2 * Copyright (C) 2004 Internet Systems Consortium, Inc. ("ISC")
3 * Copyright (C) 1997-2001 Internet Software Consortium.
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
9 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
10 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
11 * AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
12 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
13 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
14 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
15 * PERFORMANCE OF THIS SOFTWARE.
18 /* $Id: heap.c,v 1.28.12.3 2004/03/08 09:04:48 marka Exp $ */
21 * Heap implementation of priority queues adapted from the following:
23 * _Introduction to Algorithms_, Cormen, Leiserson, and Rivest,
24 * MIT Press / McGraw Hill, 1990, ISBN 0-262-03141-8, chapter 7.
26 * _Algorithms_, Second Edition, Sedgewick, Addison-Wesley, 1988,
27 * ISBN 0-201-06673-4, chapter 11.
33 #include <isc/magic.h>
35 #include <isc/string.h> /* Required for memcpy. */
39 * Note: to make heap_parent and heap_left easy to compute, the first
40 * element of the heap array is not used; i.e. heap subscripts are 1-based,
43 #define heap_parent(i) ((i) >> 1)
44 #define heap_left(i) ((i) << 1)
46 #define SIZE_INCREMENT 1024
48 #define HEAP_MAGIC ISC_MAGIC('H', 'E', 'A', 'P')
49 #define VALID_HEAP(h) ISC_MAGIC_VALID(h, HEAP_MAGIC)
52 * When the heap is in a consistent state, the following invariant
53 * holds true: for every element i > 1, heap_parent(i) has a priority
54 * higher than or equal to that of i.
56 #define HEAPCONDITION(i) ((i) == 1 || \
57 ! heap->compare(heap->array[(i)], \
58 heap->array[heap_parent(i)]))
64 unsigned int size_increment;
67 isc_heapcompare_t compare;
68 isc_heapindex_t index;
72 isc_heap_create(isc_mem_t *mctx, isc_heapcompare_t compare,
73 isc_heapindex_t index, unsigned int size_increment,
78 REQUIRE(heapp != NULL && *heapp == NULL);
79 REQUIRE(compare != NULL);
81 heap = isc_mem_get(mctx, sizeof(*heap));
83 return (ISC_R_NOMEMORY);
84 heap->magic = HEAP_MAGIC;
87 if (size_increment == 0)
88 heap->size_increment = SIZE_INCREMENT;
90 heap->size_increment = size_increment;
93 heap->compare = compare;
98 return (ISC_R_SUCCESS);
102 isc_heap_destroy(isc_heap_t **heapp) {
105 REQUIRE(heapp != NULL);
107 REQUIRE(VALID_HEAP(heap));
109 if (heap->array != NULL)
110 isc_mem_put(heap->mctx, heap->array,
111 heap->size * sizeof(void *));
113 isc_mem_put(heap->mctx, heap, sizeof(*heap));
119 resize(isc_heap_t *heap) {
123 REQUIRE(VALID_HEAP(heap));
125 new_size = heap->size + heap->size_increment;
126 new_array = isc_mem_get(heap->mctx, new_size * sizeof(void *));
127 if (new_array == NULL)
129 if (heap->array != NULL) {
130 memcpy(new_array, heap->array, heap->size * sizeof(void *));
131 isc_mem_put(heap->mctx, heap->array,
132 heap->size * sizeof(void *));
134 heap->size = new_size;
135 heap->array = new_array;
141 float_up(isc_heap_t *heap, unsigned int i, void *elt) {
144 for (p = heap_parent(i);
145 i > 1 && heap->compare(elt, heap->array[p]);
146 i = p, p = heap_parent(i)) {
147 heap->array[i] = heap->array[p];
148 if (heap->index != NULL)
149 (heap->index)(heap->array[i], i);
151 heap->array[i] = elt;
152 if (heap->index != NULL)
153 (heap->index)(heap->array[i], i);
155 INSIST(HEAPCONDITION(i));
159 sink_down(isc_heap_t *heap, unsigned int i, void *elt) {
160 unsigned int j, size, half_size;
162 half_size = size / 2;
163 while (i <= half_size) {
164 /* Find the smallest of the (at most) two children. */
166 if (j < size && heap->compare(heap->array[j+1],
169 if (heap->compare(elt, heap->array[j]))
171 heap->array[i] = heap->array[j];
172 if (heap->index != NULL)
173 (heap->index)(heap->array[i], i);
176 heap->array[i] = elt;
177 if (heap->index != NULL)
178 (heap->index)(heap->array[i], i);
180 INSIST(HEAPCONDITION(i));
184 isc_heap_insert(isc_heap_t *heap, void *elt) {
187 REQUIRE(VALID_HEAP(heap));
190 if (heap->last >= heap->size && !resize(heap))
191 return (ISC_R_NOMEMORY);
193 float_up(heap, i, elt);
195 return (ISC_R_SUCCESS);
199 isc_heap_delete(isc_heap_t *heap, unsigned int i) {
203 REQUIRE(VALID_HEAP(heap));
204 REQUIRE(i >= 1 && i <= heap->last);
206 if (i == heap->last) {
209 elt = heap->array[heap->last--];
210 less = heap->compare(elt, heap->array[i]);
211 heap->array[i] = elt;
213 float_up(heap, i, heap->array[i]);
215 sink_down(heap, i, heap->array[i]);
220 isc_heap_increased(isc_heap_t *heap, unsigned int i) {
221 REQUIRE(VALID_HEAP(heap));
222 REQUIRE(i >= 1 && i <= heap->last);
224 float_up(heap, i, heap->array[i]);
228 isc_heap_decreased(isc_heap_t *heap, unsigned int i) {
229 REQUIRE(VALID_HEAP(heap));
230 REQUIRE(i >= 1 && i <= heap->last);
232 sink_down(heap, i, heap->array[i]);
236 isc_heap_element(isc_heap_t *heap, unsigned int i) {
237 REQUIRE(VALID_HEAP(heap));
238 REQUIRE(i >= 1 && i <= heap->last);
240 return (heap->array[i]);
244 isc_heap_foreach(isc_heap_t *heap, isc_heapaction_t action, void *uap) {
247 REQUIRE(VALID_HEAP(heap));
248 REQUIRE(action != NULL);
250 for (i = 1; i <= heap->last; i++)
251 (action)(heap->array[i], uap);