diff options
author | russell <russell@f38db490-d61c-443f-a65b-d21fe96a405b> | 2009-02-17 20:51:10 +0000 |
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committer | russell <russell@f38db490-d61c-443f-a65b-d21fe96a405b> | 2009-02-17 20:51:10 +0000 |
commit | 18f52ab1e75f994e02b4da7d22c8d41e5b479f6a (patch) | |
tree | cfbb55e6ff6db212e2fdfa882d9d155d6c45a2e5 /main/heap.c | |
parent | d6b563a51dd506654db20450a81f668680f45460 (diff) |
Add an implementation of the heap data structure.
A heap is a convenient data structure for implementing a priority queue.
Code from svn/asterisk/team/russell/heap/.
Review: http://reviewboard.digium.com/r/160/
git-svn-id: http://svn.digium.com/svn/asterisk/trunk@176632 f38db490-d61c-443f-a65b-d21fe96a405b
Diffstat (limited to 'main/heap.c')
-rw-r--r-- | main/heap.c | 284 |
1 files changed, 284 insertions, 0 deletions
diff --git a/main/heap.c b/main/heap.c new file mode 100644 index 000000000..5e8a2baef --- /dev/null +++ b/main/heap.c @@ -0,0 +1,284 @@ +/* + * Asterisk -- An open source telephony toolkit. + * + * Copyright (C) 2009, Digium, Inc. + * + * Russell Bryant <russell@digium.com> + * + * See http://www.asterisk.org for more information about + * the Asterisk project. Please do not directly contact + * any of the maintainers of this project for assistance; + * the project provides a web site, mailing lists and IRC + * channels for your use. + * + * This program is free software, distributed under the terms of + * the GNU General Public License Version 2. See the LICENSE file + * at the top of the source tree. + */ + +/*! \file + * + * \brief Max Heap data structure + * + * \author Russell Bryant <russell@digium.com> + */ + +#include "asterisk.h" + +ASTERISK_FILE_VERSION(__FILE__, "$Revision$") + +#include "asterisk/heap.h" +#include "asterisk/utils.h" +#include "asterisk/cli.h" + +struct ast_heap { + ast_rwlock_t lock; + ast_heap_cmp_fn cmp_fn; + ssize_t index_offset; + size_t cur_len; + size_t avail_len; + void **heap; +}; + +static inline int left_node(int i) +{ + return 2 * i; +} + +static inline int right_node(int i) +{ + return 2 * i + 1; +} + +static inline int parent_node(int i) +{ + return i / 2; +} + +static inline void *heap_get(struct ast_heap *h, int i) +{ + return h->heap[i - 1]; +} + +static inline ssize_t get_index(struct ast_heap *h, void *elm) +{ + ssize_t *index; + + if (h->index_offset < 0) { + return -1; + } + + index = elm + h->index_offset; + + return *index; +} + +static inline void heap_set(struct ast_heap *h, int i, void *elm) +{ + h->heap[i - 1] = elm; + + if (h->index_offset >= 0) { + ssize_t *index = elm + h->index_offset; + *index = i; + } +} + +int ast_heap_verify(struct ast_heap *h) +{ + unsigned int i; + + for (i = 1; i <= (h->cur_len / 2); i++) { + int l = left_node(i); + int r = right_node(i); + + if (l <= h->cur_len) { + if (h->cmp_fn(heap_get(h, i), heap_get(h, l)) <= 0) { + return -1; + } + } + + if (r <= h->cur_len) { + if (h->cmp_fn(heap_get(h, i), heap_get(h, r)) <= 0) { + return -1; + } + } + } + + return 0; +} + +struct ast_heap *ast_heap_create(unsigned int init_height, ast_heap_cmp_fn cmp_fn, + ssize_t index_offset) +{ + struct ast_heap *h; + + if (!cmp_fn) { + ast_log(LOG_ERROR, "A comparison function must be provided\n"); + return NULL; + } + + if (!init_height) { + init_height = 8; + } + + if (!(h = ast_calloc(1, sizeof(*h)))) { + return NULL; + } + + h->cmp_fn = cmp_fn; + h->index_offset = index_offset; + h->avail_len = (1 << init_height) - 1; + + if (!(h->heap = ast_calloc(1, h->avail_len * sizeof(void *)))) { + ast_free(h); + return NULL; + } + + ast_rwlock_init(&h->lock); + + return h; +} + +struct ast_heap *ast_heap_destroy(struct ast_heap *h) +{ + ast_free(h->heap); + h->heap = NULL; + + ast_rwlock_destroy(&h->lock); + + ast_free(h); + + return NULL; +} + +/*! + * \brief Add a row of additional storage for the heap. + */ +static int grow_heap(struct ast_heap *h) +{ + h->avail_len = h->avail_len * 2 + 1; + + if (!(h->heap = ast_realloc(h->heap, h->avail_len * sizeof(void *)))) { + h->cur_len = h->avail_len = 0; + return -1; + } + + return 0; +} + +static inline void heap_swap(struct ast_heap *h, int i, int j) +{ + void *tmp; + + tmp = heap_get(h, i); + heap_set(h, i, heap_get(h, j)); + heap_set(h, j, tmp); +} + +static inline void max_heapify(struct ast_heap *h, int i) +{ + for (;;) { + int l = left_node(i); + int r = right_node(i); + int max; + + if (l <= h->cur_len && h->cmp_fn(heap_get(h, l), heap_get(h, i)) > 0) { + max = l; + } else { + max = i; + } + + if (r <= h->cur_len && h->cmp_fn(heap_get(h, r), heap_get(h, max)) > 0) { + max = r; + } + + if (max == i) { + break; + } + + heap_swap(h, i, max); + + i = max; + } +} + +int ast_heap_push(struct ast_heap *h, void *elm) +{ + int i; + + if (h->cur_len == h->avail_len && grow_heap(h)) { + return -1; + } + + heap_set(h, ++(h->cur_len), elm); + + for (i = h->cur_len; + i > 1 && h->cmp_fn(heap_get(h, parent_node(i)), heap_get(h, i)) < 0; + i = parent_node(i)) { + heap_swap(h, i, parent_node(i)); + } + + return 0; +} + +static void *_ast_heap_remove(struct ast_heap *h, unsigned int index) +{ + void *ret; + + if (!index || index > h->cur_len) { + return NULL; + } + + ret = heap_get(h, index); + heap_set(h, index, heap_get(h, (h->cur_len)--)); + + max_heapify(h, index); + + return ret; +} + +void *ast_heap_remove(struct ast_heap *h, void *elm) +{ + ssize_t i = get_index(h, elm); + + if (i == -1) { + return NULL; + } + + return _ast_heap_remove(h, i); +} + +void *ast_heap_pop(struct ast_heap *h) +{ + return _ast_heap_remove(h, 1); +} + +void *ast_heap_peek(struct ast_heap *h, unsigned int index) +{ + if (!h->cur_len || !index || index > h->cur_len) { + return NULL; + } + + return heap_get(h, index); +} + +size_t ast_heap_size(struct ast_heap *h) +{ + return h->cur_len; +} + +int ast_heap_wrlock(struct ast_heap *h) +{ + return ast_rwlock_wrlock(&h->lock); +} + +int ast_heap_rdlock(struct ast_heap *h) +{ + return ast_rwlock_rdlock(&h->lock); +} + +int ast_heap_unlock(struct ast_heap *h) +{ + return ast_rwlock_unlock(&h->lock); +} + |