[14] RFR: 8212970: TZ database in "vanguard" format support

[Joe Wang]

Hi Naoto,

The method findNegativeSavings method in TzdbZoneRulesProvider.java 
states that it "Find the minimum negative savings". While the result is 
correct since the rules all have the same value for SAVE, I wonder if 
that's ideal conceptually. Given a start LDT, shouldn't it be looking 
for the SAVE in the exact (narrower) date range (e.g. 1981 - 1989 vs 
1981 - max)?.

NegativeDSTTest verifies the tzdata, that is the adjusted data after 
import, is that correct? I wonder a comment and a bit of details in the 
test summary would be helpful since there is no negative data in the 
test itself.

Best,
Joe

On 7/23/19 3:15 PM, naoto.sato at oracle.com wrote:
> Hi,
>
> Please review the fix to the following enhancement:
>
> https://bugs.openjdk.java.net/browse/JDK-8212970
>
> The proposed changeset is located at:
>
> https://cr.openjdk.java.net/~naoto/8212970/webrev.09/
>
> This change aims to support the "vanguard" IANA time zone data format, 
> which uses the negative savings and transition time beyond a day 
> period. The change basically translates those negative savings and 
> transition times, such as 25:00, into the ones that the current JDK 
> recognizes, then produces the data file "tzdb.dat" at the build time. 
> At the run time, the data file is read and interpreted as before. This 
> way the produced tzdb.dat is compatible with the prior JDK releases so 
> that the TZ Updater can also distribute it as a time zone update.
>
> I have also refactored redundant copy of ZoneRules file in the build 
> directory, by dynamically importing the file under src. Thus some 
> build related files are modified. I am hoping folks on the build-dev 
> can review those changes.
>
> Naoto