[This message was posted by Alessio Mazzanti of List <[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/e4c679f5 - PLEASE DO NOT REPLY BY MAIL.]
Thank you very much David. I had just found that explaination in the handbook. -- Ale > The delta value for an *optional* string field will use a *nullable* > signed integer to convey the subtraction length. A non-negative nullable > integer is increased by one when encoding, and conversely decreased when > decoding. That operation is independent of the excess-1 coding used for > the subtraction length itself. > > /David > > > Many thanks for your prompt reply. For the best of my knowledge, > > positive subtraction lengths have not to be adjusted for the excess-1 > > encoding. So 1 is the value in the stream, without any manipulations. > > > > W.r.t. FAST specification, if I had received a subtraction length = > > -1, it would have been correct (because after excess-1 encoding > > I would have got subtraction length=0). > > > > So could the error be on the SWX stream (forgetting the minus)? > > > > > > P.S. In your opinion what's the lenght of the string "\0"? Is it 0 or > > is it 1? > > > > Thanks in advance. > > > > > > > > > How an empty string is represented within a particular > > > implementation is not specified by the FAST specification. However, > > > it should of course have the length 0. > > > > > > If the subtraction length is 1 and the base value is the empty > > > string, then this is indeed an error. > > > > > > When you get the subtraction length 1, is this after you've adjusted > > > it for the excess-1 coding used for nullable string deltas? > > > Otherwise that could explain the problem you're facing. > > > > > > /David > > > > > > > > > > Hi, I'm trying to decode the SWX FAST stream, and in particular an > > > > optional ASCII string attribute (named RandomisedInterval) with > > > > delta operator and no initial value (default base value 'Empty > > > > String' is used). Let suppose we have an undefined dictionary > > > > previous value (i.e. the 'Empty String' should be used as previous > > > > value) and we read from the stream an ASCII String Delta made by a > > > > Substraction Length = 1 followed by an ASCII String that in that > > > > case corresponds to the whole RandomisedInterval string > > > > "00:02:00". > > > > > > > > The problem I'm facing with is quite simple: since I consider the > > > > 'Empty String' (the default base value) as a string with lenght=0, > > > > a Substraction Length = 1 (meaning to remove 1 character from the > > > > back of base value) makes my application to report the error [ERR > > > > D7]. > > > > > > > > I would like to undertand if I'm making a mistake calculating the > > > > actual length of the 'Empty String' or if the right behaviour is > > > > actually to report the error. > > > > > > > > > > > > Furthermore, since I also consider the string "\0" as it had > > > > length=0, I think a similar problem could arise in any case I have > > > > a dictionary previous value = 'Empty String' or "\0". > > > > > > > > Many thanks in advance. [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 -~----------~----~----~----~------~----~------~--~---
