libsa/sort.c

   1 /*
   2  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_OSREFERENCE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License.  The rights granted to you under the
  10  * License may not be used to create, or enable the creation or
  11  * redistribution of, unlawful or unlicensed copies of an Apple operating
  12  * system, or to circumvent, violate, or enable the circumvention or
  13  * violation of, any terms of an Apple operating system software license
  14  * agreement.
  15  *
  16  * Please obtain a copy of the License at
  17  * http://www.opensource.apple.com/apsl/ and read it before using this
  18  * file.
  19  *
  20  * The Original Code and all software distributed under the License are
  21  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  22  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  23  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  24  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  25  * Please see the License for the specific language governing rights and
  26  * limitations under the License.
  27  *
  28  * @APPLE_LICENSE_OSREFERENCE_HEADER_END@
  29  */
  30 /*-
  31  * Copyright (c) 1991, 1993
  32  *      The Regents of the University of California.  All rights reserved.
  33  *
  34  * This code is derived from software contributed to Berkeley by
  35  * Ronnie Kon at Mindcraft Inc., Kevin Lew and Elmer Yglesias.
  36  *
  37  * Redistribution and use in source and binary forms, with or without
  38  * modification, are permitted provided that the following conditions
  39  * are met:
  40  * 1. Redistributions of source code must retain the above copyright
  41  *    notice, this list of conditions and the following disclaimer.
  42  * 2. Redistributions in binary form must reproduce the above copyright
  43  *    notice, this list of conditions and the following disclaimer in the
  44  *    documentation and/or other materials provided with the distribution.
  45  * 3. All advertising materials mentioning features or use of this software
  46  *    must display the following acknowledgement:
  47  *      This product includes software developed by the University of
  48  *      California, Berkeley and its contributors.
  49  * 4. Neither the name of the University nor the names of its contributors
  50  *    may be used to endorse or promote products derived from this software
  51  *    without specific prior written permission.
  52  *
  53  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  54  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  55  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  56  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  57  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  58  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  59  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  60  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  61  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  62  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  63  * SUCH DAMAGE.
  64  */
  65
  66 #if defined(LIBC_SCCS) && !defined(lint)
  67 static char sccsid[] = "@(#)heapsort.c  8.1 (Berkeley) 6/4/93";
  68 #endif /* LIBC_SCCS and not lint */
  69
  70
  71 #include <libsa/stdlib.h>
  72
  73
  74 /*
  75  * Swap two areas of size number of bytes.  Although qsort(3) permits random
  76  * blocks of memory to be sorted, sorting pointers is almost certainly the
  77  * common case (and, were it not, could easily be made so).  Regardless, it
  78  * isn't worth optimizing; the SWAP's get sped up by the cache, and pointer
  79  * arithmetic gets lost in the time required for comparison function calls.
  80  */
  81 #define SWAP(a, b, count, size, tmp) { \
  82         count = size; \
  83         do { \
  84                 tmp = *a; \
  85                 *a++ = *b; \
  86                 *b++ = tmp; \
  87         } while (--count); \
  88 }
  89
  90 /* Copy one block of size size to another. */
  91 #define COPY(a, b, count, size, tmp1, tmp2) { \
  92         count = size; \
  93         tmp1 = a; \
  94         tmp2 = b; \
  95         do { \
  96                 *tmp1++ = *tmp2++; \
  97         } while (--count); \
  98 }
  99
 100 /*
 101  * Build the list into a heap, where a heap is defined such that for
 102  * the records K1 ... KN, Kj/2 >= Kj for 1 <= j/2 <= j <= N.
 103  *
 104  * There two cases.  If j == nmemb, select largest of Ki and Kj.  If
 105  * j < nmemb, select largest of Ki, Kj and Kj+1.
 106  */
 107 #define CREATE(initval, nmemb, par_i, child_i, par, child, size, count, tmp) { \
 108         for (par_i = initval; (child_i = par_i * 2) <= nmemb; \
 109             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                 if (compar(child, par) <= 0) \
 117                         break; \
 118                 SWAP(par, child, count, size, tmp); \
 119         } \
 120 }
 121
 122 /*
 123  * Select the top of the heap and 'heapify'.  Since by far the most expensive
 124  * action is the call to the compar function, a considerable optimization
 125  * in the average case can be achieved due to the fact that k, the displaced
 126  * elememt, is ususally quite small, so it would be preferable to first
 127  * heapify, always maintaining the invariant that the larger child is copied
 128  * over its parent's record.
 129  *
 130  * Then, starting from the *bottom* of the heap, finding k's correct place,
 131  * again maintianing the invariant.  As a result of the invariant no element
 132  * is 'lost' when k is assigned its correct place in the heap.
 133  *
 134  * The time savings from this optimization are on the order of 15-20% for the
 135  * average case. See Knuth, Vol. 3, page 158, problem 18.
 136  *
 137  * XXX Don't break the #define SELECT line, below.  Reiser cpp gets upset.
 138  */
 139 #define SELECT(par_i, child_i, nmemb, par, child, size, k, count, tmp1, tmp2) { \
 140         for (par_i = 1; (child_i = par_i * 2) <= nmemb; par_i = child_i) { \
 141                 child = base + child_i * size; \
 142                 if (child_i < nmemb && compar(child, child + size) < 0) { \
 143                         child += size; \
 144                         ++child_i; \
 145                 } \
 146                 par = base + par_i * size; \
 147                 COPY(par, child, count, size, tmp1, tmp2); \
 148         } \
 149         for (;;) { \
 150                 child_i = par_i; \
 151                 par_i = child_i / 2; \
 152                 child = base + child_i * size; \
 153                 par = base + par_i * size; \
 154                 if (child_i == 1 || compar(k, par) < 0) { \
 155                         COPY(child, k, count, size, tmp1, tmp2); \
 156                         break; \
 157                 } \
 158                 COPY(child, par, count, size, tmp1, tmp2); \
 159         } \
 160 }
 161
 162 /* Pass heapsort off as qsort for krld. -- Nik Gervae
 163  *
 164  * Heapsort -- Knuth, Vol. 3, page 145.  Runs in O (N lg N), both average
 165  * and worst.  While heapsort is faster than the worst case of quicksort,
 166  * the BSD quicksort does median selection so that the chance of finding
 167  * a data set that will trigger the worst case is nonexistent.  Heapsort's
 168  * only advantage over quicksort is that it requires little additional memory.
 169  */
 170 __private_extern__
 171 void qsort(void * vbase, size_t nmemb, size_t size,
 172         int (*compar)(const void *, const void *)) {
 173
 174         register int cnt, i, j, l;
 175         register char tmp, *tmp1, *tmp2;
 176         char *base, *k, *p, *t;
 177
 178         if (nmemb <= 1) {
 179             return;
 180         }
 181
 182         if (!size) {
 183             return;
 184         }
 185
 186         if ((k = (char *)malloc(size)) == NULL) {
 187 //            panic();
 188             return;
 189         }
 190
 191         /*
 192          * Items are numbered from 1 to nmemb, so offset from size bytes
 193          * below the starting address.
 194          */
 195         base = (char *)vbase - size;
 196
 197         for (l = nmemb / 2 + 1; --l;)
 198                 CREATE(l, nmemb, i, j, t, p, size, cnt, tmp);
 199
 200         /*
 201          * For each element of the heap, save the largest element into its
 202          * final slot, save the displaced element (k), then recreate the
 203          * heap.
 204          */
 205         while (nmemb > 1) {
 206                 COPY(k, base + nmemb * size, cnt, size, tmp1, tmp2);
 207                 COPY(base + nmemb * size, base + size, cnt, size, tmp1, tmp2);
 208                 --nmemb;
 209                 SELECT(i, j, nmemb, t, p, size, k, cnt, tmp1, tmp2);
 210         }
 211         free(k);
 212         return;
 213 }