[erlang-questions] Padding a binary to a multiple of 4 bytes
Mon Dec 22 03:47:51 CET 2008
On 21 Dec 2008, at 2:03 am, Camille Troillard wrote:
> Hi !
> I am new to Erlang, and would like to ask experienced users some
> advices on best practices I should adopt.
> Right now, I would like to know what is the best way of padding a
> binary to a multiple of 4 bytes.
> I have written a function like this:
> pad_to4 (Bin) ->
> case (size(Bin) rem 4) of
> 0 -> Bin;
> Pad -> <<Bin/binary, 0:((4-Pad)*8)>>
> I don't find it very elegant,
I don't either, because of the excess parentheses around
"size(Bin) rem 4", and because "Pad" is *not* the amount
of padding required, but the amount of padding NOT required.
Also, "to4" is rather ugly. Treat "4" as a word here.
case (4 - size(Binary) rem 4) rem 4
of 0 -> Binary
; N -> <<Binary/binary, 0:(N*8)>>
Tested, works, doesn't copy unless it has to.
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