1  /*-
  2   * Copyright (c) 1991, 1993
  3   *	The Regents of the University of California.  All rights reserved.
  4   *
  5   * This code is derived from software contributed to Berkeley by
  6   * Ronnie Kon at Mindcraft Inc., Kevin Lew and Elmer Yglesias.
  7   *
  8   * Redistribution and use in source and binary forms, with or without
  9   * modification, are permitted provided that the following conditions
 10   * are met:
 11   * 1. Redistributions of source code must retain the above copyright
 12   *    notice, this list of conditions and the following disclaimer.
 13   * 2. Redistributions in binary form must reproduce the above copyright
 14   *    notice, this list of conditions and the following disclaimer in the
 15   *    documentation and/or other materials provided with the distribution.
 16   * 4. Neither the name of the University nor the names of its contributors
 17   *    may be used to endorse or promote products derived from this software
 18   *    without specific prior written permission.
 19   *
 20   * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 21   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 22   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 23   * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 24   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 25   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 26   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 27   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 28   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 29   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 30   * SUCH DAMAGE.
 31   */
 32  
 33  #if defined(LIBC_SCCS) && !defined(lint)
 34  static char sccsid[] = "@(#)heapsort.c	8.1 (Berkeley) 6/4/93";
 35  #endif /* LIBC_SCCS and not lint */
 36  #include <sys/cdefs.h>
 37  __FBSDID("$FreeBSD: src/lib/libc/stdlib/heapsort.c,v 1.6 2008/01/13 02:11:10 das Exp $");
 38  
 39  #include <errno.h>
 40  #include <stddef.h>
 41  #include <stdlib.h>
 42  
 43  /*
 44   * Swap two areas of size number of bytes.  Although qsort(3) permits random
 45   * blocks of memory to be sorted, sorting pointers is almost certainly the
 46   * common case (and, were it not, could easily be made so).  Regardless, it
 47   * isn't worth optimizing; the SWAP's get sped up by the cache, and pointer
 48   * arithmetic gets lost in the time required for comparison function calls.
 49   */
 50  #define	SWAP(a, b, count, size, tmp) { \
 51  	count = size; \
 52  	do { \
 53  		tmp = *a; \
 54  		*a++ = *b; \
 55  		*b++ = tmp; \
 56  	} while (--count); \
 57  }
 58  
 59  /* Copy one block of size size to another. */
 60  #define COPY(a, b, count, size, tmp1, tmp2) { \
 61  	count = size; \
 62  	tmp1 = a; \
 63  	tmp2 = b; \
 64  	do { \
 65  		*tmp1++ = *tmp2++; \
 66  	} while (--count); \
 67  }
 68  
 69  /*
 70   * Build the list into a heap, where a heap is defined such that for
 71   * the records K1 ... KN, Kj/2 >= Kj for 1 <= j/2 <= j <= N.
 72   *
 73   * There two cases.  If j == nmemb, select largest of Ki and Kj.  If
 74   * j < nmemb, select largest of Ki, Kj and Kj+1.
 75   */
 76  #define CREATE(initval, nmemb, par_i, child_i, par, child, size, count, tmp) { \
 77  	for (par_i = initval; (child_i = par_i * 2) <= nmemb; \
 78  	    par_i = child_i) { \
 79  		child = base + child_i * size; \
 80  		if (child_i < nmemb && compar(child, child + size) < 0) { \
 81  			child += size; \
 82  			++child_i; \
 83  		} \
 84  		par = base + par_i * size; \
 85  		if (compar(child, par) <= 0) \
 86  			break; \
 87  		SWAP(par, child, count, size, tmp); \
 88  	} \
 89  }
 90  
 91  /*
 92   * Select the top of the heap and 'heapify'.  Since by far the most expensive
 93   * action is the call to the compar function, a considerable optimization
 94   * in the average case can be achieved due to the fact that k, the displaced
 95   * elememt, is ususally quite small, so it would be preferable to first
 96   * heapify, always maintaining the invariant that the larger child is copied
 97   * over its parent's record.
 98   *
 99   * Then, starting from the *bottom* of the heap, finding k's correct place,
100   * again maintianing the invariant.  As a result of the invariant no element
101   * is 'lost' when k is assigned its correct place in the heap.
102   *
103   * The time savings from this optimization are on the order of 15-20% for the
104   * average case. See Knuth, Vol. 3, page 158, problem 18.
105   *
106   * XXX Don't break the #define SELECT line, below.  Reiser cpp gets upset.
107   */
108  #define SELECT(par_i, child_i, nmemb, par, child, size, k, count, tmp1, tmp2) { \
109  	for (par_i = 1; (child_i = par_i * 2) <= nmemb; par_i = child_i) { \
110  		child = base + child_i * size; \
111  		if (child_i < nmemb && compar(child, child + size) < 0) { \
112  			child += size; \
113  			++child_i; \
114  		} \
115  		par = base + par_i * size; \
116  		COPY(par, child, count, size, tmp1, tmp2); \
117  	} \
118  	for (;;) { \
119  		child_i = par_i; \
120  		par_i = child_i / 2; \
121  		child = base + child_i * size; \
122  		par = base + par_i * size; \
123  		if (child_i == 1 || compar(k, par) < 0) { \
124  			COPY(child, k, count, size, tmp1, tmp2); \
125  			break; \
126  		} \
127  		COPY(child, par, count, size, tmp1, tmp2); \
128  	} \
129  }
130  
131  /*
132   * Heapsort -- Knuth, Vol. 3, page 145.  Runs in O (N lg N), both average
133   * and worst.  While heapsort is faster than the worst case of quicksort,
134   * the BSD quicksort does median selection so that the chance of finding
135   * a data set that will trigger the worst case is nonexistent.  Heapsort's
136   * only advantage over quicksort is that it requires little additional memory.
137   */
138  int
139  heapsort_b(vbase, nmemb, size, compar)
140  	void *vbase;
141  	size_t nmemb, size;
142  	int (^compar)(const void *, const void *);
143  {
144  	size_t cnt, i, j, l;
145  	char tmp, *tmp1, *tmp2;
146  	char *base, *k, *p, *t;
147  
148  	if (nmemb <= 1)
149  		return (0);
150  
151  	if (!size) {
152  		errno = EINVAL;
153  		return (-1);
154  	}
155  
156  	if ((k = malloc(size)) == NULL)
157  		return (-1);
158  
159  	/*
160  	 * Items are numbered from 1 to nmemb, so offset from size bytes
161  	 * below the starting address.
162  	 */
163  	base = (char *)vbase - size;
164  
165  	for (l = nmemb / 2 + 1; --l;)
166  		CREATE(l, nmemb, i, j, t, p, size, cnt, tmp);
167  
168  	/*
169  	 * For each element of the heap, save the largest element into its
170  	 * final slot, save the displaced element (k), then recreate the
171  	 * heap.
172  	 */
173  	while (nmemb > 1) {
174  		COPY(k, base + nmemb * size, cnt, size, tmp1, tmp2);
175  		COPY(base + nmemb * size, base + size, cnt, size, tmp1, tmp2);
176  		--nmemb;
177  		SELECT(i, j, nmemb, t, p, size, k, cnt, tmp1, tmp2);
178  	}
179  	free(k);
180  	return (0);
181  }