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Re: Empy String and "\0" actual lenght
Alessio Mazzanti / List
20 Mar 2009 7:10AM ET 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.
Re: Empy String and "\0" actual lenght
Alessio Mazzanti / List 20 Mar 2009 7:10AM ET
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