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/*
* 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.
*
* \since 1.6.1
*/
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
* \since 1.6.1
*/
#ifdef MALLOC_DEBUG
struct ast_heap *_ast_heap_create(unsigned int init_height, ast_heap_cmp_fn cmp_fn,
ssize_t index_offset, const char *file, int lineno, const char *func);
#define ast_heap_create(a,b,c) _ast_heap_create(a,b,c,__FILE__,__LINE__,__PRETTY_FUNCTION__)
#else
struct ast_heap *ast_heap_create(unsigned int init_height, ast_heap_cmp_fn cmp_fn,
ssize_t index_offset);
#endif
/*!
* \brief Destroy a max heap
*
* \param h the heap to destroy
*
* \return NULL for convenience
* \since 1.6.1
*/
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
* \since 1.6.1
*/
#ifdef MALLOC_DEBUG
int _ast_heap_push(struct ast_heap *h, void *elm, const char *file, int lineno, const char *func);
#define ast_heap_push(a,b) _ast_heap_push(a,b,__FILE__,__LINE__,__PRETTY_FUNCTION__)
#else
int ast_heap_push(struct ast_heap *h, void *elm);
#endif
/*!
* \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.
* \since 1.6.1
*/
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.
* \since 1.6.1
*/
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.
*
* Example code for a traversal:
* \code
*
* struct ast_heap *h;
*
* ...
*
* size_t size, i;
* void *cur_obj;
*
* ast_heap_rdlock(h);
*
* size = ast_heap_size(h);
*
* for (i = 1; i <= size && (cur_obj = ast_heap_peek(h, i)); i++) {
* ... Do stuff with cur_obj ...
* }
*
* ast_heap_unlock(h);
*
* \endcode
* \since 1.6.1
*/
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
* \since 1.6.1
*/
size_t ast_heap_size(struct ast_heap *h);
/*!
* \brief Write-Lock a heap
*
* \param 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()
* \since 1.6.1
*/
int __ast_heap_wrlock(struct ast_heap *h, const char *file, const char *func, int line);
/*!
* \brief Read-Lock a heap
*
* \param 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()
* \since 1.6.1
*/
int __ast_heap_rdlock(struct ast_heap *h, const char *file, const char *func, int line);
/*!
* \brief Unlock a heap
*
* \param h the heap
*
* \return see the documentation for pthread_rwlock_unlock()
* \since 1.6.1
*/
int __ast_heap_unlock(struct ast_heap *h, const char *file, const char *func, int line);
#define ast_heap_wrlock(h) __ast_heap_wrlock(h, __FILE__, __PRETTY_FUNCTION__, __LINE__)
#define ast_heap_rdlock(h) __ast_heap_rdlock(h, __FILE__, __PRETTY_FUNCTION__, __LINE__)
#define ast_heap_unlock(h) __ast_heap_unlock(h, __FILE__, __PRETTY_FUNCTION__, __LINE__)
/*!
* \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.
* \since 1.6.1
*/
int ast_heap_verify(struct ast_heap *h);
#endif /* __AST_HEAP_H__ */
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