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+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 2012. All Rights Reserved.
+%%
+%% The contents of this file are subject to the Erlang Public License,
+%% Version 1.1, (the "License"); you may not use this file except in
+%% compliance with the License. You should have received a copy of the
+%% Erlang Public License along with this software. If not, it can be
+%% retrieved online at http://www.erlang.org/.
+%%
+%% Software distributed under the License is distributed on an "AS IS"
+%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+%% the License for the specific language governing rights and limitations
+%% under the License.
+%%
+%% %CopyrightEnd%
+%%
+-module(asn1rtt_real_common).
+
+-export([encode_real/1,decode_real/1,
+ ber_encode_real/1]).
+
+%%============================================================================
+%%
+%% Real value, ITU_T X.690 Chapter 8.5
+%%============================================================================
+%%
+%% encode real value
+%%============================================================================
+
+ber_encode_real(0) ->
+ {[],0};
+ber_encode_real('PLUS-INFINITY') ->
+ {[64],1};
+ber_encode_real('MINUS-INFINITY') ->
+ {[65],1};
+ber_encode_real(Val) when is_tuple(Val); is_list(Val) ->
+ encode_real(Val).
+
+%%%%%%%%%%%%%%
+%% only base 2 encoding!
+%% binary encoding:
+%% +------------+ +------------+ +-+-+-+-+---+---+
+%% | (tag)9 | | n + p + 1 | |1|S|BB |FF |EE |
+%% +------------+ +------------+ +-+-+-+-+---+---+
+%%
+%% +------------+ +------------+
+%% | | | |
+%% +------------+ ...+------------+
+%% n octets for exponent
+%%
+%% +------------+ +------------+
+%% | | | |
+%% +------------+ ...+------------+
+%% p octets for pos mantissa
+%%
+%% S is 0 for positive sign
+%% 1 for negative sign
+%% BB: encoding base, 00 = 2, (01 = 8, 10 = 16)
+%% 01 and 10 not used
+%% FF: scale factor 00 = 0 (used in base 2 encoding)
+%% EE: encoding of the exponent:
+%% 00 - on the following octet
+%% 01 - on the 2 following octets
+%% 10 - on the 3 following octets
+%% 11 - encoding of the length of the two's-complement encoding of
+%% exponent on the following octet, and two's-complement
+%% encoding of exponent on the other octets.
+%%
+%% In DER and base 2 encoding the mantissa is encoded as value 0 or
+%% bit shifted until it is an odd number. Thus, do this for BER as
+%% well.
+
+encode_real(Real) ->
+ encode_real([], Real).
+
+encode_real(_C, {Mantissa, Base, Exponent}) when Base =:= 2 ->
+%% io:format("Mantissa: ~w Base: ~w, Exp: ~w~n",[Man, Base, Exp]),
+ {Man,ExpAdd} = truncate_zeros(Mantissa), %% DER adjustment
+ Exp = Exponent + ExpAdd,
+ OctExp = if Exp >= 0 -> list_to_binary(encode_pos_integer(Exp, []));
+ true -> list_to_binary(encode_neg_integer(Exp, []))
+ end,
+%% ok = io:format("OctExp: ~w~n",[OctExp]),
+ SignBit = if Man > 0 -> 0; % bit 7 is pos or neg, no Zeroval
+ true -> 1
+ end,
+%% ok = io:format("SignBitMask: ~w~n",[SignBitMask]),
+ SFactor = 0,
+ OctExpLen = size(OctExp),
+ if OctExpLen > 255 ->
+ exit({error,{asn1, {to_big_exp_in_encode_real, OctExpLen}}});
+ true -> true %% make real assert later..
+ end,
+ {LenCode, EOctets} = case OctExpLen of % bit 2,1
+ 1 -> {0, OctExp};
+ 2 -> {1, OctExp};
+ 3 -> {2, OctExp};
+ _ -> {3, <<OctExpLen, OctExp/binary>>}
+ end,
+ BB = 0, %% 00 for base 2
+ FirstOctet = <<1:1,SignBit:1,BB:2,SFactor:2,LenCode:2>>,
+ OctMantissa = if Man > 0 -> list_to_binary(real_mininum_octets(Man));
+ true -> list_to_binary(real_mininum_octets(-(Man))) % signbit keeps track of sign
+ end,
+ %% ok = io:format("LenMask: ~w EOctets: ~w~nFirstOctet: ~w OctMantissa: ~w OctExpLen: ~w~n", [LenMask, EOctets, FirstOctet, OctMantissa, OctExpLen]),
+ Bin = <<FirstOctet/binary, EOctets/binary, OctMantissa/binary>>,
+ {Bin, size(Bin)};
+encode_real(C, {Mantissa,Base,Exponent})
+ when Base =:= 10, is_integer(Mantissa), is_integer(Exponent) ->
+ %% always encode as NR3 due to DER on the format
+ %% mmmm.Eseeee where
+ %% m := digit
+ %% s := '-' | '+' | []
+ %% '+' only allowed in +0
+ %% e := digit
+ %% ex: 1234.E-5679
+ ManStr = integer_to_list(Mantissa),
+
+ encode_real_as_string(C,ManStr,Exponent);
+encode_real(_C, {_,Base,_}) ->
+ exit({error,{asn1, {encode_real_non_supported_encoding, Base}}});
+%% base 10
+encode_real(C, Real) when is_list(Real) ->
+ %% The Real string may come in as a NR1, NR2 or NR3 string.
+ {Mantissa, Exponent} =
+ case string:tokens(Real,"Ee") of
+ [NR2] ->
+ {NR2,0};
+ [NR3MB,NR3E] ->
+ %% remove beginning zeros
+ {NR3MB,list_to_integer(NR3E)}
+ end,
+
+ %% .Decimal | Number | Number.Decimal
+ ZeroDecimal =
+ fun("0") -> "";
+ (L) -> L
+ end,
+ {NewMantissa,LenDecimal} =
+ case Mantissa of
+ [$.|Dec] ->
+ NewMan = remove_trailing_zeros(Dec),
+ {NewMan,length(ZeroDecimal(NewMan))};
+ _ ->
+ case string:tokens(Mantissa,",.") of
+ [Num] -> %% No decimal-mark
+ {integer_to_list(list_to_integer(Num)),0};
+ [Num,Dec] ->
+ NewDec = ZeroDecimal(remove_trailing_zeros(Dec)),
+ NewMan = integer_to_list(list_to_integer(Num)) ++ NewDec,
+ {integer_to_list(list_to_integer(NewMan)),
+ length(NewDec)}
+ end
+ end,
+
+ encode_real_as_string(C, NewMantissa, Exponent - LenDecimal).
+
+encode_real_as_string(_C, Mantissa, Exponent)
+ when is_list(Mantissa), is_integer(Exponent) ->
+ %% Remove trailing zeros in Mantissa and add this to Exponent
+ TruncMant = remove_trailing_zeros(Mantissa),
+
+ ExpIncr = length(Mantissa) - length(TruncMant),
+
+ ExpStr = integer_to_list(Exponent + ExpIncr),
+
+ ExpBin =
+ case ExpStr of
+ "0" ->
+ <<"E+0">>;
+ _ ->
+ ExpB = list_to_binary(ExpStr),
+ <<$E,ExpB/binary>>
+ end,
+ ManBin = list_to_binary(TruncMant),
+ NR3 = 3,
+ {<<NR3,ManBin/binary,$.,ExpBin/binary>>,
+ 2 + byte_size(ManBin) + byte_size(ExpBin)}.
+
+remove_trailing_zeros(IntStr) ->
+ case lists:dropwhile(fun($0)-> true;
+ (_) -> false
+ end, lists:reverse(IntStr)) of
+ [] ->
+ "0";
+ ReversedIntStr ->
+ lists:reverse(ReversedIntStr)
+ end.
+
+truncate_zeros(Num) ->
+ truncate_zeros(Num, 0).
+truncate_zeros(0, Sum) ->
+ {0,Sum};
+truncate_zeros(M, Sum) ->
+ case M band 16#f =:= M band 16#e of
+ true -> truncate_zeros(M bsr 1, Sum+1);
+ _ -> {M,Sum}
+ end.
+
+
+%%============================================================================
+%% decode real value
+%%
+%% decode_real([OctetBufferList], tuple|value, tag|notag) ->
+%% {{Mantissa, Base, Exp} | realval | PLUS-INFINITY | MINUS-INFINITY | 0,
+%% RestBuff}
+%%
+%% only for base 2 decoding sofar!!
+%%============================================================================
+
+decode_real(Buffer) ->
+ Sz = byte_size(Buffer),
+ {RealVal,<<>>,Sz} = decode_real2(Buffer, [], Sz, 0),
+ RealVal.
+
+decode_real2(Buffer, _C, 0, _RemBytes) ->
+ {0,Buffer};
+decode_real2(Buffer0, _C, Len, RemBytes1) ->
+ <<First, Buffer2/binary>> = Buffer0,
+ if
+ First =:= 2#01000000 -> {'PLUS-INFINITY', Buffer2};
+ First =:= 2#01000001 -> {'MINUS-INFINITY', Buffer2};
+ First =:= 1 orelse First =:= 2 orelse First =:= 3 ->
+ %% charcter string encoding of base 10
+ {NRx,Rest} = split_binary(Buffer2,Len-1),
+ {binary_to_list(NRx),Rest,Len};
+ true ->
+ %% have some check here to verify only supported bases (2)
+ %% not base 8 or 16
+ <<_B7:1,Sign:1,BB:2,_FF:2,EE:2>> = <<First>>,
+ Base =
+ case BB of
+ 0 -> 2; % base 2, only one so far
+ _ -> exit({error,{asn1, {non_supported_base, BB}}})
+ end,
+ {FirstLen, {Exp, Buffer3,_Rb2}, RemBytes2} =
+ case EE of
+ 0 -> {2, decode_integer2(1, Buffer2, RemBytes1), RemBytes1+1};
+ 1 -> {3, decode_integer2(2, Buffer2, RemBytes1), RemBytes1+2};
+ 2 -> {4, decode_integer2(3, Buffer2, RemBytes1), RemBytes1+3};
+ 3 ->
+ <<ExpLen1,RestBuffer/binary>> = Buffer2,
+ { ExpLen1 + 2,
+ decode_integer2(ExpLen1, RestBuffer, RemBytes1),
+ RemBytes1+ExpLen1}
+ end,
+ %% io:format("FirstLen: ~w, Exp: ~w, Buffer3: ~w ~n",
+
+ Length = Len - FirstLen,
+ <<LongInt:Length/unit:8,RestBuff/binary>> = Buffer3,
+ {{Mantissa, Buffer4}, RemBytes3} =
+ if Sign =:= 0 ->
+ %% io:format("sign plus~n"),
+ {{LongInt, RestBuff}, 1 + Length};
+ true ->
+ %% io:format("sign minus~n"),
+ {{-LongInt, RestBuff}, 1 + Length}
+ end,
+ {{Mantissa, Base, Exp}, Buffer4, RemBytes2+RemBytes3}
+ end.
+
+encode_pos_integer(0, [B|_Acc]=L) when B < 128 ->
+ L;
+encode_pos_integer(N, Acc) ->
+ encode_pos_integer(N bsr 8, [N band 16#ff| Acc]).
+
+encode_neg_integer(-1, [B1|_T]=L) when B1 > 127 ->
+ L;
+encode_neg_integer(N, Acc) ->
+ encode_neg_integer(N bsr 8, [N band 16#ff|Acc]).
+
+
+%% Val must be >= 0
+real_mininum_octets(Val) ->
+ real_mininum_octets(Val, []).
+
+real_mininum_octets(0, Acc) ->
+ Acc;
+real_mininum_octets(Val, Acc) ->
+ real_mininum_octets(Val bsr 8, [Val band 16#FF | Acc]).
+
+%% decoding postitive integer values.
+decode_integer2(Len, <<0:1,_:7,_Bs/binary>> = Bin, RemovedBytes) ->
+ <<Int:Len/unit:8,Buffer2/binary>> = Bin,
+ {Int,Buffer2,RemovedBytes};
+%% decoding negative integer values.
+decode_integer2(Len, <<1:1,B2:7,Bs/binary>>, RemovedBytes) ->
+ <<N:Len/unit:8,Buffer2/binary>> = <<B2,Bs/binary>>,
+ Int = N - (1 bsl (8 * Len - 1)),
+ {Int,Buffer2,RemovedBytes}.