[erlang-questions] Validating binaries

[Roger Lipscombe]

On 11 August 2015 at 15:39, Roger Lipscombe <roger@REDACTED> wrote:
> Simple question: what's the most efficient way to validate that a
> binary value is of a certain length, and contains only certain
> characters?
>
> I've got the following:

[snip]

It might be worth pointing out that I only have to deal with the
following combinations: 16 lower-case hex characters or 24 upper-case
hex characters. ASCII encoding. So would something like the following
be better?

validate_lower_case_hex_16(<<C1:8, C2:8, ...)
  when
    (C1 >= $0, C1 =< $9; C1 >= $a, C1 =< $f),
    (C2 >= $0, C2 =< $9; C2 >= $a, C2 =< $f),
    ... % lots of repitition here
  ->
    Value;