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using System;
using System.IO;
namespace Org.BouncyCastle.Utilities.Encoders
{
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;
}
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++]];
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;
}
internal byte[] DecodeStrict(string str, int off, int len)
{
if (null == str)
throw new ArgumentNullException("str");
if (off < 0 || len < 0 || off > (str.Length - len))
throw new IndexOutOfRangeException("invalid offset and/or length specified");
if (0 != (len & 1))
throw new ArgumentException("a hexadecimal encoding must have an even number of characters", "len");
int resultLen = len >> 1;
byte[] result = new byte[resultLen];
int strPos = off;
for (int i = 0; i < resultLen; ++i)
{
byte b1 = decodingTable[str[strPos++]];
byte b2 = decodingTable[str[strPos++]];
if ((b1 | b2) >= 0x80)
throw new IOException("invalid characters encountered in Hex data");
result[i] = (byte)((b1 << 4) | b2);
}
return result;
}
}
}
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