spdlog/include/spdlog/sinks/syslog_sink.h

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

#pragma once

#include <spdlog/details/null_mutex.h>
#include <spdlog/sinks/base_sink.h>
#include <syslog.h>

#include <array>
#include <string>
#include <mutex>

namespace spdlog {
namespace sinks {
/**
 * Sink that write to syslog using the `syscall()` library call.
 */
template <typename Mutex>
class syslog_sink final : public base_sink<Mutex> {
public:
    syslog_sink(std::string ident = "", int syslog_option = 0, int syslog_facility = LOG_USER, bool enable_formatting=false)
        : 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;

    //
    // Simply maps spdlog's log level to syslog priority level.
    //
    virtual int syslog_prio_from_level(const details::log_msg &msg) const {
        return syslog_levels_.at(static_cast<levels_array::size_type>(msg.log_level));
    }

    using levels_array = std::array<int, 7>;
    levels_array syslog_levels_;

private:
    // must store the ident because the man says openlog might use the pointer as
    // is and not a string copy
    const std::string ident_;
};

using syslog_sink_mt = syslog_sink<std::mutex>;
using syslog_sink_st = syslog_sink<details::null_mutex>;

}  // namespace sinks
}  // namespace spdlog