/* BlockCipherParameters.java -- 
   Copyright (C) 2002, 2003, 2006  Free Software Foundation, Inc.

This file is a part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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General Public License for more details.

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USA

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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permission to link this library with independent modules to produce an
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package gnu.javax.crypto.jce.params;

import gnu.java.security.Configuration;
import gnu.javax.crypto.jce.spec.BlockCipherParameterSpec;

import java.io.IOException;
import java.math.BigInteger;

import java.security.AlgorithmParametersSpi;
import java.security.spec.AlgorithmParameterSpec;
import java.security.spec.InvalidParameterSpecException;
import java.util.logging.Logger;

import javax.crypto.spec.IvParameterSpec;

/**
 * An implementation of algorithm parameters for the GNU block ciphers. This
 * encompasses the cipher's block size, its key size, and an optional
 * initialization vector (IV).
 */
public class BlockCipherParameters
    extends AlgorithmParametersSpi
{
  private static final Logger log = Logger.getLogger(BlockCipherParameters.class.getName());
  /** The underlying block cipher specification. */
  protected BlockCipherParameterSpec cipherSpec;
  private static final String DEFAULT_FORMAT = "ASN.1";

  /**
   * Return these parameters encoded in ASN.1 (DER).
   * <p>
   * For GNU block ciphers we will define these parameters as
   * <pre>
   * BlockCipherParameters ::= SEQUENCE {
   *    blockSize            INTEGER,
   *    keySize              INTEGER,
   *    initializationVector OCTET STRING OPTIONAL }
   * </pre>
   * 
   * @return The parameters, encoded an an ASN.1 DER sequence.
   * @throws java.io.IOException If encoding these parameters fails.
   */
  protected byte[] engineGetEncoded() throws IOException
  {
    return engineGetEncoded(DEFAULT_FORMAT);
  }

  protected byte[] engineGetEncoded(String format) throws IOException
  {
    if (! format.equalsIgnoreCase(DEFAULT_FORMAT)
        && ! format.equalsIgnoreCase("asn1"))
      throw new IOException("unknown format \"" + format + "\"");
    DERWriter writer = new DERWriter();
    int cipherBlockSize = cipherSpec.getBlockSize();
    int cipherKeySize = cipherSpec.getKeySize();
    byte[] iv = cipherSpec.getIV();
    return writer.joinarrays(
        writer.writeBigInteger(BigInteger.valueOf(cipherBlockSize)),
        writer.writeBigInteger(BigInteger.valueOf(cipherKeySize)),
        (iv != null) ? writer.writeBigInteger(new BigInteger(iv))
                     : new byte[0]);
  }

  protected void engineInit(AlgorithmParameterSpec spec)
      throws InvalidParameterSpecException
  {
    if (spec instanceof BlockCipherParameterSpec)
      cipherSpec = (BlockCipherParameterSpec) spec;
    else
      throw new InvalidParameterSpecException();
  }

  protected void engineInit(byte[] encoded, String format) throws IOException
  {
    if (! format.equalsIgnoreCase(DEFAULT_FORMAT)
        && ! format.equalsIgnoreCase("ASN1"))
      throw new IOException("invalid format: only accepts ASN.1");
    engineInit(encoded);
  }

  protected void engineInit(byte[] encoded) throws IOException
  {
    DERReader reader = new DERReader(encoded);
    int bs = reader.getBigInteger().intValue();
    int ks = reader.getBigInteger().intValue();
    byte[] iv = null;
    if (reader.hasMorePrimitives())
      iv = reader.getBigInteger().toByteArray();
    cipherSpec = new BlockCipherParameterSpec(iv, bs, ks);
    if (Configuration.DEBUG)
      log.fine("cipherSpec: " + cipherSpec);
  }

  protected AlgorithmParameterSpec engineGetParameterSpec(Class c)
      throws InvalidParameterSpecException
  {
    if (c.isInstance(cipherSpec))
      return cipherSpec;
    if (IvParameterSpec.class.isAssignableFrom(c))
      {
        IvParameterSpec result = new IvParameterSpec(cipherSpec.getIV());
        return result;
      }
    throw new InvalidParameterSpecException();
  }

  protected String engineToString()
  {
    return cipherSpec.toString();
  }
}