Update encoders from Java version, including catching invalid data instead of ignoring it

2 files changed, 448 insertions, 418 deletions

diff --git a/crypto/src/util/encoders/Base64Encoder.cs b/crypto/src/util/encoders/Base64Encoder.cs
index c94ce9d3c..7b53df25a 100644
--- a/crypto/src/util/encoders/Base64Encoder.cs
+++ b/crypto/src/util/encoders/Base64Encoder.cs
@@ -3,305 +3,322 @@ using System.IO;
 
 namespace Org.BouncyCastle.Utilities.Encoders
 {
-	public class Base64Encoder
-		: IEncoder
-	{
-		protected readonly byte[] encodingTable =
-		{
-			(byte)'A', (byte)'B', (byte)'C', (byte)'D', (byte)'E', (byte)'F', (byte)'G',
-			(byte)'H', (byte)'I', (byte)'J', (byte)'K', (byte)'L', (byte)'M', (byte)'N',
-			(byte)'O', (byte)'P', (byte)'Q', (byte)'R', (byte)'S', (byte)'T', (byte)'U',
-			(byte)'V', (byte)'W', (byte)'X', (byte)'Y', (byte)'Z',
-			(byte)'a', (byte)'b', (byte)'c', (byte)'d', (byte)'e', (byte)'f', (byte)'g',
-			(byte)'h', (byte)'i', (byte)'j', (byte)'k', (byte)'l', (byte)'m', (byte)'n',
-			(byte)'o', (byte)'p', (byte)'q', (byte)'r', (byte)'s', (byte)'t', (byte)'u',
-			(byte)'v',
-			(byte)'w', (byte)'x', (byte)'y', (byte)'z',
-			(byte)'0', (byte)'1', (byte)'2', (byte)'3', (byte)'4', (byte)'5', (byte)'6',
-			(byte)'7', (byte)'8', (byte)'9',
-			(byte)'+', (byte)'/'
-		};
-
-		protected byte padding = (byte)'=';
-
-		/*
-		* set up the decoding table.
-		*/
-		protected readonly byte[] decodingTable = new byte[128];
-
-		protected void InitialiseDecodingTable()
-		{
-			for (int i = 0; i < encodingTable.Length; i++)
-			{
-				decodingTable[encodingTable[i]] = (byte)i;
-			}
-		}
-
-		public Base64Encoder()
-		{
-			InitialiseDecodingTable();
-		}
-
-		/**
-		* encode the input data producing a base 64 output stream.
-		*
-		* @return the number of bytes produced.
-		*/
-		public int Encode(
-			byte[]	data,
-			int		off,
-			int		length,
-			Stream	outStream)
-		{
-			int modulus = length % 3;
-			int dataLength = (length - modulus);
-			int a1, a2, a3;
-
-			for (int i = off; i < off + dataLength; i += 3)
-			{
-				a1 = data[i] & 0xff;
-				a2 = data[i + 1] & 0xff;
-				a3 = data[i + 2] & 0xff;
-
-				outStream.WriteByte(encodingTable[(int) ((uint) a1 >> 2) & 0x3f]);
-				outStream.WriteByte(encodingTable[((a1 << 4) | (int) ((uint) a2 >> 4)) & 0x3f]);
-				outStream.WriteByte(encodingTable[((a2 << 2) | (int) ((uint) a3 >> 6)) & 0x3f]);
-				outStream.WriteByte(encodingTable[a3 & 0x3f]);
-			}
-
-			/*
-			* process the tail end.
-			*/
-			int b1, b2, b3;
-			int d1, d2;
-
-			switch (modulus)
-			{
-				case 0:        /* nothing left to do */
-					break;
-				case 1:
-					d1 = data[off + dataLength] & 0xff;
-					b1 = (d1 >> 2) & 0x3f;
-					b2 = (d1 << 4) & 0x3f;
-
-					outStream.WriteByte(encodingTable[b1]);
-					outStream.WriteByte(encodingTable[b2]);
-					outStream.WriteByte(padding);
-					outStream.WriteByte(padding);
-					break;
-				case 2:
-					d1 = data[off + dataLength] & 0xff;
-					d2 = data[off + dataLength + 1] & 0xff;
-
-					b1 = (d1 >> 2) & 0x3f;
-					b2 = ((d1 << 4) | (d2 >> 4)) & 0x3f;
-					b3 = (d2 << 2) & 0x3f;
-
-					outStream.WriteByte(encodingTable[b1]);
-					outStream.WriteByte(encodingTable[b2]);
-					outStream.WriteByte(encodingTable[b3]);
-					outStream.WriteByte(padding);
-					break;
-			}
-
-			return (dataLength / 3) * 4 + ((modulus == 0) ? 0 : 4);
-		}
-
-		private bool ignore(
-			char c)
-		{
-			return (c == '\n' || c =='\r' || c == '\t' || c == ' ');
-		}
-
-		/**
-		* decode the base 64 encoded byte data writing it to the given output stream,
-		* whitespace characters will be ignored.
-		*
-		* @return the number of bytes produced.
-		*/
-		public int Decode(
-			byte[]	data,
-			int		off,
-			int		length,
-			Stream	outStream)
-		{
-			byte b1, b2, b3, b4;
-			int outLen = 0;
-
-			int end = off + length;
-
-			while (end > off)
-			{
-				if (!ignore((char)data[end - 1]))
-				{
-					break;
-				}
-
-				end--;
-			}
-
-			int  i = off;
-			int  finish = end - 4;
-
-			i = nextI(data, i, finish);
-
-			while (i < finish)
-			{
-				b1 = decodingTable[data[i++]];
-
-				i = nextI(data, i, finish);
-
-				b2 = decodingTable[data[i++]];
-
-				i = nextI(data, i, finish);
-
-				b3 = decodingTable[data[i++]];
-
-				i = nextI(data, i, finish);
-
-				b4 = decodingTable[data[i++]];
-
-				outStream.WriteByte((byte)((b1 << 2) | (b2 >> 4)));
-				outStream.WriteByte((byte)((b2 << 4) | (b3 >> 2)));
-				outStream.WriteByte((byte)((b3 << 6) | b4));
-
-				outLen += 3;
-
-				i = nextI(data, i, finish);
-			}
-
-			outLen += decodeLastBlock(outStream, (char)data[end - 4], (char)data[end - 3], (char)data[end - 2], (char)data[end - 1]);
-
-			return outLen;
-		}
-
-		private int nextI(
-			byte[]	data,
-			int		i,
-			int		finish)
-		{
-			while ((i < finish) && ignore((char)data[i]))
-			{
-				i++;
-			}
-			return i;
-		}
-
-		/**
-		* decode the base 64 encoded string data writing it to the given output stream,
-		* whitespace characters will be ignored.
-		*
-		* @return the number of bytes produced.
-		*/
-		public int DecodeString(
-			string	data,
-			Stream	outStream)
-		{
-			// Platform Implementation
+    public class Base64Encoder
+        : IEncoder
+    {
+        protected readonly byte[] encodingTable =
+        {
+            (byte)'A', (byte)'B', (byte)'C', (byte)'D', (byte)'E', (byte)'F', (byte)'G',
+            (byte)'H', (byte)'I', (byte)'J', (byte)'K', (byte)'L', (byte)'M', (byte)'N',
+            (byte)'O', (byte)'P', (byte)'Q', (byte)'R', (byte)'S', (byte)'T', (byte)'U',
+            (byte)'V', (byte)'W', (byte)'X', (byte)'Y', (byte)'Z',
+            (byte)'a', (byte)'b', (byte)'c', (byte)'d', (byte)'e', (byte)'f', (byte)'g',
+            (byte)'h', (byte)'i', (byte)'j', (byte)'k', (byte)'l', (byte)'m', (byte)'n',
+            (byte)'o', (byte)'p', (byte)'q', (byte)'r', (byte)'s', (byte)'t', (byte)'u',
+            (byte)'v',
+            (byte)'w', (byte)'x', (byte)'y', (byte)'z',
+            (byte)'0', (byte)'1', (byte)'2', (byte)'3', (byte)'4', (byte)'5', (byte)'6',
+            (byte)'7', (byte)'8', (byte)'9',
+            (byte)'+', (byte)'/'
+        };
+
+        protected byte padding = (byte)'=';
+
+        /*
+        * set up the decoding table.
+        */
+        protected readonly byte[] decodingTable = new byte[128];
+
+        protected void InitialiseDecodingTable()
+        {
+            Arrays.Fill(decodingTable, (byte)0xff);
+
+            for (int i = 0; i < encodingTable.Length; i++)
+            {
+                decodingTable[encodingTable[i]] = (byte)i;
+            }
+        }
+
+        public Base64Encoder()
+        {
+            InitialiseDecodingTable();
+        }
+
+        /**
+        * encode the input data producing a base 64 output stream.
+        *
+        * @return the number of bytes produced.
+        */
+        public int Encode(
+            byte[]	data,
+            int		off,
+            int		length,
+            Stream	outStream)
+        {
+            int modulus = length % 3;
+            int dataLength = (length - modulus);
+            int a1, a2, a3;
+
+            for (int i = off; i < off + dataLength; i += 3)
+            {
+                a1 = data[i] & 0xff;
+                a2 = data[i + 1] & 0xff;
+                a3 = data[i + 2] & 0xff;
+
+                outStream.WriteByte(encodingTable[(int) ((uint) a1 >> 2) & 0x3f]);
+                outStream.WriteByte(encodingTable[((a1 << 4) | (int) ((uint) a2 >> 4)) & 0x3f]);
+                outStream.WriteByte(encodingTable[((a2 << 2) | (int) ((uint) a3 >> 6)) & 0x3f]);
+                outStream.WriteByte(encodingTable[a3 & 0x3f]);
+            }
+
+            /*
+            * process the tail end.
+            */
+            int b1, b2, b3;
+            int d1, d2;
+
+            switch (modulus)
+            {
+                case 0:        /* nothing left to do */
+                    break;
+                case 1:
+                    d1 = data[off + dataLength] & 0xff;
+                    b1 = (d1 >> 2) & 0x3f;
+                    b2 = (d1 << 4) & 0x3f;
+
+                    outStream.WriteByte(encodingTable[b1]);
+                    outStream.WriteByte(encodingTable[b2]);
+                    outStream.WriteByte(padding);
+                    outStream.WriteByte(padding);
+                    break;
+                case 2:
+                    d1 = data[off + dataLength] & 0xff;
+                    d2 = data[off + dataLength + 1] & 0xff;
+
+                    b1 = (d1 >> 2) & 0x3f;
+                    b2 = ((d1 << 4) | (d2 >> 4)) & 0x3f;
+                    b3 = (d2 << 2) & 0x3f;
+
+                    outStream.WriteByte(encodingTable[b1]);
+                    outStream.WriteByte(encodingTable[b2]);
+                    outStream.WriteByte(encodingTable[b3]);
+                    outStream.WriteByte(padding);
+                    break;
+            }
+
+            return (dataLength / 3) * 4 + ((modulus == 0) ? 0 : 4);
+        }
+
+        private bool ignore(
+            char c)
+        {
+            return (c == '\n' || c =='\r' || c == '\t' || c == ' ');
+        }
+
+        /**
+        * decode the base 64 encoded byte data writing it to the given output stream,
+        * whitespace characters will be ignored.
+        *
+        * @return the number of bytes produced.
+        */
+        public int Decode(
+            byte[]	data,
+            int		off,
+            int		length,
+            Stream	outStream)
+        {
+            byte b1, b2, b3, b4;
+            int outLen = 0;
+
+            int end = off + length;
+
+            while (end > off)
+            {
+                if (!ignore((char)data[end - 1]))
+                {
+                    break;
+                }
+
+                end--;
+            }
+
+            int  i = off;
+            int  finish = end - 4;
+
+            i = nextI(data, i, finish);
+
+            while (i < finish)
+            {
+                b1 = decodingTable[data[i++]];
+
+                i = nextI(data, i, finish);
+
+                b2 = decodingTable[data[i++]];
+
+                i = nextI(data, i, finish);
+
+                b3 = decodingTable[data[i++]];
+
+                i = nextI(data, i, finish);
+
+                b4 = decodingTable[data[i++]];
+
+                if ((b1 | b2 | b3 | b4) >= 0x80)
+                    throw new IOException("invalid characters encountered in base64 data");
+
+                outStream.WriteByte((byte)((b1 << 2) | (b2 >> 4)));
+                outStream.WriteByte((byte)((b2 << 4) | (b3 >> 2)));
+                outStream.WriteByte((byte)((b3 << 6) | b4));
+
+                outLen += 3;
+
+                i = nextI(data, i, finish);
+            }
+
+            outLen += decodeLastBlock(outStream, (char)data[end - 4], (char)data[end - 3], (char)data[end - 2], (char)data[end - 1]);
+
+            return outLen;
+        }
+
+        private int nextI(
+            byte[]	data,
+            int		i,
+            int		finish)
+        {
+            while ((i < finish) && ignore((char)data[i]))
+            {
+                i++;
+            }
+            return i;
+        }
+
+        /**
+        * decode the base 64 encoded string data writing it to the given output stream,
+        * whitespace characters will be ignored.
+        *
+        * @return the number of bytes produced.
+        */
+        public int DecodeString(
+            string	data,
+            Stream	outStream)
+        {
+            // Platform Implementation
 //			byte[] bytes = Convert.FromBase64String(data);
 //			outStream.Write(bytes, 0, bytes.Length);
 //			return bytes.Length;
 
-			byte b1, b2, b3, b4;
-			int length = 0;
+            byte b1, b2, b3, b4;
+            int length = 0;
 
-			int end = data.Length;
+            int end = data.Length;
 
-			while (end > 0)
-			{
-				if (!ignore(data[end - 1]))
-				{
-					break;
-				}
+            while (end > 0)
+            {
+                if (!ignore(data[end - 1]))
+                {
+                    break;
+                }
 
-				end--;
-			}
+                end--;
+            }
 
-			int  i = 0;
-			int  finish = end - 4;
+            int  i = 0;
+            int  finish = end - 4;
 
-			i = nextI(data, i, finish);
+            i = nextI(data, i, finish);
 
-			while (i < finish)
-			{
-				b1 = decodingTable[data[i++]];
+            while (i < finish)
+            {
+                b1 = decodingTable[data[i++]];
 
-				i = nextI(data, i, finish);
+                i = nextI(data, i, finish);
 
-				b2 = decodingTable[data[i++]];
+                b2 = decodingTable[data[i++]];
 
-				i = nextI(data, i, finish);
+                i = nextI(data, i, finish);
 
-				b3 = decodingTable[data[i++]];
+                b3 = decodingTable[data[i++]];
 
-				i = nextI(data, i, finish);
+                i = nextI(data, i, finish);
 
-				b4 = decodingTable[data[i++]];
+                b4 = decodingTable[data[i++]];
 
-				outStream.WriteByte((byte)((b1 << 2) | (b2 >> 4)));
-				outStream.WriteByte((byte)((b2 << 4) | (b3 >> 2)));
-				outStream.WriteByte((byte)((b3 << 6) | b4));
+                if ((b1 | b2 | b3 | b4) >= 0x80)
+                    throw new IOException("invalid characters encountered in base64 data");
 
-				length += 3;
+                outStream.WriteByte((byte)((b1 << 2) | (b2 >> 4)));
+                outStream.WriteByte((byte)((b2 << 4) | (b3 >> 2)));
+                outStream.WriteByte((byte)((b3 << 6) | b4));
 
-				i = nextI(data, i, finish);
-			}
+                length += 3;
 
-			length += decodeLastBlock(outStream, data[end - 4], data[end - 3], data[end - 2], data[end - 1]);
+                i = nextI(data, i, finish);
+            }
 
-			return length;
-		}
+            length += decodeLastBlock(outStream, data[end - 4], data[end - 3], data[end - 2], data[end - 1]);
 
-		private int decodeLastBlock(
-			Stream	outStream,
-			char	c1,
-			char	c2,
-			char	c3,
-			char	c4)
-		{
-			if (c3 == padding)
-			{
-				byte b1 = decodingTable[c1];
-				byte b2 = decodingTable[c2];
+            return length;
+        }
 
-				outStream.WriteByte((byte)((b1 << 2) | (b2 >> 4)));
+        private int decodeLastBlock(
+            Stream	outStream,
+            char	c1,
+            char	c2,
+            char	c3,
+            char	c4)
+        {
+            if (c3 == padding)
+            {
+                byte b1 = decodingTable[c1];
+                byte b2 = decodingTable[c2];
 
-				return 1;
-			}
+                if ((b1 | b2) >= 0x80)
+                    throw new IOException("invalid characters encountered at end of base64 data");
 
-			if (c4 == padding)
-			{
-				byte b1 = decodingTable[c1];
-				byte b2 = decodingTable[c2];
-				byte b3 = decodingTable[c3];
+                outStream.WriteByte((byte)((b1 << 2) | (b2 >> 4)));
 
-				outStream.WriteByte((byte)((b1 << 2) | (b2 >> 4)));
-				outStream.WriteByte((byte)((b2 << 4) | (b3 >> 2)));
+                return 1;
+            }
 
-				return 2;
-			}
+            if (c4 == padding)
+            {
+                byte b1 = decodingTable[c1];
+                byte b2 = decodingTable[c2];
+                byte b3 = decodingTable[c3];
 
-			{
-				byte b1 = decodingTable[c1];
-				byte b2 = decodingTable[c2];
-				byte b3 = decodingTable[c3];
-				byte b4 = decodingTable[c4];
+                if ((b1 | b2 | b3) >= 0x80)
+                    throw new IOException("invalid characters encountered at end of base64 data");
 
-				outStream.WriteByte((byte)((b1 << 2) | (b2 >> 4)));
-				outStream.WriteByte((byte)((b2 << 4) | (b3 >> 2)));
-				outStream.WriteByte((byte)((b3 << 6) | b4));
+                outStream.WriteByte((byte)((b1 << 2) | (b2 >> 4)));
+                outStream.WriteByte((byte)((b2 << 4) | (b3 >> 2)));
 
-				return 3;
-			}
-		}
+                return 2;
+            }
 
-		private int nextI(string data, int i, int finish)
-		{
-			while ((i < finish) && ignore(data[i]))
-			{
-				i++;
-			}
-			return i;
-		}
-	}
+            {
+                byte b1 = decodingTable[c1];
+                byte b2 = decodingTable[c2];
+                byte b3 = decodingTable[c3];
+                byte b4 = decodingTable[c4];
+
+                if ((b1 | b2 | b3 | b4) >= 0x80)
+                    throw new IOException("invalid characters encountered at end of base64 data");
+
+                outStream.WriteByte((byte)((b1 << 2) | (b2 >> 4)));
+                outStream.WriteByte((byte)((b2 << 4) | (b3 >> 2)));
+                outStream.WriteByte((byte)((b3 << 6) | b4));
+
+                return 3;
+            }
+        }
+
+        private int nextI(string data, int i, int finish)
+        {
+            while ((i < finish) && ignore(data[i]))
+            {
+                i++;
+            }
+            return i;
+        }
+    }
 }
diff --git a/crypto/src/util/encoders/HexEncoder.cs b/crypto/src/util/encoders/HexEncoder.cs
index e69a78b0b..af526e0da 100644
--- a/crypto/src/util/encoders/HexEncoder.cs
+++ b/crypto/src/util/encoders/HexEncoder.cs
@@ -3,56 +3,63 @@ using System.IO;
 
 namespace Org.BouncyCastle.Utilities.Encoders
 {
-	public class HexEncoder
-		: IEncoder
-	{
-		private static readonly byte[] encodingTable =
-		{
-			(byte)'0', (byte)'1', (byte)'2', (byte)'3', (byte)'4', (byte)'5', (byte)'6', (byte)'7',
-			(byte)'8', (byte)'9', (byte)'a', (byte)'b', (byte)'c', (byte)'d', (byte)'e', (byte)'f'
-		};
-
-        private static readonly byte[] decodingTable = ConstructDecodingTable(encodingTable);
-
-        private static byte[] ConstructDecodingTable(byte[] et)
-		{
-            byte[] dt = new byte[128];
-			for (int i = 0; i < et.Length; i++)
-			{
-				dt[et[i]] = (byte)i;
-			}
-
-			dt['A'] = dt['a'];
-			dt['B'] = dt['b'];
-			dt['C'] = dt['c'];
-			dt['D'] = dt['d'];
-			dt['E'] = dt['e'];
-			dt['F'] = dt['f'];
-
-            return dt;
-		}
+    public class HexEncoder
+        : IEncoder
+    {
+        protected readonly byte[] encodingTable =
+        {
+            (byte)'0', (byte)'1', (byte)'2', (byte)'3', (byte)'4', (byte)'5', (byte)'6', (byte)'7',
+            (byte)'8', (byte)'9', (byte)'a', (byte)'b', (byte)'c', (byte)'d', (byte)'e', (byte)'f'
+        };
+
+        /*
+         * set up the decoding table.
+         */
+        protected readonly byte[] decodingTable = new byte[128];
+
+        protected void InitialiseDecodingTable()
+        {
+            Arrays.Fill(decodingTable, (byte)0xff);
+
+            for (int i = 0; i < encodingTable.Length; i++)
+            {
+                decodingTable[encodingTable[i]] = (byte)i;
+            }
+
+            decodingTable['A'] = decodingTable['a'];
+            decodingTable['B'] = decodingTable['b'];
+            decodingTable['C'] = decodingTable['c'];
+            decodingTable['D'] = decodingTable['d'];
+            decodingTable['E'] = decodingTable['e'];
+            decodingTable['F'] = decodingTable['f'];
+        }
+
+        public HexEncoder()
+        {
+            InitialiseDecodingTable();
+        }
 
         /**
-		* encode the input data producing a Hex output stream.
-		*
-		* @return the number of bytes produced.
-		*/
-		public int Encode(
-			byte[]	data,
-			int		off,
-			int		length,
-			Stream	outStream)
-		{
-			for (int i = off; i < (off + length); i++)
-			{
-				int v = data[i];
-
-				outStream.WriteByte(encodingTable[v >> 4]);
-				outStream.WriteByte(encodingTable[v & 0xf]);
-			}
-
-			return length * 2;
-		}
+        * encode the input data producing a Hex output stream.
+        *
+        * @return the number of bytes produced.
+        */
+        public int Encode(
+            byte[]	data,
+            int		off,
+            int		length,
+            Stream	outStream)
+        {
+            for (int i = off; i < (off + length); i++)
+            {
+                int v = data[i];
+
+                outStream.WriteByte(encodingTable[v >> 4]);
+                outStream.WriteByte(encodingTable[v & 0xf]);
+            }
+
+            return length * 2;
+        }
 
         private static bool Ignore(char c)
         {
@@ -60,104 +67,110 @@ namespace Org.BouncyCastle.Utilities.Encoders
         }
 
         /**
-		* decode the Hex encoded byte data writing it to the given output stream,
-		* whitespace characters will be ignored.
-		*
-		* @return the number of bytes produced.
-		*/
-		public int Decode(
-			byte[]	data,
-			int		off,
-			int		length,
-			Stream	outStream)
-		{
-			byte b1, b2;
-			int outLen = 0;
-			int end = off + length;
-
-			while (end > off)
-			{
-				if (!Ignore((char)data[end - 1]))
-				{
-					break;
-				}
-
-				end--;
-			}
-
-			int i = off;
-			while (i < end)
-			{
-				while (i < end && Ignore((char)data[i]))
-				{
-					i++;
-				}
-
-				b1 = decodingTable[data[i++]];
-
-				while (i < end && Ignore((char)data[i]))
-				{
-					i++;
-				}
-
-				b2 = decodingTable[data[i++]];
-
-				outStream.WriteByte((byte)((b1 << 4) | b2));
-
-				outLen++;
-			}
-
-			return outLen;
-		}
-
-		/**
-		* decode the Hex encoded string data writing it to the given output stream,
-		* whitespace characters will be ignored.
-		*
-		* @return the number of bytes produced.
-		*/
-		public int DecodeString(
-			string	data,
-			Stream	outStream)
-		{
-			byte    b1, b2;
-			int     length = 0;
-
-			int     end = data.Length;
-
-			while (end > 0)
-			{
-				if (!Ignore(data[end - 1]))
-				{
-					break;
-				}
-
-				end--;
-			}
-
-			int i = 0;
-			while (i < end)
-			{
-				while (i < end && Ignore(data[i]))
-				{
-					i++;
-				}
-
-				b1 = decodingTable[data[i++]];
-
-				while (i < end && Ignore(data[i]))
-				{
-					i++;
-				}
-
-				b2 = decodingTable[data[i++]];
-
-				outStream.WriteByte((byte)((b1 << 4) | b2));
-
-				length++;
-			}
-
-			return length;
-		}
-	}
+        * decode the Hex encoded byte data writing it to the given output stream,
+        * whitespace characters will be ignored.
+        *
+        * @return the number of bytes produced.
+        */
+        public int Decode(
+            byte[]	data,
+            int		off,
+            int		length,
+            Stream	outStream)
+        {
+            byte b1, b2;
+            int outLen = 0;
+            int end = off + length;
+
+            while (end > off)
+            {
+                if (!Ignore((char)data[end - 1]))
+                {
+                    break;
+                }
+
+                end--;
+            }
+
+            int i = off;
+            while (i < end)
+            {
+                while (i < end && Ignore((char)data[i]))
+                {
+                    i++;
+                }
+
+                b1 = decodingTable[data[i++]];
+
+                while (i < end && Ignore((char)data[i]))
+                {
+                    i++;
+                }
+
+                b2 = decodingTable[data[i++]];
+
+                if ((b1 | b2) >= 0x80)
+                    throw new IOException("invalid characters encountered in Hex data");
+
+                outStream.WriteByte((byte)((b1 << 4) | b2));
+
+                outLen++;
+            }
+
+            return outLen;
+        }
+
+        /**
+        * decode the Hex encoded string data writing it to the given output stream,
+        * whitespace characters will be ignored.
+        *
+        * @return the number of bytes produced.
+        */
+        public int DecodeString(
+            string	data,
+            Stream	outStream)
+        {
+            byte    b1, b2;
+            int     length = 0;
+
+            int     end = data.Length;
+
+            while (end > 0)
+            {
+                if (!Ignore(data[end - 1]))
+                {
+                    break;
+                }
+
+                end--;
+            }
+
+            int i = 0;
+            while (i < end)
+            {
+                while (i < end && Ignore(data[i]))
+                {
+                    i++;
+                }
+
+                b1 = decodingTable[data[i++]];
+
+                while (i < end && Ignore(data[i]))
+                {
+                    i++;
+                }
+
+                b2 = decodingTable[data[i++]];
+
+                if ((b1 | b2) >= 0x80)
+                    throw new IOException("invalid characters encountered in Hex data");
+
+                outStream.WriteByte((byte)((b1 << 4) | b2));
+
+                length++;
+            }
+
+            return length;
+        }
+    }
 }