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/*
* 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
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