Example usage for java.nio.channels AsynchronousFileChannel read

Introduction

In this page you can find the example usage for java.nio.channels AsynchronousFileChannel read.

Prototype

public abstract <A> void read(ByteBuffer dst, long position, A attachment,
        CompletionHandler<Integer, ? super A> handler);

Source Link

Document

Reads a sequence of bytes from this channel into the given buffer, starting at the given file position.

Usage

From source file:Test.java

public static void main(String args[]) throws Exception {
    ExecutorService pool = new ScheduledThreadPoolExecutor(3);
    AsynchronousFileChannel fileChannel = AsynchronousFileChannel.open(Paths.get("data.txt"),
            EnumSet.of(StandardOpenOption.READ), pool);
    CompletionHandler<Integer, ByteBuffer> handler = new CompletionHandler<Integer, ByteBuffer>() {
        public synchronized void completed(Integer result, ByteBuffer attachment) {
            for (int i = 0; i < attachment.limit(); i++) {
                System.out.print((char) attachment.get(i));
            }//from   w w w .j  a  v a2 s .  co  m
        }

        public void failed(Throwable e, ByteBuffer attachment) {
        }
    };
    final int bufferCount = 5;
    ByteBuffer buffers[] = new ByteBuffer[bufferCount];
    for (int i = 0; i < bufferCount; i++) {
        buffers[i] = ByteBuffer.allocate(10);
        fileChannel.read(buffers[i], i * 10, buffers[i], handler);
    }
    pool.awaitTermination(1, TimeUnit.SECONDS);
    for (ByteBuffer byteBuffer : buffers) {
        for (int i = 0; i < byteBuffer.limit(); i++) {
            System.out.println((char) byteBuffer.get(i));
        }
    }
}

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From source file:Test.java

public static void main(String args[]) throws Exception {
    ExecutorService pool = new ScheduledThreadPoolExecutor(3);
    AsynchronousFileChannel fileChannel = AsynchronousFileChannel.open(Paths.get("data.txt"),
            EnumSet.of(StandardOpenOption.READ), pool);
    CompletionHandler<Integer, ByteBuffer> handler = new CompletionHandler<Integer, ByteBuffer>() {
        @Override//from  w  w w  .  ja  v a  2  s .co  m
        public synchronized void completed(Integer result, ByteBuffer attachment) {
            for (int i = 0; i < attachment.limit(); i++) {
                System.out.println((char) attachment.get(i));
            }
        }

        @Override
        public void failed(Throwable e, ByteBuffer attachment) {
        }
    };
    final int bufferCount = 5;
    ByteBuffer buffers[] = new ByteBuffer[bufferCount];
    for (int i = 0; i < bufferCount; i++) {
        buffers[i] = ByteBuffer.allocate(10);
        fileChannel.read(buffers[i], i * 10, buffers[i], handler);
    }
    pool.awaitTermination(1, TimeUnit.SECONDS);
    for (ByteBuffer byteBuffer : buffers) {
        for (int i = 0; i < byteBuffer.limit(); i++) {
            System.out.print((char) byteBuffer.get(i));
        }
    }
}

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From source file:ubicrypt.core.Utils.java

public static InputStream readIs(final Path path) {
    final PipedInputStream pis = new PipedInputStream();
    final AtomicLong pos = new AtomicLong(0);
    try {/*from   ww  w . j  a  v  a2s . c o m*/
        final PipedOutputStream ostream = new PipedOutputStream(pis);
        final AsynchronousFileChannel channel = AsynchronousFileChannel.open(path, StandardOpenOption.READ);
        final ByteBuffer buffer = ByteBuffer.allocate(1 << 16);
        channel.read(buffer, pos.get(), buffer, new CompletionHandler<Integer, ByteBuffer>() {
            @Override
            public void completed(final Integer result, final ByteBuffer buf) {
                try {
                    if (result == -1) {
                        ostream.close();
                        return;
                    }
                    final byte[] bytes = new byte[result];
                    System.arraycopy(buf.array(), 0, bytes, 0, result);
                    ostream.write(bytes);
                    ostream.flush();
                    if (result < 1 << 16) {
                        ostream.close();
                        return;
                    }
                    pos.addAndGet(result);
                    final ByteBuffer buffer = ByteBuffer.allocate(1 << 16);
                    channel.read(buffer, pos.get(), buffer, this);
                } catch (final IOException e) {
                    Throwables.propagate(e);
                }
            }

            @Override
            public void failed(final Throwable exc, final ByteBuffer attachment) {
                log.error(exc.getMessage(), exc);
            }
        });
    } catch (final IOException e) {
        if (e instanceof NoSuchFileException) {
            throw new NotFoundException(path);
        }
        Throwables.propagate(e);
    }
    return pis;
}

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From source file:ubicrypt.core.Utils.java

private static void read(final AtomicLong pos, final ByteBuffer buffer, final AsynchronousFileChannel channel,
        final Subscriber<? super byte[]> subscriber) {
    channel.read(buffer, pos.get(), pos, new CompletionHandler<Integer, AtomicLong>() {
        @Override// ww w  . j av  a 2 s .  c om
        public void completed(final Integer result, final AtomicLong attachment) {
            if (result == -1) {
                subscriber.onCompleted();
                return;
            }
            subscriber.onNext(buffer.array());
            if (result < 1 << 16) {
                subscriber.onCompleted();
                return;
            }
            pos.addAndGet(result);
            read(pos, ByteBuffer.allocate(1 << 16), channel, subscriber);
        }

        @Override
        public void failed(final Throwable exc, final AtomicLong attachment) {
            subscriber.onError(exc);
        }
    });
}

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