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    // Copyright(c) 2015 Gabi Melman.
    // Distributed under the MIT License (http://opensource.org/licenses/MIT)
    //
    
    #pragma once
    
    // Very fast asynchronous logger (millions of logs per second on an average
    // desktop)
    // Uses pre allocated lockfree queue for maximum throughput even under large
    // number of threads.
    // Creates a single back thread to pop messages from the queue and log them.
    //
    // Upon each log write the logger:
    //    1. Checks if its log level is enough to log the message
    //    2. Push a new copy of the message to a queue (or block the caller until
    //    space is available in the queue)
    //    3. will throw spdlog_ex upon log exceptions
    // Upon destruction, logs all remaining messages in the queue before
    // destructing..
    
    #include "spdlog/common.h"
    #include "spdlog/logger.h"
    
    #include <chrono>
    #include <memory>
    #include <string>
    
    namespace spdlog {
    
    // Async overflow policy - block by default.
    enum class async_overflow_policy
    {
        block,         // Block until message can be enqueued
        overrun_oldest // Discard oldest message in the queue if full when trying to
                       // add new item.
    };
    
    namespace details {
    class thread_pool;
    }
    
    class async_logger SPDLOG_FINAL : public std::enable_shared_from_this<async_logger>, public logger
    {
        friend class details::thread_pool;
    
    public:
        template<typename It>
        async_logger(std::string logger_name, const It &begin, const It &end, std::weak_ptr<details::thread_pool> tp,
            async_overflow_policy overflow_policy = async_overflow_policy::block);
    
        async_logger(std::string logger_name, sinks_init_list sinks, std::weak_ptr<details::thread_pool> tp,
            async_overflow_policy overflow_policy = async_overflow_policy::block);
    
        async_logger(std::string logger_name, sink_ptr single_sink, std::weak_ptr<details::thread_pool> tp,
            async_overflow_policy overflow_policy = async_overflow_policy::block);
    
    protected:
        void sink_it_(details::log_msg &msg) override;
        void flush_() override;
    
        void backend_log_(details::log_msg &incoming_log_msg);
        void backend_flush_();
    
    private:
        std::weak_ptr<details::thread_pool> thread_pool_;
        async_overflow_policy overflow_policy_;
    };
    } // namespace spdlog
    
    #include "details/async_logger_impl.h"