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pkcs7

1.0.2
1.0.2

PKCS7 binary padding for erlang

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pkcs7 src pkcs7.erl
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src/pkcs7.erl 

-module (pkcs7).



-export ([pad/1]).

-export ([unpad/1]).



pad(Bin) ->

  Diff = byte_size(Bin) rem 16,

  pad(Bin, 16-Diff).



pad(Bin, 1) ->

  <<Bin/binary,1>>;

pad(Bin, 2) ->

  <<Bin/binary,2,2>>;

pad(Bin, 3) ->

  <<Bin/binary,3,3,3>>;

pad(Bin, 4) ->

  <<Bin/binary,4,4,4,4>>;

pad(Bin, 5) ->

  <<Bin/binary,5,5,5,5,5>>;

pad(Bin, 6) ->

  <<Bin/binary,6,6,6,6,6,6>>;

pad(Bin, 7) ->

  <<Bin/binary,7,7,7,7,7,7,7>>;

pad(Bin, 8) ->

  <<Bin/binary,8,8,8,8,8,8,8,8>>;

pad(Bin, 9) ->

  <<Bin/binary,9,9,9,9,9,9,9,9,9>>;

pad(Bin, 10) ->

  <<Bin/binary,10,10,10,10,10,10,10,10,10,10>>;

pad(Bin, 11) ->

  <<Bin/binary,11,11,11,11,11,11,11,11,11,11,11>>;

pad(Bin, 12) ->

  <<Bin/binary,12,12,12,12,12,12,12,12,12,12,12,12>>;

pad(Bin, 13) ->

  <<Bin/binary,13,13,13,13,13,13,13,13,13,13,13,13,13>>;

pad(Bin, 14) ->

  <<Bin/binary,14,14,14,14,14,14,14,14,14,14,14,14,14,14>>;

pad(Bin, 15) ->

  <<Bin/binary,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15>>;

pad(Bin, 16) ->

  <<Bin/binary,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16>>.



unpad(<<>>) ->

  <<>>;

unpad(Bin) ->

  Last = binary:last(Bin),

  Size = byte_size(Bin) - Last,

  RemSize = Size rem 16,



  case Bin of

    <<Data:Size/binary,1>> when RemSize == 15 -> Data;

    <<Data:Size/binary,2,2>> when RemSize == 14 -> Data;

    <<Data:Size/binary,3,3,3>> when RemSize == 13 -> Data;

    <<Data:Size/binary,4,4,4,4>> when RemSize == 12 -> Data;

    <<Data:Size/binary,5,5,5,5,5>> when RemSize == 11 -> Data;

    <<Data:Size/binary,6,6,6,6,6,6>> when RemSize == 10 -> Data;

    <<Data:Size/binary,7,7,7,7,7,7,7>> when RemSize == 9 -> Data;

    <<Data:Size/binary,8,8,8,8,8,8,8,8>> when RemSize == 8 -> Data;

    <<Data:Size/binary,9,9,9,9,9,9,9,9,9>> when RemSize == 7 -> Data;

    <<Data:Size/binary,10,10,10,10,10,10,10,10,10,10>> when RemSize == 6 -> Data;

    <<Data:Size/binary,11,11,11,11,11,11,11,11,11,11,11>> when RemSize == 5 -> Data;

    <<Data:Size/binary,12,12,12,12,12,12,12,12,12,12,12,12>> when RemSize == 4 -> Data;

    <<Data:Size/binary,13,13,13,13,13,13,13,13,13,13,13,13,13>> when RemSize == 3 -> Data;

    <<Data:Size/binary,14,14,14,14,14,14,14,14,14,14,14,14,14,14>> when RemSize == 2 -> Data;

    <<Data:Size/binary,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15>> when RemSize == 1 -> Data;

    <<Data:Size/binary,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16>> when RemSize == 0 -> Data;

    _ -> erlang:error(bad_padding)

  end.