QTzTimeZonePrivate: introduce PosixZone class

... as a replacement for QPair<QString, int>, and move some
repsonsibilities into it.

This avoids the repeated use of the magic number INT_MIN to indicate
absence of an offset and does away with the confusing .first and
.second, replacing them instead with proper names, .name and .offset.

Change-Id: I0f6906467b8efa16bed2bf5677f2bbbd534da1ae
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 43 insertions, 26 deletions

diff --git a/src/corelib/tools/qtimezoneprivate_tz.cpp b/src/corelib/tools/qtimezoneprivate_tz.cpp
index 38dff88919..9cbe339225 100644
--- a/src/corelib/tools/qtimezoneprivate_tz.cpp
+++ b/src/corelib/tools/qtimezoneprivate_tz.cpp
@@ -452,13 +452,31 @@ static inline bool asciiIsLetter(char ch)
     return ch >= 'a' && ch <= 'z';
 }
 
+namespace {
+
+struct PosixZone
+{
+    enum {
+        InvalidOffset = INT_MIN,
+    };
+
+    QString name;
+    int offset;
+
+    static PosixZone invalid() { return {QString(), InvalidOffset}; }
+    static PosixZone parse(const char *&pos, const char *end);
+
+    bool hasValidOffset() const Q_DECL_NOTHROW { return offset != InvalidOffset; }
+};
+
+} // unnamed namespace
+
 // Returns the zone name, the offset (in seconds) and advances \a begin to
 // where the parsing ended. Returns a zone of INT_MIN in case an offset
 // couldn't be read.
-static QPair<QString, int> parsePosixZoneNameAndOffset(const char *&pos, const char *end)
+PosixZone PosixZone::parse(const char *&pos, const char *end)
 {
     static const char offsetChars[] = "0123456789:";
-    QPair<QString, int> result = qMakePair(QString(), INT_MIN);
 
     const char *nameBegin = pos;
     const char *nameEnd;
@@ -480,7 +498,7 @@ static QPair<QString, int> parsePosixZoneNameAndOffset(const char *&pos, const c
         pos = nameEnd;
     }
     if (nameEnd - nameBegin < 3)
-        return result;  // name must be at least 3 characters long
+        return invalid();  // name must be at least 3 characters long
 
     // zone offset, form [+-]hh:mm:ss
     const char *zoneBegin = pos;
@@ -493,11 +511,10 @@ static QPair<QString, int> parsePosixZoneNameAndOffset(const char *&pos, const c
         ++zoneEnd;
     }
 
-    result.first = QString::fromUtf8(nameBegin, nameEnd - nameBegin);
-    if (zoneEnd > zoneBegin)
-        result.second = parsePosixOffset(zoneBegin, zoneEnd);
+    QString name = QString::fromUtf8(nameBegin, nameEnd - nameBegin);
+    const int offset = zoneEnd > zoneBegin ? parsePosixOffset(zoneBegin, zoneEnd) : InvalidOffset;
     pos = zoneEnd;
-    return result;
+    return {std::move(name), offset};
 }
 
 static QVector<QTimeZonePrivate::Data> calculatePosixTransitions(const QByteArray &posixRule,
@@ -517,19 +534,19 @@ static QVector<QTimeZonePrivate::Data> calculatePosixTransitions(const QByteArra
     // See the section about TZ at http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html
     QList<QByteArray> parts = posixRule.split(',');
 
-    QPair<QString, int> stdZone, dstZone;
+    PosixZone stdZone, dstZone;
     {
         const QByteArray &zoneinfo = parts.at(0);
         const char *begin = zoneinfo.constBegin();
 
-        stdZone = parsePosixZoneNameAndOffset(begin, zoneinfo.constEnd());
-        if (stdZone.second == INT_MIN) {
-            stdZone.second = 0;     // reset to UTC if we failed to parse
+        stdZone = PosixZone::parse(begin, zoneinfo.constEnd());
+        if (!stdZone.hasValidOffset()) {
+            stdZone.offset = 0;     // reset to UTC if we failed to parse
         } else if (begin < zoneinfo.constEnd()) {
-            dstZone = parsePosixZoneNameAndOffset(begin, zoneinfo.constEnd());
-            if (dstZone.second == INT_MIN) {
+            dstZone = PosixZone::parse(begin, zoneinfo.constEnd());
+            if (!dstZone.hasValidOffset()) {
                 // if the dst offset isn't provided, it is 1 hour ahead of the standard offset
-                dstZone.second = stdZone.second + (60 * 60);
+                dstZone.offset = stdZone.offset + (60 * 60);
             }
         }
     }
@@ -538,10 +555,10 @@ static QVector<QTimeZonePrivate::Data> calculatePosixTransitions(const QByteArra
     if (parts.count() == 1) {
         QTimeZonePrivate::Data data;
         data.atMSecsSinceEpoch = lastTranMSecs;
-        data.offsetFromUtc = stdZone.second;
-        data.standardTimeOffset = stdZone.second;
+        data.offsetFromUtc = stdZone.offset;
+        data.standardTimeOffset = stdZone.offset;
         data.daylightTimeOffset = 0;
-        data.abbreviation = stdZone.first;
+        data.abbreviation = stdZone.name;
         result << data;
         return result;
     }
@@ -568,18 +585,18 @@ static QVector<QTimeZonePrivate::Data> calculatePosixTransitions(const QByteArra
     for (int year = startYear; year <= endYear; ++year) {
         QTimeZonePrivate::Data dstData;
         QDateTime dst(calculatePosixDate(dstDateRule, year), dstTime, Qt::UTC);
-        dstData.atMSecsSinceEpoch = dst.toMSecsSinceEpoch() - (stdZone.second * 1000);
-        dstData.offsetFromUtc = dstZone.second;
-        dstData.standardTimeOffset = stdZone.second;
-        dstData.daylightTimeOffset = dstZone.second - stdZone.second;
-        dstData.abbreviation = dstZone.first;
+        dstData.atMSecsSinceEpoch = dst.toMSecsSinceEpoch() - (stdZone.offset * 1000);
+        dstData.offsetFromUtc = dstZone.offset;
+        dstData.standardTimeOffset = stdZone.offset;
+        dstData.daylightTimeOffset = dstZone.offset - stdZone.offset;
+        dstData.abbreviation = dstZone.name;
         QTimeZonePrivate::Data stdData;
         QDateTime std(calculatePosixDate(stdDateRule, year), stdTime, Qt::UTC);
-        stdData.atMSecsSinceEpoch = std.toMSecsSinceEpoch() - (dstZone.second * 1000);
-        stdData.offsetFromUtc = stdZone.second;
-        stdData.standardTimeOffset = stdZone.second;
+        stdData.atMSecsSinceEpoch = std.toMSecsSinceEpoch() - (dstZone.offset * 1000);
+        stdData.offsetFromUtc = stdZone.offset;
+        stdData.standardTimeOffset = stdZone.offset;
         stdData.daylightTimeOffset = 0;
-        stdData.abbreviation = stdZone.first;
+        stdData.abbreviation = stdZone.name;
         // Part of the high year will overflow
         if (year == 292278994 && (dstData.atMSecsSinceEpoch < 0 || stdData.atMSecsSinceEpoch < 0)) {
             if (dstData.atMSecsSinceEpoch > 0) {