HexEncoder.cs :  » PDF » iTextSharp » Org » BouncyCastle » Utilities » Encoders » C# / CSharp Open Source

using System;
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'
    };

    /*
    * set up the decoding table.
    */
    internal static readonly byte[] decodingTable = new byte[128];

    static HexEncoder()
    {
      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'];
    }

    /**
    * 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 bool ignore(
      char c)
    {
      return (c == '\n' || c =='\r' || c == '\t' || c == ' ');
    }

    /**
    * 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;
    }
  }
}