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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_Notifier.h
* @ingroup threading
* @brief Inter-thread/process notification
*
* A 1-way event notification system. The first call to parcNotifier_SetEvent() will post an
* event to the parcNotifier_Socket(). Subsequent calls will not post an event. When the
* event consumer is ready to handle the event, it calls parcNotifier_PauseEvents(), then processes
* the events, then calls parcNotifier_StartEvents().
*
* @code
* {
* // example code on the event consumer's side
* struct pollfd pfd;
* pfd.fd = parcNotifier_Socket(notifier);
* pfd.events = POLLIN;
*
* while(1) {
* if (poll(&fd, 1, -1)) {
* parcNotifier_PauseEvents(notifier);
*
* // process events, such as reading from a RingBuffer
* void *data;
* while (parcRingBuffer1x1_Get(ring, &data)) {
* // handle data
* }
*
* parcNotifier_StartEvents(notifier);
* }
* }
* }
* @endcode
*
* The notification system guarantees that no notifications will be missed. However, there may be
* extra notifications. For example, in the above code, if an event is signalled between the
* parcNotifier_PauseEvents() and parcRingBuffer1x1_Get() calls, then on parcNotifier_StartEvents()
* an extra event will be triggered, even though the ring buffer is empty.
*
*/
#ifndef libparc_parc_Notifier_h
#define libparc_parc_Notifier_h
#include <stdbool.h>
struct parc_notifier;
typedef struct parc_notifier PARCNotifier;
/**
* Create a new instance of `PARCNotifier`
*
* @return A new instance of `PARCNotifier`
*
* Example:
* @code
* <#example#>
* @endcode
*/
PARCNotifier *parcNotifier_Create(void);
/**
* Increase the number of references to a `PARCNotifier`.
*
* Note that new `PARCNotifier` is not created,
* only that the given `PARCNotifier` reference count is incremented.
* Discard the reference by invoking `parcNotifier_Release`.
*
* @param [in] instance A pointer to a `PARCNotifier` instance.
*
* @return The input `PARCNotifier` pointer.
*
* Example:
* @code
* {
* PARCNotifier *a = parcNotifier_Create(...);
*
* PARCNotifier *b = parcNotifier_Acquire(a);
*
* parcNotifier_Release(&a);
* parcNotifier_Release(&b);
* }
* @endcode
*/
PARCNotifier *parcNotifier_Acquire(const PARCNotifier *notifier);
/**
* 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] instancePtr A pointer to a pointer to the instance to release, which will be set to NULL.
*
* Example:
* @code
* {
* PARCNotifier *a = parcNotifier_Create(...);
*
* parcNotifier_Release(&a);
* }
* @endcode
*/
void parcNotifier_Release(PARCNotifier **notifier);
/**
* Fetches the notification socket
*
* The notification socket may be used in select() or poll() or similar
* functions. You should not read or write to the socket.
*
* @param [in] notifier The instance of `PARCNotifier`
*
* @return The notification socket.
*
* Example:
* @code
* <#example#>
* @endcode
*/
int parcNotifier_Socket(PARCNotifier *notifier);
/**
* Sends a notification to the notifier socket
*
* @param [in] notifier The instance of `PARCNotifier`
*
* @return True is successsful, else false.
*
* Example:
* @code
* <#example#>
* @endcode
*/
bool parcNotifier_Notify(PARCNotifier *notifier);
/**
* Pause the event stream of the Notifier
*
* @param [in] notifier The instance of `PARCNotifier`
*
* Example:
* @code
* <#example#>
* @endcode
*/
void parcNotifier_PauseEvents(PARCNotifier *notifier);
/**
* Restart the event stream of the Notifier
*
* @param [in] notifier The instance of `PARCNotifier`
*
* Example:
* @code
* <#example#>
* @endcode
*/
void parcNotifier_StartEvents(PARCNotifier *notifier);
#endif // libparc_parc_Notifier_h
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