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FAST Protocol
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Re: swx MDI decoding issue
Rolf Andersson / Pantor Engineering
13 May 2009 12:25AM ET 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.
271 should indeed be 2 (exponent=0).
The FIX output would have been helpful earlier. Please provide a more complete description of your problem if you want any more help.
Good luck with your development.
/Rolf
> 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
Rolf Andersson / Pantor Engineering 13 May 2009 12:25AM ET
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