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The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for JDK 1.5 to JDK 1.8.
package org.bouncycastle.util.encoders;
import java.io.IOException;
import java.io.OutputStream;
/**
* A streaming Hex encoder.
*/
public class HexEncoder
implements Encoder
{
protected final 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 final byte[] decodingTable = new byte[128];
protected void initialiseDecodingTable()
{
for (int i = 0; i < decodingTable.length; i++)
{
decodingTable[i] = (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();
}
public int encode(byte[] inBuf, int inOff, int inLen, byte[] outBuf, int outOff) throws IOException
{
int inPos = inOff;
int inEnd = inOff + inLen;
int outPos = outOff;
while (inPos < inEnd)
{
int b = inBuf[inPos++] & 0xFF;
outBuf[outPos++] = encodingTable[b >>> 4];
outBuf[outPos++] = encodingTable[b & 0xF];
}
return outPos - outOff;
}
/**
* encode the input data producing a Hex output stream.
*
* @return the number of bytes produced.
*/
public int encode(byte[] buf, int off, int len, OutputStream out)
throws IOException
{
byte[] tmp = new byte[72];
while (len > 0)
{
int inLen = Math.min(36, len);
int outLen = encode(buf, off, inLen, tmp, 0);
out.write(tmp, 0, outLen);
off += inLen;
len -= inLen;
}
return len * 2;
}
private static boolean 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,
OutputStream out)
throws IOException
{
byte b1, b2;
int outLen = 0;
byte[] buf = new byte[36];
int bufOff = 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) < 0)
{
throw new IOException("invalid characters encountered in Hex data");
}
buf[bufOff++] = (byte)((b1 << 4) | b2);
if (bufOff == buf.length)
{
out.write(buf);
bufOff = 0;
}
outLen++;
}
if (bufOff > 0)
{
out.write(buf, 0, bufOff);
}
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 decode(
String data,
OutputStream out)
throws IOException
{
byte b1, b2;
int length = 0;
byte[] buf = new byte[36];
int bufOff = 0;
int end = data.length();
while (end > 0)
{
if (!ignore(data.charAt(end - 1)))
{
break;
}
end--;
}
int i = 0;
while (i < end)
{
while (i < end && ignore(data.charAt(i)))
{
i++;
}
b1 = decodingTable[data.charAt(i++)];
while (i < end && ignore(data.charAt(i)))
{
i++;
}
b2 = decodingTable[data.charAt(i++)];
if ((b1 | b2) < 0)
{
throw new IOException("invalid characters encountered in Hex string");
}
buf[bufOff++] = (byte)((b1 << 4) | b2);
if (bufOff == buf.length)
{
out.write(buf);
bufOff = 0;
}
length++;
}
if (bufOff > 0)
{
out.write(buf, 0, bufOff);
}
return length;
}
byte[] decodeStrict(String str, int off, int len) throws IOException
{
if (null == str)
{
throw new NullPointerException("'str' cannot be null");
}
if (off < 0 || len < 0 || off > (str.length() - len))
{
throw new IndexOutOfBoundsException("invalid offset and/or length specified");
}
if (0 != (len & 1))
{
throw new IOException("a hexadecimal encoding must have an even number of characters");
}
int resultLen = len >>> 1;
byte[] result = new byte[resultLen];
int strPos = off;
for (int i = 0; i < resultLen; ++i)
{
byte b1 = decodingTable[str.charAt(strPos++)];
byte b2 = decodingTable[str.charAt(strPos++)];
int n = (b1 << 4) | b2;
if (n < 0)
{
throw new IOException("invalid characters encountered in Hex string");
}
result[i] = (byte)n;
}
return result;
}
}