THUAI6/CAPI/cpp/grpc/include/grpcpp/alarm.h

/*
 *
 * 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/grpc.h>
#include <grpcpp/impl/codegen/completion_queue.h>
#include <grpcpp/impl/codegen/completion_queue_tag.h>
#include <grpcpp/impl/codegen/grpc_library.h>
#include <grpcpp/impl/codegen/time.h>
#include <grpcpp/impl/grpc_library.h>

namespace grpc
{

    class Alarm : private grpc::GrpcLibraryCodegen
    {
    public:
        /// Create an unset completion queue 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
        {
            alarm_ = rhs.alarm_;
            rhs.alarm_ = nullptr;
            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