Generic tools for the data header

[matthiasrichter]

• Generic methods to convert a string to a uint of variable size, basically it allows to change

String2uint64("DESCRIPTION") -> String2<uint64_t>("DESCRIPTION")

It goes through the same template code for all types.

• Generic implementation for N-byte descriptors, using it for the DataOrigin
• Adding also a type conversion operator for AliceO2::Header::Block to extract the first BaseHeader

[mkrzewic]

Hi Matthias, it looks good! I'm just wondering about the type conversion to BaseHeader, I think we should not expose BaseHeader directly, unless maybe in some internal implementation. MAybe a first step would be to generalize it a bit like this:

-  operator const BaseHeader*() const {return BaseHeader::get(buffer.get());}
+  template<typename T>
+  operator const T*() const {return get<T>(buffer.get());}

and then think if we can maybe hide the base class completely (at least in Header::Block API which is the public interface, some static_assert maybe), otherwise it becomes tempting to try to dynamic_cast stuff here...

[matthiasrichter]

Hi Mikolaj,good point.Its probably a good idea not to make base header that visible. I will have a second look.Ciao Matthias

[matthiasrichter]

I have removed the type cast operator for AliceO2::Header::Block. We will first think a bit longer about this matter. I did a forced push to my fork, the respective code has been removed from the updated commits.

The PR is ready for merge now.