QLocale: add toString(Q(Date|QTime)+, QStringView format) overloads

While at it, change the interface of qt_repeatCount() to just take
a single QStringView, since QStringView::mid() is so cheap. Add some
\internal docs.

[ChangeLog][QtCore][QLocale] Added toString(QDate/QTime/QDateTime)
overloads taking the format string as a QStringView.

Change-Id: Ic078796677a6db06227c8a3e276dbdb1039ceead
Reviewed-by: Anton Kudryavtsev <antkudr@mail.ru>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

6 files changed, 88 insertions, 22 deletions

diff --git a/src/corelib/tools/qdatetime.cpp b/src/corelib/tools/qdatetime.cpp
index a4a7aabacb..ab1e3672d6 100644
--- a/src/corelib/tools/qdatetime.cpp
+++ b/src/corelib/tools/qdatetime.cpp
@@ -866,7 +866,7 @@ QString QDate::toString(Qt::DateFormat format) const
     case Qt::DefaultLocaleLongDate:
         return QLocale().toString(*this, QLocale::LongFormat);
     case Qt::RFC2822Date:
-        return QLocale::c().toString(*this, QStringLiteral("dd MMM yyyy"));
+        return QLocale::c().toString(*this, QStringViewLiteral("dd MMM yyyy"));
     default:
 #ifndef QT_NO_TEXTDATE
     case Qt::TextDate:
@@ -3795,7 +3795,7 @@ QString QDateTime::toString(Qt::DateFormat format) const
     case Qt::DefaultLocaleLongDate:
         return QLocale().toString(*this, QLocale::LongFormat);
     case Qt::RFC2822Date: {
-        buf = QLocale::c().toString(*this, QStringLiteral("dd MMM yyyy hh:mm:ss "));
+        buf = QLocale::c().toString(*this, QStringViewLiteral("dd MMM yyyy hh:mm:ss "));
         buf += toOffsetString(Qt::TextDate, offsetFromUtc());
         return buf;
     }
diff --git a/src/corelib/tools/qlocale.cpp b/src/corelib/tools/qlocale.cpp
index a3995449f1..bad1481575 100644
--- a/src/corelib/tools/qlocale.cpp
+++ b/src/corelib/tools/qlocale.cpp
@@ -518,7 +518,7 @@ static const QLocaleData *findLocaleData(const QString &name)
     return QLocaleData::findLocaleData(lang, script, cntry);
 }
 
-QString qt_readEscapedFormatString(const QString &format, int *idx)
+QString qt_readEscapedFormatString(QStringView format, int *idx)
 {
     int &i = *idx;
 
@@ -552,13 +552,31 @@ QString qt_readEscapedFormatString(const QString &format, int *idx)
     return result;
 }
 
-int qt_repeatCount(const QString &s, int i)
+/*!
+    \internal
+
+    Counts the number of identical leading characters in \a s.
+
+    If \a s is empty, returns 0.
+
+    Otherwise, returns the number of consecutive \c{s.front()}
+    characters at the start of \a s.
+
+    \code
+    qt_repeatCount(u"a");   // == 1
+    qt_repeatCount(u"ab");  // == 1
+    qt_repeatCount(u"aab"); // == 2
+    \endcode
+*/
+int qt_repeatCount(QStringView s)
 {
-    QChar c = s.at(i);
-    int j = i + 1;
+    if (s.isEmpty())
+        return 0;
+    const QChar c = s.front();
+    qssize_t j = 1;
     while (j < s.size() && s.at(j) == c)
         ++j;
-    return j - i;
+    return int(j);
 }
 
 static const QLocaleData *default_data = 0;
@@ -1725,6 +1743,7 @@ QString QLocale::toString(qulonglong i) const
     return d->m_data->unsLongLongToString(i, -1, 10, -1, flags);
 }
 
+#if QT_STRINGVIEW_LEVEL < 2
 /*!
     Returns a localized string representation of the given \a date in the
     specified \a format.
@@ -1735,6 +1754,19 @@ QString QLocale::toString(const QDate &date, const QString &format) const
 {
     return d->dateTimeToString(format, QDateTime(), date, QTime(), this);
 }
+#endif
+
+/*!
+    \since 5.10
+
+    Returns a localized string representation of the given \a date in the
+    specified \a format.
+    If \a format is an empty string, an empty string is returned.
+*/
+QString QLocale::toString(const QDate &date, QStringView format) const
+{
+    return d->dateTimeToString(format, QDateTime(), date, QTime(), this);
+}
 
 /*!
     Returns a localized string representation of the given \a date according
@@ -1760,7 +1792,7 @@ QString QLocale::toString(const QDate &date, FormatType format) const
     return toString(date, format_str);
 }
 
-static bool timeFormatContainsAP(const QString &format)
+static bool timeFormatContainsAP(QStringView format)
 {
     int i = 0;
     while (i < format.size()) {
@@ -1777,6 +1809,7 @@ static bool timeFormatContainsAP(const QString &format)
     return false;
 }
 
+#if QT_STRINGVIEW_LEVEL < 2
 /*!
     Returns a localized string representation of the given \a time according
     to the specified \a format.
@@ -1786,8 +1819,22 @@ QString QLocale::toString(const QTime &time, const QString &format) const
 {
     return d->dateTimeToString(format, QDateTime(), QDate(), time, this);
 }
+#endif
 
 /*!
+    \since 5.10
+
+    Returns a localized string representation of the given \a time according
+    to the specified \a format.
+    If \a format is an empty string, an empty string is returned.
+*/
+QString QLocale::toString(const QTime &time, QStringView format) const
+{
+    return d->dateTimeToString(format, QDateTime(), QDate(), time, this);
+}
+
+#if QT_STRINGVIEW_LEVEL < 2
+/*!
     \since 4.4
 
     Returns a localized string representation of the given \a dateTime according
@@ -1799,6 +1846,19 @@ QString QLocale::toString(const QDateTime &dateTime, const QString &format) cons
 {
     return d->dateTimeToString(format, dateTime, QDate(), QTime(), this);
 }
+#endif
+
+/*!
+    \since 5.10
+
+    Returns a localized string representation of the given \a dateTime according
+    to the specified \a format.
+    If \a format is an empty string, an empty string is returned.
+*/
+QString QLocale::toString(const QDateTime &dateTime, QStringView format) const
+{
+    return d->dateTimeToString(format, dateTime, QDate(), QTime(), this);
+}
 
 /*!
     \since 4.4
@@ -2710,7 +2770,7 @@ QString QLocale::pmText() const
 }
 
 
-QString QLocalePrivate::dateTimeToString(const QString &format, const QDateTime &datetime,
+QString QLocalePrivate::dateTimeToString(QStringView format, const QDateTime &datetime,
                                          const QDate &dateOnly, const QTime &timeOnly,
                                          const QLocale *q) const
 {
@@ -2743,7 +2803,7 @@ QString QLocalePrivate::dateTimeToString(const QString &format, const QDateTime
         }
 
         const QChar c = format.at(i);
-        int repeat = qt_repeatCount(format, i);
+        int repeat = qt_repeatCount(format.mid(i));
         bool used = false;
         if (formatDate) {
             switch (c.unicode()) {
@@ -2878,7 +2938,7 @@ QString QLocalePrivate::dateTimeToString(const QString &format, const QDateTime
 
             case 'a':
                 used = true;
-                if (i + 1 < format.length() && format.at(i + 1).unicode() == 'p') {
+                if (i + 1 < format.size() && format.at(i + 1).unicode() == 'p') {
                     repeat = 2;
                 } else {
                     repeat = 1;
@@ -2888,7 +2948,7 @@ QString QLocalePrivate::dateTimeToString(const QString &format, const QDateTime
 
             case 'A':
                 used = true;
-                if (i + 1 < format.length() && format.at(i + 1).unicode() == 'P') {
+                if (i + 1 < format.size() && format.at(i + 1).unicode() == 'P') {
                     repeat = 2;
                 } else {
                     repeat = 1;
diff --git a/src/corelib/tools/qlocale.h b/src/corelib/tools/qlocale.h
index 1f20bcd241..f9482a7e3a 100644
--- a/src/corelib/tools/qlocale.h
+++ b/src/corelib/tools/qlocale.h
@@ -972,12 +972,18 @@ public:
     inline QString toString(uint i) const;
     QString toString(double i, char f = 'g', int prec = 6) const;
     inline QString toString(float i, char f = 'g', int prec = 6) const;
+
+#if QT_STRINGVIEW_LEVEL < 2
     QString toString(const QDate &date, const QString &formatStr) const;
-    QString toString(const QDate &date, FormatType format = LongFormat) const;
     QString toString(const QTime &time, const QString &formatStr) const;
+    QString toString(const QDateTime &dateTime, const QString &format) const;
+#endif
+    QString toString(const QDate &date, QStringView formatStr) const;
+    QString toString(const QTime &time, QStringView formatStr) const;
+    QString toString(const QDateTime &dateTime, QStringView format) const;
+    QString toString(const QDate &date, FormatType format = LongFormat) const;
     QString toString(const QTime &time, FormatType format = LongFormat) const;
     QString toString(const QDateTime &dateTime, FormatType format = LongFormat) const;
-    QString toString(const QDateTime &dateTime, const QString &format) const;
 
     QString dateFormat(FormatType format = LongFormat) const;
     QString timeFormat(FormatType format = LongFormat) const;
diff --git a/src/corelib/tools/qlocale_mac.mm b/src/corelib/tools/qlocale_mac.mm
index c5519bfabf..edbaaf5d18 100644
--- a/src/corelib/tools/qlocale_mac.mm
+++ b/src/corelib/tools/qlocale_mac.mm
@@ -150,7 +150,7 @@ static QString macTimeToString(const QTime &time, bool short_format)
 // See also qtbase/util/local_database/dateconverter.py
 // Makes the assumption that input formats are always well formed and consecutive letters
 // never exceed the maximum for the format code.
-static QString macToQtFormat(const QString &sys_fmt)
+static QString macToQtFormat(QStringView sys_fmt)
 {
     QString result;
     int i = 0;
@@ -166,7 +166,7 @@ static QString macToQtFormat(const QString &sys_fmt)
         }
 
         QChar c = sys_fmt.at(i);
-        int repeat = qt_repeatCount(sys_fmt, i);
+        int repeat = qt_repeatCount(sys_fmt.mid(i));
 
         switch (c.unicode()) {
             // Qt does not support the following options
diff --git a/src/corelib/tools/qlocale_p.h b/src/corelib/tools/qlocale_p.h
index 589eae3cfb..12d5c60324 100644
--- a/src/corelib/tools/qlocale_p.h
+++ b/src/corelib/tools/qlocale_p.h
@@ -362,7 +362,7 @@ public:
 
     static void updateSystemPrivate();
 
-    QString dateTimeToString(const QString &format, const QDateTime &datetime,
+    QString dateTimeToString(QStringView format, const QDateTime &datetime,
                              const QDate &dateOnly, const QTime &timeOnly,
                              const QLocale *q) const;
 
@@ -412,9 +412,9 @@ inline char QLocaleData::digitToCLocale(QChar in) const
     return 0;
 }
 
-QString qt_readEscapedFormatString(const QString &format, int *idx);
+QString qt_readEscapedFormatString(QStringView format, int *idx);
 bool qt_splitLocaleName(const QString &name, QString &lang, QString &script, QString &cntry);
-int qt_repeatCount(const QString &s, int i);
+int qt_repeatCount(QStringView s);
 
 enum { AsciiSpaceMask = (1 << (' ' - 1)) |
                         (1 << ('\t' - 1)) |   // 9: HT - horizontal tab
diff --git a/src/corelib/tools/qlocale_win.cpp b/src/corelib/tools/qlocale_win.cpp
index 2475859abd..1d80320d8e 100644
--- a/src/corelib/tools/qlocale_win.cpp
+++ b/src/corelib/tools/qlocale_win.cpp
@@ -160,7 +160,7 @@ private:
     SubstitutionType substitution();
     QString &substituteDigits(QString &string);
 
-    static QString winToQtFormat(const QString &sys_fmt);
+    static QString winToQtFormat(QStringView sys_fmt);
 
 };
 Q_GLOBAL_STATIC(QSystemLocalePrivate, systemLocalePrivate)
@@ -680,7 +680,7 @@ void QSystemLocalePrivate::update()
     zero = QChar();
 }
 
-QString QSystemLocalePrivate::winToQtFormat(const QString &sys_fmt)
+QString QSystemLocalePrivate::winToQtFormat(QStringView sys_fmt)
 {
     QString result;
     int i = 0;
@@ -696,7 +696,7 @@ QString QSystemLocalePrivate::winToQtFormat(const QString &sys_fmt)
         }
 
         QChar c = sys_fmt.at(i);
-        int repeat = qt_repeatCount(sys_fmt, i);
+        int repeat = qt_repeatCount(sys_fmt.mid(i));
 
         switch (c.unicode()) {
             // Date