diff options
Diffstat (limited to 'libparc/parc/algol/parc_Iterator.h')
| -rw-r--r-- | libparc/parc/algol/parc_Iterator.h | 250 |
1 files changed, 250 insertions, 0 deletions
diff --git a/libparc/parc/algol/parc_Iterator.h b/libparc/parc/algol/parc_Iterator.h new file mode 100644 index 00000000..275a16e7 --- /dev/null +++ b/libparc/parc/algol/parc_Iterator.h @@ -0,0 +1,250 @@ +/* + * Copyright (c) 2017 Cisco and/or its affiliates. + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at: + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +/** + * @file parc_Iterator.h + * @ingroup memory + * @brief An iterator over any kind of iteratable collection + * + * Implementations of a PARCIterator must provide the following functions, + * each of which supports the operation of the iterator. + * @code + * _TYPEIterator * PREFIX_Init(TYPE *object) + * + * bool PREFIX_Fini(TYPE *map, _TYPEIterator *state) + * + * _PARCHashMapIterator *PREFIX_Next(PARCHashMap *map, _TYPEIterator *state) + * + * void PREFIX_Remove(PARCHashMap *map, _TYPEIterator **statePtr ) + * + * bool PREFIX_HasNext(PARCHashMap *map, _TYPEIterator *state) + * + * PARCObject *PREFIX_Element(PARCHashMap *map, const _TYPEIterator *state) + * + * PARCObject *PREFIX_Element(TYPE *map, const _TYPEIterator *state) + * @endcode + * + */ +#ifndef libparc_parc_Iterator_h +#define libparc_parc_Iterator_h + +#include <stdbool.h> +#include <parc/algol/parc_Object.h> + +struct parc_iterator; +typedef struct parc_iterator PARCIterator; + +/** + * Create a new instance of `PARCIterator` + * + * Each instance must be provided pointers to functions implementing the iteration primitives for the given PARCObject. + * + * * `init` + * This function is called only when a PARCIterator is created. + * The function is expected to initialise and return a pointer to whatever internal state necessary + * to provide the subsequent operations. + * In subsequent operations of hasNext, next, getElement, and fini, this pointer is provided as a function parameter. + * + * * `hasNext` + * This function returns true if the iteration has more elements. + * + * * `next` + * Returns the next element in the iteration. + * If there are no remaining elements in the iteration, then this function must induce a trapOutOfBounds + * + * * `remove` + * Removes the element returned by the `next` function. + * + * * `getElement` + * This function is invoked only from within the `parcIterator_Next` function and + * returns the actual iteration value from the current iterator's state. + * + * * `fini` + * This function is called only when the PARCIterator is being destroyed. + * + * @param [in] object A pointer to the PARCObject that implements the underlying iteration. + * @param [in] hasNext A pointer to a function that returns true if there are more elements. + * @param [in] next A pointer to a function that returns the next element. + * @param [in] remove A pointer to a function that removes the element last returned by the @p next function. + * @param [in] getElement A pointer to a function that, given the current position, return the element at the current position. + * @param [in] fini A pointer to a function that will be invoked when the PARCIterator is finally deallocated. + * @param [in] isValid A pointer to a function that performs validation of the iterator state. + * + * @return A `PARCIterator` + */ +PARCIterator *parcIterator_Create(PARCObject *object, + void *(*init)(PARCObject *object), + bool (*hasNext)(PARCObject *object, void *state), + void *(*next)(PARCObject *object, void *state), + void (*remove)(PARCObject *, void **state), + void *(*getElement)(PARCObject *object, void *state), + void (*fini)(PARCObject *object, void *state), + void (*isValid)(const void *)); + +/** + * Determine if an instance of `PARCIterator` is valid. + * + * Valid means the internal state of the type is consistent with its required current or future behaviour. + * This may include the validation of internal instances of types. + * + * @param [in] instance A pointer to a `PARCIterator` instance. + * + * @return true The instance is valid. + * @return false The instance is not valid. + * + * Example: + * @code + * { + * PARCIterator *instance = parcIterator_Create(...); + * + * if (parcIterator_IsValid(instance)) { + * printf("Instance is valid.\n"); + * } + * } + * @endcode + */ +bool parcIterator_IsValid(const PARCIterator *instance); + +/** + * Assert that the given `PARCIterator` instance is valid. + * + * @param [in] iterator A pointer to a valid PARCIterator instance. + * + * Example: + * @code + * { + * PARCIterator *a = parcIterator_Create(...); + * + * parcIterator_AssertValid(a); + * + * printf("Instance is valid.\n"); + * + * parcIterator_Release(&b); + * } + * @endcode + */ +#ifdef PARCLibrary_DISABLE_VALIDATION +# define parcIterator_OptionalAssertValid(_instance_) +#else +# define parcIterator_OptionalAssertValid(_instance_) parcIterator_AssertValid(_instance_) +#endif +void parcIterator_AssertValid(const PARCIterator *iterator); + +/** + * Increase the number of references to a `PARCIterator`. + * + * Note that new `PARCIterator` is not created, + * only that the given `PARCIterator` reference count is incremented. + * Discard the reference by invoking `parcIterator_Release`. + * + * @param [in] instance A pointer to a `PARCIterator` instance. + * + * @return The input `PARCIterator` pointer. + * + * Example: + * @code + * { + * PARCIterator *a = parcIterator_Create(...); + * + * PARCIterator *b = parcIterator_Acquire(a); + * + * parcIterator_Release(&a); + * parcIterator_Release(&b); + * } + * @endcode + */ +PARCIterator *parcIterator_Acquire(const PARCIterator *instance); + +/** + * Release a previously acquired reference to the specified instance, + * decrementing the reference count for the instance. + * + * The pointer to the instance is set to NULL as a side-effect of this function. + * + * If the invocation causes the last reference to the instance to be released, + * the instance is deallocated and the instance's implementation will perform + * additional cleanup and release other privately held references. + * + * @param [in,out] iteratorPtr A pointer to a pointer to the instance to release, which will be set to NULL. + * + * Example: + * @code + * { + * PARCIterator *a = parcIterator_Create(...); + * + * parcIterator_Release(&a); + * } + * @endcode + */ +void parcIterator_Release(PARCIterator **iteratorPtr); + +/** + * Return the next item in the iterated list + * + * @param [in] iterator A pointer to the instance of `PARCIterator` + * + * @return A pointer to the next item in the iterated list + * + * Example: + * @code + * { + * while (parcIterator_HasNext(iterator)) { + * void *element = parcIterator_Next(iterator); + * } + * } + * @endcode + */ +void *parcIterator_Next(PARCIterator *iterator); + +/** + * Return true if there are more items left over which to iterate. + * + * @param [in] iterator A pointer to the instance of `PARCIterator` + * + * @return True if there is are more items over which to iterate; false otherwise. + * + * Example: + * @code + * { + * while (parcIterator_HasNext(iterator)) { + * void *element = parcIterator_Next(iterator); + * } + * } + * @endcode + */ +bool parcIterator_HasNext(const PARCIterator *iterator); + +/** + * Removes from the underlying collection the last element returned by the iterator (optional operation). + * This function can be called only once per call to `parcIterator_Next`. + * The behavior of an iterator is unspecified if the underlying collection is + * modified while the iteration is in progress in any way other than by calling this method. + * + * Pointers to the element after removing it via this function may point to invalid remnants of the object. + * To avoid this, acquire a reference to the element before invoking this function. + * + * @param [in] iterator A pointer to the instance of `PARCIterator` + * + * Example: + * @code + * { + * while (parcIterator_HasNext(iterator)) { + * void *element = parcIterator_Next(iterator); + * } + * } + * @endcode + */ +void parcIterator_Remove(PARCIterator *iterator); +#endif // libparc_parc_Iterator_h |