Creating binary from list variables?

[Thomas Lindgren]

--- "Ericsson, Bjorn" <Bjorn.Ericsson@REDACTED>
wrote:

> How do I create a binary, to send with gen_tcp:send,
> from variables of
> different types and dynamic length, when I want the
> final binary to be of
> fixed length? (As it usually is defined in socket
> interfaces)

As far as I know, you have to pad what you send
yourself:

  %% Length is desired length, F filler byte
  Rem_length = Length-length(Lst),
  list_to_binary([Lst, lists:duplicate(Rem_length,
F)])

or something like that.
Sometimes you can exploit a special case:

   <<0:Rem_length/unsigned-integer-unit:8>>

creates a binary of Rem_length zeroes. 

Neither of these truncate a too long message, of
course. Here is one approach (if you don't care what
gets lost):

  trunc_binary(<<TruncBin:124/binary,_/binary>>) ->
     TruncBin;
  trunc_binary(Bin) -> Bin.

Best,
Thomas



		
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