Mac.java

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package javax.crypto;

import java.security.InvalidKeyException;
import java.security.InvalidAlgorithmParameterException;
import java.security.Key;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.Provider;
import java.security.spec.AlgorithmParameterSpec;

public class Mac implements Cloneable {

  public final static Mac getInstance(String algorithm)throws NoSuchAlgorithmException{
    SecurityAction action = new SecurityAction(algorithm, "Mac.");
    return new Mac((MacSpi) action.spi, action.provider, algorithm);
  }

  public final static Mac getInstance(String algorithm, Provider provider) throws NoSuchAlgorithmException{
    SecurityAction action = new SecurityAction(algorithm, provider, "Mac.");
    return new Mac((MacSpi) action.spi, action.provider, algorithm);
  }

  public final static Mac getInstance(String algorithm, String provider)
    throws NoSuchAlgorithmException, NoSuchProviderException {

    SecurityAction action = new SecurityAction(algorithm, provider, "Mac.");
    return new Mac((MacSpi) action.spi, action.provider, algorithm);
  }

  private Provider provider;
  private MacSpi macSpi;
  private String algorithm;
  private boolean invalidState = true;

  protected Mac(MacSpi macSpi, Provider provider, String algorithm){
    if (macSpi == null || provider == null || algorithm == null){
      throw new NullPointerException();
    }
    this.macSpi = macSpi;
    this.provider = provider;
    this.algorithm = algorithm;
  }

  public final String getAlgorithm(){
    return algorithm;
  }

  public final Provider getProvider(){
    return provider;
  }

  public final Object clone() throws CloneNotSupportedException {
    Mac clone = (Mac) super.clone();
    clone.macSpi = (MacSpi) macSpi.clone();
    return clone;
  }

  public final byte[] doFinal() throws IllegalStateException {
    if(invalidState){
      throw new IllegalStateException("Mac was not initialized");
    }
    return macSpi.engineDoFinal();
  }

  public final void doFinal(byte[] bytes, int offset) throws ShortBufferException, IllegalStateException {
    if(invalidState){
      throw new IllegalStateException("Mac was not initialized");
    }
    int len = macSpi.engineGetMacLength();
    if((bytes.length - offset - len) < 0){
      throw new ShortBufferException();
    }
    System.arraycopy(macSpi.engineDoFinal(),0, bytes, offset, len);
  }

  public final byte[] doFinal(byte[] bytes) throws IllegalStateException {
    if(invalidState){
      throw new IllegalStateException("Mac was not initialized");
    }
    macSpi.engineUpdate(bytes, 0, bytes.length);
    return macSpi.engineDoFinal();
  }


  public final int getMacLength(){
    return macSpi.engineGetMacLength();
  }

  public final void init(Key key) throws InvalidKeyException {
    try {
      macSpi.engineInit(key, null);
      invalidState = false;
    }
    catch(InvalidAlgorithmParameterException iape){
      //TODO ... is this the right thing to do ?
      throw new InvalidKeyException();
    }
  }

  public final void init(Key key, AlgorithmParameterSpec params) throws InvalidKeyException, InvalidAlgorithmParameterException {
    macSpi.engineInit(key, params);
    invalidState = false;
  }

  public final void reset(){
    macSpi.engineReset();
  }

  public final void update(byte b) throws IllegalStateException {
    if(invalidState){
      throw new IllegalStateException("Mac was not initialized");
    }
    macSpi.engineUpdate(b);
  }

  public final void update(byte[] bytes) throws IllegalStateException {
    if(invalidState){
      throw new IllegalStateException("Mac was not initialized");
    }
    macSpi.engineUpdate(bytes, 0, bytes.length);
  }

  public final void update(byte[] bytes, int offset, int len) throws IllegalStateException {
    if(invalidState){
      throw new IllegalStateException("Mac was not initialized");
    }
    macSpi.engineUpdate(bytes, offset, len);
  }
}