From bb03ef8d47dbf2d5852b3304bcbec7ee17a8915c Mon Sep 17 00:00:00 2001 From: Russell Bryant Date: Tue, 17 Feb 2009 20:51:10 +0000 Subject: 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 | 218 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 218 insertions(+) create mode 100644 include/asterisk/heap.h (limited to 'include/asterisk/heap.h') diff --git a/include/asterisk/heap.h b/include/asterisk/heap.h new file mode 100644 index 000000000..6f6e52b2d --- /dev/null +++ b/include/asterisk/heap.h @@ -0,0 +1,218 @@ +/* + * Asterisk -- An open source telephony toolkit. + * + * Copyright (C) 2009, Digium, Inc. + * + * Russell Bryant + * + * 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 + */ + +#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__ */ -- cgit v1.2.3