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

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);
+}
+