Package org.apache.commons.io.input
Class ReadAheadInputStream
- java.lang.Object
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- java.io.InputStream
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- org.apache.commons.io.input.ReadAheadInputStream
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- All Implemented Interfaces:
java.io.Closeable
,java.lang.AutoCloseable
public class ReadAheadInputStream extends java.io.InputStream
ImplementsInputStream
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.This class was ported and adapted from Apache Spark commit 933dc6cb7b3de1d8ccaf73d124d6eb95b947ed19.
- Since:
- 2.9.0
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Field Summary
Fields Modifier and Type Field Description private java.nio.ByteBuffer
activeBuffer
private java.util.concurrent.locks.Condition
asyncReadComplete
private boolean
endOfStream
private java.util.concurrent.ExecutorService
executorService
private boolean
isClosed
private boolean
isReading
private boolean
isUnderlyingInputStreamBeingClosed
private java.util.concurrent.atomic.AtomicBoolean
isWaiting
private static java.lang.ThreadLocal<byte[]>
oneByte
private boolean
readAborted
private java.nio.ByteBuffer
readAheadBuffer
private java.lang.Throwable
readException
private boolean
readInProgress
private boolean
shutdownExecutorService
private java.util.concurrent.locks.ReentrantLock
stateChangeLock
private java.io.InputStream
underlyingInputStream
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Constructor Summary
Constructors Modifier Constructor Description ReadAheadInputStream(java.io.InputStream inputStream, int bufferSizeInBytes)
Creates an instance with the specified buffer size and read-ahead thresholdReadAheadInputStream(java.io.InputStream inputStream, int bufferSizeInBytes, java.util.concurrent.ExecutorService executorService)
Creates an instance with the specified buffer size and read-ahead thresholdprivate
ReadAheadInputStream(java.io.InputStream inputStream, int bufferSizeInBytes, java.util.concurrent.ExecutorService executorService, boolean shutdownExecutorService)
Creates an instance with the specified buffer size and read-ahead threshold
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description int
available()
private void
checkReadException()
void
close()
private void
closeUnderlyingInputStreamIfNecessary()
private boolean
isEndOfStream()
private static java.util.concurrent.ExecutorService
newExecutorService()
Creates a new daemon executor service.private static java.lang.Thread
newThread(java.lang.Runnable r)
Creates a new daemon thread.int
read()
int
read(byte[] b, int offset, int len)
private void
readAsync()
Read data from underlyingInputStream to readAheadBuffer asynchronously.private void
signalAsyncReadComplete()
long
skip(long n)
private long
skipInternal(long n)
Internal skip function which should be called only from skip().private void
swapBuffers()
Flips the active and read ahead bufferprivate void
waitForAsyncReadComplete()
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Field Detail
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oneByte
private static final java.lang.ThreadLocal<byte[]> oneByte
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stateChangeLock
private final java.util.concurrent.locks.ReentrantLock stateChangeLock
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activeBuffer
private java.nio.ByteBuffer activeBuffer
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readAheadBuffer
private java.nio.ByteBuffer readAheadBuffer
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endOfStream
private boolean endOfStream
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readInProgress
private boolean readInProgress
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readAborted
private boolean readAborted
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readException
private java.lang.Throwable readException
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isClosed
private boolean isClosed
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isUnderlyingInputStreamBeingClosed
private boolean isUnderlyingInputStreamBeingClosed
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isReading
private boolean isReading
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isWaiting
private final java.util.concurrent.atomic.AtomicBoolean isWaiting
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underlyingInputStream
private final java.io.InputStream underlyingInputStream
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executorService
private final java.util.concurrent.ExecutorService executorService
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shutdownExecutorService
private final boolean shutdownExecutorService
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asyncReadComplete
private final java.util.concurrent.locks.Condition asyncReadComplete
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Constructor Detail
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ReadAheadInputStream
public ReadAheadInputStream(java.io.InputStream inputStream, int bufferSizeInBytes)
Creates an instance with the specified buffer size and read-ahead threshold- Parameters:
inputStream
- The underlying input stream.bufferSizeInBytes
- The buffer size.
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ReadAheadInputStream
public ReadAheadInputStream(java.io.InputStream inputStream, int bufferSizeInBytes, java.util.concurrent.ExecutorService executorService)
Creates 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.
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ReadAheadInputStream
private ReadAheadInputStream(java.io.InputStream inputStream, int bufferSizeInBytes, java.util.concurrent.ExecutorService executorService, boolean shutdownExecutorService)
Creates 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 shutdown the given ExecutorService on close.
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Method Detail
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newExecutorService
private static java.util.concurrent.ExecutorService newExecutorService()
Creates a new daemon executor service.- Returns:
- a new daemon executor service.
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newThread
private static java.lang.Thread newThread(java.lang.Runnable r)
Creates a new daemon thread.- Parameters:
r
- the thread's runnable.- Returns:
- a new daemon thread.
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available
public int available() throws java.io.IOException
- Overrides:
available
in classjava.io.InputStream
- Throws:
java.io.IOException
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checkReadException
private void checkReadException() throws java.io.IOException
- Throws:
java.io.IOException
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close
public void close() throws java.io.IOException
- Specified by:
close
in interfacejava.lang.AutoCloseable
- Specified by:
close
in interfacejava.io.Closeable
- Overrides:
close
in classjava.io.InputStream
- Throws:
java.io.IOException
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closeUnderlyingInputStreamIfNecessary
private void closeUnderlyingInputStreamIfNecessary()
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isEndOfStream
private boolean isEndOfStream()
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read
public int read() throws java.io.IOException
- Specified by:
read
in classjava.io.InputStream
- Throws:
java.io.IOException
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read
public int read(byte[] b, int offset, int len) throws java.io.IOException
- Overrides:
read
in classjava.io.InputStream
- Throws:
java.io.IOException
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readAsync
private void readAsync() throws java.io.IOException
Read data from underlyingInputStream to readAheadBuffer asynchronously.- Throws:
java.io.IOException
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signalAsyncReadComplete
private void signalAsyncReadComplete()
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skip
public long skip(long n) throws java.io.IOException
- Overrides:
skip
in classjava.io.InputStream
- Throws:
java.io.IOException
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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
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swapBuffers
private void swapBuffers()
Flips the active and read ahead buffer
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waitForAsyncReadComplete
private void waitForAsyncReadComplete() throws java.io.IOException
- Throws:
java.io.IOException
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