[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/3fe02e91 - PLEASE DO NOT REPLY BY MAIL.]
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 -~----------~----~----~----~------~----~------~--~---
