Receives information from a communications pipe. When two threads want to pass data back and forth, one creates a piped output stream and the other one creates a piped input stream.
See Also
Constant Summary
int | PIPE_SIZE | The size of the default pipe in bytes. |
Field Summary
protected byte[] | buffer | The circular buffer through which data is passed. |
protected int | in | The index in buffer where the next byte will be written. |
protected int | out | The index in buffer where the next byte will be read. |
Public Constructor Summary
PipedInputStream()
Constructs a new unconnected
PipedInputStream . |
|
PipedInputStream(int pipeSize)
Constructs a new unconnected
PipedInputStream with the given
buffer size. |
|
PipedInputStream(PipedOutputStream out, int pipeSize)
Constructs a new
PipedInputStream connected to the given PipedOutputStream ,
with the given buffer size. |
Public Method Summary
synchronized int |
available()
Returns an estimate of the number of bytes that can be read (or
skipped over) from this input stream without blocking by the next
invocation of a method for this input stream.
Unlike most streams, |
synchronized void |
close()
Closes this stream.
|
void | |
synchronized int |
read()
Reads a single byte from this stream and returns it as an integer in the
range from 0 to 255.
|
synchronized int |
read(byte[] bytes, int offset, int byteCount)
Reads at most
byteCount bytes from this stream and stores them in the
byte array bytes starting at offset . |
Protected Method Summary
synchronized void |
receive(int oneByte)
Receives a byte and stores it in this stream's
buffer . |
Inherited Method Summary
Constants
protected static final int PIPE_SIZE
The size of the default pipe in bytes.
Fields
protected byte[] buffer
The circular buffer through which data is passed. Data is read from the
range [out, in)
and written to the range [in, out)
.
Data in the buffer is either sequential:
{ - - - X X X X X X X - - - - - } ^ ^ | | out in
{ X X X X - - - - - - - - X X X } ^ ^ | | in out
in == -1
. Reading when the buffer is
empty will block until data is available. When the buffer is full,
in == out
. Writing when the buffer is full will block until free
space is available.
protected int in
The index in buffer
where the next byte will be written.
protected int out
The index in buffer
where the next byte will be read.
Public Constructors
public PipedInputStream ()
Constructs a new unconnected PipedInputStream
. The resulting
stream must be connected to a PipedOutputStream
before data may
be read from it.
public PipedInputStream (PipedOutputStream out)
Constructs a new PipedInputStream
connected to the
PipedOutputStream
out
. Any data written to the output
stream can be read from the this input stream.
Parameters
out | the piped output stream to connect to. |
---|
Throws
IOException | if this stream or out are already connected.
|
---|
public PipedInputStream (int pipeSize)
Constructs a new unconnected PipedInputStream
with the given
buffer size. The resulting stream must be connected to a
PipedOutputStream
before data may be read from it.
Parameters
pipeSize | the size of the buffer in bytes. |
---|
Throws
IllegalArgumentException | if pipeSize is less than or equal to zero. |
---|
public PipedInputStream (PipedOutputStream out, int pipeSize)
Constructs a new PipedInputStream
connected to the given PipedOutputStream
,
with the given buffer size. Any data written to the output stream can be read from this
input stream.
Parameters
out | the PipedOutputStream to connect to. |
---|---|
pipeSize | the size of the buffer in bytes. |
Throws
IOException | if an I/O error occurs. |
---|---|
IllegalArgumentException | if pipeSize is less than or equal to zero. |
Public Methods
public synchronized int available ()
Returns an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking by the next invocation of a method for this input stream. The next invocation might be the same thread or another thread. A single read or skip of this many bytes will not block, but may read or skip fewer bytes.
Note that while some implementations of InputStream
will return
the total number of bytes in the stream, many will not. It is
never correct to use the return value of this method to allocate
a buffer intended to hold all data in this stream.
A subclass' implementation of this method may choose to throw an
IOException
if this input stream has been closed by
invoking the close()
method.
The available
method for class InputStream
always
returns 0
.
This method should be overridden by subclasses.
Unlike most streams, PipedInputStream
returns 0 rather than throwing
IOException
if the stream has been closed. Unconnected and broken pipes also
return 0.
Returns
- an estimate of the number of bytes that can be read (or skipped
over) from this input stream without blocking or
0
when it reaches the end of the input stream.
Throws
IOException | if an I/O error occurs |
---|
public synchronized void close ()
Closes this stream. This implementation releases the buffer used for the pipe and notifies all threads waiting to read or write.
Throws
IOException | if an error occurs while closing this stream. |
---|
public void connect (PipedOutputStream src)
Connects this PipedInputStream
to a PipedOutputStream
.
Any data written to the output stream becomes readable in this input
stream.
Parameters
src | the source output stream. |
---|
Throws
IOException | if either stream is already connected. |
---|
public synchronized int read ()
Reads a single byte from this stream and returns it as an integer in the range from 0 to 255. Returns -1 if the end of this stream has been reached. If there is no data in the pipe, this method blocks until data is available, the end of the stream is detected or an exception is thrown.
Separate threads should be used to read from a PipedInputStream
and to write to the connected PipedOutputStream
. If the same
thread is used, a deadlock may occur.
Returns
- the byte read or -1 if the end of the source stream has been reached.
Throws
IOException | if this stream is closed or not connected to an output stream, or if the thread writing to the connected output stream is no longer alive. |
---|
public synchronized int read (byte[] bytes, int offset, int byteCount)
Reads at most byteCount
bytes from this stream and stores them in the
byte array bytes
starting at offset
. Blocks until at
least one byte has been read, the end of the stream is detected or an
exception is thrown.
Separate threads should be used to read from a PipedInputStream
and to write to the connected PipedOutputStream
. If the same
thread is used, a deadlock may occur.
Parameters
bytes | the buffer into which the data is read. |
---|---|
offset | the start offset in array b
at which the data is written. |
byteCount | the maximum number of bytes to read. |
Returns
- the number of bytes actually read or -1 if the end of the stream has been reached.
Throws
IndexOutOfBoundsException | if offset < 0 or byteCount < 0 , or if offset + byteCount is greater than the size of bytes . |
---|---|
InterruptedIOException | if the thread reading from this stream is interrupted. |
IOException | if this stream is closed or not connected to an output stream, or if the thread writing to the connected output stream is no longer alive. |
NullPointerException | if bytes is null .
|
Protected Methods
protected synchronized void receive (int oneByte)
Receives a byte and stores it in this stream's buffer
. This
method is called by PipedOutputStream.write(int)
. The least
significant byte of the integer oneByte
is stored at index
in
in the buffer
.
This method blocks as long as buffer
is full.
Parameters
oneByte | the byte to store in this pipe. |
---|
Throws
InterruptedIOException | if the buffer is full and the thread that has called
this method is interrupted. |
---|---|
IOException | if this stream is closed or the thread that has last read from this stream is no longer alive. |