muduo庫源碼學習(base)Date

muduo在時間上選擇的是tm和timeSpec

struct tm;

namespace muduo
{

//
// Date in Gregorian calendar.
//
// This class is immutable.
// It's recommended to pass it by value, since it's passed in register on x64.
//
//格林格蘭歷
//保存的julian date是自公元前4713年1月1日中午12時起經過的天數。這樣比較大小的時候比較方便。。
class Date : public muduo::copyable
{
 public:

  struct YearMonthDay
  {
    int year; // [1900..2500]
    int month;  // [1..12]
    int day;  // [1..31]
  };

  static const int kDaysPerWeek = 7;
  static const int kJulianDayOf1970_01_01;//linux紀元日197011的編號。。。

  //
  // Constucts an invalid Date.
  //
  Date()
    : julianDayNumber_(0)
  {}

  //
  // Constucts a yyyy-mm-dd Date.
  //
  // 1 <= month <= 12
  Date(int year, int month, int day);

  ///
  /// Constucts a Date from Julian Day Number.
  ///
  explicit Date(int julianDayNum)
    : julianDayNumber_(julianDayNum)
  {}

  ///
  /// Constucts a Date from struct tm
  ///
  explicit Date(const struct tm&);

  // default copy/assignment/dtor are Okay

  void swap(Date& that)
  {
    std::swap(julianDayNumber_, that.julianDayNumber_);
  }

  bool valid() const { return julianDayNumber_ > 0; }

  ///
  /// Converts to yyyy-mm-dd format.
  ///
  string toIsoString() const;

  struct YearMonthDay yearMonthDay() const;

  int year() const
  {
    return yearMonthDay().year;
  }

  int month() const
  {
    return yearMonthDay().month;
  }

  int day() const
  {
    return yearMonthDay().day;
  }

  // [0, 1, ..., 6] => [Sunday, Monday, ..., Saturday ]
  int weekDay() const
  {
    return (julianDayNumber_+1) % kDaysPerWeek;//0,6不是工作日，也就是週六日
  }

  int julianDayNumber() const { return julianDayNumber_; }

 private:
  int julianDayNumber_;
};

inline bool operator<(Date x, Date y)
{
  return x.julianDayNumber() < y.julianDayNumber();
}

inline bool operator==(Date x, Date y)
{
  return x.julianDayNumber() == y.julianDayNumber();
}

}

namespace muduo
{
namespace detail
{

char require_32_bit_integer_at_least[sizeof(int) >= sizeof(int32_t) ? 1 : -1];

// algorithm and explanation see:
// http://www.faqs.org/faqs/calendars/faq/part2/
// http://blog.csdn.net/Solstice

int getJulianDayNumber(int year, int month, int day)
{
  (void) require_32_bit_integer_at_least; // no warning please
  int a = (14 - month) / 12;
  int y = year + 4800 - a;
  int m = month + 12 * a - 3;
  return day + (153*m + 2) / 5 + y*365 + y/4 - y/100 + y/400 - 32045;
}

struct Date::YearMonthDay getYearMonthDay(int julianDayNumber)
{
  int a = julianDayNumber + 32044;
  int b = (4 * a + 3) / 146097;
  int c = a - ((b * 146097) / 4);
  int d = (4 * c + 3) / 1461;
  int e = c - ((1461 * d) / 4);
  int m = (5 * e + 2) / 153;
  Date::YearMonthDay ymd;
  ymd.day = e - ((153 * m + 2) / 5) + 1;
  ymd.month = m + 3 - 12 * (m / 10);
  ymd.year = b * 100 + d - 4800 + (m / 10);
  return ymd;
}
}
const int Date::kJulianDayOf1970_01_01 = detail::getJulianDayNumber(1970, 1, 1);//in namespace muduo
}

using namespace muduo;
using namespace muduo::detail;

Date::Date(int y, int m, int d)
  : julianDayNumber_(getJulianDayNumber(y, m, d))
{
}

Date::Date(const struct tm& t)
  : julianDayNumber_(getJulianDayNumber(
        t.tm_year+1900,//tm year-1900
        t.tm_mon+1,//0-11
        t.tm_mday))
{
}

string Date::toIsoString() const
{
  char buf[32];
  YearMonthDay ymd(yearMonthDay());
  snprintf(buf, sizeof buf, "%4d-%02d-%02d", ymd.year, ymd.month, ymd.day);
  return buf;
}

Date::YearMonthDay Date::yearMonthDay() const
{
  return getYearMonthDay(julianDayNumber_);
}