first cut of helper module for keeping track of process monitors

1 files changed, 64 insertions, 0 deletions

diff --git a/src/pmon.erl b/src/pmon.erl
new file mode 100644
index 0000000000..61c1657839
--- /dev/null
+++ b/src/pmon.erl
@@ -0,0 +1,64 @@
+%% The contents of this file are subject to the Mozilla Public License
+%% Version 1.1 (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.mozilla.org/MPL/
+%%
+%% Software distributed under the License is distributed on an "AS IS"
+%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+%% the License for the specific language governing rights and
+%% limitations under the License.
+%%
+%% The Original Code is RabbitMQ.
+%%
+%% The Initial Developer of the Original Code is VMware, Inc.
+%% Copyright (c) 2011-2012 VMware, Inc.  All rights reserved.
+%%
+
+-module(pmon).
+
+-export([new/0, monitor/2, monitor_all/2, demonitor/2, is_monitored/2, erase/2,
+         to_list/1, is_empty/1]).
+
+-ifdef(use_specs).
+
+%%----------------------------------------------------------------------------
+
+-export_type([?MODULE/0]).
+
+-opaque(?MODULE()    :: dict()).
+
+-spec(new/0          :: () -> ?MODULE()).
+-spec(monitor/2      :: (pid(), ?MODULE()) -> ?MODULE()).
+-spec(monitor_all/2  :: ([pid()], ?MODULE()) -> ?MODULE()).
+-spec(demonitor/2    :: (pid(), ?MODULE()) -> ?MODULE()).
+-spec(is_monitored/2 :: (pid(), ?MODULE()) -> boolean()).
+-spec(erase/2        :: (pid(), ?MODULE()) -> ?MODULE()).
+-spec(to_list/1      :: (?MODULE()) -> [{pid(), reference()}]).
+-spec(is_empty/1     :: (?MODULE()) -> boolean()).
+
+-endif.
+
+new() -> dict:new().
+
+monitor(Pid, M) ->
+    case dict:is_key(Pid, M) of
+        true  -> M;
+        false -> dict:store(Pid, erlang:monitor(process, Pid), M)
+    end.
+
+monitor_all(Pids, M) -> lists:foldl(fun monitor/2, M, Pids).
+
+demonitor(Pid, M) ->
+    case dict:find(Pid, M) of
+        {ok, MRef} -> erlang:demonitor(MRef),
+                      dict:erase(Pid, M);
+        error      -> M
+    end.
+
+is_monitored(Pid, M) -> dict:is_key(Pid, M).
+
+erase(Pid, M) -> dict:erase(Pid, M).
+
+to_list(M) -> dict:to_list(M).
+
+is_empty(M) -> dict:size(M) == 0.