java.io

Class PipedInputStream

java.lang.Object

java.io.InputStream

java.io.PipedInputStream

All Implemented Interfaces:

Closeable, AutoCloseable

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. A pipe is said to be broken if a thread that was providing data bytes to the connected piped output stream is no longer alive.

Since:

JDK1.0

Author:

James Gosling

See Also:

PipedOutputStream

Field Summary

Fields

Modifier and Type	Field and Description
protected byte[]	buffer The circular buffer into which incoming data is placed.
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 default size of the pipe's circular input buffer.

Constructor Summary

Constructors

Constructor and Description
PipedInputStream() Creates a PipedInputStream so that it is not yet connected.
PipedInputStream(int pipeSize) Creates a PipedInputStream so that it is not yet connected and uses the specified pipe size for the pipe's buffer.
PipedInputStream(PipedOutputStream src) Creates a PipedInputStream so that it is connected to the piped output stream src.
PipedInputStream(PipedOutputStream src, int pipeSize) Creates a PipedInputStream so that it is connected to the piped output stream src and uses the specified pipe size for the pipe's buffer.

Method Summary

Modifier and Type	Method and Description
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.
protected void	receive(int b) Receives a byte of data.

Methods inherited from class java.io.InputStream

mark, markSupported, read, reset, skip

Methods inherited from class java.lang.Object

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

Field Detail

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

PIPE_SIZE

protected static final int PIPE_SIZE

The default size of the pipe's circular input buffer.

Since:

JDK1.1

See Also:

Constant Field Values

Constructor Detail

PipedInputStream

public PipedInputStream()

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

PipedInputStream

public PipedInputStream(int pipeSize)

Creates a PipedInputStream so that it is not yet connected and uses the specified pipe size for the pipe's buffer. It must be connected to a PipedOutputStream before being used.

Parameters:

pipeSize - the size of the pipe's buffer.

Throws:

IllegalArgumentException - if pipeSize <= 0.

Since:

1.6

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(PipedOutputStream src,
                        int pipeSize)
                 throws IOException

Creates a PipedInputStream so that it is connected to the piped output stream src and uses the specified pipe size for the pipe's buffer. Data bytes written to src will then be available as input from this stream.

Parameters:

src - the stream to connect to.

pipeSize - the size of the pipe's buffer.

Throws:

IOException - if an I/O error occurs.

IllegalArgumentException - if pipeSize <= 0.

Since:

1.6

Method Detail

available

public int available()
              throws IOException

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

Overrides:

available in class InputStream

Returns:

the number of bytes that can be read from this input stream without blocking, or 0 if this input stream has been closed by invoking its close() method, or if the pipe is unconnected, or broken.

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.

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Overrides:

close in class InputStream

Throws:

IOException - if an I/O error occurs.

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.

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. This method blocks until input data is available, the end of the stream is detected, or an exception 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 unconnected, broken, closed, or if an I/O error occurs.

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 or if len exceeds the pipe's buffer size. If len is zero, then no bytes are read and 0 is returned; otherwise, the method blocks until at least 1 byte of input is available, end of the stream has been detected, or an exception is thrown.

Overrides:

read in class InputStream

Parameters:

b - the buffer into which the data is read.

off - the start offset in the destination array b

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:

NullPointerException - If b is null.

IndexOutOfBoundsException - If off is negative, len is negative, or len is greater than b.length - off

IOException - if the pipe is broken, unconnected, closed, or if an I/O error occurs.

See Also:

InputStream.read()

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, unconnected, closed, or if an I/O error occurs.

Since:

JDK1.1