Fix ZoneInfo.useDaylightTime()

Currently implemented is "are there any offset transitions
in the future?".
This is wrong: Transitions may occur in the future because
of DST, but can also occur for other reasons (e.g. if the
raw offset for a zone changes).

We should be implementing: Is the currently active transition,
or any transition in the future, one that has
isDst == true.

This was causing a test failure in
libcore.java.util.TimeZoneTest#testDisplayNames
for Asia/Novokuznetsk and Europe/Simferopol for
tzdata2014g. This is because they have a transition entry
for October 26, 2014 (i.e. in the future).

For each, the existance of the transition entry is not
due to an offset change at all:
For Asia/Novokuznetsk it is because the abbreviation
for the zone changes on that date (information we don't
curently use).
For Europe/Simferopol it is because the offset from
UTC changes on that date (but there is no actual DST
transtion).

Bug: 17377276

(cherry-picked from commit d42af6ed0fec3cfca52912b0d8b3b459e72be4b4)

Change-Id: I148503280b8dee653bac32eec3aa58d232102628

1 files changed, 7 insertions, 8 deletions

diff --git a/luni/src/main/java/libcore/util/ZoneInfo.java b/luni/src/main/java/libcore/util/ZoneInfo.java
index fbd120b..4a70a83 100644
--- a/luni/src/main/java/libcore/util/ZoneInfo.java
+++ b/luni/src/main/java/libcore/util/ZoneInfo.java
@@ -156,22 +156,21 @@ public final class ZoneInfo extends TimeZone {
             mOffsets[i] -= mRawOffset;
         }
 
-        // Is this zone still observing DST?
+        // Is this zone observing DST currently or in the future?
         // We don't care if they've historically used it: most places have at least once.
-        // We want to know whether the last "schedule info" (the unix times in the mTransitions
-        // array) is in the future. If it is, DST is still relevant.
         // See http://code.google.com/p/android/issues/detail?id=877.
         // This test means that for somewhere like Morocco, which tried DST in 2009 but has
         // no future plans (and thus no future schedule info) will report "true" from
         // useDaylightTime at the start of 2009 but "false" at the end. This seems appropriate.
         boolean usesDst = false;
-        long currentUnixTime = System.currentTimeMillis() / 1000;
-        if (mTransitions.length > 0) {
-            // (We're really dealing with uint32_t values, so long is most convenient in Java.)
-            long latestScheduleTime = ((long) mTransitions[mTransitions.length - 1]) & 0xffffffff;
-            if (currentUnixTime < latestScheduleTime) {
+        int currentUnixTimeSeconds = (int) (System.currentTimeMillis() / 1000);
+        int i = mTransitions.length - 1;
+        while (i >= 0 && mTransitions[i] >= currentUnixTimeSeconds) {
+            if (mIsDsts[mTypes[i]] > 0) {
                 usesDst = true;
+                break;
             }
+            i--;
         }
         mUseDst = usesDst;