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Pods/gRPC-C++/include/grpcpp/alarm.h

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+//
+//
+// Copyright 2015 gRPC authors.
+//
+// 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.
+//
+//
+
+/// An Alarm posts the user-provided tag to its associated completion queue or
+/// invokes the user-provided function on expiry or cancellation.
+#ifndef GRPCPP_ALARM_H
+#define GRPCPP_ALARM_H
+
+#include <functional>
+
+#include <grpc/event_engine/event_engine.h>
+#include <grpc/grpc.h>
+#include <grpcpp/completion_queue.h>
+#include <grpcpp/impl/completion_queue_tag.h>
+#include <grpcpp/impl/grpc_library.h>
+#include <grpcpp/support/time.h>
+
+namespace grpc {
+
+/// Trigger a \a CompletionQueue event, or asynchronous callback execution,
+/// after some deadline.
+///
+/// The \a Alarm API has separate \a Set methods for CompletionQueues and
+/// callbacks, but only one can be used at any given time. After an alarm has
+/// been triggered or cancelled, the same Alarm object may reused.
+///
+/// Alarm methods are not thread-safe. Applications must ensure a strict
+/// ordering between calls to \a Set and \a Cancel. This also implies that any
+/// cancellation that occurs before the alarm has been set will have no effect
+/// on any future \a Set calls.
+class Alarm : private grpc::internal::GrpcLibrary {
+ public:
+  /// Create an unset Alarm.
+  Alarm();
+
+  /// Destroy the given completion queue alarm, cancelling it in the process.
+  ~Alarm() override;
+
+  /// DEPRECATED: Create and set a completion queue alarm instance associated to
+  /// \a cq.
+  /// This form is deprecated because it is inherently racy.
+  /// \internal We rely on the presence of \a cq for grpc initialization. If \a
+  /// cq were ever to be removed, a reference to a static
+  /// internal::GrpcLibraryInitializer instance would need to be introduced
+  /// here. \endinternal.
+  template <typename T>
+  Alarm(grpc::CompletionQueue* cq, const T& deadline, void* tag) : Alarm() {
+    SetInternal(cq, grpc::TimePoint<T>(deadline).raw_time(), tag);
+  }
+
+  /// Trigger an alarm instance on completion queue \a cq at the specified time.
+  /// Once the alarm expires (at \a deadline) or it's cancelled (see \a Cancel),
+  /// an event with tag \a tag will be added to \a cq. If the alarm expired, the
+  /// event's success bit will be true, false otherwise (ie, upon cancellation).
+  //
+  // USAGE NOTE: This is frequently used to inject arbitrary tags into \a cq by
+  // setting an immediate deadline. Such usage allows synchronizing an external
+  // event with an application's \a grpc::CompletionQueue::Next loop.
+  template <typename T>
+  void Set(grpc::CompletionQueue* cq, const T& deadline, void* tag) {
+    SetInternal(cq, grpc::TimePoint<T>(deadline).raw_time(), tag);
+  }
+
+  /// Alarms aren't copyable.
+  Alarm(const Alarm&) = delete;
+  Alarm& operator=(const Alarm&) = delete;
+
+  /// Alarms are movable.
+  Alarm(Alarm&& rhs) noexcept : alarm_(rhs.alarm_) { rhs.alarm_ = nullptr; }
+  Alarm& operator=(Alarm&& rhs) noexcept {
+    std::swap(alarm_, rhs.alarm_);
+    return *this;
+  }
+
+  /// Cancel a completion queue alarm. Calling this function over an alarm that
+  /// has already fired has no effect.
+  void Cancel();
+
+  /// Set an alarm to invoke callback \a f. The argument to the callback
+  /// states whether the alarm expired at \a deadline (true) or was cancelled
+  /// (false)
+  template <typename T>
+  void Set(const T& deadline, std::function<void(bool)> f) {
+    SetInternal(grpc::TimePoint<T>(deadline).raw_time(), std::move(f));
+  }
+
+ private:
+  void SetInternal(grpc::CompletionQueue* cq, gpr_timespec deadline, void* tag);
+  void SetInternal(gpr_timespec deadline, std::function<void(bool)> f);
+
+  grpc::internal::CompletionQueueTag* alarm_;
+};
+
+}  // namespace grpc
+
+#endif  // GRPCPP_ALARM_H