source: trunk/src/corelib/tools/qdatetime.cpp@ 651

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#include "qplatformdefs.h"
#include "private/qdatetime_p.h"

#include "qdatastream.h"
#include "qset.h"
#include "qlocale.h"
#include "qdatetime.h"
#include "qregexp.h"
#include "qdebug.h"
#if defined(Q_OS_WIN32) || defined(Q_OS_WINCE)
#include <qt_windows.h>
#endif
#ifndef Q_WS_WIN
#include <locale.h>
#endif

#include <time.h>
#if defined(Q_OS_WINCE)
#include "qfunctions_wince.h"
#endif

//#define QDATETIMEPARSER_DEBUG
#if defined (QDATETIMEPARSER_DEBUG) && !defined(QT_NO_DEBUG_STREAM)
#  define QDTPDEBUG qDebug() << QString("%1:%2").arg(__FILE__).arg(__LINE__)
#  define QDTPDEBUGN qDebug
#else
#  define QDTPDEBUG if (false) qDebug()
#  define QDTPDEBUGN if (false) qDebug
#endif

#if defined(Q_WS_MAC)
#include <private/qcore_mac_p.h>
#endif

#if defined(Q_OS_SYMBIAN)
#include <e32std.h>
#endif

QT_BEGIN_NAMESPACE

enum {
    FIRST_YEAR = -4713,
    FIRST_MONTH = 1,
    FIRST_DAY = 2,  // ### Qt 5: make FIRST_DAY = 1, by support jd == 0 as valid
    SECS_PER_DAY = 86400,
    MSECS_PER_DAY = 86400000,
    SECS_PER_HOUR = 3600,
    MSECS_PER_HOUR = 3600000,
    SECS_PER_MIN = 60,
    MSECS_PER_MIN = 60000
};

static inline QDate fixedDate(int y, int m, int d)
{
    QDate result(y, m, 1);
    result.setDate(y, m, qMin(d, result.daysInMonth()));
    return result;
}

static uint julianDayFromDate(int year, int month, int day)
{
    if (year < 0)
        ++year;

    if (year > 1582 || (year == 1582 && (month > 10 || (month == 10 && day >= 15)))) {
        // Gregorian calendar starting from October 15, 1582
        // Algorithm from Henry F. Fliegel and Thomas C. Van Flandern
        return (1461 * (year + 4800 + (month - 14) / 12)) / 4
               + (367 * (month - 2 - 12 * ((month - 14) / 12))) / 12
               - (3 * ((year + 4900 + (month - 14) / 12) / 100)) / 4
               + day - 32075;
    } else if (year < 1582 || (year == 1582 && (month < 10 || (month == 10 && day <= 4)))) {
        // Julian calendar until October 4, 1582
        // Algorithm from Frequently Asked Questions about Calendars by Claus Toendering
        int a = (14 - month) / 12;
        return (153 * (month + (12 * a) - 3) + 2) / 5
               + (1461 * (year + 4800 - a)) / 4
               + day - 32083;
    } else {
        // the day following October 4, 1582 is October 15, 1582
        return 0;
    }
}

static void getDateFromJulianDay(uint julianDay, int *year, int *month, int *day)
{
    int y, m, d;

    if (julianDay >= 2299161) {
        // Gregorian calendar starting from October 15, 1582
        // This algorithm is from Henry F. Fliegel and Thomas C. Van Flandern
        qulonglong ell, n, i, j;
        ell = qulonglong(julianDay) + 68569;
        n = (4 * ell) / 146097;
        ell = ell - (146097 * n + 3) / 4;
        i = (4000 * (ell + 1)) / 1461001;
        ell = ell - (1461 * i) / 4 + 31;
        j = (80 * ell) / 2447;
        d = ell - (2447 * j) / 80;
        ell = j / 11;
        m = j + 2 - (12 * ell);
        y = 100 * (n - 49) + i + ell;
    } else {
        // Julian calendar until October 4, 1582
        // Algorithm from Frequently Asked Questions about Calendars by Claus Toendering
        julianDay += 32082;
        int dd = (4 * julianDay + 3) / 1461;
        int ee = julianDay - (1461 * dd) / 4;
        int mm = ((5 * ee) + 2) / 153;
        d = ee - (153 * mm + 2) / 5 + 1;
        m = mm + 3 - 12 * (mm / 10);
        y = dd - 4800 + (mm / 10);
        if (y <= 0)
            --y;
    }
    if (year)
        *year = y;
    if (month)
        *month = m;
    if (day)
        *day = d;
}


static const char monthDays[] = { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

#ifndef QT_NO_TEXTDATE
static const char * const qt_shortMonthNames[] = {
    "Jan", "Feb", "Mar", "Apr", "May", "Jun",
    "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" };
#endif
#ifndef QT_NO_DATESTRING
static QString fmtDateTime(const QString& f, const QTime* dt = 0, const QDate* dd = 0);
#endif

/*****************************************************************************
  QDate member functions
 *****************************************************************************/

/*!
    \since 4.5

    \enum QDate::MonthNameType

    This enum describes the types of the string representation used
    for the month name.

    \value DateFormat This type of name can be used for date-to-string formatting.
    \value StandaloneFormat This type is used when you need to enumerate months or weekdays.
           Usually standalone names are represented in singular forms with
           capitalized first letter.
*/

/*!
    \class QDate
    \reentrant
    \brief The QDate class provides date functions.


    A QDate object contains a calendar date, i.e. year, month, and day
    numbers, in the Gregorian calendar. (see \l{QDate G and J} {Use of
    Gregorian and Julian Calendars} for dates prior to 15 October
    1582). It can read the current date from the system clock. It
    provides functions for comparing dates, and for manipulating
    dates. For example, it is possible to add and subtract days,
    months, and years to dates.

    A QDate object is typically created either by giving the year,
    month, and day numbers explicitly. Note that QDate interprets two
    digit years as is, i.e., years 0 - 99. A QDate can also be
    constructed with the static function currentDate(), which creates
    a QDate object containing the system clock's date.  An explicit
    date can also be set using setDate(). The fromString() function
    returns a QDate given a string and a date format which is used to
    interpret the date within the string.

    The year(), month(), and day() functions provide access to the
    year, month, and day numbers. Also, dayOfWeek() and dayOfYear()
    functions are provided. The same information is provided in
    textual format by the toString(), shortDayName(), longDayName(),
    shortMonthName(), and longMonthName() functions.

    QDate provides a full set of operators to compare two QDate
    objects where smaller means earlier, and larger means later.

    You can increment (or decrement) a date by a given number of days
    using addDays(). Similarly you can use addMonths() and addYears().
    The daysTo() function returns the number of days between two
    dates.

    The daysInMonth() and daysInYear() functions return how many days
    there are in this date's month and year, respectively. The
    isLeapYear() function indicates whether a date is in a leap year.

    \section1

    \target QDate G and J
    \section2 Use of Gregorian and Julian Calendars

    QDate uses the Gregorian calendar in all locales, beginning
    on the date 15 October 1582. For dates up to and including 4
    October 1582, the Julian calendar is used.  This means there is a
    10-day gap in the internal calendar between the 4th and the 15th
    of October 1582. When you use QDateTime for dates in that epoch,
    the day after 4 October 1582 is 15 October 1582, and the dates in
    the gap are invalid.

    The Julian to Gregorian changeover date used here is the date when
    the Gregorian calendar was first introduced, by Pope Gregory
    XIII. That change was not universally accepted and some localities
    only executed it at a later date (if at all).  QDateTime
    doesn't take any of these historical facts into account. If an
    application must support a locale-specific dating system, it must
    do so on its own, remembering to convert the dates using the
    Julian day.

    \section2 No Year 0

    There is no year 0. Dates in that year are considered invalid. The
    year -1 is the year "1 before Christ" or "1 before current era."
    The day before 0001-01-01 is December 31st, 1 BCE.

    \section2 Range of Valid Dates

    The range of valid dates is from January 2nd, 4713 BCE, to
    sometime in the year 11 million CE. The Julian Day returned by
    QDate::toJulianDay() is a number in the contiguous range from 1 to
    \e{overflow}, even across QDateTime's "date holes". It is suitable
    for use in applications that must convert a QDateTime to a date in
    another calendar system, e.g., Hebrew, Islamic or Chinese.

    \sa QTime, QDateTime, QDateEdit, QDateTimeEdit, QCalendarWidget
*/

/*!
    \fn QDate::QDate()

    Constructs a null date. Null dates are invalid.

    \sa isNull(), isValid()
*/

/*!
    Constructs a date with year \a y, month \a m and day \a d.

    If the specified date is invalid, the date is not set and
    isValid() returns false. A date before 2 January 4713 B.C. is
    considered invalid.

    \warning Years 0 to 99 are interpreted as is, i.e., years
             0-99.

    \sa isValid()
*/

QDate::QDate(int y, int m, int d)
{
    setDate(y, m, d);
}


/*!
    \fn bool QDate::isNull() const

    Returns true if the date is null; otherwise returns false. A null
    date is invalid.

    \note The behavior of this function is equivalent to isValid().

    \sa isValid()
*/


/*!
    Returns true if this date is valid; otherwise returns false.

    \sa isNull()
*/

bool QDate::isValid() const
{
    return !isNull();
}


/*!
    Returns the year of this date. Negative numbers indicate years
    before 1 A.D. = 1 C.E., such that year -44 is 44 B.C.

    \sa month(), day()
*/

int QDate::year() const
{
    int y;
    getDateFromJulianDay(jd, &y, 0, 0);
    return y;
}

/*!
    Returns the number corresponding to the month of this date, using
    the following convention:

    \list
    \i 1 = "January"
    \i 2 = "February"
    \i 3 = "March"
    \i 4 = "April"
    \i 5 = "May"
    \i 6 = "June"