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Diffstat (limited to 'libparc/parc/concurrent/parc_Timer.h')
| -rwxr-xr-x | libparc/parc/concurrent/parc_Timer.h | 431 |
1 files changed, 431 insertions, 0 deletions
diff --git a/libparc/parc/concurrent/parc_Timer.h b/libparc/parc/concurrent/parc_Timer.h new file mode 100755 index 00000000..416bfba4 --- /dev/null +++ b/libparc/parc/concurrent/parc_Timer.h @@ -0,0 +1,431 @@ +/* + * 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_Timer.h + * @ingroup threading + * @brief A facility for threads to schedule tasks for future execution in a background thread. + * + * Tasks may be scheduled for one-time execution, or for repeated execution at regular intervals. + * + * Corresponding to each Timer object is a single background thread that is used to execute all of the timer's tasks, + * sequentially. Timer tasks should complete quickly. + * If a timer task takes excessive time to complete, it "hogs" the timer's task execution thread. + * This can, in turn, delay the execution of subsequent tasks, + * which may "bunch up" and execute in rapid succession when (and if) the offending task finally completes. + * + * After the last live reference to a Timer object goes away and all outstanding tasks have completed execution, + * the timer's task execution thread terminates gracefully (and becomes subject to garbage collection). + * However, this can take arbitrarily long to occur. + * By default, the task execution thread does not run as a daemon thread, + * so it is capable of keeping an application from terminating. + * If a caller wants to terminate a timer's task execution thread rapidly, the caller should invoke the timer's cancel method. + * + * If the timer's task execution thread terminates unexpectedly, + * for example, because its stop method is invoked, + * any further attempt to schedule a task on the timer will result in an IllegalStateException, + * as if the timer's cancel method had been invoked. + * + * This class is thread-safe: multiple threads can share a single Timer object without the need for external synchronization. + * + * This class does not offer real-time guarantees: it schedules tasks using the Object.wait(long) method. + * + */ +#ifndef PARCLibrary_parc_Timer +#define PARCLibrary_parc_Timer +#include <stdbool.h> + +#include <parc/algol/parc_JSON.h> +#include <parc/algol/parc_HashCode.h> +#include <parc/concurrent/parc_FutureTask.h> + +struct PARCTimer; +typedef struct PARCTimer PARCTimer; + +/** + * Increase the number of references to a `PARCTimer` instance. + * + * Note that new `PARCTimer` is not created, + * only that the given `PARCTimer` reference count is incremented. + * Discard the reference by invoking `parcTimer_Release`. + * + * @param [in] instance A pointer to a valid PARCTimer instance. + * + * @return The same value as @p instance. + * + * Example: + * @code + * { + * PARCTimer *a = parcTimer_Create(); + * + * PARCTimer *b = parcTimer_Acquire(); + * + * parcTimer_Release(&a); + * parcTimer_Release(&b); + * } + * @endcode + */ +PARCTimer *parcTimer_Acquire(const PARCTimer *instance); + +#ifdef PARCLibrary_DISABLE_VALIDATION +# define parcTimer_OptionalAssertValid(_instance_) +#else +# define parcTimer_OptionalAssertValid(_instance_) parcTimer_AssertValid(_instance_) +#endif + +/** + * Assert that the given `PARCTimer` instance is valid. + * + * @param [in] instance A pointer to a valid PARCTimer instance. + * + * Example: + * @code + * { + * PARCTimer *a = parcTimer_Create(); + * + * parcTimer_AssertValid(a); + * + * printf("Instance is valid.\n"); + * + * parcTimer_Release(&b); + * } + * @endcode + */ +void parcTimer_AssertValid(const PARCTimer *instance); + +/** + * Create an instance of PARCTimer + * + * <#Paragraphs Of Explanation#> + * + * @return non-NULL A pointer to a valid PARCTimer instance. + * @return NULL An error occurred. + * + * Example: + * @code + * { + * PARCTimer *a = parcTimer_Create(); + * + * parcTimer_Release(&a); + * } + * @endcode + */ +PARCTimer *parcTimer_Create(void); + +/** + * Compares @p instance with @p other for order. + * + * Returns a negative integer, zero, or a positive integer as @p instance + * is less than, equal to, or greater than @p other. + * + * @param [in] instance A pointer to a valid PARCTimer instance. + * @param [in] other A pointer to a valid PARCTimer instance. + * + * @return <0 Instance is less than @p other. + * @return 0 Instance a and instance b compare the same. + * @return >0 Instance a is greater than instance b. + * + * Example: + * @code + * { + * PARCTimer *a = parcTimer_Create(); + * PARCTimer *b = parcTimer_Create(); + * + * if (parcTimer_Compare(a, b) == 0) { + * printf("Instances are equal.\n"); + * } + * + * parcTimer_Release(&a); + * parcTimer_Release(&b); + * } + * @endcode + * + * @see parcTimer_Equals + */ +int parcTimer_Compare(const PARCTimer *instance, const PARCTimer *other); + +/** + * Create an independent copy the given `PARCBuffer` + * + * A new buffer is created as a complete copy of the original. + * + * @param [in] original A pointer to a valid PARCTimer instance. + * + * @return NULL Memory could not be allocated. + * @return non-NULL A pointer to a new `PARCTimer` instance. + * + * Example: + * @code + * { + * PARCTimer *a = parcTimer_Create(); + * + * PARCTimer *copy = parcTimer_Copy(&b); + * + * parcTimer_Release(&b); + * parcTimer_Release(©); + * } + * @endcode + */ +PARCTimer *parcTimer_Copy(const PARCTimer *original); + +/** + * Print a human readable representation of the given `PARCTimer`. + * + * @param [in] instance A pointer to a valid PARCTimer instance. + * @param [in] indentation The indentation level to use for printing. + * + * Example: + * @code + * { + * PARCTimer *a = parcTimer_Create(); + * + * parcTimer_Display(a, 0); + * + * parcTimer_Release(&a); + * } + * @endcode + */ +void parcTimer_Display(const PARCTimer *instance, int indentation); + +/** + * Determine if two `PARCTimer` instances are equal. + * + * The following equivalence relations on non-null `PARCTimer` instances are maintained: * + * * It is reflexive: for any non-null reference value x, `parcTimer_Equals(x, x)` must return true. + * + * * It is symmetric: for any non-null reference values x and y, `parcTimer_Equals(x, y)` must return true if and only if + * `parcTimer_Equals(y x)` returns true. + * + * * It is transitive: for any non-null reference values x, y, and z, if + * `parcTimer_Equals(x, y)` returns true and + * `parcTimer_Equals(y, z)` returns true, + * then `parcTimer_Equals(x, z)` must return true. + * + * * It is consistent: for any non-null reference values x and y, multiple invocations of `parcTimer_Equals(x, y)` + * consistently return true or consistently return false. + * + * * For any non-null reference value x, `parcTimer_Equals(x, NULL)` must return false. + * + * @param [in] x A pointer to a valid PARCTimer instance. + * @param [in] y A pointer to a valid PARCTimer instance. + * + * @return true The instances x and y are equal. + * + * Example: + * @code + * { + * PARCTimer *a = parcTimer_Create(); + * PARCTimer *b = parcTimer_Create(); + * + * if (parcTimer_Equals(a, b)) { + * printf("Instances are equal.\n"); + * } + * + * parcTimer_Release(&a); + * parcTimer_Release(&b); + * } + * @endcode + * @see parcTimer_HashCode + */ +bool parcTimer_Equals(const PARCTimer *x, const PARCTimer *y); + +/** + * Returns a hash code value for the given instance. + * + * The general contract of `HashCode` is: + * + * Whenever it is invoked on the same instance more than once during an execution of an application, + * the `HashCode` function must consistently return the same value, + * provided no information used in a corresponding comparisons on the instance is modified. + * + * This value need not remain consistent from one execution of an application to another execution of the same application. + * If two instances are equal according to the {@link parcTimer_Equals} method, + * then calling the {@link parcTimer_HashCode} method on each of the two instances must produce the same integer result. + * + * It is not required that if two instances are unequal according to the + * {@link parcTimer_Equals} function, + * then calling the `parcTimer_HashCode` + * method on each of the two objects must produce distinct integer results. + * + * @param [in] instance A pointer to a valid PARCTimer instance. + * + * @return The hashcode for the given instance. + * + * Example: + * @code + * { + * PARCTimer *a = parcTimer_Create(); + * + * PARCHashCode hashValue = parcTimer_HashCode(buffer); + * parcTimer_Release(&a); + * } + * @endcode + */ +PARCHashCode parcTimer_HashCode(const PARCTimer *instance); + +/** + * Determine if an instance of `PARCTimer` 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 valid PARCTimer instance. + * + * @return true The instance is valid. + * @return false The instance is not valid. + * + * Example: + * @code + * { + * PARCTimer *a = parcTimer_Create(); + * + * if (parcTimer_IsValid(a)) { + * printf("Instance is valid.\n"); + * } + * + * parcTimer_Release(&a); + * } + * @endcode + * + */ +bool parcTimer_IsValid(const PARCTimer *instance); + +/** + * Release a previously acquired reference to the given `PARCTimer` 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] instancePtr A pointer to a pointer to the instance to release. + * + * Example: + * @code + * { + * PARCTimer *a = parcTimer_Create(); + * + * parcTimer_Release(&a); + * } + * @endcode + */ +void parcTimer_Release(PARCTimer **instancePtr); + +/** + * Create a `PARCJSON` instance (representation) of the given object. + * + * @param [in] instance A pointer to a valid PARCTimer instance. + * + * @return NULL Memory could not be allocated to contain the `PARCJSON` instance. + * @return non-NULL An allocated C string that must be deallocated via parcMemory_Deallocate(). + * + * Example: + * @code + * { + * PARCTimer *a = parcTimer_Create(); + * + * PARCJSON *json = parcTimer_ToJSON(a); + * + * printf("JSON representation: %s\n", parcJSON_ToString(json)); + * parcJSON_Release(&json); + * + * parcTimer_Release(&a); + * } + * @endcode + */ +PARCJSON *parcTimer_ToJSON(const PARCTimer *instance); + +/** + * Produce a null-terminated string representation of the specified `PARCTimer`. + * + * The result must be freed by the caller via {@link parcMemory_Deallocate}. + * + * @param [in] instance A pointer to a valid PARCTimer instance. + * + * @return NULL Cannot allocate memory. + * @return non-NULL A pointer to an allocated, null-terminated C string that must be deallocated via {@link parcMemory_Deallocate}. + * + * Example: + * @code + * { + * PARCTimer *a = parcTimer_Create(); + * + * char *string = parcTimer_ToString(a); + * + * parcTimer_Release(&a); + * + * parcMemory_Deallocate(&string); + * } + * @endcode + * + * @see parcTimer_Display + */ +char *parcTimer_ToString(const PARCTimer *timer); + +/** + * Terminates this timer, discarding any currently scheduled tasks. + * + * Does not interfere with a currently executing task (if it exists). + * Once a timer has been terminated, its execution thread terminates gracefully, + * and no more tasks may be scheduled on it. + * + * Note that calling this method from within the run method of a timer task that was invoked + * by this timer absolutely guarantees that the ongoing task execution is the last task execution + * that will ever be performed by this timer. + * + * This method may be called repeatedly; the second and subsequent calls have no effect. + */ +void parcTimer_Cancel(PARCTimer *timer); + +/** + * Removes all cancelled tasks from this timer's task queue. + * + * Calling this method has no effect on the behavior of the timer, + * but eliminates the references to the cancelled tasks from the queue. + * If there are no external references to these tasks, they become eligible for garbage collection. + * + * Most programs will have no need to call this method. + * It is designed for use by the rare application that cancels a large number of tasks. + * Calling this method trades time for space: the runtime of the method may be proportional to + * n + c log n, where n is the number of tasks in the queue and c is the number of cancelled tasks. + * + * It is permissible to call this method from within a task scheduled on this timer. + * + * @returns the number of tasks removed from the queue. + */ +int parcTimer_Purge(PARCTimer *timer); + +/** + * Schedules the specified task for execution at the specified time. + */ +void parcTimer_ScheduleAtTime(PARCTimer *timer, PARCFutureTask *task, time_t absoluteTime); + +/** + * Schedules the specified task for repeated fixed-delay execution, beginning at the specified time. + */ +void parcTimer_ScheduleAtTimeAndRepeat(PARCTimer *timer, PARCFutureTask *task, time_t firstTime, long period); + +/** + * Schedules the specified task for execution after the specified delay. + */ +void parcTimer_ScheduleAfterDelay(PARCTimer *timer, PARCFutureTask *task, long delay); + +/** + * Schedules the specified task for repeated fixed-delay execution, beginning after the specified delay. + */ +void parcTimer_ScheduleAfterDelayAndRepeat(PARCTimer *timer, PARCFutureTask *task, long delay, long period); +#endif |