Android Open Source - conceal Better Cipher Input Stream

From Project

Back to project page conceal.

License

The source code is released under:

BSD License For Conceal software Copyright (c) 2014, Facebook, Inc. All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that...

If you think the Android project conceal listed in this page is inappropriate, such as containing malicious code/tools or violating the copyright, please email info at java2s dot com, thanks.

Java Source Code

/*
 *  Copyright (c) 2014, Facebook, Inc./*from  w ww  .  j  a  v  a  2s .c  o m*/
 *  All rights reserved.
 *
 *  This source code is licensed under the BSD-style license found in the
 *  LICENSE file in the root directory of this source tree. An additional grant
 *  of patent rights can be found in the PATENTS file in the same directory.
 *
 */

package com.facebook.crypto.streams;

import javax.crypto.Cipher;
import javax.crypto.ShortBufferException;

import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;

/**
 * The Cipher stream implementation in android is really slow.
 * This provides a better cipher stream for java Ciphers.
 * </p>
 * If we ran benchmark code with the default cipher input stream in android,
 * we would beat it hands down. We use this stream so that we can have a
 * more fair comparison.
 */
public class BetterCipherInputStream extends FilterInputStream {

  private static final int UPDATE_BUFFER_SIZE = 256;

  private final Cipher mCipher;
  private final byte[] mUpdateBuffer;

  public BetterCipherInputStream(InputStream in, Cipher cipher) {
    super(in);
    mCipher = cipher;
    mUpdateBuffer = new byte[UPDATE_BUFFER_SIZE];
  }

  @Override
  public int read(byte[] buffer, int offset, int count) throws IOException {
    int read = in.read(buffer, offset, count);
    if (read == -1) {
      return -1;
    }

    int times = read / UPDATE_BUFFER_SIZE;
    int remainder = read % UPDATE_BUFFER_SIZE;

    int originalOffset = offset;
    int currentReadOffset = offset;

    try {
      for (int i = 0; i < times; ++i) {
        int bytesDecrypted = mCipher.update(buffer, offset, UPDATE_BUFFER_SIZE, mUpdateBuffer);
        System.arraycopy(mUpdateBuffer, 0, buffer, currentReadOffset, bytesDecrypted);
        currentReadOffset += bytesDecrypted;
        offset += UPDATE_BUFFER_SIZE;
      }

      if (remainder > 0) {
        int bytesDecrypted = mCipher.update(buffer, offset, remainder, mUpdateBuffer);
        System.arraycopy(mUpdateBuffer, 0, buffer, currentReadOffset, bytesDecrypted);
        currentReadOffset += bytesDecrypted;
      }
    } catch (ShortBufferException e) {
      // do nothing. This cannot happen, since we supply the correct lengths.
    }

    return currentReadOffset - originalOffset;
  }
}

Java Source Code List