Decoding Quoted printable message

Question

Iam having trouble decoding Japanese message, the final output seems to be a garbage value.

Encoded ISO-2022-JP Quoted Printable Message:

"=82=B1=82=EA=82=CD=92P=82=C8=82=E9=83e=83X=83g=82=C5=82=B7=82=DD=82=C8=82=B3=\r\n=82=F1=81A=82=B1 =82=F1=82=C9=82=BF=82=CD"

Code for decoding Quoted Printable:

 private static string Decode(string input, string bodycharset)
    {
        var i = 0;
        var output = new List<byte>();
        while (i < input.Length)
        {
            if (input[i] == '=' && input[i + 1] == '\r' && input[i + 2] == '\n')
            {
                //Skip
                i += 3;
            }
            else if (input[i] == '=')
            {
                string sHex = input;
                sHex = sHex.Substring(i + 1, 2);
                int hex = Convert.ToInt32(sHex, 16);
                byte b = Convert.ToByte(hex);
                output.Add(b);
                i += 3;
            }
            else
            {
                output.Add((byte)input[i]);
                i++;
            }
        }
        if (String.IsNullOrEmpty(bodycharset))
            return Encoding.UTF8.GetString(output.ToArray());
        else
            return Encoding.GetEncoding(bodycharset).GetString(output.ToArray());
    }

Final Output:

・ｱ・・・ﾍ・P・ﾈ・・・e・X・g・ﾅ・ｷ・ﾝ・ﾈ・ｳ・・・A・ｱ・・・ﾉ・ｿ・ﾍ

Any ideas to resolve it?.

Answer 1

Late for the party, but as i've got a solution for this annoying task.

I've found the solution in the following link: http://sourceforge.net/apps/trac/syncmldotnet/wiki/Quoted%20Printable

If you just need to decode the QPs, pull inside of your code those three functions from the link above:

    HexDecoderEvaluator(Match m)
    HexDecoder(string line)
    Decode(string encodedText)

And then just:

var humanReadable = Decode(myQPString);

Anyway the link provide functions for encoding aswell.

Enjoy

Answer 2

You can write message to file and decode it in terminal with perl:

cat message_in_file.eml | perl -MMIME::QuotedPrint -ne 'print decode_qp($_)'

Answer 3

Will something similar to this work..? just Sudu coded this kind of quickly

Encoding encoding = Encoding.GetEncoding("iso-2022-jp");
byte[] bytes  = encoding.GetBytes(output);
string uuEncoded = Convert.ToBase64String(bytes);

Answer 4

You can use a trick demonstrated in following article:

• C#: Class for decoding Quoted-Printable encoding?

So you could be something like:

private static string Decode(string input, string bodycharset)
{
    Attachment attachment = Attachment.CreateAttachmentFromString("", "=?"+bodycharset+"?"+input+"?=");
    return (attachment.Name);
}

Also you need to add:

using System.Net.Mail;

I hope this helps :-)

Answer 5

try this

var str = Decode(inp, "Shift_JIS");

or

var str = Decode(inp, "sjis");

Answer 6

This Quoted Printable saved my life. It work like a charm!

public static byte[] FromHex(byte[] hexData)
    {
        if (hexData == null)
        {
            throw new ArgumentNullException("hexData");
        }

        if (hexData.Length < 2 || (hexData.Length / (double)2 != Math.Floor(hexData.Length / (double)2)))
        {
            throw new Exception("Illegal hex data, hex data must be in two bytes pairs, for example: 0F,FF,A3,... .");
        }

        MemoryStream retVal = new MemoryStream(hexData.Length / 2);
        // Loop hex value pairs
        for (int i = 0; i < hexData.Length; i += 2)
        {
            byte[] hexPairInDecimal = new byte[2];
            // We need to convert hex char to decimal number, for example F = 15
            for (int h = 0; h < 2; h++)
            {
                if (((char)hexData[i + h]) == '0')
                {
                    hexPairInDecimal[h] = 0;
                }
                else if (((char)hexData[i + h]) == '1')
                {
                    hexPairInDecimal[h] = 1;
                }
                else if (((char)hexData[i + h]) == '2')
                {
                    hexPairInDecimal[h] = 2;
                }
                else if (((char)hexData[i + h]) == '3')
                {
                    hexPairInDecimal[h] = 3;
                }
                else if (((char)hexData[i + h]) == '4')
                {
                    hexPairInDecimal[h] = 4;
                }
                else if (((char)hexData[i + h]) == '5')
                {
                    hexPairInDecimal[h] = 5;
                }
                else if (((char)hexData[i + h]) == '6')
                {
                    hexPairInDecimal[h] = 6;
                }
                else if (((char)hexData[i + h]) == '7')
                {
                    hexPairInDecimal[h] = 7;
                }
                else if (((char)hexData[i + h]) == '8')
                {
                    hexPairInDecimal[h] = 8;
                }
                else if (((char)hexData[i + h]) == '9')
                {
                    hexPairInDecimal[h] = 9;
                }
                else if (((char)hexData[i + h]) == 'A' || ((char)hexData[i + h]) == 'a')
                {
                    hexPairInDecimal[h] = 10;
                }
                else if (((char)hexData[i + h]) == 'B' || ((char)hexData[i + h]) == 'b')
                {
                    hexPairInDecimal[h] = 11;
                }
                else if (((char)hexData[i + h]) == 'C' || ((char)hexData[i + h]) == 'c')
                {
                    hexPairInDecimal[h] = 12;
                }
                else if (((char)hexData[i + h]) == 'D' || ((char)hexData[i + h]) == 'd')
                {
                    hexPairInDecimal[h] = 13;
                }
                else if (((char)hexData[i + h]) == 'E' || ((char)hexData[i + h]) == 'e')
                {
                    hexPairInDecimal[h] = 14;
                }
                else if (((char)hexData[i + h]) == 'F' || ((char)hexData[i + h]) == 'f')
                {
                    hexPairInDecimal[h] = 15;
                }
            }

            // Join hex 4 bit(left hex cahr) + 4bit(right hex char) in bytes 8 it
            retVal.WriteByte((byte)((hexPairInDecimal[0] << 4) | hexPairInDecimal[1]));
        }

        return retVal.ToArray();
    }
    public static byte[] QuotedPrintableDecode(byte[] data)
    {
        if (data == null)
        {
            throw new ArgumentNullException("data");
        }

        MemoryStream msRetVal = new MemoryStream();
        MemoryStream msSourceStream = new MemoryStream(data);

        int b = msSourceStream.ReadByte();
        while (b > -1)
        {
            // Encoded 8-bit byte(=XX) or soft line break(=CRLF)
            if (b == '=')
            {
                byte[] buffer = new byte[2];
                int nCount = msSourceStream.Read(buffer, 0, 2);
                if (nCount == 2)
                {
                    // Soft line break, line splitted, just skip CRLF
                    if (buffer[0] == '\r' && buffer[1] == '\n')
                    {
                    }
                    // This must be encoded 8-bit byte
                    else
                    {
                        try
                        {
                            msRetVal.Write(FromHex(buffer), 0, 1);
                        }
                        catch
                        {
                            // Illegal value after =, just leave it as is
                            msRetVal.WriteByte((byte)'=');
                            msRetVal.Write(buffer, 0, 2);
                        }
                    }
                }
                // Illegal =, just leave as it is
                else
                {
                    msRetVal.Write(buffer, 0, nCount);
                }
            }
            // Just write back all other bytes
            else
            {
                msRetVal.WriteByte((byte)b);
            }

            // Read next byte
            b = msSourceStream.ReadByte();
        }

        return msRetVal.ToArray();
    }