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%%% ==================================================================== |
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%%% ``The contents of this file are subject to the Erlang Public License, |
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%%% Version 1.1, (the "License"); you may not use this file except in |
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%%% compliance with the License. You should have received a copy of the |
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%%% Erlang Public License along with this software. If not, it can be |
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%%% retrieved via the world wide web at http://www.erlang.org/. |
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%%% |
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%%% |
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%%% Software distributed under the License is distributed on an "AS IS" |
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%%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See |
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%%% the License for the specific language governing rights and limitations |
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%%% under the License. |
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%%% |
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%%% |
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%%% The Initial Developer of the Original Code is ProcessOne. |
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%%% Portions created by ProcessOne are Copyright 2006-2015, ProcessOne |
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%%% All Rights Reserved.'' |
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%%% This software is copyright 2006-2015, ProcessOne. |
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%%% |
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%%% |
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%%% @copyright 2006-2015 ProcessOne |
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%%% @author Christophe Romain <christophe.romain@process-one.net> |
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%%% [http://www.process-one.net/] |
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%%% @end |
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%%% ==================================================================== |
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%% important note: |
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%% new/1 and free/2 MUST be called inside a transaction bloc |
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-module(pubsub_index). |
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-author('christophe.romain@process-one.net'). |
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-include("pubsub.hrl"). |
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-export([init/0, new/1]). |
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init() -> |
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mongoose_mnesia:create_table(pubsub_index, |
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[{disc_copies, [node()]}, |
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{attributes, record_info(fields, pubsub_index)}]). |
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new(Index) -> |
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%% Create a new short lived transaction to reduce lock contention |
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spawn_and_call(fun() -> mnesia:transaction(fun() -> new_transaction(Index) end) end). |
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new_transaction(Index) -> |
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case mnesia:wread({pubsub_index, Index}) of |
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[I] -> |
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Id = I#pubsub_index.last + 1, |
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mnesia:write(I#pubsub_index{last = Id}), |
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Id; |
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_ -> |
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mnesia:write(#pubsub_index{index = Index, last = 1, free = []}), |
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1 |
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end. |
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spawn_and_call(F) -> |
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Ref = make_ref(), |
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Parent = self(), |
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FF = fun() -> Result = F(), Parent ! {call_result, Ref, Result} end, |
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Pid = spawn_monitor(FF), |
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receive |
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{call_result, Ref, Result} -> |
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{atomic, NewId} = Result, |
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erlang:demonitor(Ref, [flush]), |
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NewId; |
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{'DOWN', Ref, process, Pid, Reason} -> |
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:-( |
erlang:error({spawn_and_call_failed, Reason}) |
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after 5000 -> |
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erlang:demonitor(Ref, [flush]), |
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erlang:error(spawn_and_call_timeout) |
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end. |