cpp-logger/src/date_format.cxx

//
//  date_format.cxx
//  logging
//
//  Created by Sam Jaffe on 4/4/19.
//

#include <ctime>
#include <functional>
#include <string>

#include "logger/exception.h"
#include "logger/format.h"
#include "logger/logger_fwd.h"
#include "logger/logpacket.h"

namespace logging {
  std::string fmt_time(struct timeval round, char const * const fmt) {
    struct tm time;
    // Supports localtime when requested, but you can't really test that
    if (strstr(fmt, "%z") || strstr(fmt, "%Z")) {
      localtime_r(&round.tv_sec, &time);
    } else {
      gmtime_r(&round.tv_sec, &time);
    }
    char buf[64] = {'\0'};
    std::strftime(buf, sizeof(buf), fmt, &time);
    return buf;
  }
  
  std::string fmt_time(struct timeval round, std::string const & fmt) {
    return fmt_time(round, fmt.c_str());
  }
  
  std::string fmt_time_with_milis(struct timeval round,
                                  std::string const & fmt) {
    char buf[64] = {'\0'};
    snprintf(buf, sizeof(buf), fmt.c_str(), round.tv_usec/1000);
    return fmt_time(round, buf);
  }
  
  string_generator get_date_formatter(std::string fmt) {
    if (fmt.find("%_ms") != std::string::npos) {
      size_t pos = 0;
      while ((pos = fmt.find("%", pos)) != std::string::npos) {
        fmt.replace(pos, 1, "%%");
        pos += 2;
      }
      fmt.replace(fmt.find("%%_ms"), 5, "%.03d");
      return [=](logpacket const & lp) {
        return fmt_time_with_milis(lp.time, fmt);
      };
    } else {
      return [=](logpacket const & lp) {
        return fmt_time(lp.time, fmt);
      };
    }
  }
  
  string_generator parse_date_format_string(char const * str) {
    char const * const end = strchr(str, '}');
    if (end == nullptr) {
      std::string error_msg{"expected date-format specifier to terminate"};
      throw format_parsing_exception{error_msg};
    }
    return get_date_formatter(std::string(str, end));
  }
}