Grouping unused gen_server callbacks.

[cellular-automata.git] / 001 / src / life_cell.erl

diff --git a/001/src/life_cell.erl b/001/src/life_cell.erl
index 4771064..9f7b171 100644 (file)
--- a/001/src/life_cell.erl
+++ b/001/src/life_cell.erl
@@ -23,6 +23,7 @@
                ,num_neighbors   :: integer()
                ,replies_pending :: integer()
                ,gen_id          :: integer()
+               ,early_msgs      :: list()
                }).
 
 
@@ -37,6 +38,16 @@ start_link({_, Name, _}=Datum) ->
     gen_server:start_link(ServerName, ?MODULE, Args, Opts).
 
 
+%% ============================================================================
+%% Callbacks (unused)
+%% ============================================================================
+
+handle_call(_Msg, _From, State)  -> {reply, ok, State}.
+handle_info(_Msg, State)         -> {noreply, State}.
+code_change(_Old, State, _Other) -> {ok, State}.
+terminate(_Reason, State)        -> {ok, State}.
+
+
 %% ============================================================================
 %% Callbacks
 %% ============================================================================
@@ -49,53 +60,50 @@ init([{CellID, Name, NeighborNames}]) ->
                   ,num_neighbors   = length(NeighborNames)
                   ,live_neighbors  = 0
                   ,replies_pending = 0
+                  ,early_msgs      = []
                   },
     {ok, State}.
 
 
-terminate(_Reason, State) ->
-    {ok, State}.
-
-
-code_change(_Old, State, _Other) ->
-    {ok, State}.
-
-
-handle_call(_Msg, _From, State) ->
-    {reply, ok, State}.
-
-
 handle_cast({next_gen, GenID},
     #state{name=Name
+          ,cell_state=CellState
           ,neighbors=Neighbors
           ,num_neighbors=NumNeighbors
+          ,early_msgs=EarlyMsgs
           }=State) ->
 
-    ok = cast_all(Neighbors, {request_state, GenID, Name}),
-    {noreply, State#state{replies_pending=NumNeighbors, gen_id=GenID}};
+    ok = cast_one2all(Neighbors, {state_broadcast, GenID, CellState}),
+
+    % Put stashed messages back in the mailbox,
+    % now that we're ready to handle them
+    ok = cast_all2one(Name, EarlyMsgs),
 
-%% If we receive this before we receive next_gen, throw it back in the queue.
-%% (Took me a while to realize this, but sometimes it is possible. The more
-%% there're cells, the more likely this is to happen.)
-handle_cast({request_state, GenID, _Requester}=Msg,
-    #state{gen_id=MyGenID
-          ,name=Name
-          }=State) when GenID =/= MyGenID->
+    NewState = State#state{replies_pending=NumNeighbors
+                          ,gen_id=GenID
+                          ,early_msgs=[]
+                          },
 
-    gen_server:cast(Name, Msg),
-    {noreply, State};
+    {noreply, NewState};
 
-%% Now that we can be sure that this request is for the current generation, we
-%% can handle it
-handle_cast({request_state, GenID, Requester},
-    #state{gen_id=MyGenID
-          ,cell_state=CellState
-          }=State) when GenID =:= MyGenID->
 
-    ok = gen_server:cast(Requester, {response_state, MyGenID, CellState}),
-    {noreply, State};
+%% If we receive 'state_broadcast' before we receive 'next_gen',
+%% stash it until we do.
+%%
+%% Took me a while to realize this, but sometimes it is possible. The more
+%% there're cells, the more likely this is to happen.
+%%
+handle_cast({state_broadcast, ReceivedGenID, _NeighborState}=Msg,
+    #state{gen_id=GenID
+          ,early_msgs=EarlyMsgs
+          }=State) when GenID =/= ReceivedGenID ->
 
-handle_cast({response_state, GenID, NeighborState},
+    {noreply, State#state{early_msgs=[Msg|EarlyMsgs]}};
+
+
+%% Now that we can be sure that this request is for the current generation, we
+%% can handle it
+handle_cast({state_broadcast, GenID, NeighborState},
     #state{cell_id=CellID
           ,gen_id=GenID
           ,replies_pending=Pending
@@ -124,11 +132,8 @@ handle_cast({response_state, GenID, NeighborState},
             {noreply, NewState}
     end;
 
-handle_cast(_Msg, State) ->
-    {noreply, State}.
 
-
-handle_info(_Msg, State) ->
+handle_cast(_Msg, State) ->
     {noreply, State}.
 
 
@@ -136,10 +141,18 @@ handle_info(_Msg, State) ->
 %% Internal
 %% ============================================================================
 
-cast_all([], _) -> ok;
-cast_all([Server | Servers], Msg) ->
+% Cast all messages to one destination
+cast_all2one(_, []) -> ok;
+cast_all2one(Server, [Msg | Msgs]) ->
+    ok = gen_server:cast(Server, Msg),
+    cast_all2one(Server, Msgs).
+
+
+% Cast one message to all destinations
+cast_one2all([], _) -> ok;
+cast_one2all([Server | Servers], Msg) ->
     ok = gen_server:cast(Server, Msg),
-    cast_all(Servers, Msg).
+    cast_one2all(Servers, Msg).
 
 
 new_state(1, LiveNeighbors) when LiveNeighbors  <  2 -> 0;