emqx/apps/emqx_lwm2m/src/binary_util.erl

-module(binary_util).

%% copied from https://github.com/arcusfelis/binary2

%% Bytes
-export([ reverse/1
        , join/2
        , duplicate/2
        , suffix/2
        , prefix/2
        ]).

%% Bits
-export([ union/2
        , subtract/2
        , intersection/2
        , inverse/1
        ]).

%% Trimming
-export([ rtrim/1
        , rtrim/2
        , ltrim/1
        , ltrim/2
        , trim/1
        , trim/2
        ]).

%% Parsing
-export([ bin_to_int/1]).

%% Matching
-export([ optimize_patterns/1]).

%% CoAP
-export([ join_path/1]).


trim(B)  -> trim(B, 0).
ltrim(B) -> ltrim(B, 0).
rtrim(B) -> rtrim(B, 0).


rtrim(B, X) when is_binary(B), is_integer(X) ->
    S = byte_size(B),
    do_rtrim(S, B, X);
rtrim(B, [_|_]=Xs) when is_binary(B) ->
    S = byte_size(B),
    do_mrtrim(S, B, Xs).


ltrim(B, X) when is_binary(B), is_integer(X) ->
    do_ltrim(B, X);
ltrim(B, [_|_]=Xs) when is_binary(B) ->
    do_mltrim(B, Xs).


%% @doc The second element is a single integer element or an ordset of elements.
trim(B, X) when is_binary(B), is_integer(X) ->
    From = ltrimc(B, X, 0),
    case byte_size(B) of
        From ->
            <<>>;
        S ->
            To = do_rtrimc(S, B, X),
            binary:part(B, From, To - From)
    end;
trim(B, [_|_]=Xs) when is_binary(B) ->
    From = mltrimc(B, Xs, 0),
    case byte_size(B) of
        From ->
            <<>>;
        S ->
            To = do_mrtrimc(S, B, Xs),
            binary:part(B, From, To - From)
    end.

do_ltrim(<<X, B/binary>>, X) ->
    do_ltrim(B, X);
do_ltrim(B, _X) ->
    B.

%% multi, left trimming.
do_mltrim(<<X, B/binary>> = XB, Xs) ->
    case ordsets:is_element(X, Xs) of
        true  -> do_mltrim(B, Xs);
        false -> XB
    end;
do_mltrim(<<>>, _Xs) ->
    <<>>.

do_rtrim(0, _B, _X) ->
    <<>>;
do_rtrim(S, B, X) ->
    S2 = S - 1,
    case binary:at(B, S2) of
        X -> do_rtrim(S2, B, X);
        _ -> binary_part(B, 0, S)
    end.

%% Multiple version of do_rtrim.
do_mrtrim(0, _B, _Xs) ->
    <<>>;
do_mrtrim(S, B, Xs) ->
    S2 = S - 1,
    X = binary:at(B, S2),
    case ordsets:is_element(X, Xs) of
        true  -> do_mrtrim(S2, B, Xs);
        false -> binary_part(B, 0, S)
    end.


ltrimc(<<X, B/binary>>, X, C) ->
    ltrimc(B, X, C+1);
ltrimc(_B, _X, C) ->
    C.

%% multi, left trimming, returns a count of matched bytes from the left.
mltrimc(<<X, B/binary>>, Xs, C) ->
    case ordsets:is_element(X, Xs) of
        true  -> mltrimc(B, Xs, C+1);
        false -> C
    end;
mltrimc(<<>>, _Xs, C) ->
    C.

% This clause will never be matched.
%do_rtrimc(0, _B, _X) ->
%    0;
do_rtrimc(S, B, X) ->
    S2 = S - 1,
    case binary:at(B, S2) of
        X -> do_rtrimc(S2, B, X);
        _ -> S
    end.

do_mrtrimc(S, B, Xs) ->
    S2 = S - 1,
    X = binary:at(B, S2),
    case ordsets:is_element(X, Xs) of
        true  -> do_mrtrimc(S2, B, Xs);
        false -> S
    end.

%% @doc Reverse the bytes' order.
reverse(Bin) when is_binary(Bin) ->
    S = bit_size(Bin),
    <<V:S/integer-little>> = Bin,
    <<V:S/integer-big>>.

join([B|Bs], Sep) when is_binary(Sep) ->
    iolist_to_binary([B|add_separator(Bs, Sep)]);

join([], _Sep) ->
    <<>>.

add_separator([B|Bs], Sep) ->
    [Sep, B | add_separator(Bs, Sep)];
add_separator([], _) ->
    [].

%% @doc Repeat the binary `B' `C' times.
duplicate(C, B) ->
    iolist_to_binary(lists:duplicate(C, B)).

prefix(B, L) when is_binary(B), is_integer(L), L > 0 ->
    binary:part(B, 0, L).

suffix(B, L) when is_binary(B), is_integer(L), L > 0 ->
    S = byte_size(B),
    binary:part(B, S-L, L).


union(B1, B2) ->
    S = bit_size(B1),
    <<V1:S>> = B1,
    <<V2:S>> = B2,
    V3 = V1 bor V2,
    <<V3:S>>.

subtract(B1, B2) ->
    S = bit_size(B1),
    <<V1:S>> = B1,
    <<V2:S>> = B2,
    V3 = (V1 bxor V2) band V1,
    <<V3:S>>.

intersection(B1, B2) ->
    S = bit_size(B1),
    <<V1:S>> = B1,
    <<V2:S>> = B2,
    V3 = V1 band V2,
    <<V3:S>>.

inverse(B1) ->
    S = bit_size(B1),
    <<V1:S>> = B1,
    V2 = bnot V1,
    <<V2:S>>.

%% @doc string:to_integer/1 for binaries
bin_to_int(Bin) ->
    bin_to_int(Bin, 0).

bin_to_int(<<H, T/binary>>, X) when $0 =< H, H =< $9 ->
    bin_to_int(T, (X*10)+(H-$0));
bin_to_int(Bin, X) ->
    {X, Bin}.

%% Remove longer patterns if shorter pattern matches
%% Useful to run before binary:compile_pattern/1
optimize_patterns(Patterns) ->
    Sorted = lists:usort(Patterns),
    remove_long_duplicates(Sorted).

remove_long_duplicates([H|T]) ->
    %% match(Subject, Pattern)
    DedupT = [X || X <- T, binary:match(X, H) =:= nomatch],
    [H|remove_long_duplicates(DedupT)];
remove_long_duplicates([]) ->
    [].

join_path(PathList) ->
    join_path(PathList, <<>>).

join_path([], Result) -> Result;
join_path([<<>> | PathList], Result) ->
    join_path(PathList, Result);
join_path([Path | PathList], Result) ->
    join_path(PathList, <<Result/binary, "/", Path/binary>>).