1: /*
2: * Copyright (C) 2004-2007 Internet Systems Consortium, Inc. ("ISC")
3: * Copyright (C) 1997-2001 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 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: heap.c,v 1.1.1.1 2012/10/09 09:06:54 misho Exp $ */
19:
20: /*
21: * This heap implementation is taken from the BIND 9 code. It has been
22: * modified to use the DHCP memory management rather than BIND memory
23: * contexts.
24: */
25:
26: /*! \file
27: * Heap implementation of priority queues adapted from the following:
28: *
29: * \li "Introduction to Algorithms," Cormen, Leiserson, and Rivest,
30: * MIT Press / McGraw Hill, 1990, ISBN 0-262-03141-8, chapter 7.
31: *
32: * \li "Algorithms," Second Edition, Sedgewick, Addison-Wesley, 1988,
33: * ISBN 0-201-06673-4, chapter 11.
34: */
35:
36: #include "dhcpd.h"
37: #include "omapip/omapip.h"
38: #include "heap.h"
39:
40: #include <assert.h>
41: #define REQUIRE assert
42: #define INSIST assert
43:
44: /*@{*/
45: /*%
46: * Note: to make heap_parent and heap_left easy to compute, the first
47: * element of the heap array is not used; i.e. heap subscripts are 1-based,
48: * not 0-based. The parent is index/2, and the left-child is index*2.
49: * The right child is index*2+1.
50: */
51: #define heap_parent(i) ((i) >> 1)
52: #define heap_left(i) ((i) << 1)
53: /*@}*/
54:
55: #define SIZE_INCREMENT 1024
56:
57: /*%
58: * When the heap is in a consistent state, the following invariant
59: * holds true: for every element i > 1, heap_parent(i) has a priority
60: * higher than or equal to that of i.
61: */
62: #define HEAPCONDITION(i) ((i) == 1 || \
63: ! heap->compare(heap->array[(i)], \
64: heap->array[heap_parent(i)]))
65:
66: /*% ISC heap structure. */
67: struct isc_heap {
68: unsigned int size;
69: unsigned int size_increment;
70: unsigned int last;
71: void **array;
72: isc_heapcompare_t compare;
73: isc_heapindex_t index;
74: };
75:
76: isc_result_t
77: isc_heap_create(isc_heapcompare_t compare,
78: isc_heapindex_t index, unsigned int size_increment,
79: isc_heap_t **heapp)
80: {
81: isc_heap_t *heap;
82:
83: REQUIRE(heapp != NULL && *heapp == NULL);
84: REQUIRE(compare != NULL);
85:
86: heap = dmalloc(sizeof(*heap), MDL);
87: if (heap == NULL)
88: return (ISC_R_NOMEMORY);
89: heap->size = 0;
90: if (size_increment == 0)
91: heap->size_increment = SIZE_INCREMENT;
92: else
93: heap->size_increment = size_increment;
94: heap->last = 0;
95: heap->array = NULL;
96: heap->compare = compare;
97: heap->index = index;
98:
99: *heapp = heap;
100:
101: return (ISC_R_SUCCESS);
102: }
103:
104: void
105: isc_heap_destroy(isc_heap_t **heapp) {
106: isc_heap_t *heap;
107:
108: REQUIRE(heapp != NULL);
109: heap = *heapp;
110:
111: if (heap->array != NULL)
112: dfree(heap->array, MDL);
113: dfree(heap, MDL);
114:
115: *heapp = NULL;
116: }
117:
118: static isc_boolean_t
119: resize(isc_heap_t *heap) {
120: void **new_array;
121: size_t new_size;
122:
123: new_size = heap->size + heap->size_increment;
124: new_array = dmalloc(new_size * sizeof(void *), MDL);
125: if (new_array == NULL)
126: return (ISC_FALSE);
127: if (heap->array != NULL) {
128: memcpy(new_array, heap->array, heap->size * sizeof(void *));
129: dfree(heap->array, MDL);
130: }
131: heap->size = new_size;
132: heap->array = new_array;
133:
134: return (ISC_TRUE);
135: }
136:
137: static void
138: float_up(isc_heap_t *heap, unsigned int i, void *elt) {
139: unsigned int p;
140:
141: for (p = heap_parent(i) ;
142: i > 1 && heap->compare(elt, heap->array[p]) ;
143: i = p, p = heap_parent(i)) {
144: heap->array[i] = heap->array[p];
145: if (heap->index != NULL)
146: (heap->index)(heap->array[i], i);
147: }
148: heap->array[i] = elt;
149: if (heap->index != NULL)
150: (heap->index)(heap->array[i], i);
151:
152: INSIST(HEAPCONDITION(i));
153: }
154:
155: static void
156: sink_down(isc_heap_t *heap, unsigned int i, void *elt) {
157: unsigned int j, size, half_size;
158: size = heap->last;
159: half_size = size / 2;
160: while (i <= half_size) {
161: /* Find the smallest of the (at most) two children. */
162: j = heap_left(i);
163: if (j < size && heap->compare(heap->array[j+1],
164: heap->array[j]))
165: j++;
166: if (heap->compare(elt, heap->array[j]))
167: break;
168: heap->array[i] = heap->array[j];
169: if (heap->index != NULL)
170: (heap->index)(heap->array[i], i);
171: i = j;
172: }
173: heap->array[i] = elt;
174: if (heap->index != NULL)
175: (heap->index)(heap->array[i], i);
176:
177: INSIST(HEAPCONDITION(i));
178: }
179:
180: isc_result_t
181: isc_heap_insert(isc_heap_t *heap, void *elt) {
182: unsigned int i;
183:
184: i = ++heap->last;
185: if (heap->last >= heap->size && !resize(heap))
186: return (ISC_R_NOMEMORY);
187:
188: float_up(heap, i, elt);
189:
190: return (ISC_R_SUCCESS);
191: }
192:
193: void
194: isc_heap_delete(isc_heap_t *heap, unsigned int index) {
195: void *elt;
196: isc_boolean_t less;
197:
198: REQUIRE(index >= 1 && index <= heap->last);
199:
200: if (index == heap->last) {
201: heap->last--;
202: } else {
203: elt = heap->array[heap->last--];
204: less = heap->compare(elt, heap->array[index]);
205: heap->array[index] = elt;
206: if (less)
207: float_up(heap, index, heap->array[index]);
208: else
209: sink_down(heap, index, heap->array[index]);
210: }
211: }
212:
213: void
214: isc_heap_increased(isc_heap_t *heap, unsigned int index) {
215: REQUIRE(index >= 1 && index <= heap->last);
216:
217: float_up(heap, index, heap->array[index]);
218: }
219:
220: void
221: isc_heap_decreased(isc_heap_t *heap, unsigned int index) {
222: REQUIRE(index >= 1 && index <= heap->last);
223:
224: sink_down(heap, index, heap->array[index]);
225: }
226:
227: void *
228: isc_heap_element(isc_heap_t *heap, unsigned int index) {
229: REQUIRE(index >= 1 && index <= heap->last);
230:
231: return (heap->array[index]);
232: }
233:
234: void
235: isc_heap_foreach(isc_heap_t *heap, isc_heapaction_t action, void *uap) {
236: unsigned int i;
237:
238: REQUIRE(action != NULL);
239:
240: for (i = 1 ; i <= heap->last ; i++)
241: (action)(heap->array[i], uap);
242: }
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