Add the RFC2822Date format

QDateTime can now be converted to strings compliant to RFC 2822.
Additionally, it supports RFC 850 and RFC 1036 during parsing.
By having them all together, all type of dates found in exchanged
messages on the internet (including USENET) get supported.

Change-Id: I771066c23f409d20b31b7d802f37852ea68ca2a0
Reviewed-by: David Faure <david.faure@kdab.com>
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@digia.com>

3 files changed, 141 insertions, 1 deletions

diff --git a/src/corelib/global/qnamespace.h b/src/corelib/global/qnamespace.h
index 6f1a089670..e714839f26 100644
--- a/src/corelib/global/qnamespace.h
+++ b/src/corelib/global/qnamespace.h
@@ -1181,7 +1181,8 @@ public:
         SystemLocaleShortDate,
         SystemLocaleLongDate,
         DefaultLocaleShortDate,
-        DefaultLocaleLongDate
+        DefaultLocaleLongDate,
+        RFC2822Date        // RFC 2822 (+ 850 and 1036 during parsing)
     };
 
     enum TimeSpec {
diff --git a/src/corelib/global/qnamespace.qdoc b/src/corelib/global/qnamespace.qdoc
index 5cd1812b54..4a5285fa5d 100644
--- a/src/corelib/global/qnamespace.qdoc
+++ b/src/corelib/global/qnamespace.qdoc
@@ -585,6 +585,10 @@
     \value LocalDate \e{This enum value is deprecated.} Use Qt::SystemLocaleShortDate
     instead (or Qt::SystemLocaleLongDate if you want long dates).
 
+    \value RFC2822Date \l{RFC 2822}, \l{RFC 850} and \l{RFC 1036} format: either
+    \c{[ddd,] dd MMM yyyy hh:mm[:ss] +/-TZ} or \c{ddd MMM dd yyyy hh:mm[:ss] +/-TZ}
+    for combined dates and times.
+
     \note For \c ISODate formats, each \c Y, \c M and \c D represents a single digit
     of the year, month and day used to specify the date. Each \c H, \c M and \c S
     represents a single digit of the hour, minute and second used to specify the time.
diff --git a/src/corelib/tools/qdatetime.cpp b/src/corelib/tools/qdatetime.cpp
index 0b4761d5b4..7b99aa1e06 100644
--- a/src/corelib/tools/qdatetime.cpp
+++ b/src/corelib/tools/qdatetime.cpp
@@ -158,9 +158,19 @@ static const char monthDays[] = { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30,
 static const char * const qt_shortMonthNames[] = {
     "Jan", "Feb", "Mar", "Apr", "May", "Jun",
     "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" };
+
+int qt_monthNumberFromShortName(const QString &shortName)
+{
+    for (unsigned int i = 0; i < sizeof(qt_shortMonthNames) / sizeof(qt_shortMonthNames[0]); ++i) {
+        if (shortName == QLatin1String(qt_shortMonthNames[i]))
+            return i + 1;
+    }
+    return -1;
+}
 #endif
 #ifndef QT_NO_DATESTRING
 static QString fmtDateTime(const QString& f, const QTime* dt = 0, const QDate* dd = 0);
+static void rfcDateImpl(const QString &s, QDate *dd = 0, QTime *dt = 0, int *utfcOffset = 0);
 #endif
 
 /*****************************************************************************
@@ -735,6 +745,10 @@ QString QDate::longDayName(int weekday, MonthNameType type)
     QLocale::ShortFormat) or QLocale().toString(date,
     QLocale::LongFormat).
 
+    If the \a format is Qt::RFC2822Date, the string is formatted in
+    an \l{RFC 2822} compatible way. An example of this formatting is
+    "20 May 1995".
+
     If the date is invalid, an empty string will be returned.
 
     \warning The Qt::ISODate format is only valid for years in the
@@ -771,6 +785,8 @@ QString QDate::toString(Qt::DateFormat f) const
                 .arg(y);
         }
 #endif
+    case Qt::RFC2822Date:
+        return toString(QStringLiteral("dd MMM yyyy"));
     case Qt::ISODate:
         {
             if (year() < 0 || year() > 9999)
@@ -1124,6 +1140,11 @@ QDate QDate::fromString(const QString& s, Qt::DateFormat f)
     case Qt::DefaultLocaleLongDate:
         return fromString(s, QLocale().dateFormat(f == Qt::DefaultLocaleLongDate ? QLocale::LongFormat
                                                                                  : QLocale::ShortFormat));
+    case Qt::RFC2822Date: {
+        QDate date;
+        rfcDateImpl(s, &date);
+        return date;
+    }
     default:
 #ifndef QT_NO_TEXTDATE
     case Qt::TextDate: {
@@ -1498,6 +1519,10 @@ int QTime::msec() const
     QLocale::ShortFormat) or QLocale().toString(time,
     QLocale::LongFormat).
 
+    If the \a format is Qt::RFC2822Date, the string is formatted in
+    an \l{RFC 2822} compatible way. An example of this formatting is
+    "23:59:20".
+
     If the time is invalid, an empty string will be returned.
 */
 
@@ -1518,6 +1543,11 @@ QString QTime::toString(Qt::DateFormat format) const
         return QLocale().toString(*this, format == Qt::DefaultLocaleLongDate ? QLocale::LongFormat
                                   : QLocale::ShortFormat);
 
+    case Qt::RFC2822Date:
+        return QString::fromLatin1("%1:%2:%3")
+            .arg(hour(), 2, 10, QLatin1Char('0'))
+            .arg(minute(), 2, 10, QLatin1Char('0'))
+            .arg(second(), 2, 10, QLatin1Char('0'));
     default:
     case Qt::ISODate:
     case Qt::TextDate:
@@ -1790,6 +1820,11 @@ QTime fromStringImpl(const QString &s, Qt::DateFormat f, bool &isMidnight24)
         QLocale::FormatType formatType(f == Qt::DefaultLocaleLongDate ? QLocale::LongFormat : QLocale::ShortFormat);
         return QTime::fromString(s, QLocale().timeFormat(formatType));
     }
+    case Qt::RFC2822Date: {
+        QTime time;
+        rfcDateImpl(s, 0, &time);
+        return time;
+    }
     case Qt::TextDate:
     case Qt::ISODate:
     {
@@ -2490,6 +2525,9 @@ void QDateTime::setTime_t(uint secsSince1Jan1970UTC)
     QLocale::ShortFormat) or QLocale().toString(datetime,
     QLocale::LongFormat).
 
+    If the \a format is Qt::RFC2822Date, the string is formatted
+    following \l{RFC 2822}.
+
     If the datetime is invalid, an empty string will be returned.
 
     \warning The Qt::ISODate format is only valid for years in the
@@ -2526,6 +2564,28 @@ QString QDateTime::toString(Qt::DateFormat f) const
         default:
             break;
         }
+    } else if (f == Qt::RFC2822Date) {
+        buf = toString(QStringLiteral("dd MMM yyyy hh:mm:ss "));
+
+        int utcOffset = d->utcOffset;
+        if (timeSpec() == Qt::LocalTime) {
+            QDateTime utc = toUTC();
+            utc.setTimeSpec(timeSpec());
+            utcOffset = utc.secsTo(*this);
+        }
+
+        const int offset = qAbs(utcOffset);
+        buf += QLatin1Char((offset == utcOffset) ? '+' : '-');
+
+        const int hour = offset / 3600;
+        if (hour < 10)
+            buf += QLatin1Char('0');
+        buf += QString::number(hour);
+
+        const int min = (offset - (hour * 3600)) / 60;
+        if (min < 10)
+            buf += QLatin1Char('0');
+        buf += QString::number(min);
     }
 #ifndef QT_NO_TEXTDATE
     else if (f == Qt::TextDate) {
@@ -3333,6 +3393,19 @@ QDateTime QDateTime::fromString(const QString& s, Qt::DateFormat f)
 
         return QDateTime(date, time, ts);
     }
+    case Qt::RFC2822Date: {
+        QDate date;
+        QTime time;
+        int utcOffset = 0;
+        rfcDateImpl(s, &date, &time, &utcOffset);
+
+        if (!date.isValid() || !time.isValid())
+            return QDateTime();
+
+        QDateTime dateTime(date, time, Qt::UTC);
+        dateTime.setUtcOffset(utcOffset);
+        return dateTime;
+    }
     case Qt::SystemLocaleDate:
     case Qt::SystemLocaleShortDate:
     case Qt::SystemLocaleLongDate:
@@ -3953,6 +4026,68 @@ static QString fmtDateTime(const QString& f, const QTime* dt, const QDate* dd)
 
     return buf;
 }
+
+static void rfcDateImpl(const QString &s, QDate *dd, QTime *dt, int *utcOffset)
+{
+    int day = -1;
+    int month = -1;
+    int year = -1;
+    int hour = -1;
+    int min = -1;
+    int sec = -1;
+    int hourOffset = 0;
+    int minOffset = 0;
+    bool positiveOffset = false;
+
+    // Matches "Wdy, DD Mon YYYY HH:MM:SS ±hhmm" (Wdy, being optional)
+    QRegExp rex(QStringLiteral("^(?:[A-Z][a-z]+,)?[ \\t]*(\\d{1,2})[ \\t]+([A-Z][a-z]+)[ \\t]+(\\d\\d\\d\\d)(?:[ \\t]+(\\d\\d):(\\d\\d)(?::(\\d\\d))?)?[ \\t]*(?:([+-])(\\d\\d)(\\d\\d))?"));
+    if (s.indexOf(rex) == 0) {
+        if (dd) {
+            day = rex.cap(1).toInt();
+            month = qt_monthNumberFromShortName(rex.cap(2));
+            year = rex.cap(3).toInt();
+        }
+        if (dt) {
+            if (!rex.cap(4).isEmpty()) {
+                hour = rex.cap(4).toInt();
+                min = rex.cap(5).toInt();
+                sec = rex.cap(6).toInt();
+            }
+            positiveOffset = (rex.cap(7) == QStringLiteral("+"));
+            hourOffset = rex.cap(8).toInt();
+            minOffset = rex.cap(9).toInt();
+        }
+        if (utcOffset)
+            *utcOffset = ((hourOffset * 60 + minOffset) * (positiveOffset ? 60 : -60));
+    } else {
+        // Matches "Wdy Mon DD HH:MM:SS YYYY"
+        QRegExp rex(QStringLiteral("^[A-Z][a-z]+[ \\t]+([A-Z][a-z]+)[ \\t]+(\\d\\d)(?:[ \\t]+(\\d\\d):(\\d\\d):(\\d\\d))?[ \\t]+(\\d\\d\\d\\d)[ \\t]*(?:([+-])(\\d\\d)(\\d\\d))?"));
+        if (s.indexOf(rex) == 0) {
+            if (dd) {
+                month = qt_monthNumberFromShortName(rex.cap(1));
+                day = rex.cap(2).toInt();
+                year = rex.cap(6).toInt();
+            }
+            if (dt) {
+                if (!rex.cap(3).isEmpty()) {
+                    hour = rex.cap(3).toInt();
+                    min = rex.cap(4).toInt();
+                    sec = rex.cap(5).toInt();
+                }
+                positiveOffset = (rex.cap(7) == QStringLiteral("+"));
+                hourOffset = rex.cap(8).toInt();
+                minOffset = rex.cap(9).toInt();
+            }
+            if (utcOffset)
+                *utcOffset = ((hourOffset * 60 + minOffset) * (positiveOffset ? 60 : -60));
+        }
+    }
+
+    if (dd)
+        *dd = QDate(year, month, day);
+    if (dt)
+        *dt = QTime(hour, min, sec);
+}
 #endif // QT_NO_DATESTRING
 
 #ifdef Q_OS_WIN