Example usage for java.nio.channels SeekableByteChannel position

Introduction

In this page you can find the example usage for java.nio.channels SeekableByteChannel position.

Prototype

SeekableByteChannel position(long newPosition) throws IOException;

Source Link

Document

Sets this channel's position.

Usage

From source file:org.cryptomator.crypto.aes256.Aes256Cryptor.java

@Override
public Long encryptFile(InputStream plaintextFile, SeekableByteChannel encryptedFile) throws IOException {
    // truncate file
    encryptedFile.truncate(0);//w  ww .  j a va2s  .c  o m

    // use an IV, whose last 8 bytes store a long used in counter mode and write initial value to file.
    final ByteBuffer countingIv = ByteBuffer.wrap(randomData(AES_BLOCK_LENGTH));
    countingIv.putLong(AES_BLOCK_LENGTH - Long.BYTES, 0l);
    countingIv.position(0);
    encryptedFile.write(countingIv);

    // init crypto stuff:
    final Mac mac = this.hmacSha256(hMacMasterKey);
    final Cipher cipher = this.aesCtrCipher(primaryMasterKey, countingIv.array(), Cipher.ENCRYPT_MODE);

    // init mac buffer and skip 32 bytes
    final ByteBuffer macBuffer = ByteBuffer.allocate(mac.getMacLength());
    encryptedFile.write(macBuffer);

    // init filesize buffer and skip 16 bytes
    final ByteBuffer encryptedFileSizeBuffer = ByteBuffer.allocate(AES_BLOCK_LENGTH);
    encryptedFile.write(encryptedFileSizeBuffer);

    // write content:
    final OutputStream out = new SeekableByteChannelOutputStream(encryptedFile);
    final OutputStream macOut = new MacOutputStream(out, mac);
    final OutputStream cipheredOut = new CipherOutputStream(macOut, cipher);
    final OutputStream blockSizeBufferedOut = new BufferedOutputStream(cipheredOut, AES_BLOCK_LENGTH);
    final Long plaintextSize = IOUtils.copyLarge(plaintextFile, blockSizeBufferedOut);

    // ensure total byte count is a multiple of the block size, in CTR mode:
    final int remainderToFillLastBlock = AES_BLOCK_LENGTH - (int) (plaintextSize % AES_BLOCK_LENGTH);
    blockSizeBufferedOut.write(new byte[remainderToFillLastBlock]);

    // append a few blocks of fake data:
    final int numberOfPlaintextBlocks = (int) Math.ceil(plaintextSize / AES_BLOCK_LENGTH);
    final int upToTenPercentFakeBlocks = (int) Math.ceil(Math.random() * 0.1 * numberOfPlaintextBlocks);
    final byte[] emptyBytes = new byte[AES_BLOCK_LENGTH];
    for (int i = 0; i < upToTenPercentFakeBlocks; i += AES_BLOCK_LENGTH) {
        blockSizeBufferedOut.write(emptyBytes);
    }
    blockSizeBufferedOut.flush();

    // write MAC of total ciphertext:
    macBuffer.position(0);
    macBuffer.put(mac.doFinal());
    macBuffer.position(0);
    encryptedFile.position(16); // right behind the IV
    encryptedFile.write(macBuffer); // 256 bit MAC

    // encrypt and write plaintextSize
    try {
        final ByteBuffer fileSizeBuffer = ByteBuffer.allocate(Long.BYTES);
        fileSizeBuffer.putLong(plaintextSize);
        final Cipher sizeCipher = aesEcbCipher(primaryMasterKey, Cipher.ENCRYPT_MODE);
        final byte[] encryptedFileSize = sizeCipher.doFinal(fileSizeBuffer.array());
        encryptedFileSizeBuffer.position(0);
        encryptedFileSizeBuffer.put(encryptedFileSize);
        encryptedFileSizeBuffer.position(0);
        encryptedFile.position(48); // right behind the IV and MAC
        encryptedFile.write(encryptedFileSizeBuffer);
    } catch (IllegalBlockSizeException | BadPaddingException e) {
        throw new IllegalStateException(
                "Block size must be valid, as padding is requested. BadPaddingException not possible in encrypt mode.",
                e);
    }

    return plaintextSize;
}

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From source file:org.mycore.common.content.util.MCRServletContentHelper.java

/**
 * Consumes the content and writes it to the ServletOutputStream.
 *
 * @param content  The source resource// w w  w  .  j  a v  a  2 s.  c om
 * @param out   The outputBufferSize stream to write to
 * @param range     Range the client wanted to retrieve
 */
private static void copy(final MCRContent content, final ServletOutputStream out, final Range range,
        // TODO: beautify this
        final int inputBufferSize, final int outputBufferSize) throws IOException {
    if (content.isReusable()) {
        try (ReadableByteChannel readableByteChannel = content.getReadableByteChannel()) {
            if (readableByteChannel instanceof SeekableByteChannel) {
                endCurrentTransaction();
                SeekableByteChannel seekableByteChannel = (SeekableByteChannel) readableByteChannel;
                seekableByteChannel.position(range.start);
                long bytesToCopy = range.end - range.start + 1;
                while (bytesToCopy > 0) {
                    ByteBuffer byteBuffer;
                    if (bytesToCopy > (long) MCRServletContentHelper.DEFAULT_BUFFER_SIZE) {
                        byteBuffer = ByteBuffer.allocate(MCRServletContentHelper.DEFAULT_BUFFER_SIZE);
                    } else {
                        byteBuffer = ByteBuffer.allocate((int) bytesToCopy);
                    }

                    int bytesRead = seekableByteChannel.read(byteBuffer);
                    bytesToCopy -= bytesRead;
                    out.write(byteBuffer.array());
                }
                return;
            }
        }
    }

    try (final InputStream resourceInputStream = content.getInputStream();
            final InputStream in = isInputStreamBuffered(resourceInputStream, content) ? resourceInputStream
                    : new BufferedInputStream(resourceInputStream, inputBufferSize)) {
        endCurrentTransaction();
        final IOException exception = copyRange(in, out, 0, range.start, range.end, outputBufferSize);
        if (exception != null) {
            throw exception;
        }
    }
}

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From source file:srebrinb.compress.sevenzip.SevenZOutputFile.java

/**
 * Prepares channel to write a 7z archive to.
 *
 * <p>{@link/*  w  w  w. j a  v  a  2 s  .  c  om*/
 * org.apache.commons.compress.utils.SeekableInMemoryByteChannel}
 * allows you to write to an in-memory archive.</p>
 *
 * @param channel the channel to write to
 * @throws IOException if the channel cannot be positioned properly
 * @since 1.13
 */
public SevenZOutputFile(final SeekableByteChannel channel) throws IOException {
    this.channel = channel;
    channel.position(SevenZFile.SIGNATURE_HEADER_SIZE);
}

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