1 /*
2 * Copyright (C) 2004-2007, 2010-2012 Internet Systems Consortium, Inc. ("ISC")
3 * Copyright (C) 1997-2001 Internet Software Consortium.
4 *
5 * Permission to use, copy, modify, and/or 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.
8 *
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.
16 */
17
18 /* $Id$ */
19
20 /*! \file
21 * Heap implementation of priority queues adapted from the following:
22 *
23 * \li "Introduction to Algorithms," Cormen, Leiserson, and Rivest,
24 * MIT Press / McGraw Hill, 1990, ISBN 0-262-03141-8, chapter 7.
25 *
26 * \li "Algorithms," Second Edition, Sedgewick, Addison-Wesley, 1988,
27 * ISBN 0-201-06673-4, chapter 11.
28 */
29
30 #include <config.h>
31
32 #include <isc/heap.h>
33 #include <isc/magic.h>
34 #include <isc/mem.h>
35 #include <isc/string.h> /* Required for memcpy. */
36 #include <isc/util.h>
37
38 /*@{*/
39 /*%
40 * Note: to make heap_parent and heap_left easy to compute, the first
41 * element of the heap array is not used; i.e. heap subscripts are 1-based,
42 * not 0-based. The parent is index/2, and the left-child is index*2.
43 * The right child is index*2+1.
44 */
45 #define heap_parent(i) ((i) >> 1)
46 #define heap_left(i) ((i) << 1)
47 /*@}*/
48
49 #define SIZE_INCREMENT 1024
50
51 #define HEAP_MAGIC ISC_MAGIC('H', 'E', 'A', 'P')
52 #define VALID_HEAP(h) ISC_MAGIC_VALID(h, HEAP_MAGIC)
53
54 /*%
55 * When the heap is in a consistent state, the following invariant
56 * holds true: for every element i > 1, heap_parent(i) has a priority
57 * higher than or equal to that of i.
58 */
59 #define HEAPCONDITION(i) ((i) == 1 || \
60 ! heap->compare(heap->array[(i)], \
61 heap->array[heap_parent(i)]))
62
63 /*% ISC heap structure. */
64 struct isc_heap {
65 unsigned int magic;
66 isc_mem_t * mctx;
67 unsigned int size;
68 unsigned int size_increment;
69 unsigned int last;
70 void **array;
71 isc_heapcompare_t compare;
72 isc_heapindex_t index;
73 };
74
75 isc_result_t
isc_heap_create(isc_mem_t * mctx,isc_heapcompare_t compare,isc_heapindex_t index,unsigned int size_increment,isc_heap_t ** heapp)76 isc_heap_create(isc_mem_t *mctx, isc_heapcompare_t compare,
77 isc_heapindex_t index, unsigned int size_increment,
78 isc_heap_t **heapp)
79 {
80 isc_heap_t *heap;
81
82 REQUIRE(heapp != NULL && *heapp == NULL);
83 REQUIRE(compare != NULL);
84
85 heap = isc_mem_get(mctx, sizeof(*heap));
86 if (heap == NULL)
87 return (ISC_R_NOMEMORY);
88 heap->magic = HEAP_MAGIC;
89 heap->size = 0;
90 heap->mctx = NULL;
91 isc_mem_attach(mctx, &heap->mctx);
92 if (size_increment == 0)
93 heap->size_increment = SIZE_INCREMENT;
94 else
95 heap->size_increment = size_increment;
96 heap->last = 0;
97 heap->array = NULL;
98 heap->compare = compare;
99 heap->index = index;
100
101 *heapp = heap;
102
103 return (ISC_R_SUCCESS);
104 }
105
106 void
isc_heap_destroy(isc_heap_t ** heapp)107 isc_heap_destroy(isc_heap_t **heapp) {
108 isc_heap_t *heap;
109
110 REQUIRE(heapp != NULL);
111 heap = *heapp;
112 REQUIRE(VALID_HEAP(heap));
113
114 if (heap->array != NULL)
115 isc_mem_put(heap->mctx, heap->array,
116 heap->size * sizeof(void *));
117 heap->magic = 0;
118 isc_mem_putanddetach(&heap->mctx, heap, sizeof(*heap));
119
120 *heapp = NULL;
121 }
122
123 static isc_boolean_t
resize(isc_heap_t * heap)124 resize(isc_heap_t *heap) {
125 void **new_array;
126 size_t new_size;
127
128 REQUIRE(VALID_HEAP(heap));
129
130 new_size = heap->size + heap->size_increment;
131 new_array = isc_mem_get(heap->mctx, new_size * sizeof(void *));
132 if (new_array == NULL)
133 return (ISC_FALSE);
134 if (heap->array != NULL) {
135 memcpy(new_array, heap->array, heap->size * sizeof(void *));
136 isc_mem_put(heap->mctx, heap->array,
137 heap->size * sizeof(void *));
138 }
139 heap->size = new_size;
140 heap->array = new_array;
141
142 return (ISC_TRUE);
143 }
144
145 static void
float_up(isc_heap_t * heap,unsigned int i,void * elt)146 float_up(isc_heap_t *heap, unsigned int i, void *elt) {
147 unsigned int p;
148
149 for (p = heap_parent(i) ;
150 i > 1 && heap->compare(elt, heap->array[p]) ;
151 i = p, p = heap_parent(i)) {
152 heap->array[i] = heap->array[p];
153 if (heap->index != NULL)
154 (heap->index)(heap->array[i], i);
155 }
156 heap->array[i] = elt;
157 if (heap->index != NULL)
158 (heap->index)(heap->array[i], i);
159
160 INSIST(HEAPCONDITION(i));
161 }
162
163 static void
sink_down(isc_heap_t * heap,unsigned int i,void * elt)164 sink_down(isc_heap_t *heap, unsigned int i, void *elt) {
165 unsigned int j, size, half_size;
166 size = heap->last;
167 half_size = size / 2;
168 while (i <= half_size) {
169 /* Find the smallest of the (at most) two children. */
170 j = heap_left(i);
171 if (j < size && heap->compare(heap->array[j+1],
172 heap->array[j]))
173 j++;
174 if (heap->compare(elt, heap->array[j]))
175 break;
176 heap->array[i] = heap->array[j];
177 if (heap->index != NULL)
178 (heap->index)(heap->array[i], i);
179 i = j;
180 }
181 heap->array[i] = elt;
182 if (heap->index != NULL)
183 (heap->index)(heap->array[i], i);
184
185 INSIST(HEAPCONDITION(i));
186 }
187
188 isc_result_t
isc_heap_insert(isc_heap_t * heap,void * elt)189 isc_heap_insert(isc_heap_t *heap, void *elt) {
190 unsigned int new_last;
191
192 REQUIRE(VALID_HEAP(heap));
193
194 new_last = heap->last + 1;
195 RUNTIME_CHECK(new_last > 0); /* overflow check */
196 if (new_last >= heap->size && !resize(heap))
197 return (ISC_R_NOMEMORY);
198 heap->last = new_last;
199
200 float_up(heap, new_last, elt);
201
202 return (ISC_R_SUCCESS);
203 }
204
205 void
isc_heap_delete(isc_heap_t * heap,unsigned int index)206 isc_heap_delete(isc_heap_t *heap, unsigned int index) {
207 void *elt;
208 isc_boolean_t less;
209
210 REQUIRE(VALID_HEAP(heap));
211 REQUIRE(index >= 1 && index <= heap->last);
212
213 if (index == heap->last) {
214 heap->array[heap->last] = NULL;
215 heap->last--;
216 } else {
217 elt = heap->array[heap->last];
218 heap->array[heap->last] = NULL;
219 heap->last--;
220
221 less = heap->compare(elt, heap->array[index]);
222 heap->array[index] = elt;
223 if (less)
224 float_up(heap, index, heap->array[index]);
225 else
226 sink_down(heap, index, heap->array[index]);
227 }
228 }
229
230 void
isc_heap_increased(isc_heap_t * heap,unsigned int index)231 isc_heap_increased(isc_heap_t *heap, unsigned int index) {
232 REQUIRE(VALID_HEAP(heap));
233 REQUIRE(index >= 1 && index <= heap->last);
234
235 float_up(heap, index, heap->array[index]);
236 }
237
238 void
isc_heap_decreased(isc_heap_t * heap,unsigned int index)239 isc_heap_decreased(isc_heap_t *heap, unsigned int index) {
240 REQUIRE(VALID_HEAP(heap));
241 REQUIRE(index >= 1 && index <= heap->last);
242
243 sink_down(heap, index, heap->array[index]);
244 }
245
246 void *
isc_heap_element(isc_heap_t * heap,unsigned int index)247 isc_heap_element(isc_heap_t *heap, unsigned int index) {
248 REQUIRE(VALID_HEAP(heap));
249 REQUIRE(index >= 1);
250
251 if (index <= heap->last)
252 return (heap->array[index]);
253 return (NULL);
254 }
255
256 void
isc_heap_foreach(isc_heap_t * heap,isc_heapaction_t action,void * uap)257 isc_heap_foreach(isc_heap_t *heap, isc_heapaction_t action, void *uap) {
258 unsigned int i;
259
260 REQUIRE(VALID_HEAP(heap));
261 REQUIRE(action != NULL);
262
263 for (i = 1 ; i <= heap->last ; i++)
264 (action)(heap->array[i], uap);
265 }
266