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: https://origsvn.digium.com/svn/asterisk/trunk@176632 65c4cc65-6c06-0410-ace0-fbb531ad65f3

include/asterisk/heap.h

+/*
+ * 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>
+ */
+
+#ifndef __AST_HEAP_H__
+#define __AST_HEAP_H__
+
+/*!
+ * \brief A max heap.
+ *
+ * \note Thread-safety is left to the user of the API.  The heap API provides
+ *       no locking of its own.  If the heap will be accessed by multiple threads,
+ *       then a lock must be used to ensure that only a single operation is
+ *       done on the heap at a time.  For the sake of convenience, a lock is
+ *       provided for the user of the API to use if another lock is not already
+ *       available to protect the heap.
+ */
+struct ast_heap;
+
+/*!
+ * \brief Function type for comparing nodes in a heap
+ *
+ * \param elm1 the first element
+ * \param elm2 the second element
+ *
+ * \retval negative if elm1 < elm2
+ * \retval 0 if elm1 == elm2
+ * \retval positive if elm1 > elm2
+ *
+ * \note This implementation is of a max heap.  However, if a min heap is
+ *       desired, simply swap the return values of this function.
+ */
+typedef int (*ast_heap_cmp_fn)(void *elm1, void *elm2);
+
+/*!
+ * \brief Create a max heap
+ *
+ * \param init_height The initial height of the heap to allocate space for.
+ *        To start out, there will be room for (2 ^ init_height) - 1 entries.
+ *        However, the heap will grow as needed.
+ * \param cmp_fn The function that should be used to compare elements in the heap.
+ * \param index_offset This parameter is optional, but must be provided to be able
+ *        to use ast_heap_remove().  This is the number of bytes into the element
+ *        where an ssize_t has been made available for the heap's internal
+ *        use.  The heap will use this field to keep track of the element's current
+ *        position in the heap.  The offsetof() macro is useful for providing a
+ *        proper value for this argument.  If ast_heap_remove() will not be used,
+ *        then a negative value can be provided to indicate that no field for an
+ *        offset has been allocated.
+ *
+ * Example Usage:
+ *
+ * \code
+ *
+ * struct myobj {
+ *    int foo;
+ *    int bar;
+ *    char stuff[8];
+ *    char things[8];
+ *    ssize_t __heap_index;
+ * };
+ *
+ * ...
+ *
+ * static int myobj_cmp(void *obj1, void *obj2);
+ *
+ * ...
+ *
+ * struct ast_heap *h;
+ *
+ * h = ast_heap_create(8, myobj_cmp, offsetof(struct myobj, __heap_index));
+ *
+ * \endcode
+ *
+ * \return An instance of a max heap
+ */
+struct ast_heap *ast_heap_create(unsigned int init_height, ast_heap_cmp_fn cmp_fn,
+		ssize_t index_offset);
+
+/*!
+ * \brief Destroy a max heap
+ *
+ * \param h the heap to destroy
+ *
+ * \return NULL for convenience
+ */
+struct ast_heap *ast_heap_destroy(struct ast_heap *h);
+
+/*!
+ * \brief Push an element on to a heap
+ *
+ * \param h the heap being added to
+ * \param elm the element being put on the heap
+ *
+ * \retval 0 success
+ * \retval non-zero failure
+ */
+int ast_heap_push(struct ast_heap *h, void *elm);
+
+/*!
+ * \brief Pop the max element off of the heap
+ *
+ * \param h the heap
+ *
+ * \return this will return the element on the top of the heap, which has the
+ *         largest value according to the element comparison function that was
+ *         provided when the heap was created.  The element will be removed before
+ *         being returned.
+ */
+void *ast_heap_pop(struct ast_heap *h);
+
+/*!
+ * \brief Remove a specific element from a heap
+ *
+ * \param h the heap to remove from
+ * \param elm the element to remove
+ *
+ * \return elm, if the removal was successful, or NULL if it failed
+ *
+ * \note the index_offset parameter to ast_heap_create() is required to be able
+ *       to use this function.
+ */
+void *ast_heap_remove(struct ast_heap *h, void *elm);
+
+/*!
+ * \brief Peek at an element on a heap
+ *
+ * \param h the heap
+ * \param index index of the element to return.  The first element is at index 1,
+ *        and the last element is at the index == the size of the heap.
+ *
+ * \return an element at the specified index on the heap.  This element will \b not
+ *         be removed before being returned.
+ *
+ * \note If this function is being used in combination with ast_heap_size() for
+ *       purposes of traversing the heap, the heap must be locked for the entire
+ *       duration of the traversal.
+ */
+void *ast_heap_peek(struct ast_heap *h, unsigned int index);
+
+/*!
+ * \brief Get the current size of a heap
+ *
+ * \param h the heap
+ *
+ * \return the number of elements currently in the heap
+ */
+size_t ast_heap_size(struct ast_heap *h);
+
+/*!
+ * \brief Write-Lock a heap
+ *
+ * \arg h the heap
+ *
+ * A lock is provided for convenience.  It can be assumed that none of the
+ * ast_heap API calls are thread safe.  This lock does not have to be used
+ * if another one is already available to protect the heap.
+ *
+ * \return see the documentation for pthread_rwlock_wrlock()
+ */
+int ast_heap_wrlock(struct ast_heap *h);
+
+/*!
+ * \brief Read-Lock a heap
+ *
+ * \arg h the heap
+ *
+ * A lock is provided for convenience.  It can be assumed that none of the
+ * ast_heap API calls are thread safe.  This lock does not have to be used
+ * if another one is already available to protect the heap.
+ *
+ * \return see the documentation for pthread_rwlock_rdlock()
+ */
+int ast_heap_rdlock(struct ast_heap *h);
+
+/*!
+ * \brief Unlock a heap
+ *
+ * \arg h the heap
+ *
+ * \return see the documentation for pthread_rwlock_unlock()
+ */
+int ast_heap_unlock(struct ast_heap *h);
+
+/*!
+ * \brief Verify that a heap has been properly constructed
+ *
+ * \param h a heap
+ *
+ * \retval 0 success
+ * \retval non-zero failure
+ *
+ * \note This function is mostly for debugging purposes.  It traverses an existing
+ *       heap and verifies that every node is properly placed relative to its children.
+ */
+int ast_heap_verify(struct ast_heap *h);
+
+#endif /* __AST_HEAP_H__ */

main/Makefile

@@ -18,7 +18,7 @@ all: asterisk
 include $(ASTTOPDIR)/Makefile.moddir_rules
 
 OBJS= tcptls.o io.o sched.o logger.o frame.o loader.o config.o channel.o \
-	translate.o file.o pbx.o cli.o md5.o term.o \
+	translate.o file.o pbx.o cli.o md5.o term.o heap.o \
 	ulaw.o alaw.o callerid.o fskmodem.o image.o app.o \
 	cdr.o tdd.o acl.o rtp.o udptl.o manager.o asterisk.o \
 	dsp.o chanvars.o indications.o autoservice.o db.o privacy.o \

main/heap.c

+/*
+ * 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);
+}
+