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%% 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,
monitored/1, is_empty/1]).
-compile({no_auto_import, [monitor/2]}).
-ifdef(use_specs).
%%----------------------------------------------------------------------------
-export_type([?MODULE/0]).
-opaque(?MODULE() :: dict()).
-type(item() :: pid() | {atom(), node()}).
-spec(new/0 :: () -> ?MODULE()).
-spec(monitor/2 :: (item(), ?MODULE()) -> ?MODULE()).
-spec(monitor_all/2 :: ([item()], ?MODULE()) -> ?MODULE()).
-spec(demonitor/2 :: (item(), ?MODULE()) -> ?MODULE()).
-spec(is_monitored/2 :: (item(), ?MODULE()) -> boolean()).
-spec(erase/2 :: (item(), ?MODULE()) -> ?MODULE()).
-spec(monitored/1 :: (?MODULE()) -> [item()]).
-spec(is_empty/1 :: (?MODULE()) -> boolean()).
-endif.
new() -> dict:new().
monitor(Item, M) ->
case dict:is_key(Item, M) of
true -> M;
false -> dict:store(Item, erlang:monitor(process, Item), M)
end.
monitor_all([], M) -> M; %% optimisation
monitor_all([Item], M) -> monitor(Item, M); %% optimisation
monitor_all(Items, M) -> lists:foldl(fun monitor/2, M, Items).
demonitor(Item, M) ->
case dict:find(Item, M) of
{ok, MRef} -> erlang:demonitor(MRef),
dict:erase(Item, M);
error -> M
end.
is_monitored(Item, M) -> dict:is_key(Item, M).
erase(Item, M) -> dict:erase(Item, M).
monitored(M) -> dict:fetch_keys(M).
is_empty(M) -> dict:size(M) == 0.
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