shout.erl

-module(shout).
-export([start/0]).
-import(lists, [map/2, reverse/1]).

-define(CHUNKSIZE, 24576).

start() ->
    spawn(fun() -> 
		  start_parallel_server(9000),
		  %% now go to sleep - otherwise the listening socket will be closed
		  lib_misc:sleep(infinity)
	  end).

start_parallel_server(Port) -> 
	%%{packet, 0}Erlang系统会把TCP数据原封不动直接传递给应用程序
    {ok, Listen} = gen_tcp:listen(Port, [binary, {packet, 0}, {reuseaddr, true}, {active, true}]),
    PidSongServer = spawn(fun() -> songs() end),
    spawn(fun() -> par_connect(Listen, PidSongServer) end).

par_connect(Listen, PidSongServer) ->
    {ok, Socket} = gen_tcp:accept(Listen),
    spawn(fun() -> par_connect(Listen, PidSongServer) end),
    inet:setopts(Socket, [{packet, 0}, binary, {nodelay, true}, {active, true}]),
    get_request(Socket, PidSongServer, []).

get_request(Socket, PidSongServer, L) ->
    receive
		{tcp, Socket, Bin} ->
		    L1 = L ++ binary_to_list(Bin),
		    %% split checks if the header is complete
		    case split(L1, []) of
				more ->
				    %% the header is incomplete we need more data
				    get_request(Socket, PidSongServer, L1);
				{Request, _Rest} ->
				    %% header is complete
				    got_request_from_client(Request, Socket, PidSongServer)
		    end;
		{tcp_closed, Socket} ->
		    void;
		_Any  ->
		    %% skip this
		    get_request(Socket, PidSongServer, L)
    end.
		      
split("\r\n\r\n" ++ T, L) -> {reverse(L), T};
split([H|T], L)           -> split(T, [H|L]);
split([], _)              -> more.
    
got_request_from_client(Request, Socket, PidSongServer) ->
    Cmds = string:tokens(Request, "\r\n"),
    Cmds1 = map(fun(I) -> string:tokens(I, " ") end, Cmds),
    is_request_for_stream(Cmds1),
    gen_tcp:send(Socket, [response()]),
    play_songs(Socket, PidSongServer, <<>>).

response() ->
    ["ICY 200 OK\r\n",
     "icy-notice1: <BR>This stream requires",
     "<a href=\"http://www.winamp.com/\">Winamp</a><BR>\r\n",
     "icy-notice2: Erlang Shoutcast server<BR>\r\n",
     "icy-name: Erlang mix\r\n",
     "icy-genre: Pop Top 40 Dance Rock\r\n",
     "icy-url: http://localhost:9000\r\n",
     "content-type: audio/mpeg\r\n",
     "icy-pub: 1\r\n",
     "icy-metaint: ", integer_to_list(?CHUNKSIZE), "\r\n",
     "icy-br: 96\r\n\r\n"]. 

play_songs(Socket, PidSongServer, SoFar) ->
    Song = rpc(PidSongServer, random_song),
    {File, PrintStr, Header} = unpack_song_descriptor(Song),
    case id3_tag_lengths:file(File) of
		error ->
		    play_songs(Socket, PidSongServer, SoFar);
		{Start, Stop} ->
		    io:format("Playing:~p~n", [PrintStr]),
		    {ok, S} = file:open(File, [read, binary, raw]), 
		    SoFar1 = send_file(S, {0, Header}, Start, Stop, Socket, SoFar),
		    file:close(S),
		    play_songs(Socket, PidSongServer, SoFar1)
    end.

send_file(S, Header, OffSet, Stop, Socket, SoFar) ->
    %% OffSet = first byte to play
    %% Stop   = The last byte we can play
    Need = ?CHUNKSIZE - size(SoFar),
    Last = OffSet + Need,
    if
		Last >= Stop ->
		    %% not enough data so read as much as possible and return
		    Max = Stop - OffSet,
		    {ok, Bin} = file:pread(S, OffSet, Max),
		    list_to_binary([SoFar, Bin]);
		true ->
		    {ok, Bin} = file:pread(S, OffSet, Need),
		    write_data(Socket, SoFar, Bin, Header),
		    send_file(S, bump(Header),
			      OffSet + Need,  Stop, Socket, <<>>)
    end.

write_data(Socket, B0, B1, Header) ->
    %% Check that we really have got a block of the right size
    %% this is a very useful check that our program logic is correct
    case size(B0) + size(B1) of	?CHUNKSIZE ->
	    case gen_tcp:send(Socket, [B0, B1, the_header(Header)]) of
			ok -> true;
			{error, closed} ->
			    %% this happens if the player terminates the connection
			    exit(playerClosed)
	    end;
	_Other ->
	    %% don't send the block - report an error
	    io:format("Block length Error: B0 = ~p b1=~p~n", [size(B0), size(B1)])
    end.

bump({K, H}) -> {K+1, H}.

the_header({K, H}) ->
    case K rem 5 of
		0 -> H;
		_ -> <<0>>
    end.

is_request_for_stream(_) -> true.

songs() ->
    {ok,[SongList]} = file:consult("mp3data.tmp"),
    lib_misc:random_seed(),
    songs_loop(SongList).

songs_loop(SongList) ->
    receive
		{From, random_song} ->
		    I = random:uniform(length(SongList)),
		    Song = lists:nth(I, SongList),
		    From ! {self(), Song},
		    songs_loop(SongList)
    end.

rpc(Pid, Q) ->
    Pid ! {self(), Q},
    receive
		{Pid, Reply} ->
		    Reply
    end.

unpack_song_descriptor({File, {_Tag,Info}}) ->
    PrintStr = list_to_binary(make_header1(Info)),
    L1 = ["StreamTitle='",PrintStr,
	  "';StreamUrl='http://localhost:9000';"],
    %% io:format("L1=~p~n",[L1]),
    Bin = list_to_binary(L1),
    Nblocks = ((size(Bin) - 1) div 16) + 1,
    NPad = Nblocks * 16 - size(Bin), 
    Extra = lists:duplicate(NPad, 0),
    Header = list_to_binary([Nblocks, Bin, Extra]),
    %% Header is the Shoutcast header
    {File, PrintStr, Header}.

make_header1([{track,_}|T]) -> 
    make_header1(T);    
make_header1([{Tag,X}|T]) ->
    [atom_to_list(Tag), ": ", X, " "|make_header1(T)];
make_header1([]) ->
    [].