add a sample of FLUX code

These samples were taken from the paper "Flux: A Language for
Programming High-Performance Servers", by Burns et al and Flux V0.02
which can be found here:

https://plasma.cs.umass.edu/emery/flux.1.html

samples/FLUX/mbittorrent.fx

@@ -0,0 +1,151 @@
+typedef choke TestChoke;
+typedef unchoke TestUnchoke;
+typedef interested TestInterested;
+typedef uninterested TestUninterested;
+typedef request TestRequest;
+typedef cancel TestCancel;
+typedef piece TestPiece;
+typedef bitfield TestBitfield;
+typedef have TestHave;
+typedef piececomplete TestPieceComplete;
+
+CheckinWithTracker (torrent_data_t *tdata)
+    => ();
+
+SendRequestToTracker (torrent_data_t *tdata)
+    => (torrent_data_t *tdata, int socket);
+    
+GetTrackerResponse (torrent_data_t *tdata, int socket)
+    => ();
+
+UpdateChokeList (torrent_data_t *tdata)
+    => ();
+
+PickChoked (torrent_data_t *tdata)
+    => (torrent_data_t *tdata, chokelist_t clist);
+    
+SendChokeUnchoke (torrent_data_t *tdata, chokelist_t clist)
+    => ();
+    
+SetupConnection (torrent_data_t *tdata, int socket)
+    => ();
+    
+Handshake (torrent_data_t *tdata, int socket)
+    => (torrent_data_t *tdata, client_data_t *client);
+    
+SendBitfield (torrent_data_t *tdata, client_data_t *client)
+    => ();
+
+Message (torrent_data_t *tdata, client_data_t *client)
+    => ();
+    
+ReadMessage (torrent_data_t *tdata, client_data_t *client)
+    => (torrent_data_t *tdata, client_data_t *client, int type, int length, char *payload);
+    
+HandleMessage (torrent_data_t *tdata, client_data_t *client, int type, int length, char *payload)
+    => (client_data_t *client);
+    
+MessageDone (client_data_t *client)
+    => ();
+    
+CompletePiece (torrent_data_t *tdata, client_data_t *client, int piece)
+    => (torrent_data_t *tdata, client_data_t *client);
+
+VerifyPiece (torrent_data_t *tdata, client_data_t *client, int piece)
+    => (torrent_data_t *tdata, client_data_t *client, int piece);
+
+SendHave (torrent_data_t *tdata, client_data_t *client, int piece)
+    => (torrent_data_t *tdata, client_data_t *client);
+
+SendUninterested (torrent_data_t *tdata, client_data_t *client)
+    => (torrent_data_t *tdata, client_data_t *client);
+    
+Choke (torrent_data_t *tdata, client_data_t *client, int type, int length, char *payload)
+    => (client_data_t *client);
+    
+Cancel (torrent_data_t *tdata, client_data_t *client, int type, int length, char *payload)
+    => (client_data_t *client);
+
+Interested (torrent_data_t *tdata, client_data_t *client, int type, int length, char *payload)
+    => (client_data_t *client);
+
+Uninterested (torrent_data_t *tdata, client_data_t *client, int type, int length, char *payload)
+    => (client_data_t *client);
+
+Bitfield (torrent_data_t *tdata, client_data_t *client, int type, int length, char *payload)
+    => (client_data_t *client);
+
+Unchoke (torrent_data_t *tdata, client_data_t *client, int type, int length, char *payload)
+    => (torrent_data_t *tdata, client_data_t *client);
+
+SendRequest (torrent_data_t *tdata, client_data_t *client)
+    => (client_data_t *client);
+
+Have (torrent_data_t *tdata, client_data_t *client, int type, int length, char *payload)
+    => (torrent_data_t *tdata, client_data_t *client);
+
+Piece (torrent_data_t *tdata, client_data_t *client, int type, int length, char *payload)
+    => (torrent_data_t *tdata, client_data_t *client, int piece);
+
+Request (torrent_data_t *tdata, client_data_t *client, int type, int length, char *payload)
+    => (client_data_t *client);
+    
+SendKeepAlives (torrent_data_t *tdata)
+    => ();
+
+GetClients () 
+    => (int maxfd, fd_set *fds);
+
+SelectSockets (int maxfd, fd_set *fds)
+    => (fd_set *fds);
+
+CheckSockets (fd_set *fds)
+    => (torrent_data_t *tdata, client_data_t *client);
+
+TrackerTimer () 
+    => (torrent_data_t *tdata);
+
+ChokeTimer ()
+    => (torrent_data_t *tdata);
+
+Connect ()
+    => (torrent_data_t *tdata, int socket);
+
+KeepAliveTimer ()
+    => (torrent_data_t *tdata);
+
+Listen ()
+    => (torrent_data_t *tdata, client_data_t *client);
+
+source TrackerTimer => CheckinWithTracker;
+source ChokeTimer => UpdateChokeList;
+source Connect => SetupConnection;
+source Listen => Message;
+source KeepAliveTimer => SendKeepAlives;
+
+Listen = GetClients -> SelectSockets -> CheckSockets;
+CheckinWithTracker = SendRequestToTracker -> GetTrackerResponse;
+UpdateChokeList = PickChoked -> SendChokeUnchoke;
+SetupConnection = Handshake -> SendBitfield;
+Message = ReadMessage -> HandleMessage -> MessageDone;
+
+CompletePiece:[_, _, piececomplete] = VerifyPiece -> SendHave -> SendUninterested;
+
+HandleMessage:[_, _, choke, _, _] = Choke;
+HandleMessage:[_, _, unchoke, _, _] = Unchoke -> SendRequest;
+HandleMessage:[_, _, interested, _, _] = Interested;
+
+HandleMessage:[_, _, uninterested, _, _] = Uninterested;
+HandleMessage:[_, _, request, _, _] = Request;
+HandleMessage:[_, _, cancel, _, _] = Cancel;
+HandleMessage:[_, _, piece, _, _] = Piece -> CompletePiece -> SendRequest;
+HandleMessage:[_, _, bitfield, _, _] = Bitfield;
+HandleMessage:[_, _, have, _, _] = Have -> SendRequest;
+
+atomic GetClients:{BigLock};
+atomic CheckSockets:{BigLock};
+atomic Message:{BigLock};
+atomic CheckinWithTracker:{BigLock};
+atomic UpdateChokeList:{BigLock};
+atomic SetupConnection:{BigLock};
+atomic SendKeepAlives:{BigLock};