Add emqx_mountpoint module

src/emqx_mountpoint.erl

@@ -0,0 +1,52 @@
+%% Copyright (c) 2018 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_mountpoint).
+
+-include("emqx.hrl").
+
+-export([mount/2, unmount/2]).
+-export([replvar/2]).
+
+-type(mountpoint() :: binary()).
+-export_type([mountpoint/0]).
+
+mount(undefined, Any) ->
+    Any;
+mount(MountPoint, Msg = #message{topic = Topic}) ->
+    Msg#message{topic = <<MountPoint/binary, Topic/binary>>};
+
+mount(MountPoint, TopicFilters) when is_list(TopicFilters) ->
+    [{<<MountPoint/binary, Topic/binary>>, SubOpts} || {Topic, SubOpts} <- TopicFilters].
+
+unmount(undefined, Msg) ->
+    Msg;
+unmount(MountPoint, Msg = #message{topic = Topic}) ->
+    case catch split_binary(Topic, byte_size(MountPoint)) of
+        {MountPoint, Topic1} -> Msg#message{topic = Topic1};
+        _Other -> Msg
+    end.
+
+replvar(undefined, _Vars) ->
+    undefined;
+replvar(MountPoint, #{client_id := ClientId, username := Username}) ->
+    lists:foldl(fun feed_var/2, MountPoint, [{<<"%c">>, ClientId}, {<<"%u">>, Username}]).
+
+feed_var({<<"%c">>, ClientId}, MountPoint) ->
+    emqx_topic:feed_var(<<"%c">>, ClientId, MountPoint);
+feed_var({<<"%u">>, undefined}, MountPoint) ->
+    MountPoint;
+feed_var({<<"%u">>, Username}, MountPoint) ->
+    emqx_topic:feed_var(<<"%u">>, Username, MountPoint).
+