67 lines
2.4 KiB
Erlang
67 lines
2.4 KiB
Erlang
%%--------------------------------------------------------------------
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%% Copyright (c) 2024 EMQ Technologies Co., Ltd. All Rights Reserved.
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%%
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%% Licensed under the Apache License, Version 2.0 (the "License");
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%% you may not use this file except in compliance with the License.
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%% You may obtain a copy of the License at
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%% http://www.apache.org/licenses/LICENSE-2.0
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%%
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%% Unless required by applicable law or agreed to in writing, software
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%% distributed under the License is distributed on an "AS IS" BASIS,
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%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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%% See the License for the specific language governing permissions and
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%% limitations under the License.
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%%--------------------------------------------------------------------
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%% @doc Similar to Elixir's [`Agent'](https://hexdocs.pm/elixir/Agent.html).
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-module(emqx_utils_agent).
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%% API
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-export([start_link/1, get/1, get_and_update/2]).
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%% `gen_server' API
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-export([init/1, handle_call/3]).
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%%------------------------------------------------------------------------------
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%% Type declarations
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%%------------------------------------------------------------------------------
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-type state() :: term().
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-type get_and_update_fn() :: fun((state()) -> {term(), state()}).
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-record(get_and_update, {fn :: get_and_update_fn()}).
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%%------------------------------------------------------------------------------
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%% API
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%%------------------------------------------------------------------------------
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-spec start_link(state()) -> gen_server:start_ret().
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start_link(InitState) ->
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gen_server:start_link(?MODULE, InitState, []).
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-spec get(gen_server:server_ref()) -> term().
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get(ServerRef) ->
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Fn = fun(St) -> {St, St} end,
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gen_server:call(ServerRef, #get_and_update{fn = Fn}).
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-spec get_and_update(gen_server:server_ref(), get_and_update_fn()) -> term().
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get_and_update(ServerRef, Fn) ->
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gen_server:call(ServerRef, #get_and_update{fn = Fn}).
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%%------------------------------------------------------------------------------
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%% `gen_server' API
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%%------------------------------------------------------------------------------
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init(InitState) ->
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{ok, InitState}.
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handle_call(#get_and_update{fn = Fn}, _From, State0) ->
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{Reply, State} = Fn(State0),
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{reply, Reply, State}.
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%%------------------------------------------------------------------------------
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%% Internal fns
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%%------------------------------------------------------------------------------
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