pipelining.h

/*
 * Copyright (c) 2008-2021, 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.
 */
#pragma once
 
#include <vector>
#include <mutex>
#include <condition_variable>
 
#include <boost/thread/future.hpp>
 
#include "hazelcast/util/Preconditions.h"
 
namespace hazelcast {
    namespace client {
        template<typename E>
        class pipelining : public std::enable_shared_from_this<pipelining<E> > {
        public:
            static std::shared_ptr<pipelining> create(int depth) {
                util::Preconditions::check_positive(depth, "depth must be positive");
 
                return std::shared_ptr<pipelining>(new pipelining(depth));
            }
 
            std::vector<boost::optional<E>> results() {
                std::vector<boost::optional<E>> result;
                result.reserve(futures_.size());
                auto result_futures = when_all(futures_.begin(), futures_.end());
                for (auto &f : result_futures.get()) {
                    result.emplace_back(f.get());
                }
                return result;
            }
 
            void add(boost::future<boost::optional<E>> future) {
                down();
 
                futures_.push_back(future.share());
            }
 
        private:
            pipelining(int depth) : permits_(util::Preconditions::check_positive(depth, "depth must be positive")) {
            }
 
            void down() {
                int usedPermits = 0;
                for (auto &f : futures_) {
                    if (!f.is_ready()) {
                        ++usedPermits;
                    }
                }
                if (usedPermits >= permits_) {
                    decltype(futures_) outStandingFutures;
                    for (auto &f : futures_) {
                        if (!f.is_ready()) {
                            outStandingFutures.push_back(f);
                        }
                    }
 
                    if (!outStandingFutures.empty()) {
                        boost::when_any(outStandingFutures.begin(), outStandingFutures.end()).get();
                    }
                }
            }
 
            int permits_;
            std::vector<boost::shared_future<boost::optional<E>>> futures_;
        };
    }
}