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/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: heap.c,v 1.1.1.1 2012/05/29 12:08:38 misho Exp $ */
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
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->mctx = mctx;
90: heap->size = 0;
91: if (size_increment == 0)
92: heap->size_increment = SIZE_INCREMENT;
93: else
94: heap->size_increment = size_increment;
95: heap->last = 0;
96: heap->array = NULL;
97: heap->compare = compare;
98: heap->index = index;
99:
100: *heapp = heap;
101:
102: return (ISC_R_SUCCESS);
103: }
104:
105: void
106: isc_heap_destroy(isc_heap_t **heapp) {
107: isc_heap_t *heap;
108:
109: REQUIRE(heapp != NULL);
110: heap = *heapp;
111: REQUIRE(VALID_HEAP(heap));
112:
113: if (heap->array != NULL)
114: isc_mem_put(heap->mctx, heap->array,
115: heap->size * sizeof(void *));
116: heap->magic = 0;
117: isc_mem_put(heap->mctx, heap, sizeof(*heap));
118:
119: *heapp = NULL;
120: }
121:
122: static isc_boolean_t
123: resize(isc_heap_t *heap) {
124: void **new_array;
125: size_t new_size;
126:
127: REQUIRE(VALID_HEAP(heap));
128:
129: new_size = heap->size + heap->size_increment;
130: new_array = isc_mem_get(heap->mctx, new_size * sizeof(void *));
131: if (new_array == NULL)
132: return (ISC_FALSE);
133: if (heap->array != NULL) {
134: memcpy(new_array, heap->array, heap->size * sizeof(void *));
135: isc_mem_put(heap->mctx, heap->array,
136: heap->size * sizeof(void *));
137: }
138: heap->size = new_size;
139: heap->array = new_array;
140:
141: return (ISC_TRUE);
142: }
143:
144: static void
145: float_up(isc_heap_t *heap, unsigned int i, void *elt) {
146: unsigned int p;
147:
148: for (p = heap_parent(i) ;
149: i > 1 && heap->compare(elt, heap->array[p]) ;
150: i = p, p = heap_parent(i)) {
151: heap->array[i] = heap->array[p];
152: if (heap->index != NULL)
153: (heap->index)(heap->array[i], i);
154: }
155: heap->array[i] = elt;
156: if (heap->index != NULL)
157: (heap->index)(heap->array[i], i);
158:
159: INSIST(HEAPCONDITION(i));
160: }
161:
162: static void
163: sink_down(isc_heap_t *heap, unsigned int i, void *elt) {
164: unsigned int j, size, half_size;
165: size = heap->last;
166: half_size = size / 2;
167: while (i <= half_size) {
168: /* Find the smallest of the (at most) two children. */
169: j = heap_left(i);
170: if (j < size && heap->compare(heap->array[j+1],
171: heap->array[j]))
172: j++;
173: if (heap->compare(elt, heap->array[j]))
174: break;
175: heap->array[i] = heap->array[j];
176: if (heap->index != NULL)
177: (heap->index)(heap->array[i], i);
178: i = j;
179: }
180: heap->array[i] = elt;
181: if (heap->index != NULL)
182: (heap->index)(heap->array[i], i);
183:
184: INSIST(HEAPCONDITION(i));
185: }
186:
187: isc_result_t
188: isc_heap_insert(isc_heap_t *heap, void *elt) {
189: unsigned int i;
190:
191: REQUIRE(VALID_HEAP(heap));
192:
193: i = ++heap->last;
194: if (heap->last >= heap->size && !resize(heap))
195: return (ISC_R_NOMEMORY);
196:
197: float_up(heap, i, elt);
198:
199: return (ISC_R_SUCCESS);
200: }
201:
202: void
203: isc_heap_delete(isc_heap_t *heap, unsigned int index) {
204: void *elt;
205: isc_boolean_t less;
206:
207: REQUIRE(VALID_HEAP(heap));
208: REQUIRE(index >= 1 && index <= heap->last);
209:
210: if (index == heap->last) {
211: heap->array[heap->last] = NULL;
212: heap->last--;
213: } else {
214: elt = heap->array[heap->last];
215: heap->array[heap->last] = NULL;
216: heap->last--;
217:
218: less = heap->compare(elt, heap->array[index]);
219: heap->array[index] = elt;
220: if (less)
221: float_up(heap, index, heap->array[index]);
222: else
223: sink_down(heap, index, heap->array[index]);
224: }
225: }
226:
227: void
228: isc_heap_increased(isc_heap_t *heap, unsigned int index) {
229: REQUIRE(VALID_HEAP(heap));
230: REQUIRE(index >= 1 && index <= heap->last);
231:
232: float_up(heap, index, heap->array[index]);
233: }
234:
235: void
236: isc_heap_decreased(isc_heap_t *heap, unsigned int index) {
237: REQUIRE(VALID_HEAP(heap));
238: REQUIRE(index >= 1 && index <= heap->last);
239:
240: sink_down(heap, index, heap->array[index]);
241: }
242:
243: void *
244: isc_heap_element(isc_heap_t *heap, unsigned int index) {
245: REQUIRE(VALID_HEAP(heap));
246: REQUIRE(index >= 1);
247:
248: if (index <= heap->last)
249: return (heap->array[index]);
250: return (NULL);
251: }
252:
253: void
254: isc_heap_foreach(isc_heap_t *heap, isc_heapaction_t action, void *uap) {
255: unsigned int i;
256:
257: REQUIRE(VALID_HEAP(heap));
258: REQUIRE(action != NULL);
259:
260: for (i = 1 ; i <= heap->last ; i++)
261: (action)(heap->array[i], uap);
262: }
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