Common Format Buffer (CFB)

Introduction › Distributed Processing Concepts and Terminology › Data Representation › Common Format Buffer (CFB)

Common Format Buffer (CFB)

The Common Format Buffer (CFB) is an encoded byte stream that CA Gen uses to exchange view data during the processing of a cooperative flow. In addition to the import and export view, a CFB contains various pieces of control data that is used to process the cooperative flow.

The format and encoding rules of a CFB are proprietary. Therefore, the explicit details of how a CFB is structured are not discussed. However, here are some characteristics concerning the encoding of a CFB to provide a general sense of its structure and content.

Applications that target IMS using TCP/IP as the transport require the CFB to include the IMS Request Message (IRM) and a 4-byte trailer. CA Gen uses a 32-byte IRM; therefore, the maximum CFB size is reduced by 36 bytes.
Many data types are placed into a CFB in a compressed form.
Numeric data is encoded using a two's complement form with significant ending byte order.
Null or non-populated fields are encoded as being skipped.
The uncompressed strings are encoded as fixed-length strings or as null terminated.

The following table gives an overview of the CFB structure. The two types of areas within a CFB are the fixed portion and the relocatable portion. Some relocatable portions are optional depending on the type of CFB being constructed. An offset references the relocatable items and can appear anywhere in the buffer following the header.

Area	Type	Notes
CFB Header	Fixed	Structured data area containing control information primarily used by the runtimes involved in processing a cooperative flow.
User Action (UA)	relocatable	Structured data area containing data detailing the action performed by the user resulting in the cooperative flow.
Next Location	relocatable	Null terminated string containing Next Location system variable.
Model Name	relocatable	Null terminated string containing the model name.
Dialect	relocatable	A compressed string containing the dialect in effect on the client.
Exit States	relocatable	A compressed string containing a dialog flow exit state set by the DPC for use by the DPS.
View Data	relocatable encryptable	An encoded order set of fields containing the import or export view data being exchanged between the DPC and DPS.
Security	relocatable encryptable	Structured data area containing fields used for CA Gen Enhanced Security.