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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