external/bsd/libbind/dist/isc/heap.c

   1 /*      $NetBSD$        */
   2
   3 /*
   4  * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
   5  * Copyright (c) 1997,1999 by Internet Software Consortium.
   6  *
   7  * Permission to use, copy, modify, and distribute this software for any
   8  * purpose with or without fee is hereby granted, provided that the above
   9  * copyright notice and this permission notice appear in all copies.
  10  *
  11  * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
  12  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  13  * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
  14  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  15  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  16  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
  17  * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  18  */
  19
  20 /*%
  21  * Heap implementation of priority queues adapted from the following:
  22  *
  23  *      _Introduction to Algorithms_, Cormen, Leiserson, and Rivest,
  24  *      MIT Press / McGraw Hill, 1990, ISBN 0-262-03141-8, chapter 7.
  25  *
  26  *      _Algorithms_, Second Edition, Sedgewick, Addison-Wesley, 1988,
  27  *      ISBN 0-201-06673-4, chapter 11.
  28  */
  29
  30 #if !defined(LINT) && !defined(CODECENTER)
  31 static const char rcsid[] = "Id: heap.c,v 1.4 2006/03/09 23:57:56 marka Exp";
  32 #endif /* not lint */
  33
  34 #include "port_before.h"
  35
  36 #include <stddef.h>
  37 #include <stdlib.h>
  38 #include <errno.h>
  39
  40 #include "port_after.h"
  41
  42 #include <isc/heap.h>
  43
  44 /*%
  45  * Note: to make heap_parent and heap_left easy to compute, the first
  46  * element of the heap array is not used; i.e. heap subscripts are 1-based,
  47  * not 0-based.
  48  */
  49 #define heap_parent(i) ((i) >> 1)
  50 #define heap_left(i) ((i) << 1)
  51
  52 #define ARRAY_SIZE_INCREMENT 512
  53
  54 heap_context
  55 heap_new(heap_higher_priority_func higher_priority, heap_index_func index,
  56          int array_size_increment) {
  57         heap_context ctx;
  58
  59         if (higher_priority == NULL)
  60                 return (NULL);
  61
  62         ctx = (heap_context)malloc(sizeof (struct heap_context));
  63         if (ctx == NULL)
  64                 return (NULL);
  65
  66         ctx->array_size = 0;
  67         if (array_size_increment == 0)
  68                 ctx->array_size_increment = ARRAY_SIZE_INCREMENT;
  69         else
  70                 ctx->array_size_increment = array_size_increment;
  71         ctx->heap_size = 0;
  72         ctx->heap = NULL;
  73         ctx->higher_priority = higher_priority;
  74         ctx->index = index;
  75         return (ctx);
  76 }
  77
  78 int
  79 heap_free(heap_context ctx) {
  80         if (ctx == NULL) {
  81                 errno = EINVAL;
  82                 return (-1);
  83         }
  84
  85         if (ctx->heap != NULL)
  86                 free(ctx->heap);
  87         free(ctx);
  88
  89         return (0);
  90 }
  91
  92 static int
  93 heap_resize(heap_context ctx) {
  94         void **new_heap;
  95
  96         ctx->array_size += ctx->array_size_increment;
  97         new_heap = (void **)realloc(ctx->heap,
  98                                     (ctx->array_size) * (sizeof (void *)));
  99         if (new_heap == NULL) {
 100                 errno = ENOMEM;
 101                 return (-1);
 102         }
 103         ctx->heap = new_heap;
 104         return (0);
 105 }
 106
 107 static void
 108 float_up(heap_context ctx, int i, void *elt) {
 109         int p;
 110
 111         for ( p = heap_parent(i);
 112               i > 1 && ctx->higher_priority(elt, ctx->heap[p]);
 113               i = p, p = heap_parent(i) ) {
 114                 ctx->heap[i] = ctx->heap[p];
 115                 if (ctx->index != NULL)
 116                         (ctx->index)(ctx->heap[i], i);
 117         }
 118         ctx->heap[i] = elt;
 119         if (ctx->index != NULL)
 120                 (ctx->index)(ctx->heap[i], i);
 121 }
 122
 123 static void
 124 sink_down(heap_context ctx, int i, void *elt) {
 125         int j, size, half_size;
 126
 127         size = ctx->heap_size;
 128         half_size = size / 2;
 129         while (i <= half_size) {
 130                 /* find smallest of the (at most) two children */
 131                 j = heap_left(i);
 132                 if (j < size && ctx->higher_priority(ctx->heap[j+1],
 133                                                      ctx->heap[j]))
 134                         j++;
 135                 if (ctx->higher_priority(elt, ctx->heap[j]))
 136                         break;
 137                 ctx->heap[i] = ctx->heap[j];
 138                 if (ctx->index != NULL)
 139                         (ctx->index)(ctx->heap[i], i);
 140                 i = j;
 141         }
 142         ctx->heap[i] = elt;
 143         if (ctx->index != NULL)
 144                 (ctx->index)(ctx->heap[i], i);
 145 }
 146
 147 int
 148 heap_insert(heap_context ctx, void *elt) {
 149         int i;
 150
 151         if (ctx == NULL || elt == NULL) {
 152                 errno = EINVAL;
 153                 return (-1);
 154         }
 155
 156         i = ++ctx->heap_size;
 157         if (ctx->heap_size >= ctx->array_size && heap_resize(ctx) < 0)
 158                 return (-1);
 159
 160         float_up(ctx, i, elt);
 161
 162         return (0);
 163 }
 164
 165 int
 166 heap_delete(heap_context ctx, int i) {
 167         void *elt;
 168         int less;
 169
 170         if (ctx == NULL || i < 1 || i > ctx->heap_size) {
 171                 errno = EINVAL;
 172                 return (-1);
 173         }
 174
 175         if (i == ctx->heap_size) {
 176                 ctx->heap_size--;
 177         } else {
 178                 elt = ctx->heap[ctx->heap_size--];
 179                 less = ctx->higher_priority(elt, ctx->heap[i]);
 180                 ctx->heap[i] = elt;
 181                 if (less)
 182                         float_up(ctx, i, ctx->heap[i]);
 183                 else
 184                         sink_down(ctx, i, ctx->heap[i]);
 185         }
 186
 187         return (0);
 188 }
 189
 190 int
 191 heap_increased(heap_context ctx, int i) {
 192         if (ctx == NULL || i < 1 || i > ctx->heap_size) {
 193                 errno = EINVAL;
 194                 return (-1);
 195         }
 196
 197         float_up(ctx, i, ctx->heap[i]);
 198
 199         return (0);
 200 }
 201
 202 int
 203 heap_decreased(heap_context ctx, int i) {
 204         if (ctx == NULL || i < 1 || i > ctx->heap_size) {
 205                 errno = EINVAL;
 206                 return (-1);
 207         }
 208
 209         sink_down(ctx, i, ctx->heap[i]);
 210
 211         return (0);
 212 }
 213
 214 void *
 215 heap_element(heap_context ctx, int i) {
 216         if (ctx == NULL || i < 1 || i > ctx->heap_size) {
 217                 errno = EINVAL;
 218                 return (NULL);
 219         }
 220
 221         return (ctx->heap[i]);
 222 }
 223
 224 int
 225 heap_for_each(heap_context ctx, heap_for_each_func action, void *uap) {
 226         int i;
 227
 228         if (ctx == NULL || action == NULL) {
 229                 errno = EINVAL;
 230                 return (-1);
 231         }
 232
 233         for (i = 1; i <= ctx->heap_size; i++)
 234                 (action)(ctx->heap[i], uap);
 235         return (0);
 236 }
 237
 238 /*! \file */