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Re: swx MDI decoding issue
Michael Wong / Chi-X Global Technology
14 May 2009 2:11AM ET Rolf,
Let's say there is a field is optional. operator is tail. field type is string and no initial value.
Then when I recevie 0x80 which means is null value, how to proceed?
Here is another case. There is a field is optional and the operator is constant. If the pmap bit is set, should the value appear in the stream or just use the default value?
BTW Can I say that the initial value is used if the field is absent no matter what operator is?
Michael
> that depends on the field definition. type? operators? inital value?
>
> please be more specific
>
> /Rolf
>
> > Rolf,
> >
> > Oh I made a mistake that I think mantissa is optional. so the value is
> > decreased by 1.
> >
> > I want to know how to handle if a field is absent.
> >
> > Michael
> >
> > > > Rolf,
> > > >
> > > > I am sorry I got confused again. For tag 271, the pmap bit is 0.
> > > > so the default value 0 is used for exponent. Can we say that the
> > > > exponent has a value so that we need to decode mantissa? If so,
> > > > the encoded value is 0x82 for the mantissa. The decoded value
> > > > should be 1 since it is delta operator, Right?
> > >
> > > Yes, 0x82 is for the mantissa. No, the decoded mantissa value is 2.
> > > Why do you think the value should be 1?
> > >
> > > > BTW, if the length field of a sequence field is greater than 1,
> > > > does the sequence pmap appear each iteration?
> > >
> > > yes, as noted in my mail below
> > >
> > > (FAST 1.1 spec section 6.2.5 says: "If any instruction of the group
> > > needs to allocate a bit in a presence map, each element is
> > > represented as a segment in the transfer encoding." "element" in
> > > this context is synonymous with my use of "iteration" in my mail
> > > below)
> > >
> > > /Rolf
> > >
> > > ... snip ...
> > >
> > > >> Michael,
> > > >>
> > > >> The pmap entry for the length field is located in the _message_
> > > >> level pmap (bit 7 in this case). The sequence level pmap occurs
> > > >> for every iteration (repetition) of the sequence and provides
> > > >> presence info for the fields in the current iteration.
Re: swx MDI decoding issue
Michael Wong / Chi-X Global Technology 14 May 2009 2:11AM ET
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