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 idx)
62 void *last_key, *last_data;
64 last_key = heap->data[idx*2];
65 last_data = heap->data[idx*2+1];
67 parent = (idx - 1) >> 1;
68 res = heap->comparator(last_key, heap->data[parent*2]);
70 heap->data[idx*2] = heap->data[parent*2];
71 heap->data[idx*2+1] = heap->data[parent*2+1];
74 heap->data[idx*2] = last_key;
75 heap->data[idx*2+1] = last_data;
79 * Insert a key/data pair into the heap.
82 heap_insert(heap_t heap, void *key, void *data)
84 if (heap->data_used == heap->data_alloc) {
85 heap->data_alloc *= 2;
86 heap->data = realloc(heap->data, 2*heap->data_alloc*sizeof(void*));
88 heap->data[heap->data_used*2] = key;
89 heap->data[heap->data_used*2+1] = data;
90 heap_heapify_up(heap, heap->data_used++);
94 * Return what's on top of the heap.
95 * If the heap is empty, put NULL into *key and *data.
96 * (Either key or data may be NULL, in which case the relevant
97 * data will not be returned to the caller.)
100 heap_peek(heap_t heap, void **key, void **data)
102 if (key) *key = heap->data_used ? heap->data[0] : NULL;
103 if (data) *data = heap->data_used ? heap->data[1] : NULL;
107 * Push the element at "pos" down the heap as far as it will go.
110 heap_heapify_down(heap_t heap, int pos)
114 void *last_key, *last_data;
115 last_key = heap->data[pos*2];
116 last_data = heap->data[pos*2+1];
117 /* start at left child */
118 while ((child=pos*2+1) < heap->data_used) {
119 /* use right child if it exists and is smaller */
120 if (child+1 < heap->data_used) {
121 res = heap->comparator(heap->data[(child+1)*2], heap->data[child*2]);
122 if (res < 0) child = child+1;
124 res = heap->comparator(last_key, heap->data[child*2]);
126 heap->data[pos*2] = heap->data[child*2];
127 heap->data[pos*2+1] = heap->data[child*2+1];
130 heap->data[pos*2] = last_key;
131 heap->data[pos*2+1] = last_data;
135 * Remove the element at "idx" from the heap (preserving the heap ordering).
138 heap_remove(heap_t heap, unsigned int idx)
141 if (heap->data_used <= idx) return;
142 /* swap idx with last element */
144 heap->data[idx*2] = heap->data[heap->data_used*2];
145 heap->data[idx*2+1] = heap->data[heap->data_used*2+1];
146 /* heapify down if idx has children */
147 if (heap->data_used >= 2*idx+1) heap_heapify_down(heap, idx);
148 if ((idx > 0) && (idx < heap->data_used)) heap_heapify_up(heap, idx);
152 * Pop the topmost element from the heap (preserving the heap ordering).
155 heap_pop(heap_t heap)
157 heap_remove(heap, 0);
161 * Remove all elements from the heap if pred(key, data, extra) returns
162 * non-zero on the element's key/data pair. Can be abused to iterate
163 * over the entire heap, by always returning 0 from pred.
165 * Returns non-zero if the predicate causes the top of the heap to be
169 heap_remove_pred(heap_t heap, int (*pred)(void *key, void *data, void *extra), void *extra)
171 unsigned int pos, rem_first;
173 if (heap->data_used == 0) return 0;
174 if (pred(heap->data[0], heap->data[1], extra)) {
175 heap_remove(heap, 0);
182 while (pos < heap->data_used) {
183 if (pred(heap->data[pos*2], heap->data[pos*2+1], extra)) {
184 heap_remove(heap, pos);
194 * Remove all entries from a heap.
197 heap_delete(heap_t heap)
204 * Return number of entries in the heap.
207 heap_size(heap_t heap)
209 return heap->data_used;
212 /* prepackaged comparators */
214 ulong_comparator(const void *a, const void *b)
216 return (a < b) ? -1 : (a > b) ? 1 : 0;