[This message was posted by Rolf Andersson of Pantor Engineering <[EMAIL PROTECTED]> to the "FAST Protocol" discussion forum at http://fixprotocol.org/discuss/46. You can reply to it on-line at http://fixprotocol.org/discuss/read/7c6169ad - PLEASE DO NOT REPLY BY MAIL.]
sorry, I was a bit too quick posting ... why shouldn't map combine with other operators? /Rolf > using the pbit to distinguish between definition and reference has > the following effects: > > 1. multiple pmap bits must be used to apply other operators > 2. one pbit is used for each occurrence of a map field > 3. the wire representation of definitions will be one byte shorter > > More than one pbit may be used by decimal fields. > > The effect of 2 and 3 is that the one byte in 3 gets amortized over > 8 reference occurrences of the field. Less than 8 references per > definitions results in pmap being more compact, more than 8 > references means leading zero byte results in definition being more > compact. > > (Nullability can be expressed for the by using a nullable > representation for the first byte of both reference and definition) > > /Rolf > >> My vote is for the following implementation >> >> 1. Map should not be able to combine with other operators >> 2. The presence bit should indicate reference or definition >> 3. Nullable fields should be encoded as a 0 presence bit and a zero >> reference >> >> Example: >> >> 4. Defining a new value: >> >> PBIT: 1 ENCODING: 0x81 0x49 0x42 0xCD >> >> Store the value "IBM" into cache index 1. Set field value to "IBM" >> >> 5. Referencing a value: >> >> PBIT: 0 ENCODING: 0x81 >> >> Set field value to cached value "IBM" >> >> 6. Sending a null value: >> >> PBIT: 0 ENCODING: 0x80 >> >> Set field value to null [You can unsubscribe from this discussion group by sending a message to mailto:[EMAIL PROTECTED] --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Financial Information eXchange" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/FIX-Protocol?hl=en -~----------~----~----~----~------~----~------~--~---
