Simple C++ implementation of Golang channels

chan.hpp

/*
    The MIT License (MIT)

    Copyright (c) 2018 Federico Barcelona <[email protected]>

    Permission is hereby granted, free of charge, to any person obtaining a copy of
    this software and associated documentation files (the "Software"), to deal in the Software
    without restriction, including without limitation the rights to use, copy, modify, merge,
    publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
    to whom the Software is furnished to do so, subject to the following conditions:

    The above copyright notice and this permission notice shall be included in all copies or
    substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
    INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
    PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
    FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
    OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
    DEALINGS IN THE SOFTWARE.
*/

#ifndef CHANNELS_CHAN_H
#define CHANNELS_CHAN_H


#include <queue>
#include <cstdint>
#include <mutex>
#include <condition_variable>


/*
 Channels are the pipes that connect concurrent threads.
 You can send values into channels from one thread and receive those values into another thread.
 They have been created inspired in Golang channels: https://gobyexample.com/channels
 */
template<typename T>
class chan {
    static_assert(std::is_default_constructible<T>::value && std::is_copy_constructible<T>::value,
                  "Channels only work with default constructible and copy constructible elements");

    typedef std::unique_lock<std::recursive_mutex> lock;
    std::queue<T> queue;
    uint8_t count;
    std::recursive_mutex mtx;
    std::condition_variable_any cv;
    bool open;

public:
    chan(uint8_t size = 1) : count(size), open(true) {}

    chan(const chan &) = delete; // Delete copy constructor
    chan &operator=(chan const &) = delete; // Delete copy assignation

    void put(T item) noexcept {
        lock lck(mtx);

        // Wait until its closed or until the count is higher than 0
        cv.wait(lck, [this]() { return !open || count > 0; });

        if (!open) return;

        count--;
        queue.emplace(item);
        cv.notify_all();
    }

    T get() noexcept {
        lock lck(mtx);

        // Wait until its closed or the queue is not empty
        cv.wait(lck, [this]() { return !open || !queue.empty(); });

        if (!open) return T();

        count++;
        T item = queue.front();
        queue.pop();

        cv.notify_all();
        return item;
    }

    bool isOpen() {
        lock(mtx);
        return open;
    }

    void close() {
        lock(mtx);
        open = false;
        std::queue<T> empty;
        std::swap(queue, empty); // clear the queue
        cv.notify_all();
    }
};


#endif //CHANNELS_CHAN_H