libsa/sort.c

   1 /*
   2  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
   7  *
   8  * This file contains Original Code and/or Modifications of Original Code
   9  * as defined in and that are subject to the Apple Public Source License
  10  * Version 2.0 (the 'License'). You may not use this file except in
  11  * compliance with the License. Please obtain a copy of the License at
  12  * http://www.opensource.apple.com/apsl/ and read it before using this
  13  * file.
  14  *
  15  * The Original Code and all software distributed under the License are
  16  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  17  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  18  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  20  * Please see the License for the specific language governing rights and
  21  * limitations under the License.
  22  *
  23  * @APPLE_LICENSE_HEADER_END@
  24  */
  25 /*-
  26  * Copyright (c) 1991, 1993
  27  *      The Regents of the University of California.  All rights reserved.
  28  *
  29  * This code is derived from software contributed to Berkeley by
  30  * Ronnie Kon at Mindcraft Inc., Kevin Lew and Elmer Yglesias.
  31  *
  32  * Redistribution and use in source and binary forms, with or without
  33  * modification, are permitted provided that the following conditions
  34  * are met:
  35  * 1. Redistributions of source code must retain the above copyright
  36  *    notice, this list of conditions and the following disclaimer.
  37  * 2. Redistributions in binary form must reproduce the above copyright
  38  *    notice, this list of conditions and the following disclaimer in the
  39  *    documentation and/or other materials provided with the distribution.
  40  * 3. All advertising materials mentioning features or use of this software
  41  *    must display the following acknowledgement:
  42  *      This product includes software developed by the University of
  43  *      California, Berkeley and its contributors.
  44  * 4. Neither the name of the University nor the names of its contributors
  45  *    may be used to endorse or promote products derived from this software
  46  *    without specific prior written permission.
  47  *
  48  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  49  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  50  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  51  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  52  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  53  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  54  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  55  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  56  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  57  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  58  * SUCH DAMAGE.
  59  */
  60
  61 #if defined(LIBC_SCCS) && !defined(lint)
  62 static char sccsid[] = "@(#)heapsort.c  8.1 (Berkeley) 6/4/93";
  63 #endif /* LIBC_SCCS and not lint */
  64
  65
  66 #include <libsa/stdlib.h>
  67
  68
  69 /*
  70  * Swap two areas of size number of bytes.  Although qsort(3) permits random
  71  * blocks of memory to be sorted, sorting pointers is almost certainly the
  72  * common case (and, were it not, could easily be made so).  Regardless, it
  73  * isn't worth optimizing; the SWAP's get sped up by the cache, and pointer
  74  * arithmetic gets lost in the time required for comparison function calls.
  75  */
  76 #define SWAP(a, b, count, size, tmp) { \
  77         count = size; \
  78         do { \
  79                 tmp = *a; \
  80                 *a++ = *b; \
  81                 *b++ = tmp; \
  82         } while (--count); \
  83 }
  84
  85 /* Copy one block of size size to another. */
  86 #define COPY(a, b, count, size, tmp1, tmp2) { \
  87         count = size; \
  88         tmp1 = a; \
  89         tmp2 = b; \
  90         do { \
  91                 *tmp1++ = *tmp2++; \
  92         } while (--count); \
  93 }
  94
  95 /*
  96  * Build the list into a heap, where a heap is defined such that for
  97  * the records K1 ... KN, Kj/2 >= Kj for 1 <= j/2 <= j <= N.
  98  *
  99  * There two cases.  If j == nmemb, select largest of Ki and Kj.  If
 100  * j < nmemb, select largest of Ki, Kj and Kj+1.
 101  */
 102 #define CREATE(initval, nmemb, par_i, child_i, par, child, size, count, tmp) { \
 103         for (par_i = initval; (child_i = par_i * 2) <= nmemb; \
 104             par_i = child_i) { \
 105                 child = base + child_i * size; \
 106                 if (child_i < nmemb && compar(child, child + size) < 0) { \
 107                         child += size; \
 108                         ++child_i; \
 109                 } \
 110                 par = base + par_i * size; \
 111                 if (compar(child, par) <= 0) \
 112                         break; \
 113                 SWAP(par, child, count, size, tmp); \
 114         } \
 115 }
 116
 117 /*
 118  * Select the top of the heap and 'heapify'.  Since by far the most expensive
 119  * action is the call to the compar function, a considerable optimization
 120  * in the average case can be achieved due to the fact that k, the displaced
 121  * elememt, is ususally quite small, so it would be preferable to first
 122  * heapify, always maintaining the invariant that the larger child is copied
 123  * over its parent's record.
 124  *
 125  * Then, starting from the *bottom* of the heap, finding k's correct place,
 126  * again maintianing the invariant.  As a result of the invariant no element
 127  * is 'lost' when k is assigned its correct place in the heap.
 128  *
 129  * The time savings from this optimization are on the order of 15-20% for the
 130  * average case. See Knuth, Vol. 3, page 158, problem 18.
 131  *
 132  * XXX Don't break the #define SELECT line, below.  Reiser cpp gets upset.
 133  */
 134 #define SELECT(par_i, child_i, nmemb, par, child, size, k, count, tmp1, tmp2) { \
 135         for (par_i = 1; (child_i = par_i * 2) <= nmemb; par_i = child_i) { \
 136                 child = base + child_i * size; \
 137                 if (child_i < nmemb && compar(child, child + size) < 0) { \
 138                         child += size; \
 139                         ++child_i; \
 140                 } \
 141                 par = base + par_i * size; \
 142                 COPY(par, child, count, size, tmp1, tmp2); \
 143         } \
 144         for (;;) { \
 145                 child_i = par_i; \
 146                 par_i = child_i / 2; \
 147                 child = base + child_i * size; \
 148                 par = base + par_i * size; \
 149                 if (child_i == 1 || compar(k, par) < 0) { \
 150                         COPY(child, k, count, size, tmp1, tmp2); \
 151                         break; \
 152                 } \
 153                 COPY(child, par, count, size, tmp1, tmp2); \
 154         } \
 155 }
 156
 157 /* Pass heapsort off as qsort for krld. -- Nik Gervae
 158  *
 159  * Heapsort -- Knuth, Vol. 3, page 145.  Runs in O (N lg N), both average
 160  * and worst.  While heapsort is faster than the worst case of quicksort,
 161  * the BSD quicksort does median selection so that the chance of finding
 162  * a data set that will trigger the worst case is nonexistent.  Heapsort's
 163  * only advantage over quicksort is that it requires little additional memory.
 164  */
 165 __private_extern__
 166 void qsort(void * vbase, size_t nmemb, size_t size,
 167         int (*compar)(const void *, const void *)) {
 168
 169         register int cnt, i, j, l;
 170         register char tmp, *tmp1, *tmp2;
 171         char *base, *k, *p, *t;
 172
 173         if (nmemb <= 1) {
 174             return;
 175         }
 176
 177         if (!size) {
 178             return;
 179         }
 180
 181         if ((k = (char *)malloc(size)) == NULL) {
 182 //            panic();
 183             return;
 184         }
 185
 186         /*
 187          * Items are numbered from 1 to nmemb, so offset from size bytes
 188          * below the starting address.
 189          */
 190         base = (char *)vbase - size;
 191
 192         for (l = nmemb / 2 + 1; --l;)
 193                 CREATE(l, nmemb, i, j, t, p, size, cnt, tmp);
 194
 195         /*
 196          * For each element of the heap, save the largest element into its
 197          * final slot, save the displaced element (k), then recreate the
 198          * heap.
 199          */
 200         while (nmemb > 1) {
 201                 COPY(k, base + nmemb * size, cnt, size, tmp1, tmp2);
 202                 COPY(base + nmemb * size, base + size, cnt, size, tmp1, tmp2);
 203                 --nmemb;
 204                 SELECT(i, j, nmemb, t, p, size, k, cnt, tmp1, tmp2);
 205         }
 206         free(k);
 207         return;
 208 }