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FAST Protocol
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Re: Presence Map
Hei Chan / N/A
12 Jan 2010 4:30PM ET Thanks for the cheat sheet. It is very helpful ;-)
> Hi Hei,
>
> > I am trying to understand the presence map better.
>
> The presence map bits are only used for fields that might not be on the
> wire. The combination of field operator and presence attribute
> determines whether the bit is needed.
>
> As Rolf explained, in your example, a field with no operator is ALWAYS
> on the wire, so no presence map bit is needed. If the string field is
> optional, and not included in the message it is still encoded on the
> wire as a null string.
>
> Take a look at http://code.google.com/p/quickfast/wiki/FastFieldRules
>
> This, along with careful reading of the specification that you can find
> at http://www.fixprotocol.org/fast should give you the information you
> need to understand how the presence map bits are used by various
> combinations of operator and presence attributes.
>
> Dale
Re: Presence Map
Hei Chan / N/A 12 Jan 2010 4:30PM ET
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