Package uk.ac.starlink.util
Class PipeReaderThread
- java.lang.Object
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- java.lang.Thread
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- uk.ac.starlink.util.PipeReaderThread
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- All Implemented Interfaces:
java.lang.Runnable
public abstract class PipeReaderThread extends java.lang.Thread
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 itsdoReading(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 thewrite
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 throwIOException
). Secondly it shields the user from the implementation of the piped connection. Performance of thePipedInputStream
/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()
andgetOutputStream()
.- Author:
- Mark Taylor (Starlink)
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Constructor Summary
Constructors Constructor Description PipeReaderThread()
Constructs a new reader thread.
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description protected abstract void
doReading(java.io.InputStream dataIn)
This method should be implemented to consume all the bytes in the given input stream.void
finishReading()
Waits until the doReading method has finished reading the bytes written down the output stream, and returns.protected java.io.InputStream
getInputStream()
Returns the stream at the input end of the pipe.java.io.OutputStream
getOutputStream()
Returns the stream at the output end of the pipe.void
run()
Implements the thread's run 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, join, join, join, onSpinWait, resume, setContextClassLoader, setDaemon, setDefaultUncaughtExceptionHandler, setName, setPriority, setUncaughtExceptionHandler, sleep, sleep, start, stop, suspend, toString, yield
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Method Detail
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getInputStream
protected java.io.InputStream getInputStream()
Returns the stream at the input end of the pipe.- Returns:
- input stream
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getOutputStream
public java.io.OutputStream 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's run method to invoke doReading, catching and saving IOExceptions.- Specified by:
run
in interfacejava.lang.Runnable
- Overrides:
run
in classjava.lang.Thread
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doReading
protected abstract void doReading(java.io.InputStream dataIn) throws java.io.IOException
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 read dataIn 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.- Parameters:
dataIn
- stream which will supply bytes- Throws:
java.io.IOException
- if any I/O error occurs; this exception will be saved and thrown later by the finishReading method
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finishReading
public void finishReading() throws java.io.IOException
Waits until the doReading method has finished reading the bytes written down the output stream, and returns. Any IOException which has occurred during the read will be thrown by this method.- Throws:
java.io.IOException
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