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CA CXC 138 21 Certificate Authority

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ca src oid.erl
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src/oid.erl 

-module(oid).

-export([decode/1, hex/1, unhex/1]).



digit(X) when X >= 0  andalso X =< 9  -> X + 48;

digit(X) when X >= 10 andalso X =< 15 -> X + 87.



hex(Bin)   -> << << (digit(A1)),(digit(A2)) >> || <<A1:4,A2:4>> <= Bin >>.

unhex(Hex) -> << << (erlang:list_to_integer([H1,H2], 16)) >> || <<H1,H2>> <= Hex >>.



match_tags({T,   V}, [T])              -> V;

match_tags({T,   V}, [T | Tt])         -> match_tags(V, Tt);

match_tags([{T,  V}], [T | Tt])        -> match_tags(V, Tt);

match_tags([{T, _V} | _] = Vlist, [T]) -> Vlist;

match_tags(Tlv,  [])                   -> Tlv;

match_tags({Tag, _V} = Tlv, [T | _Tt]) -> {error, {asn1, {wrong_tag, {{expected, T}, {got, Tag, Tlv}}}}}.



dec_subidentifiers(<<>>, _Av, Al)                -> lists:reverse(Al);

dec_subidentifiers(<<1:1,H:7,T/binary>>, Av, Al) -> dec_subidentifiers(T, Av bsl 7 + H, Al);

dec_subidentifiers(<<H,T/binary>>, Av, Al)       -> dec_subidentifiers(T, 0, [Av bsl 7 + H | Al]).



decode(Tlv) ->

    Val = match_tags(Tlv, []),

    [AddedObjVal | ObjVals] = dec_subidentifiers(Val, 0, []),

    {Val1, Val2} =

        if

            AddedObjVal < 40 ->    {0, AddedObjVal};

            AddedObjVal < 80 ->    {1, AddedObjVal - 40};

            true ->                {2, AddedObjVal - 80}

        end,

    list_to_tuple([Val1, Val2 | ObjVals]).