ?
106	       (CMP(thunk, b, c) < 0 ? b : (CMP(thunk, a, c) < 0 ? c : a ))
107	      :(CMP(thunk, b, c) > 0 ? b : (CMP(thunk, a, c) < 0 ? a : c ));
108}
109
110#ifdef I_AM_QSORT_R
111void
112qsort_r(void *a, size_t n, size_t es, void *thunk, cmp_t *cmp)
113#else
114#define	thunk NULL
115void
116qsort(void *a, size_t n, size_t es, cmp_t *cmp)
117#endif
118{
119	char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
120	size_t d1, d2;
121	int cmp_result;
122	int swaptype_long, swaptype_int, swap_cnt;
123
124loop:	SWAPINIT(long, a, es);
125	SWAPINIT(int, a, es);
126	swap_cnt = 0;
127	if (n < 7) {
128		for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
129			for (pl = pm;
130			     pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
131			     pl -= es)
132				swap(pl, pl - es);
133		return;
134	}
135	pm = (char *)a + (n / 2) * es;
136	if (n > 7) {
137		pl = a;
138		pn = (char *)a + (n - 1) * es;
139		if (n > 40) {
140			size_t d = (n / 8) * es;
141
142			pl = med3(pl, pl + d, pl + 2 * d, cmp, thunk);
143			pm = med3(pm - d, pm, pm + d, cmp, thunk);
144			pn = med3(pn - 2 * d, pn - d, pn, cmp, thunk);
145		}
146		pm = med3(pl, pm, pn, cmp, thunk);
147	}
148	swap(a, pm);
149	pa = pb = (char *)a + es;
150
151	pc = pd = (char *)a + (n - 1) * es;
152	for (;;) {
153		while (pb <= pc && (cmp_result = CMP(thunk, pb, a)) <= 0) {
154			if (cmp_result == 0) {
155				swap_cnt = 1;
156				swap(pa, pb);
157				pa += es;
158			}
159			pb += es;
160		}
161		while (pb <= pc && (cmp_result = CMP(thunk, pc, a)) >= 0) {
162			if (cmp_result == 0) {
163				swap_cnt = 1;
164				swap(pc, pd);
165				pd -= es;
166			}
167			pc -= es;
168		}
169		if (pb > pc)
170			break;
171		swap(pb, pc);
172		swap_cnt = 1;
173		pb += es;
174		pc -= es;
175	}
176	if (swap_cnt == 0) {  /* Switch to insertion sort */
177		for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
178			for (pl = pm;
179			     pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
180			     pl -= es)
181				swap(pl, pl - es);
182		return;
183	}
184
185	pn = (char *)a + n * es;
186	d1 = MIN(pa - (char *)a, pb - pa);
187	vecswap(a, pb - d1, d1);
188	d1 = MIN(pd - pc, pn - pd - es);
189	vecswap(pb, pn - d1, d1);
190
191	d1 = pb - pa;
192	d2 = pd - pc;
193	if (d1 <= d2) {
194		/* Recurse on left partition, then iterate on right partition */
195		if (d1 > es) {
196#ifdef I_AM_QSORT_R
197			qsort_r(a, d1 / es, es, thunk, cmp);
198#else
199			qsort(a, d1 / es, es, cmp);
200#endif
201		}
202		if (d2 > es) {
203			/* Iterate rather than recurse to save stack space */
204			/* qsort(pn - d2, d2 / es, es, cmp); */
205			a = pn - d2;
206			n = d2 / es;
207			goto loop;
208		}
209	} else {
210		/* Recurse on right partition, then iterate on left partition */
211		if (d2 > es) {
212#ifdef I_AM_QSORT_R
213			qsort_r(pn - d2, d2 / es, es, thunk, cmp);
214#else
215			qsort(pn - d2, d2 / es, es, cmp);
216#endif
217		}
218		if (d1 > es) {
219			/* Iterate rather than recurse to save stack space */
220			/* qsort(a, d1 / es, es, cmp); */
221			n = d1 / es;
222			goto loop;
223		}
224	}
225}
226