spdlog/include/c11log/formatter.h

#pragma once

#include <string>
#include <chrono>

#include <iomanip>
#include <thread>
#include <cstring>
#include <sstream>

#include "common_types.h"
#include "details/os.h"
#include "details/log_msg.h"
#include "details/fast_oss.h"


namespace c11log
{
namespace formatters
{

class formatter
{
public:
    virtual void format(details::log_msg& msg) = 0;
};


class default_formatter: public formatter
{
public:
    // Format: [2013-12-29 01:04:42.900] [logger_name:Info] Message body
    void format(details::log_msg& msg) override
    {
        details::fast_oss oss;
        _format_time(msg.time, oss);

        if(!msg.logger_name.empty())
            oss << " [" <<  msg.logger_name << ':' << c11log::level::to_str(msg.level) << "] ";
        else
            oss << " [" << c11log::level::to_str(msg.level) << "] ";

        oss << msg.raw << details::os::eol();
        msg.formatted = oss.str();
    }
private:
    void _format_time(const log_clock::time_point& tp, std::ostream& output);

};


} //namespace formatter
} //namespace c11log

// Format datetime like this: [2014-03-14 17:15:22]
inline void c11log::formatters::default_formatter::_format_time(const log_clock::time_point& tp, std::ostream &output)
{
    using namespace c11log::details::os;
    using namespace std::chrono;

#ifdef _WIN32 //VS2013 doesn't support yet thread_local keyword    
    __declspec(thread) static char s_cache_timestr[128];
    __declspec(thread) static int s_cache_timesize = 0;
    __declspec(thread) static std::time_t s_cache_time_t = 0;
#else
    thread_local static char s_cache_timestr[128];
    thread_local static int s_cache_timesize = 0;
    thread_local static std::time_t s_cache_time_t = 0;
#endif

    //Cache every second
    std::time_t tp_time_t = log_clock::to_time_t(tp);
    if(tp_time_t != s_cache_time_t)
    {
        auto tm_now = details::os::localtime(tp_time_t);
        std::ostringstream time_oss;
        time_oss.fill('0');
        time_oss << '[' << tm_now.tm_year + 1900 << '-';
        time_oss.width(2);
        time_oss << tm_now.tm_mon + 1 << '-';
        time_oss.width(2);
        time_oss << tm_now.tm_mday << ' ';
        time_oss.width(2);
        time_oss << tm_now.tm_hour << ':';
        time_oss.width(2);
        time_oss << tm_now.tm_min << ':';
        time_oss.width(2);
        time_oss << tm_now.tm_sec << ']';
        //Cache the resulted string and its size
        s_cache_time_t = tp_time_t;
        const std::string s = time_oss.str();
        s_cache_timesize = s.size();
        std::memcpy(s_cache_timestr, s.c_str(), s_cache_timesize);
    }
    output.write(s_cache_timestr, s_cache_timesize);
}