//

// Simple Usenet article decoders; includes classes to decode

// either yEnc or UuEncoded binaries. In either case you

// instantiate the appropriate class passing it the stream

// you want output written to, and then feed it the input lines

// via the DecodeLine method.

//

// by Steve Tibbett

//

using System;

using System.Collections;

using System.Collections.Specialized;

using System.Diagnostics;

using System.Text;

using System.IO;

namespace NntpLib

{

public abstract class ArticleDecoder

{

protected Stream outStream = null;

public ArticleDecoder(Stream OutputStream)

{

outStream = OutputStream;

}

public abstract bool DecodeLine(string line);

}

public class YencDecoder : ArticleDecoder

{

bool inBody = false;

bool inCode = false;

string beginLine;

public YencDecoder(Stream OutputStream, string BeginLine) : base(OutputStream)

{

this.beginLine = BeginLine;

}

/// <summary>

/// Returns true when we're done (we've found the

/// encoded block, and completed decoding it)

/// </summary>

public override bool DecodeLine(string line)

{

if (!inBody)

{

if (line.StartsWith("=ybegin "))

{

inBody = true;

return false;

};

}

if (line.StartsWith("=yend "))

{

// Done

return true;

}

if (!inCode)

{

if (line.StartsWith("=ypart "))

inCode = true;

return false;

};

if (line.EndsWith("="))

{

Debugger.Break();

};

byte[] lineBytes = Encoding.UTF8.GetBytes(line);

byte[] outBytes = new byte[lineBytes.Length];

int outByte = 0;

for (int i=0; i<lineBytes.Length; i++)

{

lineBytes[i] = (byte)((lineBytes[i] + 42) & 0xff);

char ch = (char)lineBytes[i];

if (ch == '=')

{

i++;

outBytes[outByte++] = (byte)((lineBytes[i]+64)&0xff);

} else

{

outBytes[outByte++] = lineBytes[i];

};

};

outStream.Write(outBytes, 0, outByte);

return false;

}

}

/// <summary>

/// Summary description for Article.

/// </summary>

public class UuDecoder : ArticleDecoder

{

bool inBody = false;

bool inCode = false;

string beginLine;

public UuDecoder(Stream OutputStream, string BeginLine) : base(OutputStream)

{

beginLine = BeginLine;

}

public static byte[] uuDecode(string sBuffer)

{

// Create an output array

byte[] outBuffer = new byte[(sBuffer.Length-1)/4*3];

int outIdx = 0;

// Get the string as an array of ASCII bytes

byte[] asciiBytes = Encoding.ASCII.GetBytes(sBuffer);

for (int i=0; i<asciiBytes.Length; i++)

asciiBytes[i] = (byte)((asciiBytes[i]-0x20) & 0x3f);

// Convert each block fo 4 input bytes into 3

// output bytes

for (int i = 1; i <= (asciiBytes.Length-1); i += 4)

{

outBuffer[outIdx++] = (byte)(asciiBytes[i] << 2 | asciiBytes[i+1] >> 4);

outBuffer[outIdx++] = (byte)(asciiBytes[i+1] << 4 | asciiBytes[i+2] >> 2);

outBuffer[outIdx++] = (byte)(asciiBytes[i+2] << 6 | asciiBytes[i+3]);

}

return outBuffer;

}

/// <summary>

/// Returns true when we're done (we've found the

/// encoded block, and completed decoding it)

/// </summary>

public override bool DecodeLine(string line)

{

if (line.Length == 0 && !inBody)

{

inBody = true;

return false;

};

if (inBody && line.StartsWith("begin"))

{

inCode = true;

return false;

};

if (inCode)

{

if (line.Length < 5)

return true;

byte[] data = uuDecode(line);

outStream.Write(data, 0, data.Length);

};

return false;

}

}

}