emqx/apps/emqx_utils/src/emqx_utils_ets.erl

90 lines
2.2 KiB
Erlang

%%--------------------------------------------------------------------
%% Copyright (c) 2018-2024 EMQ Technologies Co., Ltd. All Rights Reserved.
%%
%% Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing, software
%% distributed under the License is distributed on an "AS IS" BASIS,
%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%% See the License for the specific language governing permissions and
%% limitations under the License.
%%--------------------------------------------------------------------
-module(emqx_utils_ets).
-export([
new/1,
new/2
]).
-export([
lookup_value/2,
lookup_value/3
]).
-export([keyfoldl/3]).
-export([delete/1]).
%% Create an ets table.
-spec new(atom()) -> ok.
new(Tab) ->
new(Tab, []).
%% Create a named_table ets.
-spec new(atom(), list()) -> ok.
new(Tab, Opts) ->
case ets:info(Tab, name) of
undefined ->
_ = ets:new(Tab, lists:usort([named_table | Opts])),
ok;
Tab ->
ok
end.
%% KV lookup
-spec lookup_value(ets:tab(), term()) -> any().
lookup_value(Tab, Key) ->
lookup_value(Tab, Key, undefined).
-spec lookup_value(ets:tab(), term(), any()) -> any().
lookup_value(Tab, Key, Def) ->
try
ets:lookup_element(Tab, Key, 2)
catch
error:badarg -> Def
end.
-spec keyfoldl(fun((_Key :: term(), Acc) -> Acc), Acc, ets:tab()) -> Acc.
keyfoldl(F, Acc, Tab) ->
true = ets:safe_fixtable(Tab, true),
First = ets:first(Tab),
try
keyfoldl(F, Acc, First, Tab)
after
ets:safe_fixtable(Tab, false)
end.
keyfoldl(F, Acc, Key, Tab) ->
case Key of
'$end_of_table' ->
Acc;
_ ->
keyfoldl(F, F(Key, Acc), ets:next(Tab, Key), Tab)
end.
%% Delete the ets table.
-spec delete(ets:tab()) -> ok.
delete(Tab) ->
case ets:info(Tab, name) of
undefined ->
ok;
Tab ->
ets:delete(Tab),
ok
end.