Re: [PROPOSAL 5.4] alternate way of format/pack/unpack (in the string library)

[tobias@...]

Quoting Sean Conner <sean@conman.org>:

>   I don't find the pack/unpack minilanguage all that bad, per se.  Lowercase
> letters are signed quantities, uppercase unsigned and there's some mneumonic
> meaning to the letters used.  But it can get silly (sample from an SMPP
> parser):
>
> 	result.service_type,
> 	result.source.addr_ton,
> 	result.source.addr_npi,
> 	result.source.addr,
> 	result.dest.addr_ton,
> 	result.dest.addr_npi,
> 	result.dest.addr,
> 	result.esm_class,
> 	result.protocol_id,
> 	result.prority,
> 	result.schedule_time,
> 	result.validity_period,
> 	result.registered_delivery,
> 	result.replace_if_present,
> 	result.data_coding,
> 	result.sm_default_msg_id,
> 	result.message =
> 	string.unpack(">z I1 I1 z I1 I1 z I1 I1 I1 z z I1 I1 I1 I1 s1",blob,13)
>
>   It was hard to debug, and the obvious solution:
>
> 	result.service_type,pos    = string.unpack(">z",blob,pos)
> 	result.source.addr_ton,pos = string.unpack(">I1",blob,pos)
> 	result.source.addr_npi,pos = string.unpack(">I1",blob,pos)
> 	--- and so on

This is exactly what I'm trying to solve with lua-t library Pack module.  It
doesn't support zero terminated strings yet but once it does your code could
look like:

snppParser = Pack(
   { service_type         = ">z" },
   { source               = Pack(
      { addr_ton                 = 'I1' },
      { addr_npi                 = 'I1' },
      { addr                     = 'z'  }
   ) },
   { dest                 = Pack(
      { addr_ton                 = 'I1' },
      { addr_npi                 = 'I1' },
      { addr                     = 'z'  }
   ) },
   { esm_class            = 'I1' },
   { protocol_id          = 'I1' },
   { prority              = 'I1' },
   { schedule_time        = 'z' },
   { validity_period      = 'z' },
   { registered_delivery  = 'I1' },
   { replace_if_present   = 'I1' },
   { data_coding          = 'I1' },
   { sm_default_msg_id    = 'I1' },
   { message              = 's1' }
)

result = snppParser( blob )

--access via
valA = result.service_type
valB = result.dest.addr
-- ...

https://github.com/tobbik/lua-t

  -tobbik