Merge branch 'jn/supervisor_child_count_only' into ccase/r13b04_dev

* jn/supervisor_child_count_only:
  Add count_children/1 to supervisor.erl to determine the number of

OTP-8436  Added supervisor:count_children/1 to count the number of children
          being managed without the memory impact of which_children/1.
          (Thanks to Jay Nelson.)

1 files changed, 52 insertions, 7 deletions

diff --git a/lib/stdlib/src/supervisor.erl b/lib/stdlib/src/supervisor.erl
index fb1303d1eb..22269a8d1b 100644
--- a/lib/stdlib/src/supervisor.erl
+++ b/lib/stdlib/src/supervisor.erl
@@ -1,19 +1,19 @@
 %%
 %% %CopyrightBegin%
-%% 
-%% Copyright Ericsson AB 1996-2009. All Rights Reserved.
-%% 
+%%
+%% Copyright Ericsson AB 1996-2010. All Rights Reserved.
+%%
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
 %% compliance with the License. You should have received a copy of the
 %% Erlang Public License along with this software. If not, it can be
 %% retrieved online at http://www.erlang.org/.
-%% 
+%%
 %% 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.
-%% 
+%%
 %% %CopyrightEnd%
 %%
 -module(supervisor).
@@ -24,7 +24,7 @@
 -export([start_link/2,start_link/3,
 	 start_child/2, restart_child/2,
 	 delete_child/2, terminate_child/2,
-	 which_children/1,
+	 which_children/1, count_children/1,
 	 check_childspecs/1]).
 
 -export([behaviour_info/1]).
@@ -95,6 +95,9 @@ terminate_child(Supervisor, Name) ->
 which_children(Supervisor) ->
     call(Supervisor, which_children).
 
+count_children(Supervisor) ->
+    call(Supervisor, count_children).
+
 call(Supervisor, Req) ->
     gen_server:call(Supervisor, Req, infinity).
 
@@ -297,7 +300,49 @@ handle_call(which_children, _From, State) ->
 		    {Name, Pid, ChildType, Mods}
 		  end,
 		  State#state.children),
-    {reply, Resp, State}.
+    {reply, Resp, State};
+
+handle_call(count_children, _From, State) when ?is_simple(State) ->
+    [#child{child_type = CT}] = State#state.children,
+    {Active, Count} =
+	?DICT:fold(fun(Pid, _Val, {Alive, Tot}) ->
+			   if is_pid(Pid) -> {Alive+1, Tot +1};
+			      true -> {Alive, Tot + 1} end
+		   end, {0, 0}, State#state.dynamics),
+    Reply = case CT of
+		supervisor -> [{specs, 1}, {active, Active},
+			       {supervisors, Count}, {workers, 0}];
+		worker -> [{specs, 1}, {active, Active},
+			   {supervisors, 0}, {workers, Count}]
+	    end,
+    {reply, Reply, State};
+
+handle_call(count_children, _From, State) ->
+
+    %% Specs and children are together on the children list...
+    {Specs, Active, Supers, Workers} =
+	lists:foldl(fun(Child, Counts) ->
+			   count_child(Child, Counts)
+		   end, {0,0,0,0}, State#state.children),
+
+    %% Reformat counts to a property list.
+    Reply = [{specs, Specs}, {active, Active},
+	     {supervisors, Supers}, {workers, Workers}],
+    {reply, Reply, State}.
+
+
+count_child(#child{pid = Pid, child_type = worker},
+	    {Specs, Active, Supers, Workers}) ->
+    case is_pid(Pid) andalso is_process_alive(Pid) of
+	true ->  {Specs+1, Active+1, Supers, Workers+1};
+	false -> {Specs+1, Active, Supers, Workers+1}
+    end;
+count_child(#child{pid = Pid, child_type = supervisor},
+	    {Specs, Active, Supers, Workers}) ->
+    case is_pid(Pid) andalso is_process_alive(Pid) of
+	true ->  {Specs+1, Active+1, Supers+1, Workers};
+	false -> {Specs+1, Active, Supers+1, Workers}
+    end.
 
 
 %%% Hopefully cause a function-clause as there is no API function