Pipelining.h

/*
 * Copyright (c) 2008-2019, Hazelcast, Inc. All Rights Reserved.
 *
 * 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.
 */
#ifndef HAZELCAST_CLIENT_PIPELINING_H_
#define HAZELCAST_CLIENT_PIPELINING_H_

#include <vector>

#include "hazelcast/client/ICompletableFuture.h"
#include "hazelcast/util/Preconditions.h"
#include "hazelcast/util/ConditionVariable.h"
#include "hazelcast/util/concurrent/ConcurrencyUtil.h"

namespace hazelcast {
    namespace client {
        template<typename E>
        class Pipelining : public boost::enable_shared_from_this<Pipelining<E> > {
        public:
            static boost::shared_ptr<Pipelining> create(int depth) {
                util::Preconditions::checkPositive(depth, "depth must be positive");

                return boost::shared_ptr<Pipelining>(new Pipelining(depth));
            }

            std::vector<boost::shared_ptr<E> > results() {
                std::vector<boost::shared_ptr<E> > result(futures.size());
                size_t index = 0;
                for (typename FuturesVector::const_iterator it = futures.begin(); it != futures.end(); ++it, ++index) {
                    result[index] = (*it)->get();
                }
                return result;
            }

            const boost::shared_ptr<ICompletableFuture<E> > &
            add(const boost::shared_ptr<ICompletableFuture<E> > &future) {
                util::Preconditions::checkNotNull<ICompletableFuture<E> >(future, "future can't be null");

                down();
                futures.push_back(future);
                future->andThen(boost::shared_ptr<ExecutionCallback<E> >(
                        new PipeliningExecutionCallback(this->shared_from_this())),
                                util::concurrent::ConcurrencyUtil::CALLER_RUNS());
                return future;
            }

        private:
            class PipeliningExecutionCallback : public ExecutionCallback<E> {
            public:
                PipeliningExecutionCallback(const boost::shared_ptr<Pipelining> &pipelining) : pipelining(pipelining) {}

                virtual void onResponse(const boost::shared_ptr<E> &response) {
                    pipelining->up();
                }

                virtual void onFailure(const boost::shared_ptr<exception::IException> &e) {
                    pipelining->up();
                }

            private:
                const boost::shared_ptr<Pipelining> pipelining;
            };

            Pipelining(int depth) : permits(util::Preconditions::checkPositive(depth, "depth must be positive")) {
            }

            // TODO: Change with lock-free implementation when atomic is integrated into the library
            void down() {
                util::LockGuard lockGuard(mutex);
                while (permits == 0) {
                    conditionVariable.wait(mutex);
                }
                --permits;
            }

            void up() {
                util::LockGuard lockGuard(mutex);
                if (permits == 0) {
                    conditionVariable.notify_all();
                }
                ++permits;
            }

            typedef std::vector<boost::shared_ptr<ICompletableFuture<E> > > FuturesVector;
            int permits;
            std::vector<boost::shared_ptr<ICompletableFuture<E> > > futures;
            util::ConditionVariable conditionVariable;
            util::Mutex mutex;
        };
    }
}

#endif //HAZELCAST_CLIENT_PIPELINING_H_