Use gproc to simplify some code

torrent_client/README.txt

@@ -6,16 +6,17 @@ This directory holds a simple torrent client in Erlang.
 
 In building this, the major challenge is to keep the project under 500
 lines, since we're building it almost from first principles.  Right
-now it is ~750 lines (of which ~150 are blank or comments); I'll
+now it is ~690 lines (of which ~140 are blank or comments); I'll
 rework the code and the requirements to fit.
 
 The easiest way to get Erlang, is to download it from www.erlang-solutions.org.
 Don't use the Erlang distributed with Ubuntu.
 
 compile:
+  ./rebar get-deps
   ./rebar compile
 
 run:
-  erl -pa ebin
+  erl -pa ebin -pa deps/gproc/ebin
   1> torrent_file:download("../path/to.torrent")
 

torrent_client/rebar.config

@@ -0,0 +1,6 @@
+
+
+{deps, [
+%    {nat_upnp, ".*", {git, "git://github.com/benoitc/nat_upnp", {branch, "master"}}},
+    {gproc, ".*", {git, "git://github.com/uwiger/gproc", {branch, "master"}}}
+]}.

torrent_client/src/torrent_client.erl

@@ -14,14 +14,14 @@ start() ->
   application:start(torrent_client).
 
 start_link() ->
-  ok = application:ensure_started(inets),
-  ok = application:ensure_started(crypto),
+    ok = application:ensure_started(inets),
+    ok = application:ensure_started(crypto),
+    ok = application:ensure_started(gproc),
     proc_lib:start_link(?MODULE, init, [self()]).
 
 init(Caller) ->
     erlang:register(torrent_client, self()),
 
-    ets:new(torrent_owners, [public,named_table]),
     ets:new(torrent_stats,  [public,named_table]),
 
     Rand = crypto:rand_bytes(12),

torrent_client/src/torrent_file.erl

@@ -5,7 +5,7 @@
 
 -behavior(gen_server).
 -export([init/1,terminate/2,handle_call/3,handle_cast/2,handle_info/2]).
--export([download/1,downloaded/2,find/1,piece_offset/2,piece_sha/2,piece_length/2]).
+-export([download/1,downloaded/2,piece_offset/2,piece_sha/2,piece_length/2]).
 -export([verify_piece/3]).
 
 -record(state, { info       :: #info{},
@@ -21,26 +21,20 @@
 download(TorrentFile) ->
     ok = application:ensure_started(torrent_client),
     Info = read_torrent_file(TorrentFile),
-    case torrent_file:find(Info#info.info_hash) of
-        {ok, PID} ->
+    case gproc:lookup_pids({n,l,Info#info.info_hash}) of
+        [PID] ->
             {ok, PID};
-        false ->
+        [] ->
             gen_server:start_link(?MODULE, [Info], [])
     end.
 
-find(InfoHash) ->
-    case ets:lookup(torrent_owners, InfoHash) of
-        [{InfoHash,PID}] -> {ok, PID};
-        [] -> false
-    end.
-
 downloaded(PID, Index) ->
     gen_server:cast(PID, {downloaded, Index}).
 
 init([Info]) ->
     % erlang:process_flag(trap_exit, true),
+  gproc:add_local_name(Info#info.info_hash),
   Blocks = ets:new(torrent_blocks, [public,ordered_set]),
-  true = ets:insert(torrent_owners, {Info#info.info_hash, self()}),
   true = ets:insert(torrent_stats, {Info#info.info_hash, 0, 0}),
   {ok, State=#state{ missing=Missing }} = init_download_file(#state{ info=Info, blocks=Blocks }),
   case Missing of
@@ -49,7 +43,6 @@ init([Info]) ->
   end.
 
 terminate(_Reason, #state{ info=Info }) ->
-    ets:delete(torrent_owners, Info#info.info_hash),
     ok.
 
 handle_call(_Call,_,State) -> {stop, {error, unexpected_call, _Call}, State}.