xref: /illumos-gate/usr/src/lib/libresolv2/common/isc/heap.c (revision 55fea89dcaa64928bed4327112404dcb3e07b79f)
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