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FAST Protocol
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Re: FAST Extension proposal - MAP
Rolf Andersson / Pantor Engineering
29 Sep 2008 12:50PM ETsorry, I was a bit too quick posting ...
why shouldn't map combine with other operators?
/Rolf
> using the pbit to distinguish between definition and reference has
> the following effects:
>
> 1. multiple pmap bits must be used to apply other operators
> 2. one pbit is used for each occurrence of a map field
> 3. the wire representation of definitions will be one byte shorter
>
> More than one pbit may be used by decimal fields.
>
> The effect of 2 and 3 is that the one byte in 3 gets amortized over
> 8 reference occurrences of the field. Less than 8 references per
> definitions results in pmap being more compact, more than 8
> references means leading zero byte results in definition being more
> compact.
>
> (Nullability can be expressed for the by using a nullable
> representation for the first byte of both reference and definition)
>
> /Rolf
>
>> My vote is for the following implementation
>>
>> 1. Map should not be able to combine with other operators
>> 2. The presence bit should indicate reference or definition
>> 3. Nullable fields should be encoded as a 0 presence bit and a zero
>> reference
>>
>> Example:
>>
>> 4. Defining a new value:
>>
>> PBIT: 1 ENCODING: 0x81 0x49 0x42 0xCD
>>
>> Store the value "IBM" into cache index 1. Set field value to "IBM"
>>
>> 5. Referencing a value:
>>
>> PBIT: 0 ENCODING: 0x81
>>
>> Set field value to cached value "IBM"
>>
>> 6. Sending a null value:
>>
>> PBIT: 0 ENCODING: 0x80
>>
>> Set field value to null
Re: FAST Extension proposal - MAP
Rolf Andersson / Pantor Engineering 29 Sep 2008 12:50PM ET
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