Why the background loaded dictionaries are not public accessible in EMA

Reinhold.Blank

For building efficently applications access to the dictionary is important. E.g. creating fieldlist to reduce message. overhead. I think it is not usefull tho load required dictionaries twice and handle this by usercode.

andrzej.czop

Here are some general directions that the architects and developers of the EMA had in mind while developing the EMA.

A) In general, the dictionaries are accessed only during the decoding of field list, e.g. to expand FID# into type and meaning, plus some more like enums expansions, etc.

Though this is possible to access dictionaries during encoding of field list to verify correctness of the encoding (e.g. data type) this is mostly skipped due to: 1) performance overhead, 2) limited error detection possibility.

C) EMA hides the dictionary from the user's view to simplify the encoding and decoding of field list. Please refer to the RFA and UPA dev guides how much dictionary code is needed to handle decoding of field list. Of course, these approaches have their own advantages too.

D) the hiding of the dictionaries in the EMA makes the encoding and decoding of element list and field list identical.

Hope these general guidelines provide some light on the situation.

Feel free to provide more details about your case so we can provide a better answer for you.

Jirapongse

Yes, the loaded data dictionary is used internally in EMA. In EMA, you can create a fieldlist by using the following code.

try {
   FieldList fieldList;
   fieldList.info( 1, 1 )
      .addUInt( 1, 64 )
      .addReal( 6, 11, OmmReal::ExponentNeg2Enum )
      .addDate( 16, 1999, 11, 7 )
      .addTime( 18, 02, 03, 04, 005 )
      .complete();
} catch ( const OmmException & excp  ) {
   cout << excp << endl;
}

Reinhold.Blank

I use the EMA C++ edition

Reinhold.Blank

Hey,

for better understanding, i need the posibility to translate fieldnames into fieldids, for

1. Creating FieldID-List for view in MarketPrice-Request-Message.

2. Efficiently mapping of incoming messages in consumer, while decoding payload to application side databuffer. Excessively using of fieldlist.decoders-method "forth(EmaString&)" is insuffucient.

zoya faberov

To pull the "tangible" dictionary that you can use, please see the example 332 Dictionary_Streaming

Reinhold.Blank

That's it, what I don't want to do. In this case i can continue using of RFA with more comfort.

veerapath.rungruengrayubkul

Hi @Reinhold.Blank

The
New version of Elektron SDK - C++, 1.1.0, has been released. The package is available in this link. This
version implements features which allow you to get access to the
internal EMA dictionary via the thomsonreuters::ema::rdm::DataDictioanry
class.

To get internal EMA dictionary, application needs to request "RWFFld" and

"RWFEnum"
without service name and then create a new DataDictioanry instance with
dictionary response's payload. Please see the
"332__Dictionary__Streaming" example.

Application can also
extract a DataDictionary object used by FieldList when decoding it via
the DictionaryUtility::dataDictionary() static method.

Reinhold.Blank

Hi veerapath,

is was not there a longer time, so was really suprised that my request had got a positive responce.

Thanks!

Reinhold