Merge pull request drfloob#11 from arkdro/master

add api to check whether the dst is active

Author: drfloob

src/ezic.erl

@@ -5,6 +5,8 @@
 	 localtime/1
 	 , utc_to_local/2
 	 , local_to_utc/2
+	 , has_dst_utc/2
+	 , has_dst_local/2
 	]).
 
 
@@ -30,7 +32,11 @@ local_to_utc(LocalDatetime, TzName) ->
     local_to_utc_handleFlatzone(LocalDatetime, ezic_db:flatzone(NormalDatetime, TzName)).
 
 
+has_dst_utc(Datetime, TzName) ->
+    has_dst(Datetime, TzName, u).
 
+has_dst_local(Datetime, TzName) ->
+    has_dst(Datetime, TzName, w).
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 % PRIVATE
@@ -55,3 +61,12 @@ local_to_utc_handleFlatzone(LocalDatetime, #flatzone{offset=Offset, dstoffset=DS
     	, Offset, {0,0,0})
       , DSTOffset, {0,0,0}).
 
+has_dst(Datetime, TzName, Flag) ->
+    NormalDatetime = ezic_date:normalize(Datetime, Flag),
+    case ezic_db:flatzone(NormalDatetime, TzName) of
+        #flatzone{dstoffset={0,0,0}} ->
+            false;
+        #flatzone{dstoffset={_,_,_}} ->
+            true
+    end.
+

test/ezic_tests.erl

@@ -43,3 +43,30 @@ local_to_utc_funkyDST_test_() ->
      , ?_assertMatch({{1951,9,7},{17,0,0}}, ezic:local_to_utc({{1951,9,8},{2,0,0}}, "Asia/Tokyo")) %% DST off for the last time
      , ?_assertMatch({{1952,5,3},{17,0,0}}, ezic:local_to_utc({{1952,5,4},{2,0,0}}, "Asia/Tokyo")) %% ensure DST not in effect for 1952
     ].
+
+has_dst_local_test_() ->
+    [
+     ?_assertMatch(false, ezic:has_dst_local({{1998,3,1},{1,30,0}}, "Europe/Paris")),
+     ?_assertMatch(true, ezic:has_dst_local({{1998,9,30},{1,30,0}}, "Europe/Paris")),
+     ?_assertMatch(true, ezic:has_dst_local({{1998,8,30},{3,30,0}}, "America/Denver")),
+     ?_assertMatch(false, ezic:has_dst_local({{1998,10,30},{3,30,0}}, "America/Denver")),
+     %% weird date
+     ?_assertMatch(false, ezic:has_dst_local({{1998,2,31},{10,30,0}}, "Europe/Paris")),
+     %% invalid zone
+     ?_assertException(error, {case_clause, {error, no_zone}}, ezic:has_dst_local({{1998,10,20},{12,30,0}}, "non_existent")),
+     %% ambiguous zone
+     ?_assertException(error, {case_clause, {error, {ambiguous_zone, _}}}, ezic:has_dst_local({{1998,10,25},{1,30,0}}, "America/Denver"))
+    ].
+
+has_dst_utc_test_() ->
+    [
+     ?_assertMatch(false, ezic:has_dst_utc({{1998,3,28},{13,30,0}}, "Europe/Paris")),
+     ?_assertMatch(true, ezic:has_dst_utc({{1998,3,29},{1,30,0}}, "Europe/Paris")),
+     ?_assertMatch(true, ezic:has_dst_utc({{1998,10,25},{7,59,59}}, "America/Denver")),
+     ?_assertMatch(false, ezic:has_dst_utc({{1998,10,25},{8,0,0}}, "America/Denver")),
+     %% weird date
+     ?_assertMatch(false, ezic:has_dst_utc({{1998,2,31},{13,30,0}}, "Europe/Paris")),
+     %% invalid zone
+     ?_assertException(error, {case_clause, {error, no_zone}}, ezic:has_dst_utc({{1998,10,25},{1,30,0}}, "non_existent"))
+    ].
+