1 /* heap.c - Abstract heap type
2 * Copyright 2000-2002 srvx Development Team
4 * This file is part of srvx.
6 * srvx is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with srvx; if not, write to the Free Software Foundation,
18 * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
24 /* Possible optimizations:
26 * Use another type of heap (rather than binary) if our heaps are big enough.
28 * Coalesce multiple entries with the same key into the same chunk, and have
29 * a new API function to return all of the entries at the top of the heap.
33 comparator_f comparator;
35 unsigned int data_used, data_alloc;
39 * Allocate a new heap.
42 heap_new(comparator_f comparator)
44 heap_t heap = malloc(sizeof(struct heap));
45 heap->comparator = comparator;
48 heap->data = malloc(2*heap->data_alloc*sizeof(void*));
53 * Move the element at "index" in the heap as far up the heap as is
54 * proper (i.e., as long as its parent node is less than or equal to
58 heap_heapify_up(heap_t heap, unsigned int index)
62 void *last_key, *last_data;
63 last_key = heap->data[index*2];
64 last_data = heap->data[index*2+1];
66 parent = (index - 1) >> 1;
67 res = heap->comparator(last_key, heap->data[parent*2]);
69 heap->data[index*2] = heap->data[parent*2];
70 heap->data[index*2+1] = heap->data[parent*2+1];
73 heap->data[index*2] = last_key;
74 heap->data[index*2+1] = last_data;
78 * Insert a key/data pair into the heap.
81 heap_insert(heap_t heap, void *key, void *data)
83 if (heap->data_used == heap->data_alloc) {
84 heap->data_alloc *= 2;
85 heap->data = realloc(heap->data, 2*heap->data_alloc*sizeof(void*));
87 heap->data[heap->data_used*2] = key;
88 heap->data[heap->data_used*2+1] = data;
89 heap_heapify_up(heap, heap->data_used++);
93 * Return what's on top of the heap.
94 * If the heap is empty, put NULL into *key and *data.
95 * (Either key or data may be NULL, in which case the relevant
96 * data will not be returned to the caller.)
99 heap_peek(heap_t heap, void **key, void **data)
101 if (key) *key = heap->data_used ? heap->data[0] : NULL;
102 if (data) *data = heap->data_used ? heap->data[1] : NULL;
106 * Push the element at "pos" down the heap as far as it will go.
109 heap_heapify_down(heap_t heap, int pos)
113 void *last_key, *last_data;
114 last_key = heap->data[pos*2];
115 last_data = heap->data[pos*2+1];
116 /* start at left child */
117 while ((child=pos*2+1) < heap->data_used) {
118 /* use right child if it exists and is smaller */
119 if (child+1 < heap->data_used) {
120 res = heap->comparator(heap->data[(child+1)*2], heap->data[child*2]);
121 if (res < 0) child = child+1;
123 res = heap->comparator(last_key, heap->data[child*2]);
125 heap->data[pos*2] = heap->data[child*2];
126 heap->data[pos*2+1] = heap->data[child*2+1];
129 heap->data[pos*2] = last_key;
130 heap->data[pos*2+1] = last_data;
134 * Remove the element at "index" from the heap (preserving the heap ordering).
137 heap_remove(heap_t heap, unsigned int index)
140 if (heap->data_used <= index) return;
141 /* swap index with last element */
143 heap->data[index*2] = heap->data[heap->data_used*2];
144 heap->data[index*2+1] = heap->data[heap->data_used*2+1];
145 /* heapify down if index has children */
146 if (heap->data_used >= 2*index+1) heap_heapify_down(heap, index);
147 if ((index > 0) && (index < heap->data_used)) heap_heapify_up(heap, index);
151 * Pop the topmost element from the heap (preserving the heap ordering).
154 heap_pop(heap_t heap)
156 heap_remove(heap, 0);
160 * Remove all elements from the heap if pred(key, data, extra) returns
161 * non-zero on the element's key/data pair. Can be abused to iterate
162 * over the entire heap, by always returning 0 from pred.
164 * Returns non-zero if the predicate causes the top of the heap to be
168 heap_remove_pred(heap_t heap, int (*pred)(void *key, void *data, void *extra), void *extra)
170 unsigned int pos, rem_first;
172 if (heap->data_used == 0) return 0;
173 if (pred(heap->data[0], heap->data[1], extra)) {
174 heap_remove(heap, 0);
181 while (pos < heap->data_used) {
182 if (pred(heap->data[pos*2], heap->data[pos*2+1], extra)) {
183 heap_remove(heap, pos);
193 * Remove all entries from a heap.
196 heap_delete(heap_t heap)
203 * Return number of entries in the heap.
206 heap_size(heap_t heap)
208 return heap->data_used;
211 /* prepackaged comparators */
213 int_comparator(const void *a, const void *b)
215 return (time_t)a-(time_t)b;