libsa/sort.c

   1 /*
   2  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_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 License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28 /*-
  29  * Copyright (c) 1991, 1993
  30  *      The Regents of the University of California.  All rights reserved.
  31  *
  32  * This code is derived from software contributed to Berkeley by
  33  * Ronnie Kon at Mindcraft Inc., Kevin Lew and Elmer Yglesias.
  34  *
  35  * Redistribution and use in source and binary forms, with or without
  36  * modification, are permitted provided that the following conditions
  37  * are met:
  38  * 1. Redistributions of source code must retain the above copyright
  39  *    notice, this list of conditions and the following disclaimer.
  40  * 2. Redistributions in binary form must reproduce the above copyright
  41  *    notice, this list of conditions and the following disclaimer in the
  42  *    documentation and/or other materials provided with the distribution.
  43  * 3. All advertising materials mentioning features or use of this software
  44  *    must display the following acknowledgement:
  45  *      This product includes software developed by the University of
  46  *      California, Berkeley and its contributors.
  47  * 4. Neither the name of the University nor the names of its contributors
  48  *    may be used to endorse or promote products derived from this software
  49  *    without specific prior written permission.
  50  *
  51  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  52  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  53  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  54  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  55  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  56  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  57  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  58  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  59  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  60  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  61  * SUCH DAMAGE.
  62  */
  63
  64 #if defined(LIBC_SCCS) && !defined(lint)
  65 static char sccsid[] = "@(#)heapsort.c  8.1 (Berkeley) 6/4/93";
  66 #endif /* LIBC_SCCS and not lint */
  67
  68
  69 #include <libsa/stdlib.h>
  70
  71
  72 /*
  73  * Swap two areas of size number of bytes.  Although qsort(3) permits random
  74  * blocks of memory to be sorted, sorting pointers is almost certainly the
  75  * common case (and, were it not, could easily be made so).  Regardless, it
  76  * isn't worth optimizing; the SWAP's get sped up by the cache, and pointer
  77  * arithmetic gets lost in the time required for comparison function calls.
  78  */
  79 #define SWAP(a, b, count, size, tmp) { \
  80         count = size; \
  81         do { \
  82                 tmp = *a; \
  83                 *a++ = *b; \
  84                 *b++ = tmp; \
  85         } while (--count); \
  86 }
  87
  88 /* Copy one block of size size to another. */
  89 #define COPY(a, b, count, size, tmp1, tmp2) { \
  90         count = size; \
  91         tmp1 = a; \
  92         tmp2 = b; \
  93         do { \
  94                 *tmp1++ = *tmp2++; \
  95         } while (--count); \
  96 }
  97
  98 /*
  99  * Build the list into a heap, where a heap is defined such that for
 100  * the records K1 ... KN, Kj/2 >= Kj for 1 <= j/2 <= j <= N.
 101  *
 102  * There two cases.  If j == nmemb, select largest of Ki and Kj.  If
 103  * j < nmemb, select largest of Ki, Kj and Kj+1.
 104  */
 105 #define CREATE(initval, nmemb, par_i, child_i, par, child, size, count, tmp) { \
 106         for (par_i = initval; (child_i = par_i * 2) <= nmemb; \
 107             par_i = child_i) { \
 108                 child = base + child_i * size; \
 109                 if (child_i < nmemb && compar(child, child + size) < 0) { \
 110                         child += size; \
 111                         ++child_i; \
 112                 } \
 113                 par = base + par_i * size; \
 114                 if (compar(child, par) <= 0) \
 115                         break; \
 116                 SWAP(par, child, count, size, tmp); \
 117         } \
 118 }
 119
 120 /*
 121  * Select the top of the heap and 'heapify'.  Since by far the most expensive
 122  * action is the call to the compar function, a considerable optimization
 123  * in the average case can be achieved due to the fact that k, the displaced
 124  * elememt, is ususally quite small, so it would be preferable to first
 125  * heapify, always maintaining the invariant that the larger child is copied
 126  * over its parent's record.
 127  *
 128  * Then, starting from the *bottom* of the heap, finding k's correct place,
 129  * again maintianing the invariant.  As a result of the invariant no element
 130  * is 'lost' when k is assigned its correct place in the heap.
 131  *
 132  * The time savings from this optimization are on the order of 15-20% for the
 133  * average case. See Knuth, Vol. 3, page 158, problem 18.
 134  *
 135  * XXX Don't break the #define SELECT line, below.  Reiser cpp gets upset.
 136  */
 137 #define SELECT(par_i, child_i, nmemb, par, child, size, k, count, tmp1, tmp2) { \
 138         for (par_i = 1; (child_i = par_i * 2) <= nmemb; par_i = child_i) { \
 139                 child = base + child_i * size; \
 140                 if (child_i < nmemb && compar(child, child + size) < 0) { \
 141                         child += size; \
 142                         ++child_i; \
 143                 } \
 144                 par = base + par_i * size; \
 145                 COPY(par, child, count, size, tmp1, tmp2); \
 146         } \
 147         for (;;) { \
 148                 child_i = par_i; \
 149                 par_i = child_i / 2; \
 150                 child = base + child_i * size; \
 151                 par = base + par_i * size; \
 152                 if (child_i == 1 || compar(k, par) < 0) { \
 153                         COPY(child, k, count, size, tmp1, tmp2); \
 154                         break; \
 155                 } \
 156                 COPY(child, par, count, size, tmp1, tmp2); \
 157         } \
 158 }
 159
 160 /* Pass heapsort off as qsort for krld. -- Nik Gervae
 161  *
 162  * Heapsort -- Knuth, Vol. 3, page 145.  Runs in O (N lg N), both average
 163  * and worst.  While heapsort is faster than the worst case of quicksort,
 164  * the BSD quicksort does median selection so that the chance of finding
 165  * a data set that will trigger the worst case is nonexistent.  Heapsort's
 166  * only advantage over quicksort is that it requires little additional memory.
 167  */
 168 __private_extern__
 169 void qsort(void * vbase, size_t nmemb, size_t size,
 170         int (*compar)(const void *, const void *)) {
 171
 172         register int cnt, i, j, l;
 173         register char tmp, *tmp1, *tmp2;
 174         char *base, *k, *p, *t;
 175
 176         if (nmemb <= 1) {
 177             return;
 178         }
 179
 180         if (!size) {
 181             return;
 182         }
 183
 184         if ((k = (char *)malloc(size)) == NULL) {
 185 //            panic();
 186             return;
 187         }
 188
 189         /*
 190          * Items are numbered from 1 to nmemb, so offset from size bytes
 191          * below the starting address.
 192          */
 193         base = (char *)vbase - size;
 194
 195         for (l = nmemb / 2 + 1; --l;)
 196                 CREATE(l, nmemb, i, j, t, p, size, cnt, tmp);
 197
 198         /*
 199          * For each element of the heap, save the largest element into its
 200          * final slot, save the displaced element (k), then recreate the
 201          * heap.
 202          */
 203         while (nmemb > 1) {
 204                 COPY(k, base + nmemb * size, cnt, size, tmp1, tmp2);
 205                 COPY(base + nmemb * size, base + size, cnt, size, tmp1, tmp2);
 206                 --nmemb;
 207                 SELECT(i, j, nmemb, t, p, size, k, cnt, tmp1, tmp2);
 208         }
 209         free(k);
 210         return;
 211 }