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%%% The Registry is a gen_server process that keeps track of the
%%% currently active set of connection-path processes. The listeners
%%% add the processes to the list as they're created. The manager
%%% looks stuff up in order to send commands to the proper place.
%%%
%%% Note that "Count" is a count of the number of paths we've *ever*
%%% registered, not the current length of the list. (Otherwise I
%%% would have simply called lists:length/1 when needed.) It's used
%%% to tag each entry with an identifying serial number, I guess.
-module(registry).
-behaviour(gen_server).
-export([start/0,lookup/1,register/1,unregister/1,all/0]).
-export([init/1, handle_call/3]).
-export([code_change/3,handle_cast/2,handle_info/2,terminate/2]).
-import(lists,[dropwhile/2]).
start() ->
{ok,_Pid} = gen_server:start({local,registry}, registry, [], []),
ok.
init(_) ->
{ok,{[],0}}.
handle_call({register,Path, Pid}, _From, State) ->
{Paths,Count} = State,
Num = Count + 1,
{reply, ok, {[{Num,Path,Pid}|Paths],Count+1}};
%% Someday we may want to look up by Id, but for now no one is using it.
handle_call({lookup,Query}, _, State) ->
{Paths,_Count} = State,
Ans = [Pid || {_Num, Path, Pid} <- Paths, util:match(Path, Query)],
{reply, Ans, State};
handle_call({unregister,Path}, _, State) ->
{Paths,Count} = State,
{reply, ok, {lists:keydelete(Path, 2, Paths),Count}};
handle_call(all, _, State) ->
{Paths,_Count} = State,
{reply, Paths, State}.
lookup(Query) ->
gen_server:call(registry, {lookup, Query}).
register(Path) ->
gen_server:call(registry, {register, Path, self()}).
unregister(Path) ->
gen_server:call(registry, {unregister, Path}).
all() ->
gen_server:call(registry, all).
%%%
%%% The following functions defined in the gen_server behavior are not
%%% used. But we include them in order to avoid distracting
%%% compilation warnings.
%%%
code_change(_,_,_) ->
ok.
handle_cast(_,_) ->
ok.
handle_info(_,_) ->
ok.
terminate(_,_) ->
ok.
|
