gistfile1.hrl

% copied from Mochiweb's mochiweb_uitl.erl
-module(url_encoder).
-export([encode/1]).

-define(PERCENT, 37).  % $\%
-define(FULLSTOP, 46). % $\.
-define(IS_HEX(C), ((C >= $0 andalso C =< $9) orelse
                    (C >= $a andalso C =< $f) orelse
                    (C >= $A andalso C =< $F))).
-define(QS_SAFE(C), ((C >= $a andalso C =< $z) orelse
                     (C >= $A andalso C =< $Z) orelse
                     (C >= $0 andalso C =< $9) orelse
                     (C =:= ?FULLSTOP orelse C =:= $- orelse C =:= $~ orelse
                      C =:= $_))).

encode(S) -> quote_plus(S).

%% @spec quote_plus(atom() | integer() | float() | string() | binary()) -> string()
%% @doc URL safe encoding of the given term.
quote_plus(Atom) when is_atom(Atom) ->
    quote_plus(atom_to_list(Atom));
quote_plus(Int) when is_integer(Int) ->
    quote_plus(integer_to_list(Int));
quote_plus(Binary) when is_binary(Binary) ->
    quote_plus(binary_to_list(Binary));
quote_plus(Float) when is_float(Float) ->
    quote_plus(mochinum:digits(Float));
quote_plus(String) ->
    quote_plus(String, []).

quote_plus([], Acc) ->
    lists:reverse(Acc);
quote_plus([C | Rest], Acc) when ?QS_SAFE(C) ->
    quote_plus(Rest, [C | Acc]);
quote_plus([$\s | Rest], Acc) ->
    quote_plus(Rest, [$+ | Acc]);
quote_plus([C | Rest], Acc) ->
    <<Hi:4, Lo:4>> = <<C>>,
    quote_plus(Rest, [hexdigit(Lo), hexdigit(Hi), ?PERCENT | Acc]).

hexdigit(C) when C < 10 -> $0 + C;
hexdigit(C) when C < 16 -> $A + (C - 10).