/*
* Copyright (C) Internet Systems Consortium, Inc. ("ISC")
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, you can obtain one at https://mozilla.org/MPL/2.0/.
*
* See the COPYRIGHT file distributed with this work for additional
* information regarding copyright ownership.
*/
#ifndef ISC_HEAP_H
#define ISC_HEAP_H 1
/*! \file isc/heap.h */
#include <stdbool.h>
#include <isc/lang.h>
#include <isc/types.h>
ISC_LANG_BEGINDECLS
/*%
* The comparison function returns true if the first argument has
* higher priority than the second argument, and false otherwise.
*/
typedef bool (*isc_heapcompare_t)(void *, void *);
/*%
* The index function allows the client of the heap to receive a callback
* when an item's index number changes. This allows it to maintain
* sync with its external state, but still delete itself, since deletions
* from the heap require the index be provided.
*/
typedef void (*isc_heapindex_t)(void *, unsigned int);
/*%
* The heapaction function is used when iterating over the heap.
*
* NOTE: The heap structure CANNOT BE MODIFIED during the call to
* isc_heap_foreach().
*/
typedef void (*isc_heapaction_t)(void *, void *);
typedef struct isc_heap isc_heap_t;
isc_result_t
isc_heap_create(isc_mem_t *mctx, isc_heapcompare_t compare,
isc_heapindex_t index, unsigned int size_increment,
isc_heap_t **heapp);
/*!<
* \brief Create a new heap. The heap is implemented using a space-efficient
* storage method. When the heap elements are deleted space is not freed
* but will be reused when new elements are inserted.
*
* Heap elements are indexed from 1.
*
* Requires:
*\li "mctx" is valid.
*\li "compare" is a function which takes two void * arguments and
* returns true if the first argument has a higher priority than
* the second, and false otherwise.
*\li "index" is a function which takes a void *, and an unsigned int
* argument. This function will be called whenever an element's
* index value changes, so it may continue to delete itself from the
* heap. This option may be NULL if this functionality is unneeded.
*\li "size_increment" is a hint about how large the heap should grow
* when resizing is needed. If this is 0, a default size will be
* used, which is currently 1024, allowing space for an additional 1024
* heap elements to be inserted before adding more space.
*\li "heapp" is not NULL, and "*heap" is NULL.
*
* Returns:
*\li ISC_R_SUCCESS - success
*\li ISC_R_NOMEMORY - insufficient memory
*/
void
isc_heap_destroy(isc_heap_t **heapp);
/*!<
* \brief Destroys a heap.
*
* Requires:
*\li "heapp" is not NULL and "*heap" points to a valid isc_heap_t.
*/
isc_result_t
isc_heap_insert(isc_heap_t *heap, void *elt);
/*!<
* \brief Inserts a new element into a heap.
*
* Requires:
*\li "heapp" is not NULL and "*heap" points to a valid isc_heap_t.
*/
void
isc_heap_delete(isc_heap_t *heap, unsigned int index);
/*!<
* \brief Deletes an element from a heap, by element index.
*
* Requires:
*\li "heapp" is not NULL and "*heap" points to a valid isc_heap_t.
*\li "index" is a valid element index, as provided by the "index" callback
* provided during heap creation.
*/
void
isc_heap_increased(isc_heap_t *heap, unsigned int index);
/*!<
* \brief Indicates to the heap that an element's priority has increased.
* This function MUST be called whenever an element has increased in priority.
*
* Requires:
*\li "heapp" is not NULL and "*heap" points to a valid isc_heap_t.
*\li "index" is a valid element index, as provided by the "index" callback
* provided during heap creation.
*/
void
isc_heap_decreased(isc_heap_t *heap, unsigned int index);
/*!<
* \brief Indicates to the heap that an element's priority has decreased.
* This function MUST be called whenever an element has decreased in priority.
*
* Requires:
*\li "heapp" is not NULL and "*heap" points to a valid isc_heap_t.
*\li "index" is a valid element index, as provided by the "index" callback
* provided during heap creation.
*/
void *
isc_heap_element(isc_heap_t *heap, unsigned int index);
/*!<
* \brief Returns the element for a specific element index.
*
* Requires:
*\li "heapp" is not NULL and "*heap" points to a valid isc_heap_t.
*\li "index" is a valid element index, as provided by the "index" callback
* provided during heap creation.
*
* Returns:
*\li A pointer to the element for the element index.
*/
void
isc_heap_foreach(isc_heap_t *heap, isc_heapaction_t action, void *uap);
/*!<
* \brief Iterate over the heap, calling an action for each element. The
* order of iteration is not sorted.
*
* Requires:
*\li "heapp" is not NULL and "*heap" points to a valid isc_heap_t.
*\li "action" is not NULL, and is a function which takes two arguments.
* The first is a void *, representing the element, and the second is
* "uap" as provided to isc_heap_foreach.
*\li "uap" is a caller-provided argument, and may be NULL.
*
* Note:
*\li The heap structure CANNOT be modified during this iteration. The only
* safe function to call while iterating the heap is isc_heap_element().
*/
ISC_LANG_ENDDECLS
#endif /* ISC_HEAP_H */
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