Erlang url encode with unicode/utf8 support working on binary instead of lists/strings

encode_uri_rfc3986_binary.erl

-module(encode_uri_rfc3986_binary).
-author('Renato Albano <renatoalbano@gmail.com>').
-author('JLarky <jlarky@gmail.com>').

-export([encode/1]).

%% Taken from <http://erlangexamples.com/>,
%% from <http://github.com/CapnKernul/httparadise>
%% and <http://www.erlang.org/doc/man/edoc_lib.html>

encode(Binary) when is_binary(Binary) ->
  escape(Binary).

escape(<<C, Cs/binary>>) when C >= $a, C =< $z ->
  <<C, (escape(Cs))/binary>>;
escape(<<C, Cs/binary>>) when C >= $A, C =< $Z ->
  <<C, (escape(Cs))/binary>>;
escape(<<C, Cs/binary>>) when C >= $0, C =< $9 ->
  <<C, (escape(Cs))/binary>>;

escape(<<C, Cs/binary>>) when C == 16#20 -> % space to +
  <<"+", (escape(Cs))/binary>>;

% unreserved
escape(<<C, Cs/binary>>) when C =:= $- ->
  <<C, (escape(Cs))/binary>>;
escape(<<C, Cs/binary>>) when C =:= $_ ->
  <<C, (escape(Cs))/binary>>;
escape(<<C, Cs/binary>>) when C =:= 46 -> % .
  <<C, (escape(Cs))/binary>>;
escape(<<C, Cs/binary>>) when C =:= $! ->
  <<C, (escape(Cs))/binary>>;
escape(<<C, Cs/binary>>) when C =:= $~ ->
  <<C, (escape(Cs))/binary>>;
escape(<<C, Cs/binary>>) when C =:= $* ->
  <<C, (escape(Cs))/binary>>;
escape(<<C, Cs/binary>>) when C =:= 39 -> % '
  <<C, (escape(Cs))/binary>>;
escape(<<C, Cs/binary>>) when C =:= $( ->
  <<C, (escape(Cs))/binary>>;
escape(<<C, Cs/binary>>) when C =:= $) ->
  <<C, (escape(Cs))/binary>>;

escape(<<C, Cs/binary>>) ->
  <<(escape_byte(C))/binary, (escape(Cs))/binary>>;

escape(<<>>) -> <<>>.

% from edoc_lib source
hex_octet(N) when N =< 9 ->
  $0 + N;
hex_octet(N) when N =< 15 ->
  $a + N - 10.

escape_byte(C) ->
  <<"%", (hex_octet(C bsr 4)), (hex_octet(C band 15))>>.