Re: protobuff for Ada

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On 2018-12-29 06:53, Shark8 wrote:

> Though, it should be noted that ASN.1 is *probably* the better technology in cases where ProtoBufs are being considered:
> http://ttsiodras.github.io/asn1.html

Sorry to disappoint you in this festive time, but this approach has the 
same fundamental flaw as prepared SQL statements do. You have to bind 
native Ada objects to protocol/serialized/persistent objects forth and 
back. This does not work well in practice. In fact, it barely work at 
all considering the overhead and hazards of type conversions.

A different approach is Ada's representation clauses which describe both 
objects same. Beyond simple textbook cases that does not work either.

The best practical method so far is using manually written stream 
attributes. Unfortunately it has shortcomings too:

1. Reuse is limited and composition is unsafe because stream attributes 
are non-primitive operations.

2. Introspection is almost non-existed. Only tagged types could have it.

3. No support of error handling and versioning. Though it is possible to 
do manually that is extremely error-prone and totally lacks static 
verification when the number of test cases is huge to potentially 
infinite. Even worse, the offending cases do not show up in a normally 
functioning system. So, when detected, it is always too late.

P.S. Needless to say, the problems 1-3 fully apply to other two methods 
as well.

P.P.S. And nothing was said about referential and recursive types...

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de