%% -*- erlang-indent-level: 2 -*-
%%==========================================================================
%% From: Tomas Stejskal -- 23/02/2008
%% I've found some strange behavior regarding binary matching. The module's
%% purpose is reading an id3 version 1 or version 1.1 tag from an mp3 bin.
%% When I use the function read_v1_or_v11_tag on a mp3 binary containing
%% version 1 tag, it returns an error. However, when the function
%% read_only_v1_tag is applied on the same file, it reads the tag data
%% correctly. The only difference between these two functions is that the
%% former has an extra branch to read version 1.1 tag.
%% This was a BEAM compiler bug which was fixed by a patch to beam_dead.
%%==========================================================================
-module(bs_id3).
-export([test/0]).
-define(BIN, <<84,65,71,68,117,154,105,232,107,121,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,68,97,110,105,101,108,32,76,97,110,
100,97,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,66,101,115,116,
32,79,102,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
50,48,48,48,50,48,48,48,32,45,32,66,101,115,116,32,79,102,
32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,12>>).
test() ->
R1 = parse_only_v1_tag(?BIN),
R2 = parse_v1_or_v11_tag(?BIN),
%% io:format("~p\n~p\n", [R1, R2]),
R1 = R2, % crash if not equal
ok.
parse_only_v1_tag(<<"TAG", Title:30/binary,
Artist:30/binary, Album:30/binary,
_Year:4/binary, _Comment:30/binary,
_Genre:8>>) ->
{ok,
{"ID3v1",
[{title, trim(Title)},
{artist, trim(Artist)},
{album, trim(Album)}]}};
parse_only_v1_tag(_) ->
error.
parse_v1_or_v11_tag(<<"TAG", Title:30/binary,
Artist:30/binary, Album:30/binary,
_Year:4/binary, _Comment:28/binary,
0:8, Track:8, _Genre:8>>) ->
{ok,
{"ID3v1.1",
[{track, Track}, {title, trim(Title)},
{artist, trim(Artist)}, {album, trim(Album)}]}};
parse_v1_or_v11_tag(<<"TAG", Title:30/binary,
Artist:30/binary, Album:30/binary,
_Year:4/binary, _Comment:30/binary,
_Genre:8>>) ->
{ok,
{"ID3v1",
[{title, trim(Title)},
{artist, trim(Artist)},
{album, trim(Album)}]}};
parse_v1_or_v11_tag(_) ->
error.
trim(Bin) ->
list_to_binary(trim_blanks(binary_to_list(Bin))).
trim_blanks(L) ->
lists:reverse(skip_blanks_and_zero(lists:reverse(L))).
skip_blanks_and_zero([$\s|T]) ->
skip_blanks_and_zero(T);
skip_blanks_and_zero([0|T]) ->
skip_blanks_and_zero(T);
skip_blanks_and_zero(L) ->
L.
