binaryDecode with variable number of parameters

Mark Wieder mwieder at ahsoftware.net
Sun Feb 19 19:43:53 EST 2012


Len-

Sunday, February 19, 2012, 4:08:24 PM, you wrote:

> Related to my problem with reading binary data from a socket, how do I
> handle a variable number of numbers that will come in with binaryDecode?

> To explain, I get a number in the packet header that tells me there are
> x number of bytes to follow in this packet.  I know the first byte is a
> remote ID and the second is a function code.  Based on the function 
> code, the number of two byte integers that follows is going to be (the
> number of bytes in the message / 2) - 1 (for the function code and 
> remote ID).  One time there might be 2 integers to follow, another there
> might be 10.  There is a "number of words" number that is part of the
> command so I know how many words there will be but the binaryDecode 
> function requires that I specify a name for each variable that is going
> to get a value.

> Ideally, I'd like to put all of these words in an array so I can process
> them, but this doesn't seem to be an option for the binaryDecode 
> command.  Should I build up a string that has 
> "...,var[0],var[1],...,var[x] in it to account for all the variables and
> then use a "do" or "dispatch" to actually do the binaryDecode?

> Also, if I use var[0], var[1], etc., do I need to create ALL of the 
> indexes first (for binaryDecode) or will just creating the first one
> (var[0]) be sufficient?

I think I'd do something like:

read from socket for 1 bytes
put it into tRemoteID
read from socket for 1 bytes
put it into tFunctionCode
switch tFunctionCode
  case kFunc1
    put 2 into tWordCount
    break
  case kFunc2
    put 10 into tWordCount
    break
  case -- ok - you get the idea
    break
end switch
read from socket for (2*tWordCount) bytes
put it into tData
put binaryDecode("m3", tData, tSeq, tProto, tBytes) into tActual
if tActual is not tWordCount then
  -- oops
end if

...and yes, you do need to have the maximum number of variables
already defined. There's no penalty for having extra compartments in
the binaryDecode line, but you don't want to have too few.

-- 
-Mark Wieder
 mwieder at ahsoftware.net





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