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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.crypto.util;
import java.util.HashMap;
import java.util.Map;
import org.bouncycastle.crypto.AlphabetMapper;
/**
* A basic alphabet mapper that just creates a mapper based on the
* passed in array of characters.
*/
public class BasicAlphabetMapper
implements AlphabetMapper
{
private Map indexMap = new HashMap();
private Map charMap = new HashMap();
/**
* Base constructor.
*
* @param alphabet a String of characters making up the alphabet.
*/
public BasicAlphabetMapper(String alphabet)
{
this(alphabet.toCharArray());
}
/**
* Base constructor.
*
* @param alphabet an array of characters making up the alphabet.
*/
public BasicAlphabetMapper(char[] alphabet)
{
for (int i = 0; i != alphabet.length; i++)
{
if (indexMap.containsKey(alphabet[i]))
{
throw new IllegalArgumentException("duplicate key detected in alphabet: " + alphabet[i]);
}
indexMap.put(alphabet[i], i);
charMap.put(i, alphabet[i]);
}
}
public int getRadix()
{
return indexMap.size();
}
public byte[] convertToIndexes(char[] input)
{
byte[] out;
if (indexMap.size() <= 256)
{
out = new byte[input.length];
for (int i = 0; i != input.length; i++)
{
out[i] = indexMap.get(input[i]).byteValue();
}
}
else
{
out = new byte[input.length * 2];
for (int i = 0; i != input.length; i++)
{
int idx = indexMap.get(input[i]);
out[i * 2] = (byte)((idx >> 8) & 0xff);
out[i * 2 + 1] = (byte)(idx & 0xff);
}
}
return out;
}
public char[] convertToChars(byte[] input)
{
char[] out;
if (charMap.size() <= 256)
{
out = new char[input.length];
for (int i = 0; i != input.length; i++)
{
out[i] = charMap.get(input[i] & 0xff);
}
}
else
{
if ((input.length & 0x1) != 0)
{
throw new IllegalArgumentException("two byte radix and input string odd length");
}
out = new char[input.length / 2];
for (int i = 0; i != input.length; i += 2)
{
out[i / 2] = charMap.get(((input[i] << 8) & 0xff00) | (input[i + 1] & 0xff));
}
}
return out;
}
}