spdlog/include/spdlog/details/thread_pool.h

// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
// Distributed under the MIT License (http://opensource.org/licenses/MIT)

#pragma once

#include "spdlog/details/log_msg.h"
#include "spdlog/details/mpmc_blocking_q.h"
#include "spdlog/details/os.h"

#include <chrono>
#include <memory>
#include <thread>
#include <vector>
#include <functional>

namespace spdlog {
class async_logger;

namespace details {

using async_logger_ptr = std::shared_ptr<spdlog::async_logger>;

enum class async_msg_type
{
    log,
    flush,
    terminate
};

// Async msg to move to/from the queue
// Movable only. should never be copied
struct async_msg
{
    async_msg_type msg_type;
    level::level_enum level;
    log_clock::time_point time;
    size_t thread_id;
    fmt::basic_memory_buffer<char, 176> raw;

    source_loc source;
    async_logger_ptr worker_ptr;

    async_msg()
        : msg_type(async_msg_type::log)
        , level(level::info)
        , thread_id(0)
    {}
    ~async_msg() = default;

    // should only be moved in or out of the queue..
    async_msg(const async_msg &) = delete;

// support for vs2013 move
#if defined(_MSC_VER) && _MSC_VER <= 1800
    async_msg(async_msg &&other)
        : msg_type(other.msg_type)
        , level(other.level)
        , time(other.time)
        , thread_id(other.thread_id)
        , raw(move(other.raw))
        , msg_id(other.msg_id)
        , source(other.source)
        , worker_ptr(std::move(other.worker_ptr))
    {}

    async_msg &operator=(async_msg &&other)
    {
        msg_type = other.msg_type;
        level = other.level;
        time = other.time;
        thread_id = other.thread_id;
        raw = std::move(other.raw);
        msg_id = other.msg_id;
        source = other.source;
        worker_ptr = std::move(other.worker_ptr);
        return *this;
    }
#else // (_MSC_VER) && _MSC_VER <= 1800
    async_msg(async_msg &&) = default;
    async_msg &operator=(async_msg &&) = default;
#endif

    // construct from log_msg with given type
    async_msg(async_logger_ptr &&worker, async_msg_type the_type, details::log_msg &m)
        : msg_type(the_type)
        , level(m.level)
        , time(m.time)
        , thread_id(m.thread_id)
        , source(m.source)
        , worker_ptr(std::move(worker))
    {
        raw.append(m.payload.data(), m.payload.data() + m.payload.size());
    }

    async_msg(async_logger_ptr &&worker, async_msg_type the_type)
        : msg_type(the_type)
        , level(level::off)
        , time()
        , thread_id(0)
        , source()
        , worker_ptr(std::move(worker))
    {}

    explicit async_msg(async_msg_type the_type)
        : async_msg(nullptr, the_type)
    {}

    // copy into log_msg
    log_msg to_log_msg()
    {
        log_msg msg(string_view_t(worker_ptr->name()), level, string_view_t(raw.data(), raw.size()));
        msg.time = time;
        msg.thread_id = thread_id;
        msg.source = source;
        msg.color_range_start = 0;
        msg.color_range_end = 0;
        return msg;
    }
};

class thread_pool
{
public:
    using item_type = async_msg;
    using q_type = details::mpmc_blocking_queue<item_type>;

    thread_pool(size_t q_max_items, size_t threads_n, std::function<void()> on_thread_start);
    thread_pool(size_t q_max_items, size_t threads_n);

    // message all threads to terminate gracefully join them
    ~thread_pool();

    thread_pool(const thread_pool &) = delete;
    thread_pool &operator=(thread_pool &&) = delete;

    void post_log(async_logger_ptr &&worker_ptr, details::log_msg &msg, async_overflow_policy overflow_policy);
    void post_flush(async_logger_ptr &&worker_ptr, async_overflow_policy overflow_policy);
    size_t overrun_counter();

private:
    q_type q_;

    std::vector<std::thread> threads_;

    void post_async_msg_(async_msg &&new_msg, async_overflow_policy overflow_policy);
    void worker_loop_();

    // process next message in the queue
    // return true if this thread should still be active (while no terminate msg
    // was received)
    bool process_next_msg_();
};

} // namespace details
} // namespace spdlog

#ifdef SPDLOG_HEADER_ONLY
#include "thread_pool-inl.h"
#endif