datetime.h

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//
// DateTime.h
//
// $Id: //poco/Main/Foundation/include/Foundation/DateTime.h#5 $
//
// Definition of the DateTime class.
//
// Copyright (c) 2004, Guenter Obiltschnig/Applied Informatics.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
//
// 1. Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
//    documentation and/or other materials provided with the distribution.
//
// 3. Redistributions in any form must be accompanied by information on
//    how to obtain complete source code for this software and any
//    accompanying software that uses this software.  The source code
//    must either be included in the distribution or be available for no
//    more than the cost of distribution plus a nominal fee, and must be
//    freely redistributable under reasonable conditions.  For an
//    executable file, complete source code means the source code for all
//    modules it contains.  It does not include source code for modules or
//    files that typically accompany the major components of the operating
//    system on which the executable file runs.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
// COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
// ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.
//


#ifndef Foundation_DateTime_INCLUDED
#define Foundation_DateTime_INCLUDED


#ifndef Foundation_Foundation_INCLUDED
#include "Foundation/Foundation.h"
#endif
#ifndef Foundation_Timestamp_INCLUDED
#include "Foundation/Timestamp.h"
#endif


Foundation_BEGIN


class Foundation_API DateTime
	/// This class represents an instant in time, expressed
	/// in years, months, days, hours, minutes, seconds
	/// and milliseconds based on the Gregorian calendar.
	/// The class is mainly useful for conversions between
	/// UTC, Julian day and Gregorian calendar dates.
	///
	/// Conversion calculations are based on algorithms
	/// collected and described by Peter Baum at
	/// http://vsg.cape.com/~pbaum/date/date0.htm
	///
	/// Internally, this class stores a date/time in three
	/// forms for performance reasons. Only use this
	/// class for conversions between date/time representations.
	/// Use the Timestamp class for everything else.
{
public:
	enum Months
		/// Symbolic names for month numbers (1 to 12).
	{
		JANUARY = 1,
		FEBRUARY,
		MARCH,
		APRIL,
		MAY,
		JUNE,
		JULY,
		AUGUST,
		SEPTEMBER,
		OCTOBER,
		NOVEMBER,
		DECEMBER
	};
	
	enum DaysOfWeek
		/// Symbolic names for week day numbers (0 to 6).
	{
		SUNDAY = 0,
		MONDAY,
		TUESDAY,
		WEDNESDAY,
		THURSDAY,
		FRIDAY,
		SATURDAY
	};
	
	DateTime();
		/// Creates a DateTime for the current date and time.

	DateTime(const Timestamp& timestamp);
		/// Creates a DateTime for the date and time given in
		/// a Timestamp.
		
	DateTime(int year, int month, int day, int hour = 0, int minute = 0, int second = 0, int millisecond = 0, int microsecond = 0);
		/// Creates a DateTime for the given Gregorian date and time.
		///   * year is from 0 to 9999.
		///   * month is from 1 to 12.
		///   * day is from 1 to 31.
		///   * hour is from 0 to 23.
		///   * minute is from 0 to 59.
		///   * second is from 0 to 59.
		///   * millisecond is from 0 to 999.
		///   * microsecond is from 0 to 999.

	DateTime(double julianDay);
		/// Creates a DateTime for the given Julian day.

	DateTime(const DateTime& dateTime);
		/// Copy constructor. Creates the DateTime from another one.

	~DateTime();
		/// Destroys the DateTime.

	DateTime& operator = (const DateTime& dateTime);
		/// Assigns another DateTime.
		
	DateTime& operator = (const Timestamp& timestamp);
		/// Assigns a Timestamp.

	DateTime& operator = (double julianDay);
		/// Assigns a Julian day.

	DateTime& assign(int year, int month, int day, int hour = 0, int minute = 0, int second = 0, int millisecond = 0, int microseconds = 0);
		/// Assigns a Gregorian date and time.
		///   * year is from 0 to 9999.
		///   * month is from 1 to 12.
		///   * day is from 1 to 31.
		///   * hour is from 0 to 23.
		///   * minute is from 0 to 59.
		///   * second is from 0 to 59.
		///   * millisecond is from 0 to 999.
		///   * microsecond is from 0 to 999.

	int year() const;
		/// Returns the year.
		
	int month() const;
		/// Returns the month (1 to 12).
	
	int week(int firstDayOfWeek = MONDAY) const;
		/// Returns the week number within the year.
		/// FirstDayOfWeek should be either SUNDAY (0) or MONDAY (1).
		/// The returned week number will be from 0 to 53. Week number 1 is the week 
		/// containing January 4. This is in accordance to ISO 8601.
		/// 
		/// The following example assumes that firstDayOfWeek is MONDAY. For 2005, which started
		/// on a Saturday, week 1 will be the week starting on Monday, January 3.
		/// January 1 and 2 will fall within week 0 (or the last week of the previous year).
		///
		/// For 2007, which starts on a Monday, week 1 will be the week startung on Monday, January 1.
		/// There will be no week 0 in 2007.
	
	int day() const;
		/// Returns the day witin the month (1 to 31).
		
	int dayOfWeek() const;
		/// Returns the weekday (0 to 6, where
		/// 0 = Sunday, 1 = Monday, ..., 6 = Saturday).
	
	int dayOfYear() const;
		/// Returns the number of the day in the year.
		/// January 1 is 1, February 1 is 32, etc.
	
	int hour() const;
		/// Returns the hour (0 to 23).
		
	int hourAMPM() const;
		/// Returns the hour (0 to 12).
	
	bool isAM() const;
		/// Returns true if hour < 12;

	bool isPM() const;
		/// Returns true if hour >= 12.
		
	int minute() const;
		/// Returns the minute (0 to 59).
		
	int second() const;
		/// Returns the second (0 to 59).
		
	int millisecond() const;
		/// Returns the millisecond (0 to 999)
	
	int microsecond() const;
		/// Returns the microsecond (0 to 999)
	
	double julianDay() const;
		/// Returns the julian day for the date.
		
	Timestamp timestamp() const;
		/// Returns the date and time expressed as a Timestamp.

	Timestamp::UtcTimeVal utcTime() const;
		/// Returns the date and time expressed in UTC-based
		/// time. UTC base time is midnight, October 15, 1582.
		/// Resolution is 100 nanoseconds.
		
	static bool isLeapYear(int year);
		/// Returns true if the given year is a leap year;
		/// false otherwise.
		
	static int daysOfMonth(int year, int month);
		/// Returns the number of days in the given month
		/// and year. Month is from 1 to 12.

protected:
	static double toJulianDay(Timestamp::UtcTimeVal utcTime);
		/// Computes the Julian day for an UTC time.
	
	static double toJulianDay(int year, int month, int day, int hour, int minute, int second, int millisecond, int microsecond);
		/// Computes the Julian day for a gregorian calendar date and time.
		/// See <http://vsg.cape.com/~pbaum/date/jdimp.htm>, section 2.3.1 for the algorithm.
	
	static Timestamp::UtcTimeVal toUtcTime(double julianDay);
		/// Computes the UTC time for a Julian day.

	void computeGregorian();
		/// Computes the Gregorian date for the stored Julian day.
		/// See <http://vsg.cape.com/~pbaum/date/injdimp.htm>, section 3.3.1 for the algorithm.

private:
	Timestamp::UtcTimeVal _utcTime;
	double _julianDay;
	short  _year;
	short  _month;
	short  _day;
	short  _hour;
	short  _minute;
	short  _second;
	short  _millisecond;
	short  _microsecond;
};


//
// inlines
//
inline Timestamp DateTime::timestamp() const
{
	return Timestamp::fromUtcTime(_utcTime);
}


inline Timestamp::UtcTimeVal DateTime::utcTime() const
{
	return _utcTime;
}


inline int DateTime::year() const
{
	return _year;
}

	
inline int DateTime::month() const
{
	return _month;
}

	
inline int DateTime::day() const
{
	return _day;
}

	
inline int DateTime::hour() const
{
	return _hour;
}


inline int DateTime::hourAMPM() const
{
	if (_hour < 1)
		return 12;
	else if (_hour > 12)
		return _hour - 12;
	else
		return _hour;
}


inline bool DateTime::isAM() const
{
	return _hour < 12;
}


inline bool DateTime::isPM() const
{
	return _hour >= 12;
}

	
inline int DateTime::minute() const
{
	return _minute;
}

	
inline int DateTime::second() const
{
	return _second;
}

	
inline int DateTime::millisecond() const
{
	return _millisecond;
}


inline int DateTime::microsecond() const
{
	return _microsecond;
}


inline double DateTime::julianDay() const
{
	return _julianDay;
}


inline bool DateTime::isLeapYear(int year)
{
	return (year % 4) == 0 && ((year % 100) != 0 || (year % 400) == 0);
}


Foundation_END


#endif // Foundation_DateTime_INCLUDED