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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'
};
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;
}
/**
* 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)
{
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;
}
}
}
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