emqx4.3/src/emqttd_topic.erl

%%%-----------------------------------------------------------------------------
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%%% IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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%%%-----------------------------------------------------------------------------
%%% @doc
%%% MQTT Topic
%%%
%%% @end
%%%-----------------------------------------------------------------------------

-module(emqttd_topic).

-author("Feng Lee <feng@emqtt.io>").

-import(lists, [reverse/1]).
 
-export([match/2, validate/1, triples/1, words/1, wildcard/1]).

-export([join/1, feed_var/3, is_queue/1, systop/1]).

%-type type()   :: static | dynamic.

-type word()   :: '' | '+' | '#' | binary().

-type words()  :: list(word()).

-type triple() :: {root | binary(), word(), binary()}.

-export_type([word/0, triple/0]).

-define(MAX_TOPIC_LEN, 4096).

%%%-----------------------------------------------------------------------------
%% @doc Is wildcard topic?
%% @end
%%%-----------------------------------------------------------------------------
-spec wildcard(binary()) -> true | false.
wildcard(Topic) when is_binary(Topic) ->
	wildcard(words(Topic));
wildcard([]) -> 
    false;
wildcard(['#'|_]) ->
    true;
wildcard(['+'|_]) ->
    true;
wildcard([_H|T]) ->
    wildcard(T).

%%------------------------------------------------------------------------------
%% @doc Match Topic name with filter
%% @end
%%------------------------------------------------------------------------------
-spec match(Name, Filter) -> boolean() when
    Name    :: binary() | words(),
    Filter  :: binary() | words().
match(Name, Filter) when is_binary(Name) and is_binary(Filter) ->
	match(words(Name), words(Filter));
match([], []) ->
	true;
match([H|T1], [H|T2]) ->
	match(T1, T2);
match([<<$$, _/binary>>|_], ['+'|_]) ->
    false;
match([_H|T1], ['+'|T2]) ->
	match(T1, T2);
match([<<$$, _/binary>>|_], ['#']) ->
    false;
match(_, ['#']) ->
	true;
match([_H1|_], [_H2|_]) ->
	false;
match([_H1|_], []) ->
	false;
match([], [_H|_T2]) ->
	false.

%%------------------------------------------------------------------------------
%% @doc Validate Topic
%% @end
%%------------------------------------------------------------------------------
-spec validate({name | filter, binary()}) -> boolean().
validate({_, <<>>}) ->
	false;
validate({_, Topic}) when is_binary(Topic) and (size(Topic) > ?MAX_TOPIC_LEN) ->
	false;
validate({filter, Topic}) when is_binary(Topic) ->
	validate2(words(Topic));
validate({name, Topic}) when is_binary(Topic) ->
	Words = words(Topic),
	validate2(Words) and (not wildcard(Words)).

validate2([]) ->
    true;
validate2(['#']) -> % end with '#'
    true;
validate2(['#'|Words]) when length(Words) > 0 -> 
    false; 
validate2([''|Words]) ->
    validate2(Words);
validate2(['+'|Words]) ->
    validate2(Words);
validate2([W|Words]) ->
    case validate3(W) of
        true -> validate2(Words);
        false -> false
    end.

validate3(<<>>) ->
    true;
validate3(<<C/utf8, _Rest/binary>>) when C == $#; C == $+; C == 0 ->
    false;
validate3(<<_/utf8, Rest/binary>>) ->
    validate3(Rest).

%%%-----------------------------------------------------------------------------
%% @doc Topic to Triples
%% @end
%%%-----------------------------------------------------------------------------
-spec triples(binary()) -> list(triple()).
triples(Topic) when is_binary(Topic) ->
	triples(words(Topic), root, []).

triples([], _Parent, Acc) ->
    reverse(Acc);

triples([W|Words], Parent, Acc) ->
    Node = join(Parent, W),
    triples(Words, Node, [{Parent, W, Node}|Acc]).

join(root, W) ->
    bin(W);
join(Parent, W) ->
    <<(bin(Parent))/binary, $/, (bin(W))/binary>>.

bin('')  -> <<>>;
bin('+') -> <<"+">>;
bin('#') -> <<"#">>;
bin(B) when is_binary(B) -> B.

%%------------------------------------------------------------------------------
%% @doc Split Topic Path to Words
%% @end
%%------------------------------------------------------------------------------
-spec words(binary()) -> words().
words(Topic) when is_binary(Topic) ->
    [word(W) || W <- binary:split(Topic, <<"/">>, [global])].

word(<<>>)    -> '';
word(<<"+">>) -> '+';
word(<<"#">>) -> '#';
word(Bin)     -> Bin.

%%------------------------------------------------------------------------------
%% @doc Queue is a special topic name that starts with "$Q/"
%% @end
%%------------------------------------------------------------------------------
-spec is_queue(binary()) -> boolean().
is_queue(<<"$Q/", _Queue/binary>>) ->
    true;
is_queue(_) ->
    false.

%%------------------------------------------------------------------------------
%% @doc '$SYS' Topic.
%% @end
%%------------------------------------------------------------------------------

systop(Name) when is_atom(Name) ->
    list_to_binary(lists:concat(["$SYS/brokers/", node(), "/", Name]));

systop(Name) when is_binary(Name) ->
    list_to_binary(["$SYS/brokers/", atom_to_list(node()), "/", Name]).

-spec feed_var(binary(), binary(), binary()) -> binary().
feed_var(Var, Val, Topic) ->
    feed_var(Var, Val, words(Topic), []).
feed_var(_Var, _Val, [], Acc) ->
    join(lists:reverse(Acc));
feed_var(Var, Val, [Var|Words], Acc) ->
    feed_var(Var, Val, Words, [Val|Acc]);
feed_var(Var, Val, [W|Words], Acc) ->
    feed_var(Var, Val, Words, [W|Acc]).

-spec join(list(binary())) -> binary().
join([]) ->
    <<>>;
join([W]) ->
    bin(W);
join(Words) ->
    {_, Bin} =
    lists:foldr(fun(W, {true, Tail}) ->
                        {false, <<W/binary, Tail/binary>>};
                   (W, {false, Tail}) ->
                        {false, <<W/binary, "/", Tail/binary>>}
                end, {true, <<>>}, [bin(W) || W <- Words]),
    Bin.