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