Package org.apache.commons.io.input

Class ReadAheadInputStream

  • All Implemented Interfaces:
    java.io.Closeable, java.lang.AutoCloseable
    public class ReadAheadInputStream
extends java.io.FilterInputStream
    Implements InputStream to asynchronously read ahead from an underlying input stream when a specified amount of data has been read from the current buffer. It does so by maintaining two buffers: an active buffer and a read ahead buffer. The active buffer contains data which should be returned when a read() call is issued. The read ahead buffer is used to asynchronously read from the underlying input stream. When the current active buffer is exhausted, we flip the two buffers so that we can start reading from the read ahead buffer without being blocked by disk I/O.

    To build an instance, use ReadAheadInputStream.Builder.

    This class was ported and adapted from Apache Spark commit 933dc6cb7b3de1d8ccaf73d124d6eb95b947ed19.

    Since:
    2.9.0
    See Also:
    ReadAheadInputStream.Builder

    • Field Detail

      • BYTE_ARRAY_1

        private static final java.lang.ThreadLocal<byte[]> BYTE_ARRAY_1

      • stateChangeLock

        private final java.util.concurrent.locks.ReentrantLock stateChangeLock

      • activeBuffer

        private java.nio.ByteBuffer activeBuffer

      • readAheadBuffer

        private java.nio.ByteBuffer readAheadBuffer

      • endOfStream

        private boolean endOfStream

      • readInProgress

        private boolean readInProgress

      • readAborted

        private boolean readAborted

      • readException

        private java.lang.Throwable readException

      • isClosed

        private boolean isClosed

      • isUnderlyingInputStreamBeingClosed

        private boolean isUnderlyingInputStreamBeingClosed

      • isReading

        private boolean isReading

      • isWaiting

        private final java.util.concurrent.atomic.AtomicBoolean isWaiting

      • executorService

        private final java.util.concurrent.ExecutorService executorService

      • shutdownExecutorService

        private final boolean shutdownExecutorService

      • asyncReadComplete

        private final java.util.concurrent.locks.Condition asyncReadComplete

    • Constructor Detail

      • ReadAheadInputStream

        @Deprecated
public ReadAheadInputStream​(java.io.InputStream inputStream,
                            int bufferSizeInBytes)
        Deprecated.
        Use builder(), ReadAheadInputStream.Builder, and ReadAheadInputStream.Builder.get()
        Constructs an instance with the specified buffer size and read-ahead threshold
        Parameters:
        inputStream - The underlying input stream.
        bufferSizeInBytes - The buffer size.

      • ReadAheadInputStream

        @Deprecated
public ReadAheadInputStream​(java.io.InputStream inputStream,
                            int bufferSizeInBytes,
                            java.util.concurrent.ExecutorService executorService)
        Deprecated.
        Use builder(), ReadAheadInputStream.Builder, and ReadAheadInputStream.Builder.get()
        Constructs an instance with the specified buffer size and read-ahead threshold
        Parameters:
        inputStream - The underlying input stream.
        bufferSizeInBytes - The buffer size.
        executorService - An executor service for the read-ahead thread.

      • ReadAheadInputStream

        private ReadAheadInputStream​(java.io.InputStream inputStream,
                             int bufferSizeInBytes,
                             java.util.concurrent.ExecutorService executorService,
                             boolean shutdownExecutorService)
        Constructs an instance with the specified buffer size and read-ahead threshold
        Parameters:
        inputStream - The underlying input stream.
        bufferSizeInBytes - The buffer size.
        executorService - An executor service for the read-ahead thread.
        shutdownExecutorService - Whether or not to shut down the given ExecutorService on close.

    • Method Detail

      • newDaemonThread

        private static java.lang.Thread newDaemonThread​(java.lang.Runnable r)
        Constructs a new daemon thread.
        Parameters:
        r - the thread's runnable.
        Returns:
        a new daemon thread.

      • newExecutorService

        private static java.util.concurrent.ExecutorService newExecutorService()
        Constructs a new daemon executor service.
        Returns:
        a new daemon executor service.

      • available

        public int available()
              throws java.io.IOException
        Overrides:
        available in class java.io.FilterInputStream
        Throws:
        java.io.IOException

      • checkReadException

        private void checkReadException()
                         throws java.io.IOException
        Throws:
        java.io.IOException

      • close

        public void close()
           throws java.io.IOException
        Specified by:
        close in interface java.lang.AutoCloseable
        Specified by:
        close in interface java.io.Closeable
        Overrides:
        close in class java.io.FilterInputStream
        Throws:
        java.io.IOException

      • closeUnderlyingInputStreamIfNecessary

        private void closeUnderlyingInputStreamIfNecessary()

      • isEndOfStream

        private boolean isEndOfStream()

      • read

        public int read()
         throws java.io.IOException
        Overrides:
        read in class java.io.FilterInputStream
        Throws:
        java.io.IOException

      • read

        public int read​(byte[] b,
                int offset,
                int len)
         throws java.io.IOException
        Overrides:
        read in class java.io.FilterInputStream
        Throws:
        java.io.IOException

      • readAsync

        private void readAsync()
                throws java.io.IOException
        Read data from underlyingInputStream to readAheadBuffer asynchronously.
        Throws:
        java.io.IOException - if an I/O error occurs.

      • signalAsyncReadComplete

        private void signalAsyncReadComplete()

      • skip

        public long skip​(long n)
          throws java.io.IOException
        Overrides:
        skip in class java.io.FilterInputStream
        Throws:
        java.io.IOException

      • skipInternal

        private long skipInternal​(long n)
                   throws java.io.IOException
        Internal skip function which should be called only from skip(). The assumption is that the stateChangeLock is already acquired in the caller before calling this function.
        Parameters:
        n - the number of bytes to be skipped.
        Returns:
        the actual number of bytes skipped.
        Throws:
        java.io.IOException - if an I/O error occurs.

      • swapBuffers

        private void swapBuffers()
        Flips the active and read ahead buffer

      • waitForAsyncReadComplete

        private void waitForAsyncReadComplete()
                               throws java.io.IOException
        Throws:
        java.io.IOException