[tz] zdump with version 1 files

[Brian Inglis]

On 2020-03-21 16:24, Paul Eggert wrote:
> On 3/21/20 2:08 PM, Brian Inglis wrote:
>> This appears to be the process doc:
>>     https://source.android.com/devices/tech/config/timezone-rules
>> and this appears to be the main code:
>> https://android.googlesource.com/platform/system/timezone/+/refs/heads/master/update-tzdata.py

> Thanks for the links. They talk about how TZif files are assembled together into
> a single tzdata file. However, as I vaguely recall the Android folks modified
> zic to generate 32-bit only TZif files. I don't offhand know whether that is
> still true, or how to verify whether it's true. Perhaps it was true long ago but
> became false when Android started supporting 64-bit CPUs; a bit of Googling
> suggests this occurred with Android 5.0 Lollipop (2014).

At linked code line 53:

https://android.googlesource.com/platform/system/timezone/+/refs/heads/master/update-tzdata.py#53

def GenerateZicInputFile(extracted_iana_data_dir):
  # Android APIs assume DST means "summer time" so we follow the rearguard format
  # introduced in 2018e.
  zic_input_file_name = 'rearguard.zi'

[now appears rearguard.zi is the only input]
  # 'NDATA=' is used to remove unnecessary rules files.
  subprocess.check_call(['make', '-C', extracted_iana_data_dir, 'NDATA=',
zic_input_file_name])

At linked code line 134:

https://android.googlesource.com/platform/system/timezone/+/refs/heads/master/update-tzdata.py#134

[everything is untarred to a zic build dir and make built]
  zic_build_dir = '%s/zic' % tmp_dir
  ExtractTarFile(iana_zic_code_tar_file, zic_build_dir)
  ExtractTarFile(iana_zic_data_tar_file, zic_build_dir)

  # zic
  print('Building zic...')
  # VERSION_DEPS= is to stop the build process looking for files that might not
  # be present across different versions.
  subprocess.check_call(['make', '-C', zic_build_dir, 'zic'])

  zic_binary_file = '%s/zic' % zic_build_dir
...
  print('Generating zic input file...')
  zic_input_file = GenerateZicInputFile(extracted_iana_data_dir)
  print('Calling zic...')
  zic_output_dir = '%s/data' % tmp_dir
  os.mkdir(zic_output_dir)
[everything is generated from rearguard]
  zic_cmd = [zic_binary_file, '-d', zic_output_dir, zic_input_file]

-- 
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

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