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FAST Protocol
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Re: swx MDI decoding issue
Michael Wong / Chi-X Global Technology
12 May 2009 9:59PM ET Rolf,
First, since the length field has an operator, does it occupy the first bit of sequence PMAP? if so, I would like to know why pmap bit 5 is for 271.
For 271, exponent=0(not -2) (copy not default) mantissa=2 => 2*10^0 = 2
the operator of exponent is copy. In this situation, PMAP bit is 0, use the initial value, so exp. = 0, right? If the value is not present in the stream and the state is undefined, then use the intial value. If the value is present and is null value, the field is absent if it is optional i.e. do not use the initial value. Am I right?
BTW, this is the output for the first msg provided by swx
8=FIXT.1.135=X1128=749=SWXGROUP-MDI.M0156=SWXGROUP-MDC34=1057697=N52=20080623-03:55:01.7991021=1268=1279=0269=048=CH000367144022=4271=2273=03:45:00.003336=ABQ5346=16566=083=1
Michael
> Michael,
>
> your decoding up to 270 looks alright if I have understood the context
> correctly.
>
> For 271 (field 5 in the sequence), pmap bit 5 is 0 so the wire
> representation 0x82 corresponds to: exponent=-2 (default) mantissa=2
> => 2*10^-2?
>
> 270=NULL followed by 271=2*10^-2 don't make much sense though?
>
> I suggest you contact SWX for assistance on this. Let us know
> what they say.
>
> Best, Rolf
>
> > Rolf,
> >
> > The previous message can be decoded successfully after you told me the
> > sequence field PMAP. However, I have another messege that I fail to
> > decode it
> >
> > msg (block size field is omitted):
> >
> > F7 01 C8 53 57 58 47 52 4F 55 50 2D 4D 44 49 2E 4D 30 B1 52 D0 32 30
> > 30 38 30 36 32 33 2D 30 33 3A 35 35 3A 30 31 2E 37 39 B9 81 81 1B B0
> > 43 48 30 30 30 33 36 37 31 34 34 B0 80 82 30 33 3A 34 35 3A 30 30 2E
> > 30 30 B3 41 42 51 B5 81 FF 80 80 40 B0 02 AC 32 30 30 38 30 36 32 33
> > 2D 30 33 3A 34 35 3A 30 30 2E 30 30 B3 82 C5 01 C8 38 30 B0 82 14 88
> > 39 37 37 31 39 B3 82 80 81 81 81 A0 B1 FF 81 81 C0 02 AC C1 01 C8 81
> > 34 88 B0 36 32 32 37 36 31 B2 81 98 81 81 81 C0 02 AC C0 01 C8 14 88
> > 37 31 38 36 39 38 B1 82 E8 81 81 81 C0 02 AC C5 01 C8 B1 82 18 88 31
> > 30 35 37 30 37 35 B9 81 03 CB AF 81 81 81 A0 B1 A0 A5 81 81 81 81 18
> > 88 4C 49 30 30 31 30 37 33 37 32 31 B6 82 7C B0 C4 81 81 81 85 B4 82
> > 38 88 B0 43 48 30 30 30 39 36 39 31 36 30 B8 80 EB 84 81 81 A4 B1 81
> > FF FD 81 C0 02 AC C0 01 C8 3C 88 B0 31 31 31 37 38 32 35 B5 81 00 F7
> > 82 00 C8 81 81 81 A0 B1 8D 01 B4 81 81 81 81 3C 88 B0 36 39 33 36 30
> > B0 82 7E FB 81 7E 82 81 81 81 80 18 88 34 38 34 30 36 B7 80 81 81 81
> > 81 C0 02 AC C0 01 C8 14 88 32 33 33 37 34 32 B1 83 FF 81 81 81 C0 02
> > AC C0 01 C8 3C 88 B1 35 35 34 B0 81 93 82 00 FC 81 81 81 80 3C 88 B0
> > 35 38 33 34 30 B4 80 84 7F BB 82 81 81 C0 02 AC C0 01 C8 1C 88 32 37
> > 31 36 38 B7 82 FC 83 CA FF
> >
> > PMAP = F7 (1 1110111) TID = 01 C8 49 = 53 57 58 47 52 4F 55 50 2D 4D
> > 44 49 2E 4D 30 B1 34 = 52 D0 52 = 32 30 30 38 30 36 32 33 2D 30 33 3A
> > 35 35 3A 30 31 2E 37 39 B9 1021 = 81 268 = 81 Seq PMAP = 1B B0
> > (0011011 1 0110000) 48 = 43 48 30 30 30 33 36 37 31 34 34 B0 270 = 80
> > 271 = 82 ?
> >
> > I don't know how to proceed after tag 270. Template
> > http://www.2shared.com/file/5736462/b9436b42/template1.html
> >
> > Thanks Michael
> > > Michael,
> > >
> > > the length field occupies a bit in the message pmap if there is an
> > > operator specified for the length field of the sequence.
> > >
> > > I don't have the FAST spec in front of me but IIRC section 6.2.5
> > > contains info about sequences.
> > >
> > > I can check more closely if you send me the template you are using.
> > >
> > > /Rolf
> > >
> > > > Rolf,
> > > >
> > > > I want to know if the first bit of PMAP for sequence field
> > > > indicate the presence of length field or not. Is there related
> > > > information in the spec?
> > > >
> > > > Thanks Michael
Re: swx MDI decoding issue
Michael Wong / Chi-X Global Technology 12 May 2009 9:59PM ET
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