1  /*	$OpenBSD: qsort.c,v 1.11 2010/02/08 11:04:07 otto 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  
 34  static __inline char	*med3(char *, char *, char *, int (*)(const void *, const void *));
 35  static __inline void	 swapfunc(char *, char *, size_t, 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  	size_t 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  
 56  static __inline void
 57  swapfunc(char *a, char *b, size_t 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  
 75  static __inline char *
 76  med3(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  
 83  void
 84  qsort(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 cmp_result, swaptype, swap_cnt;
 88  	size_t d, r;
 89  	char *a = aa;
 90  
 91  loop:	SWAPINIT(a, es);
 92  	swap_cnt = 0;
 93  	if (n < 7) {
 94  		for (pm = (char *)a + es; pm < (char *) a + n * es; pm += es)
 95  			for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
 96  			     pl -= es)
 97  				swap(pl, pl - es);
 98  		return;
 99  	}
100  	pm = (char *)a + (n / 2) * es;
101  	if (n > 7) {
102  		pl = (char *)a;
103  		pn = (char *)a + (n - 1) * es;
104  		if (n > 40) {
105  			d = (n / 8) * es;
106  			pl = med3(pl, pl + d, pl + 2 * d, cmp);
107  			pm = med3(pm - d, pm, pm + d, cmp);
108  			pn = med3(pn - 2 * d, pn - d, pn, cmp);
109  		}
110  		pm = med3(pl, pm, pn, cmp);
111  	}
112  	swap(a, pm);
113  	pa = pb = (char *)a + es;
114  
115  	pc = pd = (char *)a + (n - 1) * es;
116  	for (;;) {
117  		while (pb <= pc && (cmp_result = cmp(pb, a)) <= 0) {
118  			if (cmp_result == 0) {
119  				swap_cnt = 1;
120  				swap(pa, pb);
121  				pa += es;
122  			}
123  			pb += es;
124  		}
125  		while (pb <= pc && (cmp_result = cmp(pc, a)) >= 0) {
126  			if (cmp_result == 0) {
127  				swap_cnt = 1;
128  				swap(pc, pd);
129  				pd -= es;
130  			}
131  			pc -= es;
132  		}
133  		if (pb > pc)
134  			break;
135  		swap(pb, pc);
136  		swap_cnt = 1;
137  		pb += es;
138  		pc -= es;
139  	}
140  	if (swap_cnt == 0) {  /* Switch to insertion sort */
141  		for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
142  			for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
143  			     pl -= es)
144  				swap(pl, pl - es);
145  		return;
146  	}
147  
148  	pn = (char *)a + n * es;
149  	r = min(pa - (char *)a, pb - pa);
150  	vecswap(a, pb - r, r);
151  	r = min(pd - pc, pn - pd - es);
152  	vecswap(pb, pn - r, r);
153  	if ((r = pb - pa) > es)
154  		qsort(a, r / es, es, cmp);
155  	if ((r = pd - pc) > es) {
156  		/* Iterate rather than recurse to save stack space */
157  		a = pn - r;
158  		n = r / es;
159  		goto loop;
160  	}
161  /*		qsort(pn - r, r / es, es, cmp);*/
162  }