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%% @author Bob Ippolito <bob@mochimedia.com>
%% @copyright 2006 Mochi Media, Inc.
%% @doc Utilities for working with hexadecimal strings.
-module(mochihex).
-author('bob@mochimedia.com').
-export([to_hex/1, to_bin/1, to_int/1, dehex/1, hexdigit/1]).
%% @spec to_hex(integer | iolist()) -> string()
%% @doc Convert an iolist to a hexadecimal string.
to_hex(0) ->
"0";
to_hex(I) when is_integer(I), I > 0 ->
to_hex_int(I, []);
to_hex(B) ->
to_hex(iolist_to_binary(B), []).
%% @spec to_bin(string()) -> binary()
%% @doc Convert a hexadecimal string to a binary.
to_bin(L) ->
to_bin(L, []).
%% @spec to_int(string()) -> integer()
%% @doc Convert a hexadecimal string to an integer.
to_int(L) ->
erlang:list_to_integer(L, 16).
%% @spec dehex(char()) -> integer()
%% @doc Convert a hex digit to its integer value.
dehex(C) when C >= $0, C =< $9 ->
C - $0;
dehex(C) when C >= $a, C =< $f ->
C - $a + 10;
dehex(C) when C >= $A, C =< $F ->
C - $A + 10.
%% @spec hexdigit(integer()) -> char()
%% @doc Convert an integer less than 16 to a hex digit.
hexdigit(C) when C >= 0, C =< 9 ->
C + $0;
hexdigit(C) when C =< 15 ->
C + $a - 10.
%% Internal API
to_hex(<<>>, Acc) ->
lists:reverse(Acc);
to_hex(<<C1:4, C2:4, Rest/binary>>, Acc) ->
to_hex(Rest, [hexdigit(C2), hexdigit(C1) | Acc]).
to_hex_int(0, Acc) ->
Acc;
to_hex_int(I, Acc) ->
to_hex_int(I bsr 4, [hexdigit(I band 15) | Acc]).
to_bin([], Acc) ->
iolist_to_binary(lists:reverse(Acc));
to_bin([C1, C2 | Rest], Acc) ->
to_bin(Rest, [(dehex(C1) bsl 4) bor dehex(C2) | Acc]).
%%
%% Tests
%%
-ifdef(TEST).
-include_lib("eunit/include/eunit.hrl").
to_hex_test() ->
"ff000ff1" = to_hex([255, 0, 15, 241]),
"ff000ff1" = to_hex(16#ff000ff1),
"0" = to_hex(16#0),
ok.
to_bin_test() ->
<<255, 0, 15, 241>> = to_bin("ff000ff1"),
<<255, 0, 10, 161>> = to_bin("Ff000aA1"),
ok.
to_int_test() ->
16#ff000ff1 = to_int("ff000ff1"),
16#ff000aa1 = to_int("FF000Aa1"),
16#0 = to_int("0"),
ok.
-endif.
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