Package uk.ac.starlink.util
Class PipeReaderThread
java.lang.Object
java.lang.Thread
uk.ac.starlink.util.PipeReaderThread
- All Implemented Interfaces:
Runnable
Thread which reads data from a pipe. Having got an instance
of this class, you can call its getOutputStream method to
acquire a stream to write into, and then implement its
doReading(java.io.InputStream)
method to process the data; this method runs
in the new thread.
Here is an example of using the class to count the bytes written down a stream:
PipeReaderThread reader = new PipeReaderThread() { protected void doReading( InputStream dataIn ) throws IOException { int i; while ( dataIn.read() >= 0 ) i++; System.out.println( i ); } }; reader.start(); OutputStream dataOut = reader.getOutputStream(); // write bytes down dataOut ... dataOut.close(); reader.finishReading();Other uses will look pretty similar, but just override
doReading
in different ways. Note that any exceptions thrown by doReading
are caught and eventually thrown in the reader thread by
finishReading
. The same exception may also be thrown by
the write
method of the writer thread.
This class serves two purposes. Firstly it copes with IOExceptions
encountered during the read, and makes sure they get thrown at the
writing end of the pipe (doReading
is declared to
throw IOException
).
Secondly it shields the user from the implementation of the piped
connection.
Performance of the
PipedInputStream
/PipedOutputStream
is dismal - this class may be able to do better.
The current implementation uses a couple of drop-in Piped*Stream
replacements, but performance still isn't great - it may be possible
to do better in future. You can provide your own paired pipes
by overriding both getInputStream()
and getOutputStream()
.
- Author:
- Mark Taylor (Starlink)
-
Nested Class Summary
Nested classes/interfaces inherited from class java.lang.Thread
Thread.Builder, Thread.State, Thread.UncaughtExceptionHandler
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Field Summary
Fields inherited from class java.lang.Thread
MAX_PRIORITY, MIN_PRIORITY, NORM_PRIORITY
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionprotected abstract void
doReading
(InputStream dataIn) This method should be implemented to consume all the bytes in the given input stream.void
Waits until thedoReading
method has finished reading the bytes written down the output stream, closes the input stream, and returns.protected InputStream
Returns the stream at the input end of the pipe.Returns the stream at the output end of the pipe.void
run()
Implements the thread'srun
method to invoke doReading, catching and saving IOExceptions.Methods inherited from class java.lang.Thread
activeCount, checkAccess, clone, countStackFrames, currentThread, dumpStack, enumerate, getAllStackTraces, getContextClassLoader, getDefaultUncaughtExceptionHandler, getId, getName, getPriority, getStackTrace, getState, getThreadGroup, getUncaughtExceptionHandler, holdsLock, interrupt, interrupted, isAlive, isDaemon, isInterrupted, isVirtual, join, join, join, join, ofPlatform, ofVirtual, onSpinWait, resume, setContextClassLoader, setDaemon, setDefaultUncaughtExceptionHandler, setName, setPriority, setUncaughtExceptionHandler, sleep, sleep, sleep, start, startVirtualThread, stop, suspend, threadId, toString, yield
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Constructor Details
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PipeReaderThread
Constructs a new reader thread.- Throws:
IOException
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Method Details
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getInputStream
Returns the stream at the input end of the pipe.- Returns:
- input stream
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getOutputStream
Returns the stream at the output end of the pipe.- Returns:
- output stream
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run
public void run()Implements the thread'srun
method to invoke doReading, catching and saving IOExceptions. -
doReading
This method should be implemented to consume all the bytes in the given input stream. It is probably a good idea for implementations to buffer the supplied input stream for efficiency. Note that any implementation of this method which does not readdataIn
to the end of the stream (either closing it early or just stopping reading) may cause an IOException to be thrown in the thread which is writing to the PipedOutputStream. Implementations should not close the supplied input stream.- Parameters:
dataIn
- stream which will supply bytes- Throws:
IOException
- if any I/O error occurs; this exception will be saved and thrown later by thefinishReading
method
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finishReading
Waits until thedoReading
method has finished reading the bytes written down the output stream, closes the input stream, and returns. Any IOException which has occurred during the read will be thrown by this method.- Throws:
InterruptedIOException
- if failure was caused by interruption; thebytesTransferred
field of this exception is not set to a useful valueIOException
- in case of some other IO failure
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