luatz/tzfile: Add support for version 3 files (partial fix for Issue #2)

diff --git a/luatz/tzfile.lua b/luatz/tzfile.lua
index 36fd8a765a775e12a67715ec63cc8f6215a3fc41..a3fa7941171e5c5d188481a7aa6b7dd9fe7e9e72 100644 (file)
--- a/luatz/tzfile.lua
+++ b/luatz/tzfile.lua
@@ -97,7 +97,7 @@ local function read_tz ( fd )
 
                local TZ
 
-               if version == "2" then
+               if version == "2" or version == "3" then
                        --[[
                        For version-2-format timezone files, the above header and data is followed by a second header and data,
                        identical in format except that eight bytes are used for each transition time or leap-second time.
@@ -159,6 +159,17 @@ local function read_tz ( fd )
                        for use in handling instants after the last transition time stored in the file
                        (with nothing between the newlines if there is no POSIX representation for such instants).
                        ]]
+
+                       --[[
+                       For version-3-format time zone files, the POSIX-TZ-style string may
+                       use two minor extensions to the POSIX TZ format, as described in newtzset (3).
+                       First, the hours part of its transition times may be signed and range from
+                       -167 through 167 instead of the POSIX-required unsigned values
+                       from 0 through 24.  Second, DST is in effect all year if it starts
+                       January 1 at 00:00 and ends December 31 at 24:00 plus the difference
+                       between daylight saving and standard time.
+                       ]]
+
                        assert ( assert ( fd:read ( 1 ) ) == "\n" , "Expected newline at end of version 2 header" )
 
                        TZ = assert ( fd:read ( "*l" ) )