[tz] Looking for a way to cut down binary zoneinfo size. Does anyone have the way to?

[Paul.Koning at dell.com]

> On May 18, 2017, at 12:16 PM, Viktor Sergiienko <singalen at gmail.com> wrote:
> 
> Hello,
> 
> I'm developing for a pretty small-sized embedded system, and 2.9M of
> binaries is a bit too much for us.
> The system never uses a date before 2007.
> 
> I estimate I can slim it down too 500K by cutting down the old data.
> 
> 1. I made a script to cut down the source data: all the rules and all
> the zonelines before 2001.
> Compiling this data, I get a lot of errors like:
> 
>> "northamerica", line 2537: %s in ruleless zone
>> "northamerica", line 2618: unruly zone
> 
> because some zones are left without rules, but with %s format in them.
> 
> 2. I tried to modify zic itself, but apparently understanding it will
> take me days.
> Just setting min_year to 2001 results in bunch of
> 
>> can't determine time zone abbreviation to use just after until time
> 
> Does anyone have a ready solution?

Not completely ready, but...  I had the same need some time ago.  I made a small change to zic to add a switch that says "omit data from before Y" (with in our case, Y=2001).  That produces files that are much shorter, but also a lot of duplicates -- because often two zones differ only in early rules.  So I create hardlinks for any duplicate files.  The result is about 100kB of actual data.

I don't remember if I tried it at the source level, as you did.  I think that's a bit messy for cases where the most recent rule is from before your cutoff.  The change in zic was pretty easy.

	paul