[tz] zic option to generate smaller output files?

Ken Murchison murch at fastmail.com
Wed Nov 22 21:41:56 UTC 2017

On 11/22/2017 01:49 PM, Paul Eggert wrote:
> On 11/22/2017 02:30 AM, Zefram wrote:
>> The binary tzfile usually provides a ruleset applicable to indefinitely
>> many years, in the form of a POSIX TZ string.  But that's not the 
>> current
>> rules, it's the rules to be applied when all of the file's explicit
>> transitions have run out.
> Changing the subject (and subject line)....
> Currently zic generates a bunch of explicit transitions at the end of 
> the time transition table, even if these transitions merely repeat 
> what a TZ string would generate. This is to support older clients that 
> grok only version-1 tzfile format, and which don't know about the TZ 
> string (which was introduced in version 2 tzfile format). Since 
> version 2 format was introduced in release 2006b, I'm thinking now may 
> be a good time to add an option to zic to suppress explicit 
> transitions at the end of the table if these transitions agree with 
> the TZ string. This will help uncover buggy client code that 
> mishandles TZ string values and therefore mishandles future 
> timestamps. By default this option will be off now (meaning no change 
> to the default behavior), but we could turn it on later.

This option makes sense to me.

Would it also be possible to have this option (or a separate one) create 
the first header and body (32-bit time values) with counts of zero?  All 
of the data that would appear in that body is duplicated in the second 
body anyways.

Kenneth Murchison
Cyrus Development Team
FastMail Pty Ltd

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