Introduce plain_rpc

Institutionalize the way hanoi_level handles RPC.
This is embodied in a new module, which should be
pushed to plain_fsm, but we'll keep it here for
now.

include/plain_rpc.hrl

@@ -0,0 +1,29 @@
+%% ----------------------------------------------------------------------------
+%%
+%% plain_rpc: RPC module to accompany plain_fsm
+%%
+%% Copyright 2011-2012 (c) Trifork A/S.  All Rights Reserved.
+%% http://trifork.com/ info@trifork.com
+%%
+%% This file is provided to you under the Apache License, Version 2.0 (the
+%% "License"); you may not use this file except in compliance with the License.
+%% You may obtain a copy of the License at
+%%
+%%   http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing, software
+%% distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+%% WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+%% License for the specific language governing permissions and limitations
+%% under the License.
+%%
+%% ----------------------------------------------------------------------------
+
+%%
+%% This module really belongs in the plain_fsm distro.
+%%
+
+-define(CALL(From,Msg), {'$call', From, Msg}).
+-define(REPLY(Ref,Msg), {'$reply', Ref, Msg}).
+-define(CAST(From,Msg), {'$cast', From, Msg}).
+

src/plain_rpc.erl

@@ -0,0 +1,62 @@
+%% ----------------------------------------------------------------------------
+%%
+%% plain_rpc: RPC module to accompany plain_fsm
+%%
+%% Copyright 2011-2012 (c) Trifork A/S.  All Rights Reserved.
+%% http://trifork.com/ info@trifork.com
+%%
+%% This file is provided to you under the Apache License, Version 2.0 (the
+%% "License"); you may not use this file except in compliance with the License.
+%% You may obtain a copy of the License at
+%%
+%%   http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing, software
+%% distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+%% WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+%% License for the specific language governing permissions and limitations
+%% under the License.
+%%
+%% ----------------------------------------------------------------------------
+
+-module(plain_rpc).
+-author('Kresten Krab Thorup <krab@trifork.com>').
+
+-export([send_call/2, receive_reply/1, send_reply/2, call/2, send_cast/2]).
+
+-include("include/plain_rpc.hrl").
+
+
+send_call(PID, Request) ->
+    Ref = erlang:monitor(process, PID),
+    PID ! ?CALL({self(), Ref}, Request),
+    Ref.
+
+send_cast(PID, Msg) ->
+    PID ! ?CAST(self(), Msg).
+
+receive_reply(MRef) ->
+    receive
+        ?REPLY(MRef, Reply) ->
+            erlang:demonitor(MRef, [flush]),
+            Reply;
+                {'DOWN', MRef, _, _, Reason} ->
+                    exit(Reason)
+    end.
+
+send_reply({PID,Ref}, Reply) ->
+    erlang:send(PID, ?REPLY(Ref, Reply)),
+    ok.
+
+call(PID,Request) ->
+    MRef = erlang:monitor(process, PID),
+    PID ! ?CALL({self(), MRef}, Request),
+    receive
+        ?REPLY(MRef, Reply) ->
+            erlang:demonitor(MRef, [flush]),
+            Reply;
+        {'DOWN', MRef, _, _, Reason} ->
+            exit(Reason)
+    end.
+
+