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heap.h
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/* * 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 */