syslog_sink.h

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// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
// Distributed under the MIT License (http://opensource.org/licenses/MIT)
 
#pragma once
 
#include <spdlog/sinks/base_sink.h>
#include <spdlog/details/null_mutex.h>
#include <spdlog/details/synchronous_factory.h>
 
#include <array>
#include <string>
#include <syslog.h>
 
namespace spdlog
{
    namespace sinks
    {
        template <typename Mutex>
        class syslog_sink : public base_sink<Mutex>
        {
 
        public:
            syslog_sink(std::string ident, int syslog_option, int syslog_facility, bool enable_formatting)
                : enable_formatting_{enable_formatting}, syslog_levels_{{/* spdlog::level::trace      */ LOG_DEBUG,
                                                                         /* spdlog::level::debug      */ LOG_DEBUG,
                                                                         /* spdlog::level::info       */ LOG_INFO,
                                                                         /* spdlog::level::warn       */ LOG_WARNING,
                                                                         /* spdlog::level::err        */ LOG_ERR,
                                                                         /* spdlog::level::critical   */ LOG_CRIT,
                                                                         /* spdlog::level::off        */ LOG_INFO}},
                  ident_{std::move(ident)}
            {
                // set ident to be program name if empty
                ::openlog(ident_.empty() ? nullptr : ident_.c_str(), syslog_option, syslog_facility);
            }
 
            ~syslog_sink() override
            {
                ::closelog();
            }
 
            syslog_sink(const syslog_sink&)            = delete;
            syslog_sink& operator=(const syslog_sink&) = delete;
 
        protected:
            void sink_it_(const details::log_msg& msg) override
            {
                string_view_t payload;
                memory_buf_t  formatted;
                if (enable_formatting_)
                {
                    base_sink<Mutex>::formatter_->format(msg, formatted);
                    payload = string_view_t(formatted.data(), formatted.size());
                }
                else
                {
                    payload = msg.payload;
                }
 
                size_t length = payload.size();
                // limit to max int
                if (length > static_cast<size_t>(std::numeric_limits<int>::max()))
                {
                    length = static_cast<size_t>(std::numeric_limits<int>::max());
                }
 
                ::syslog(syslog_prio_from_level(msg), "%.*s", static_cast<int>(length), payload.data());
            }
 
            void flush_() override
            {
            }
            bool enable_formatting_ = false;
 
        private:
            using levels_array = std::array<int, 7>;
            levels_array syslog_levels_;
            // must store the ident because the man says openlog might use the pointer as
            // is and not a string copy
            const std::string ident_;
 
            //
            // Simply maps spdlog's log level to syslog priority level.
            //
            int syslog_prio_from_level(const details::log_msg& msg) const
            {
                return syslog_levels_.at(static_cast<levels_array::size_type>(msg.level));
            }
        };
 
        using syslog_sink_mt = syslog_sink<std::mutex>;
        using syslog_sink_st = syslog_sink<details::null_mutex>;
    } // namespace sinks
 
    // Create and register a syslog logger
    template <typename Factory = spdlog::synchronous_factory>
    inline std::shared_ptr<logger> syslog_logger_mt(const std::string& logger_name, const std::string& syslog_ident = "", int syslog_option = 0, int syslog_facility = LOG_USER, bool enable_formatting = false)
    {
        return Factory::template create<sinks::syslog_sink_mt>(logger_name, syslog_ident, syslog_option, syslog_facility, enable_formatting);
    }
 
    template <typename Factory = spdlog::synchronous_factory>
    inline std::shared_ptr<logger> syslog_logger_st(const std::string& logger_name, const std::string& syslog_ident = "", int syslog_option = 0, int syslog_facility = LOG_USER, bool enable_formatting = false)
    {
        return Factory::template create<sinks::syslog_sink_st>(logger_name, syslog_ident, syslog_option, syslog_facility, enable_formatting);
    }
} // namespace spdlog