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FAST Protocol
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Re: Help with pmap
Shashank Bhatt / Faculties India
18 Feb 2010 11:33PM ETYou are welcome Deniel,
Anyway, I am also working on CME Group FAST Decoder, currently in CME FIX/FAST v2.0. Already old version of decoder is functioning in production enviornment for us.
Thanks & Regards
Shashank
> Hi Shashank, that's very helpful, thanks! Daniel
>
> > Hello Daniel,
> >
> > pmap will not have a fixed length of 1 or 2 bytes, it's length depends
> > on the number of fields in message that needs pmap bit to be present.
> > We need to determine from stop bit everytime.
> >
> > You can refer 1.1 spec doc: Section 10.5 Presence Map: "A presence map
> > is represented as a stop bit encoded entity. Logically a presence map
> > has an infinite suffix of zeroes. This makes it possible to truncate a
> > presence map that ends in a sequence where the bits are all zero. The
> > length of the remaining part must be a multiple of seven."
> >
> > Suppose, in one message, total 7 fields need pmap, then pmap length
> > will be one byte (1 stop bit and 7 pmap bit). e.g. 10011011 If in
> > second message, 10 fields need pmap, then pmap length will be 2 bytes.
> > e.g. 00011011 10010000 Now in third message, 21 fields need pmap, and
> > last 7 fields are having pmap bit as 0 (from encoder side), then PMAP
> > in wire will be 01100111 10011011. For last 7 fields, pmap bit will be
> > taken implicitly as 0 in decoder side.
> >
> > Regards Shashank
> >
> > > I'm trying to implement a FAST decoder for CME. I'm wondering if the
> > > pmap always has a fixed length of 1 or 2 byte or ｄｏ Ｉ need to
> > > determine from stop bit everytime？ thx!
Re: Help with pmap
Shashank Bhatt / Faculties India 18 Feb 2010 11:33PM ET
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