java.io
Class PipedInputStream

java.lang.Object
  java.io.InputStream
      java.io.PipedInputStream

public class PipedInputStream

extends InputStream

A piped input stream should be connected to a piped output stream; the piped input stream then provides whatever data bytes are written to the piped output stream. Typically, data is read from a PipedInputStream object by one thread and data is written to the corresponding PipedOutputStream by some other thread. Attempting to use both objects from a single thread is not recommended, as it may deadlock the thread. The piped input stream contains a buffer, decoupling read operations from write operations, within limits.

Since:

JDK1.0

Author:

James Gosling

See Also:

PipedOutputStream

Field Summary

protected byte[]	buffer The circular buffer into which incoming data is placed.
(package private) boolean	closedByReader
(package private) boolean	closedByWriter
(package private) boolean	connected
protected int	in The index of the position in the circular buffer at which the next byte of data will be stored when received from the connected piped output stream.
protected int	out The index of the position in the circular buffer at which the next byte of data will be read by this piped input stream.
protected static int	PIPE_SIZE The size of the pipe's circular input buffer.
(package private) Thread	readSide
(package private) Thread	writeSide

Fields inherited from class java.io.InputStream

Constructor Summary

PipedInputStream()
Creates a PipedInputStream so that it is not yet connected.

PipedInputStream(PipedOutputStream src)
Creates a PipedInputStream so that it is connected to the piped output stream src.

Method Summary

int	available() Returns the number of bytes that can be read from this input stream without blocking.
void	close() Closes this piped input stream and releases any system resources associated with the stream.
void	connect(PipedOutputStream src) Causes this piped input stream to be connected to the piped output stream src.
int	read() Reads the next byte of data from this piped input stream.
int	read(byte[] b, int off, int len) Reads up to len bytes of data from this piped input stream into an array of bytes.
(package private) void	receive(byte[] b, int off, int len) Receives data into an array of bytes.
protected void	receive(int b) Receives a byte of data.
(package private) void	receivedLast() Notifies all waiting threads that the last byte of data has been received.

Methods inherited from class java.io.InputStream

mark, markSupported, read, reset, skip

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

closedByWriter

boolean closedByWriter

closedByReader

boolean closedByReader

connected

boolean connected

readSide

Thread readSide

writeSide

Thread writeSide

PIPE_SIZE

protected static final int PIPE_SIZE

The size of the pipe's circular input buffer.

Since:

JDK1.1

See Also:

Constant Field Values

buffer

protected byte[] buffer

The circular buffer into which incoming data is placed.

Since:

JDK1.1

in

protected int in

The index of the position in the circular buffer at which the next byte of data will be stored when received from the connected piped output stream. in<0 implies the buffer is empty, in==out implies the buffer is full

Since:

JDK1.1

out

protected int out

The index of the position in the circular buffer at which the next byte of data will be read by this piped input stream.

Since:

JDK1.1

Constructor Detail

PipedInputStream

public PipedInputStream(PipedOutputStream src)
                 throws IOException

Creates a PipedInputStream so that it is connected to the piped output stream src. Data bytes written to src will then be available as input from this stream.

Parameters:

src - the stream to connect to.

Throws:

IOException - if an I/O error occurs.

PipedInputStream

public PipedInputStream()

Creates a PipedInputStream so that it is not yet connected. It must be connected to a PipedOutputStream before being used.

See Also:

connect(java.io.PipedOutputStream), PipedOutputStream.connect(java.io.PipedInputStream)

Method Detail

connect

public void connect(PipedOutputStream src)
             throws IOException

Causes this piped input stream to be connected to the piped output stream src. If this object is already connected to some other piped output stream, an IOException is thrown.

If src is an unconnected piped output stream and snk is an unconnected piped input stream, they may be connected by either the call:

snk.connect(src) 

or the call:

src.connect(snk) 

The two calls have the same effect.

Parameters:

src - The piped output stream to connect to.

Throws:

IOException - if an I/O error occurs.

receive

protected void receive(int b)
                throws IOException

Receives a byte of data. This method will block if no input is available.

Parameters:

b - the byte being received

Throws:

IOException - If the pipe is broken.

Since:

JDK1.1

receive

void receive(byte[] b,
             int off,
             int len)
       throws IOException

Receives data into an array of bytes. This method will block until some input is available.

Parameters:

b - the buffer into which the data is received

off - the start offset of the data

len - the maximum number of bytes received

Returns:

the actual number of bytes received, -1 is returned when the end of the stream is reached.

Throws:

IOException - If an I/O error has occurred.

receivedLast

void receivedLast()

Notifies all waiting threads that the last byte of data has been received.

read

public int read()
         throws IOException

Reads the next byte of data from this piped input stream. The value byte is returned as an int in the range 0 to 255. If no byte is available because the end of the stream has been reached, the value -1 is returned. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown. If a thread was providing data bytes to the connected piped output stream, but the thread is no longer alive, then an IOException is thrown.

Specified by:

read in class InputStream

Returns:

the next byte of data, or -1 if the end of the stream is reached.

Throws:

IOException - if the pipe is broken.

read

public int read(byte[] b,
                int off,
                int len)
         throws IOException

Reads up to len bytes of data from this piped input stream into an array of bytes. Less than len bytes will be read if the end of the data stream is reached. This method blocks until at least one byte of input is available. If a thread was providing data bytes to the connected piped output stream, but the thread is no longer alive, then an IOException is thrown.

Overrides:

read in class InputStream

Parameters:

b - the buffer into which the data is read.

off - the start offset of the data.

len - the maximum number of bytes read.

Returns:

the total number of bytes read into the buffer, or -1 if there is no more data because the end of the stream has been reached.

Throws:

IOException - if an I/O error occurs.

See Also:

InputStream.read()

available

public int available()
              throws IOException

Returns the number of bytes that can be read from this input stream without blocking. This method overrides the available method of the parent class.

Overrides:

available in class InputStream

Returns:

the number of bytes that can be read from this input stream without blocking.

Throws:

IOException - if an I/O error occurs.

Since:

JDK1.0.2

close

public void close()
           throws IOException

Closes this piped input stream and releases any system resources associated with the stream.

Overrides:

close in class InputStream

Throws:

IOException - if an I/O error occurs.