Java Code Examples for java.nio.file.Files#newByteChannel()

@Test
public void givenPath_whenWriteToItUsingMappedByteBuffer_thenShouldSuccessfullyWrite() throws Exception {
    // given
    final CharBuffer charBuffer = CharBuffer.wrap("This will be written to the file");
    final Path pathToWrite = getFileURIFromResources("fileToWriteTo.txt");

    // when
    try (FileChannel fileChannel = (FileChannel) Files.newByteChannel(pathToWrite, EnumSet.of(StandardOpenOption.READ, StandardOpenOption.WRITE, StandardOpenOption.TRUNCATE_EXISTING))) {
        MappedByteBuffer mappedByteBuffer = fileChannel.map(FileChannel.MapMode.READ_WRITE, 0, charBuffer.length());

        if (mappedByteBuffer != null) {
            mappedByteBuffer.put(Charset.forName("utf-8").encode(charBuffer));
        }
    }

    // then
    final List<String> fileContent = Files.readAllLines(pathToWrite);
    assertEquals(fileContent.get(0), "This will be written to the file");

}
 

@Test
public void writeWritableByteChannelErrorInFlux() throws Exception {
	DataBuffer foo = stringBuffer("foo");
	DataBuffer bar = stringBuffer("bar");
	Flux<DataBuffer> flux = Flux.just(foo, bar).concatWith(Flux.error(new RuntimeException()));

	WritableByteChannel channel = Files.newByteChannel(tempFile, StandardOpenOption.WRITE);

	Flux<DataBuffer> writeResult = DataBufferUtils.write(flux, channel);
	StepVerifier.create(writeResult)
			.consumeNextWith(stringConsumer("foo"))
			.consumeNextWith(stringConsumer("bar"))
			.expectError()
			.verify(Duration.ofSeconds(5));

	String result = String.join("", Files.readAllLines(tempFile));

	assertEquals("foobar", result);
	channel.close();
}
 

@Test
public void writeWritableByteChannelCancel() throws Exception {
	DataBuffer foo = stringBuffer("foo");
	DataBuffer bar = stringBuffer("bar");
	Flux<DataBuffer> flux = Flux.just(foo, bar);

	WritableByteChannel channel = Files.newByteChannel(tempFile, StandardOpenOption.WRITE);

	Flux<DataBuffer> writeResult = DataBufferUtils.write(flux, channel);
	StepVerifier.create(writeResult, 1)
			.consumeNextWith(stringConsumer("foo"))
			.thenCancel()
			.verify(Duration.ofSeconds(5));

	String result = String.join("", Files.readAllLines(tempFile));

	assertEquals("foo", result);
	channel.close();

	flux.subscribe(DataBufferUtils::release);
}
 

/**
 * Make a request.
 *  Scans the origin request until the boundary reached. Caches
 *  the  content into a temporary file and returns it as a new request.
 * @param boundary Boundary
 * @param body Origin request body
 * @return Request
 * @throws IOException If fails
 */
private Request make(final byte[] boundary,
    final ReadableByteChannel body) throws IOException {
    final File file = File.createTempFile(
        RqMultipart.class.getName(), ".tmp"
    );
    try (WritableByteChannel channel = Files.newByteChannel(
        file.toPath(),
        StandardOpenOption.READ,
        StandardOpenOption.WRITE
    )
    ) {
        channel.write(
            ByteBuffer.wrap(
                this.head().iterator().next().getBytes(RqMtBase.ENCODING)
            )
        );
        channel.write(
            ByteBuffer.wrap(RqMtBase.CRLF.getBytes(RqMtBase.ENCODING))
        );
        this.copy(channel, boundary, body);
    }
    return new RqTemp(file);
}
 

private static void expunge(Path p, KerberosTime currTime)
        throws IOException {
    Path p2 = Files.createTempFile(p.getParent(), "rcache", null);
    try (SeekableByteChannel oldChan = Files.newByteChannel(p);
            SeekableByteChannel newChan = createNoClose(p2)) {
        long timeLimit = currTime.getSeconds() - readHeader(oldChan);
        while (true) {
            try {
                AuthTime at = AuthTime.readFrom(oldChan);
                if (at.ctime > timeLimit) {
                    ByteBuffer bb = ByteBuffer.wrap(at.encode(true));
                    newChan.write(bb);
                }
            } catch (BufferUnderflowException e) {
                break;
            }
        }
    }
    makeMine(p2);
    Files.move(p2, p,
            StandardCopyOption.REPLACE_EXISTING,
            StandardCopyOption.ATOMIC_MOVE);
}
 

public static BufferedImage readTile(Path iviewFileRoot, ImageReader imageReader, int zoomLevel, int x, int y)
    throws IOException {
    String tileName = new MessageFormat("{0}/{1}/{2}.jpg", Locale.ROOT).format(new Object[] { zoomLevel, y, x });
    Path tile = iviewFileRoot.resolve(tileName);
    if (Files.exists(tile)) {
        try (SeekableByteChannel fileChannel = Files.newByteChannel(tile)) {
            ImageInputStream iis = ImageIO.createImageInputStream(fileChannel);
            if (iis == null) {
                throw new IOException("Could not acquire ImageInputStream from SeekableByteChannel: " + tile);
            }
            imageReader.setInput(iis, true);
            BufferedImage image = imageReader.read(0);
            imageReader.reset();
            iis.close();
            return image;
        }
    } else {
        throw new NoSuchFileException(iviewFileRoot.toString(), tileName, null);
    }
}
 

/** Save the backing queue to a file */
protected synchronized void saveToFile() {
  lastSaveMs = System.currentTimeMillis();
  dequeuesSinceLastSave = 0;
  ByteArrayParamGenerator.TestCase[] testCases;
  synchronized (queue) {
    testCases = new ByteArrayParamGenerator.TestCase[queue.size()];
    queue.toArray(testCases);
  }
  try (SeekableByteChannel file = Files.newByteChannel(config.filePath,
      StandardOpenOption.WRITE, StandardOpenOption.TRUNCATE_EXISTING, StandardOpenOption.CREATE)) {
    // Just a simple buf, the testCaseToBytes can overwrite it if needed
    ByteBuffer buf = ByteBuffer.allocateDirect(1024);
    buf.putInt(testCases.length);
    buf.flip();
    file.write(buf);
    for (ByteArrayParamGenerator.TestCase testCase : testCases) {
      buf.clear();
      buf = testCaseToBytes(testCase, buf);
      buf.flip();
      file.write(buf);
    }
  } catch (IOException e) {
    throw new UncheckedIOException(e);
  }
}
 

/**
 * Creates M4A reader from file input stream, sets up metadata generation flag.
 *
 * @param f
 *            File input stream
 * @throws IOException
 *             on IO error
 */
public M4AReader(File f) throws IOException {
    if (null == f) {
        log.warn("Reader was passed a null file");
        log.debug("{}", ToStringBuilder.reflectionToString(this));
    }
    String fileName = f.getName();
    if (fileName.endsWith("m4a") || fileName.endsWith("mp4")) {
        // create a datasource / channel
        dataSource = Files.newByteChannel(Paths.get(f.toURI()));
        // instance an iso file from mp4parser
        isoFile = new IsoFile(dataSource);
        //decode all the info that we want from the atoms
        decodeHeader();
        //analyze the samples/chunks and build the keyframe meta data
        analyzeFrames();
        //add meta data
        firstTags.add(createFileMeta());
        //create / add the pre-streaming (decoder config) tags
        createPreStreamingTags();
    } else {
        log.info("Unsupported file extension: {}", fileName);
    }
}
 

private static void chCopy(Path src, Path dst) throws IOException
{
    Set<OpenOption> read = new HashSet<>();
    read.add(READ);
    Set<OpenOption> openwrite = new HashSet<>();
    openwrite.add(CREATE_NEW);
    openwrite.add(WRITE);

    try (SeekableByteChannel srcCh = Files.newByteChannel(src, read);
         SeekableByteChannel dstCh = Files.newByteChannel(dst, openwrite))
    {

        ByteBuffer bb = ByteBuffer.allocate(8192);
        while (srcCh.read(bb) >= 0) {
            bb.flip();
            dstCh.write(bb);
            bb.clear();
        }

        // Check if source read position is at the end
        if (srcCh.position() != srcCh.size()) {
            System.out.printf("src[%s]: size=%d, position=%d%n",
                              srcCh.toString(), srcCh.size(), srcCh.position());
            throw new RuntimeException("CHECK FAILED!");
        }

        // Check if destination write position is at the end
        if (dstCh.position() != dstCh.size()) {
            System.out.printf("dst[%s]: size=%d, position=%d%n",
                              dstCh.toString(), dstCh.size(), dstCh.position());
            throw new RuntimeException("CHECK FAILED!");
        }
    }
}
 

public static ByteBuffer ioResourceToByteBuffer(String resource, int bufferSize) throws IOException {
    ByteBuffer buffer;

    Path path = Paths.get(resource);
    if (Files.isReadable(path)) {
        try (SeekableByteChannel fc = Files.newByteChannel(path)) {
            buffer = BufferUtils.createByteBuffer((int) fc.size() + 1);
            while (fc.read(buffer) != -1) ;
        }
    } else {
        try (
                InputStream source = Utils.class.getResourceAsStream(resource);
                ReadableByteChannel rbc = Channels.newChannel(source)) {
            buffer = createByteBuffer(bufferSize);

            while (true) {
                int bytes = rbc.read(buffer);
                if (bytes == -1) {
                    break;
                }
                if (buffer.remaining() == 0) {
                    buffer = resizeBuffer(buffer, buffer.capacity() * 2);
                }
            }
        }
    }

    buffer.flip();
    return buffer;
}
 

public static void main(String[] args) throws Exception {

        AuthTimeWithHash a1 = new AuthTimeWithHash(client, server, time(0), 0,
                "1111111111111111");
        AuthTimeWithHash a2 = new AuthTimeWithHash(client, server, time(0), 0,
                "2222222222222222");
        KerberosTime now = new KerberosTime(time(0)*1000L);

        // When all new styles, must exact match
        ReplayCache cache = ReplayCache.getInstance("dfl:./c1");
        cache.checkAndStore(now, a1);
        cache.checkAndStore(now, a2);

        // When only old style in cache, partial match
        cache = ReplayCache.getInstance("dfl:./c2");
        cache.checkAndStore(now, a1);
        // A small surgery to remove the new style from the cache file
        SeekableByteChannel ch = Files.newByteChannel(Paths.get("c2"),
                StandardOpenOption.WRITE,
                StandardOpenOption.READ);
        ch.position(6);
        ch.write(ByteBuffer.wrap(a1.encode(false)));
        ch.truncate(ch.position());
        ch.close();
        try {
            cache.checkAndStore(now, a2);
            throw new Exception();
        } catch (KrbException ke) {
            // Correct
            System.out.println(ke);
        }
    }
 

@Override
public SeekableByteChannel newByteChannel(Path file,
                                          Set<? extends OpenOption> options,
                                          FileAttribute<?>... attrs)
    throws IOException
{
    triggerEx(file, "newByteChannel");
    return Files.newByteChannel(unwrap(file), options, attrs);
}
 

public static void main(String[] args) throws Exception {

        AuthTimeWithHash a1 = new AuthTimeWithHash(client, server, time(0), 0,
                "1111111111111111");
        AuthTimeWithHash a2 = new AuthTimeWithHash(client, server, time(0), 0,
                "2222222222222222");
        KerberosTime now = new KerberosTime(time(0)*1000L);

        // When all new styles, must exact match
        ReplayCache cache = ReplayCache.getInstance("dfl:./c1");
        cache.checkAndStore(now, a1);
        cache.checkAndStore(now, a2);

        // When only old style in cache, partial match
        cache = ReplayCache.getInstance("dfl:./c2");
        cache.checkAndStore(now, a1);
        // A small surgery to remove the new style from the cache file
        SeekableByteChannel ch = Files.newByteChannel(Paths.get("c2"),
                StandardOpenOption.WRITE,
                StandardOpenOption.READ);
        ch.position(6);
        ch.write(ByteBuffer.wrap(a1.encode(false)));
        ch.truncate(ch.position());
        ch.close();
        try {
            cache.checkAndStore(now, a2);
            throw new Exception();
        } catch (KrbException ke) {
            // Correct
            System.out.println(ke);
        }
    }
 

/**
 * This implementation opens a Channel for the underlying file.
 * @see Files#newByteChannel(Path, OpenOption...)
 */
@Override
public WritableByteChannel writableChannel() throws IOException {
	return Files.newByteChannel(this.path, StandardOpenOption.WRITE);
}
 

public static void main(String[] args) {

		Path file = Paths.get(System.getProperty("user.dir")).resolve("randomnums.txt");

		System.out.println("Will write file to: " + file);
		
		// this is just like an array that you don't need to size
		java.util.List<String> numbers = new ArrayList<>();

		for (int i = 0; i < 100; i++) {
			// casting to string from int, casting to int from double!
			numbers.add("" + (int)Math.floor((Math.random() * 1000*1000) + 1000*1000));
		}

		// temporary buffer, for each iteration.
		ByteBuffer buf = null;
		try {
			
			/***
			 * Why use a fileChannel over other methods?
			 * 
			 * https://dzone.com/articles/java-nio-vs-io
			 * 
			 * NIO vs IO
			 * 
			 * NIO uses buffers
			 * IO uses streams
			 * 
			 * Read about the differences, however you may not understand them until you understand what a "Thread" is.
			 * 
			 * 
			 * FileChannels are NIO.
			 * 
			 * InputStream / OutputStream ar IO.
			 * 
			 * 
			 * Streams are byte by byte, buffers work in blocks of bytes.
			 * 
			 * 
			 */
			// the file channel 
			WritableByteChannel channel =
					Files.newByteChannel(file, EnumSet.of(StandardOpenOption.CREATE, StandardOpenOption.WRITE));

			for (String num : numbers) {
				buf = ByteBuffer.wrap((num + "\n").getBytes());
				channel.write(buf);
			}
			System.out.println("File written.");
		} catch (IOException e) {
			e.printStackTrace();
		}

	}
 

@Test(expected = NonWritableChannelException.class)
public void nonWritableGitByteChannelTest() throws IOException {
  try(SeekableByteChannel channel = Files.newByteChannel(file, StandardOpenOption.READ)) {
    channel.write(ByteBuffer.wrap(someBytes()));
  }
}
 

private int loadAndCheck(Path p, AuthTimeWithHash time,
        KerberosTime currTime)
        throws IOException, KrbApErrException {
    int missed = 0;
    if (Files.isSymbolicLink(p)) {
        throw new IOException("Symlink not accepted");
    }
    try {
        Set<PosixFilePermission> perms =
                Files.getPosixFilePermissions(p);
        if (uid != -1 &&
                (Integer)Files.getAttribute(p, "unix:uid") != uid) {
            throw new IOException("Not mine");
        }
        if (perms.contains(PosixFilePermission.GROUP_READ) ||
                perms.contains(PosixFilePermission.GROUP_WRITE) ||
                perms.contains(PosixFilePermission.GROUP_EXECUTE) ||
                perms.contains(PosixFilePermission.OTHERS_READ) ||
                perms.contains(PosixFilePermission.OTHERS_WRITE) ||
                perms.contains(PosixFilePermission.OTHERS_EXECUTE)) {
            throw new IOException("Accessible by someone else");
        }
    } catch (UnsupportedOperationException uoe) {
        // No POSIX permissions? Ignore it.
    }
    chan = Files.newByteChannel(p, StandardOpenOption.WRITE,
            StandardOpenOption.READ);

    long timeLimit = currTime.getSeconds() - readHeader(chan);

    long pos = 0;
    boolean seeNewButNotSame = false;
    while (true) {
        try {
            pos = chan.position();
            AuthTime a = AuthTime.readFrom(chan);
            if (a instanceof AuthTimeWithHash) {
                if (time.equals(a)) {
                    // Exact match, must be a replay
                    throw new KrbApErrException(Krb5.KRB_AP_ERR_REPEAT);
                } else if (time.isSameIgnoresHash(a)) {
                    // Two different authenticators in the same second.
                    // Remember it
                    seeNewButNotSame = true;
                }
            } else {
                if (time.isSameIgnoresHash(a)) {
                    // Two authenticators in the same second. Considered
                    // same if we haven't seen a new style version of it
                    if (!seeNewButNotSame) {
                        throw new KrbApErrException(Krb5.KRB_AP_ERR_REPEAT);
                    }
                }
            }
            if (a.ctime < timeLimit) {
                missed++;
            } else {
                missed--;
            }
        } catch (BufferUnderflowException e) {
            // Half-written file?
            chan.position(pos);
            break;
        }
    }
    return missed;
}
 

/**
 * Reads all the bytes from a file. The method ensures that the file is
 * closed when all bytes have been read or an I/O error, or other runtime
 * exception, is thrown.
 *
 * <p>This is an implementation that follow {@link java.nio.file.Files#readAllBytes(java.nio.file.Path)},
 * and the difference is that it limits the size of the direct buffer to avoid
 * direct-buffer OutOfMemoryError. When {@link java.nio.file.Files#readAllBytes(java.nio.file.Path)}
 * or other interfaces in java API can do this in the future, we should remove it.
 *
 * @param path
 *        the path to the file
 * @return a byte array containing the bytes read from the file
 *
 * @throws IOException
 *         if an I/O error occurs reading from the stream
 * @throws OutOfMemoryError
 *         if an array of the required size cannot be allocated, for
 *         example the file is larger that {@code 2GB}
 */
public static byte[] readAllBytes(java.nio.file.Path path) throws IOException {
	try (SeekableByteChannel channel = Files.newByteChannel(path);
		InputStream in = Channels.newInputStream(channel)) {

		long size = channel.size();
		if (size > (long) MAX_BUFFER_SIZE) {
			throw new OutOfMemoryError("Required array size too large");
		}

		return read(in, (int) size);
	}
}
 

/**
 * Reads all the bytes from a file. The method ensures that the file is
 * closed when all bytes have been read or an I/O error, or other runtime
 * exception, is thrown.
 *
 * <p>This is an implementation that follow {@link java.nio.file.Files#readAllBytes(java.nio.file.Path)},
 * and the difference is that it limits the size of the direct buffer to avoid
 * direct-buffer OutOfMemoryError. When {@link java.nio.file.Files#readAllBytes(java.nio.file.Path)}
 * or other interfaces in java API can do this in the future, we should remove it.
 *
 * @param path
 *        the path to the file
 * @return a byte array containing the bytes read from the file
 *
 * @throws IOException
 *         if an I/O error occurs reading from the stream
 * @throws OutOfMemoryError
 *         if an array of the required size cannot be allocated, for
 *         example the file is larger that {@code 2GB}
 */
public static byte[] readAllBytes(java.nio.file.Path path) throws IOException {
	try (SeekableByteChannel channel = Files.newByteChannel(path);
		InputStream in = Channels.newInputStream(channel)) {

		long size = channel.size();
		if (size > (long) MAX_BUFFER_SIZE) {
			throw new OutOfMemoryError("Required array size too large");
		}

		return read(in, (int) size);
	}
}
 

/**
 * Create the stream output file; the flv itself.
 * 
 * @throws IOException
 */
private void createOutputFile() throws IOException {
    this.fileChannel = Files.newByteChannel(Paths.get(filePath), StandardOpenOption.CREATE, StandardOpenOption.WRITE, StandardOpenOption.TRUNCATE_EXISTING);
}