1/*	$OpenBSD: qsort.c,v 1.10 2005/08/08 08:05:37 espie Exp $ */
2/*-
3 * Copyright (c) 1992, 1993
4 *	The Regents of the University of California.  All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 * 3. Neither the name of the University nor the names of its contributors
15 *    may be used to endorse or promote products derived from this software
16 *    without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGE.
29 */
30
31#include <sys/types.h>
32#include <stdlib.h>
33
34static __inline char	*med3(char *, char *, char *, int (*)(const void *, const void *));
35static __inline void	 swapfunc(char *, char *, int, int);
36
37#define min(a, b)	(a) < (b) ? a : b
38
39/*
40 * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
41 */
42#define swapcode(TYPE, parmi, parmj, n) {		\
43	long i = (n) / sizeof (TYPE);			\
44	TYPE *pi = (TYPE *) (parmi);			\
45	TYPE *pj = (TYPE *) (parmj);			\
46	do {						\
47		TYPE	t = *pi;			\
48		*pi++ = *pj;				\
49		*pj++ = t;				\
50        } while (--i > 0);				\
51}
52
53#define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
54	es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
55
56static __inline void
57swapfunc(char *a, char *b, int n, int swaptype)
58{
59	if (swaptype <= 1)
60		swapcode(long, a, b, n)
61	else
62		swapcode(char, a, b, n)
63}
64
65#define swap(a, b)					\
66	if (swaptype == 0) {				\
67		long t = *(long *)(a);			\
68		*(long *)(a) = *(long *)(b);		\
69		*(long *)(b) = t;			\
70	} else						\
71		swapfunc(a, b, es, swaptype)
72
73#define vecswap(a, b, n)	if ((n) > 0) swapfunc(a, b, n, swaptype)
74
75static __inline char *
76med3(char *a, char *b, char *c, int (*cmp)(const void *, const void *))
77{
78	return cmp(a, b) < 0 ?
79	       (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a ))
80              :(cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c ));
81}
82
83void
84qsort(void *aa, size_t n, size_t es, int (*cmp)(const void *, const void *))
85{
86	char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
87	int d, r, swaptype, swap_cnt;
88	char *a = aa;
89
90loop:	SWAPINIT(a, es);
91	swap_cnt = 0;
92	if (n < 7) {
93		for (pm = (char *)a + es; pm < (char *) a + n * es; pm += es)
94			for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
95			     pl -= es)
96				swap(pl, pl - es);
97		return;
98	}
99	pm = (char *)a + (n / 2) * es;
100	if (n > 7) {
101		pl = (char *)a;
102		pn = (char *)a + (n - 1) * es;
103		if (n > 40) {
104			d = (n / 8) * es;
105			pl = med3(pl, pl + d, pl + 2 * d, cmp);
106			pm = med3(pm - d, pm, pm + d, cmp);
107			pn = med3(pn - 2 * d, pn - d, pn, cmp);
108		}
109		pm = med3(pl, pm, pn, cmp);
110	}
111	swap(a, pm);
112	pa = pb = (char *)a + es;
113
114	pc = pd = (char *)a + (n - 1) * es;
115	for (;;) {
116		while (pb <= pc && (r = cmp(pb, a)) <= 0) {
117			if (r == 0) {
118				swap_cnt = 1;
119				swap(pa, pb);
120				pa += es;
121			}
122			pb += es;
123		}
124		while (pb <= pc && (r = cmp(pc, a)) >= 0) {
125			if (r == 0) {
126				swap_cnt = 1;
127				swap(pc, pd);
128				pd -= es;
129			}
130			pc -= es;
131		}
132		if (pb > pc)
133			break;
134		swap(pb, pc);
135		swap_cnt = 1;
136		pb += es;
137		pc -= es;
138	}
139	if (swap_cnt == 0) {  /* Switch to insertion sort */
140		for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
141			for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
142			     pl -= es)
143				swap(pl, pl - es);
144		return;
145	}
146
147	pn = (char *)a + n * es;
148	r = min(pa - (char *)a, pb - pa);
149	vecswap(a, pb - r, r);
150	r = min(pd - pc, pn - pd - (int)es);
151	vecswap(pb, pn - r, r);
152	if ((r = pb - pa) > (int)es)
153		qsort(a, r / es, es, cmp);
154	if ((r = pd - pc) > (int)es) {
155		/* Iterate rather than recurse to save stack space */
156		a = pn - r;
157		n = r / es;
158		goto loop;
159	}
160	/* qsort(pn - r, r / es, es, cmp); */
161}
162