QTimeZone: make UTC offset range available for other code to reuse

When QDateTimeParser learns to parse zones, it'll need to know the
valid range of offsets.

Change-Id: I44cd88a140ebaf6a2b98b0f9a1be0cbc7a35bae4
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

3 files changed, 12 insertions, 5 deletions

diff --git a/src/corelib/tools/qtimezone.cpp b/src/corelib/tools/qtimezone.cpp
index ec2f7c4af6..0b331be503 100644
--- a/src/corelib/tools/qtimezone.cpp
+++ b/src/corelib/tools/qtimezone.cpp
@@ -338,12 +338,9 @@ QTimeZone::QTimeZone(const QByteArray &ianaId)
 */
 
 QTimeZone::QTimeZone(int offsetSeconds)
+    : d((offsetSeconds >= MinUtcOffsetSecs && offsetSeconds <= MaxUtcOffsetSecs)
+        ? new QUtcTimeZonePrivate(offsetSeconds) : nullptr)
 {
-    // offsetSeconds must fall between -14:00 and +14:00 hours
-    if (offsetSeconds >= -50400 && offsetSeconds <= 50400)
-        d = new QUtcTimeZonePrivate(offsetSeconds);
-    else
-        d = 0;
 }
 
 /*!
diff --git a/src/corelib/tools/qtimezone.h b/src/corelib/tools/qtimezone.h
index bd87139f5b..29d8a4dbe5 100644
--- a/src/corelib/tools/qtimezone.h
+++ b/src/corelib/tools/qtimezone.h
@@ -59,6 +59,14 @@ class QTimeZonePrivate;
 class Q_CORE_EXPORT QTimeZone
 {
 public:
+    // Sane UTC offsets range from -14 to +14 hours:
+    enum {
+        // No known zone > 12 hrs West of Greenwich (Baker Island, USA)
+        MinUtcOffsetSecs = -14 * 3600,
+        // No known zone > 14 hrs East of Greenwich (Kiritimati, Christmas Island, Kiribati)
+        MaxUtcOffsetSecs = +14 * 3600
+    };
+
     enum TimeType {
         StandardTime = 0,
         DaylightTime = 1,
diff --git a/src/corelib/tools/qtimezoneprivate.cpp b/src/corelib/tools/qtimezoneprivate.cpp
index 7b780ecf7d..e45dd48de0 100644
--- a/src/corelib/tools/qtimezoneprivate.cpp
+++ b/src/corelib/tools/qtimezoneprivate.cpp
@@ -258,6 +258,8 @@ QTimeZonePrivate::Data QTimeZonePrivate::dataForLocalTime(qint64 forLocalMSecs,
       brackets the correct time and at most one DST transition.
     */
     const qint64 sixteenHoursInMSecs(16 * 3600 * 1000);
+    Q_STATIC_ASSERT(-sixteenHoursInMSecs / 1000 < QTimeZone::MinUtcOffsetSecs
+                  && sixteenHoursInMSecs / 1000 > QTimeZone::MaxUtcOffsetSecs);
     /*
       Offsets are Local - UTC, positive to the east of Greenwich, negative to
       the west; DST offset always exceeds standard offset, when DST applies.