1 /*
2 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
3 * Copyright (c) 1997,1999 by Internet Software Consortium.
4 *
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.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
15 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
18 /*%
19 * Heap implementation of priority queues adapted from the following:
20 *
21 * _Introduction to Algorithms_, Cormen, Leiserson, and Rivest,
22 * MIT Press / McGraw Hill, 1990, ISBN 0-262-03141-8, chapter 7.
23 *
24 * _Algorithms_, Second Edition, Sedgewick, Addison-Wesley, 1988,
25 * ISBN 0-201-06673-4, chapter 11.
26 */
27
28 #include "port_before.h"
29
30 #include <stddef.h>
31 #include <stdlib.h>
32 #include <errno.h>
33
34 #include "port_after.h"
35
36 #include <isc/heap.h>
37
38 /*%
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,
41 * not 0-based.
42 */
43 #define heap_parent(i) ((i) >> 1)
44 #define heap_left(i) ((i) << 1)
45
46 #define ARRAY_SIZE_INCREMENT 512
47
48 heap_context
heap_new(heap_higher_priority_func higher_priority,heap_index_func index,int array_size_increment)49 heap_new(heap_higher_priority_func higher_priority, heap_index_func index,
50 int array_size_increment) {
51 heap_context ctx;
52
53 if (higher_priority == NULL)
54 return (NULL);
55
56 ctx = (heap_context)malloc(sizeof (struct heap_context));
57 if (ctx == NULL)
58 return (NULL);
59
60 ctx->array_size = 0;
61 if (array_size_increment == 0)
62 ctx->array_size_increment = ARRAY_SIZE_INCREMENT;
63 else
64 ctx->array_size_increment = array_size_increment;
65 ctx->heap_size = 0;
66 ctx->heap = NULL;
67 ctx->higher_priority = higher_priority;
68 ctx->index = index;
69 return (ctx);
70 }
71
72 int
heap_free(heap_context ctx)73 heap_free(heap_context ctx) {
74 if (ctx == NULL) {
75 errno = EINVAL;
76 return (-1);
77 }
78
79 if (ctx->heap != NULL)
80 free(ctx->heap);
81 free(ctx);
82
83 return (0);
84 }
85
86 static int
heap_resize(heap_context ctx)87 heap_resize(heap_context ctx) {
88 void **new_heap;
89
90 ctx->array_size += ctx->array_size_increment;
91 new_heap = (void **)realloc(ctx->heap,
92 (ctx->array_size) * (sizeof (void *)));
93 if (new_heap == NULL) {
94 errno = ENOMEM;
95 return (-1);
96 }
97 ctx->heap = new_heap;
98 return (0);
99 }
100
101 static void
float_up(heap_context ctx,int i,void * elt)102 float_up(heap_context ctx, int i, void *elt) {
103 int p;
104
105 for ( p = heap_parent(i);
106 i > 1 && ctx->higher_priority(elt, ctx->heap[p]);
107 i = p, p = heap_parent(i) ) {
108 ctx->heap[i] = ctx->heap[p];
109 if (ctx->index != NULL)
110 (ctx->index)(ctx->heap[i], i);
111 }
112 ctx->heap[i] = elt;
113 if (ctx->index != NULL)
114 (ctx->index)(ctx->heap[i], i);
115 }
116
117 static void
sink_down(heap_context ctx,int i,void * elt)118 sink_down(heap_context ctx, int i, void *elt) {
119 int j, size, half_size;
120
121 size = ctx->heap_size;
122 half_size = size / 2;
123 while (i <= half_size) {
124 /* find smallest of the (at most) two children */
125 j = heap_left(i);
126 if (j < size && ctx->higher_priority(ctx->heap[j+1],
127 ctx->heap[j]))
128 j++;
129 if (ctx->higher_priority(elt, ctx->heap[j]))
130 break;
131 ctx->heap[i] = ctx->heap[j];
132 if (ctx->index != NULL)
133 (ctx->index)(ctx->heap[i], i);
134 i = j;
135 }
136 ctx->heap[i] = elt;
137 if (ctx->index != NULL)
138 (ctx->index)(ctx->heap[i], i);
139 }
140
141 int
heap_insert(heap_context ctx,void * elt)142 heap_insert(heap_context ctx, void *elt) {
143 int i;
144
145 if (ctx == NULL || elt == NULL) {
146 errno = EINVAL;
147 return (-1);
148 }
149
150 i = ++ctx->heap_size;
151 if (ctx->heap_size >= ctx->array_size && heap_resize(ctx) < 0)
152 return (-1);
153
154 float_up(ctx, i, elt);
155
156 return (0);
157 }
158
159 int
heap_delete(heap_context ctx,int i)160 heap_delete(heap_context ctx, int i) {
161 void *elt;
162 int less;
163
164 if (ctx == NULL || i < 1 || i > ctx->heap_size) {
165 errno = EINVAL;
166 return (-1);
167 }
168
169 if (i == ctx->heap_size) {
170 ctx->heap_size--;
171 } else {
172 elt = ctx->heap[ctx->heap_size--];
173 less = ctx->higher_priority(elt, ctx->heap[i]);
174 ctx->heap[i] = elt;
175 if (less)
176 float_up(ctx, i, ctx->heap[i]);
177 else
178 sink_down(ctx, i, ctx->heap[i]);
179 }
180
181 return (0);
182 }
183
184 int
heap_increased(heap_context ctx,int i)185 heap_increased(heap_context ctx, int i) {
186 if (ctx == NULL || i < 1 || i > ctx->heap_size) {
187 errno = EINVAL;
188 return (-1);
189 }
190
191 float_up(ctx, i, ctx->heap[i]);
192
193 return (0);
194 }
195
196 int
heap_decreased(heap_context ctx,int i)197 heap_decreased(heap_context ctx, int i) {
198 if (ctx == NULL || i < 1 || i > ctx->heap_size) {
199 errno = EINVAL;
200 return (-1);
201 }
202
203 sink_down(ctx, i, ctx->heap[i]);
204
205 return (0);
206 }
207
208 void *
heap_element(heap_context ctx,int i)209 heap_element(heap_context ctx, int i) {
210 if (ctx == NULL || i < 1 || i > ctx->heap_size) {
211 errno = EINVAL;
212 return (NULL);
213 }
214
215 return (ctx->heap[i]);
216 }
217
218 int
heap_for_each(heap_context ctx,heap_for_each_func action,void * uap)219 heap_for_each(heap_context ctx, heap_for_each_func action, void *uap) {
220 int i;
221
222 if (ctx == NULL || action == NULL) {
223 errno = EINVAL;
224 return (-1);
225 }
226
227 for (i = 1; i <= ctx->heap_size; i++)
228 (action)(ctx->heap[i], uap);
229 return (0);
230 }
231
232 /*! \file */
233