libsa/sort.c

   1 /*
   2  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22 /*-
  23  * Copyright (c) 1991, 1993
  24  *      The Regents of the University of California.  All rights reserved.
  25  *
  26  * This code is derived from software contributed to Berkeley by
  27  * Ronnie Kon at Mindcraft Inc., Kevin Lew and Elmer Yglesias.
  28  *
  29  * Redistribution and use in source and binary forms, with or without
  30  * modification, are permitted provided that the following conditions
  31  * are met:
  32  * 1. Redistributions of source code must retain the above copyright
  33  *    notice, this list of conditions and the following disclaimer.
  34  * 2. Redistributions in binary form must reproduce the above copyright
  35  *    notice, this list of conditions and the following disclaimer in the
  36  *    documentation and/or other materials provided with the distribution.
  37  * 3. All advertising materials mentioning features or use of this software
  38  *    must display the following acknowledgement:
  39  *      This product includes software developed by the University of
  40  *      California, Berkeley and its contributors.
  41  * 4. Neither the name of the University nor the names of its contributors
  42  *    may be used to endorse or promote products derived from this software
  43  *    without specific prior written permission.
  44  *
  45  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  46  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  47  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  48  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  49  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  50  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  51  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  52  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  53  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  54  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  55  * SUCH DAMAGE.
  56  */
  57
  58 #if defined(LIBC_SCCS) && !defined(lint)
  59 static char sccsid[] = "@(#)heapsort.c  8.1 (Berkeley) 6/4/93";
  60 #endif /* LIBC_SCCS and not lint */
  61
  62
  63 #include <libsa/stdlib.h>
  64
  65
  66 /*
  67  * Swap two areas of size number of bytes.  Although qsort(3) permits random
  68  * blocks of memory to be sorted, sorting pointers is almost certainly the
  69  * common case (and, were it not, could easily be made so).  Regardless, it
  70  * isn't worth optimizing; the SWAP's get sped up by the cache, and pointer
  71  * arithmetic gets lost in the time required for comparison function calls.
  72  */
  73 #define SWAP(a, b, count, size, tmp) { \
  74         count = size; \
  75         do { \
  76                 tmp = *a; \
  77                 *a++ = *b; \
  78                 *b++ = tmp; \
  79         } while (--count); \
  80 }
  81
  82 /* Copy one block of size size to another. */
  83 #define COPY(a, b, count, size, tmp1, tmp2) { \
  84         count = size; \
  85         tmp1 = a; \
  86         tmp2 = b; \
  87         do { \
  88                 *tmp1++ = *tmp2++; \
  89         } while (--count); \
  90 }
  91
  92 /*
  93  * Build the list into a heap, where a heap is defined such that for
  94  * the records K1 ... KN, Kj/2 >= Kj for 1 <= j/2 <= j <= N.
  95  *
  96  * There two cases.  If j == nmemb, select largest of Ki and Kj.  If
  97  * j < nmemb, select largest of Ki, Kj and Kj+1.
  98  */
  99 #define CREATE(initval, nmemb, par_i, child_i, par, child, size, count, tmp) { \
 100         for (par_i = initval; (child_i = par_i * 2) <= nmemb; \
 101             par_i = child_i) { \
 102                 child = base + child_i * size; \
 103                 if (child_i < nmemb && compar(child, child + size) < 0) { \
 104                         child += size; \
 105                         ++child_i; \
 106                 } \
 107                 par = base + par_i * size; \
 108                 if (compar(child, par) <= 0) \
 109                         break; \
 110                 SWAP(par, child, count, size, tmp); \
 111         } \
 112 }
 113
 114 /*
 115  * Select the top of the heap and 'heapify'.  Since by far the most expensive
 116  * action is the call to the compar function, a considerable optimization
 117  * in the average case can be achieved due to the fact that k, the displaced
 118  * elememt, is ususally quite small, so it would be preferable to first
 119  * heapify, always maintaining the invariant that the larger child is copied
 120  * over its parent's record.
 121  *
 122  * Then, starting from the *bottom* of the heap, finding k's correct place,
 123  * again maintianing the invariant.  As a result of the invariant no element
 124  * is 'lost' when k is assigned its correct place in the heap.
 125  *
 126  * The time savings from this optimization are on the order of 15-20% for the
 127  * average case. See Knuth, Vol. 3, page 158, problem 18.
 128  *
 129  * XXX Don't break the #define SELECT line, below.  Reiser cpp gets upset.
 130  */
 131 #define SELECT(par_i, child_i, nmemb, par, child, size, k, count, tmp1, tmp2) { \
 132         for (par_i = 1; (child_i = par_i * 2) <= nmemb; par_i = child_i) { \
 133                 child = base + child_i * size; \
 134                 if (child_i < nmemb && compar(child, child + size) < 0) { \
 135                         child += size; \
 136                         ++child_i; \
 137                 } \
 138                 par = base + par_i * size; \
 139                 COPY(par, child, count, size, tmp1, tmp2); \
 140         } \
 141         for (;;) { \
 142                 child_i = par_i; \
 143                 par_i = child_i / 2; \
 144                 child = base + child_i * size; \
 145                 par = base + par_i * size; \
 146                 if (child_i == 1 || compar(k, par) < 0) { \
 147                         COPY(child, k, count, size, tmp1, tmp2); \
 148                         break; \
 149                 } \
 150                 COPY(child, par, count, size, tmp1, tmp2); \
 151         } \
 152 }
 153
 154 /* Pass heapsort off as qsort for krld. -- Nik Gervae
 155  *
 156  * Heapsort -- Knuth, Vol. 3, page 145.  Runs in O (N lg N), both average
 157  * and worst.  While heapsort is faster than the worst case of quicksort,
 158  * the BSD quicksort does median selection so that the chance of finding
 159  * a data set that will trigger the worst case is nonexistent.  Heapsort's
 160  * only advantage over quicksort is that it requires little additional memory.
 161  */
 162 __private_extern__
 163 void qsort(void * vbase, size_t nmemb, size_t size,
 164         int (*compar)(const void *, const void *)) {
 165
 166         register int cnt, i, j, l;
 167         register char tmp, *tmp1, *tmp2;
 168         char *base, *k, *p, *t;
 169
 170         if (nmemb <= 1) {
 171             return;
 172         }
 173
 174         if (!size) {
 175             return;
 176         }
 177
 178         if ((k = (char *)malloc(size)) == NULL) {
 179 //            panic();
 180             return;
 181         }
 182
 183         /*
 184          * Items are numbered from 1 to nmemb, so offset from size bytes
 185          * below the starting address.
 186          */
 187         base = (char *)vbase - size;
 188
 189         for (l = nmemb / 2 + 1; --l;)
 190                 CREATE(l, nmemb, i, j, t, p, size, cnt, tmp);
 191
 192         /*
 193          * For each element of the heap, save the largest element into its
 194          * final slot, save the displaced element (k), then recreate the
 195          * heap.
 196          */
 197         while (nmemb > 1) {
 198                 COPY(k, base + nmemb * size, cnt, size, tmp1, tmp2);
 199                 COPY(base + nmemb * size, base + size, cnt, size, tmp1, tmp2);
 200                 --nmemb;
 201                 SELECT(i, j, nmemb, t, p, size, k, cnt, tmp1, tmp2);
 202         }
 203         free(k);
 204         return;
 205 }