com.Ostermiller.util
Class CircularByteBuffer

java.lang.Object
  extended by com.Ostermiller.util.CircularByteBuffer

public class CircularByteBuffer
extends java.lang.Object

Implements the Circular Buffer producer/consumer model for bytes. More information about this class is available from ostermiller.org.

Using this class is a simpler alternative to using a PipedInputStream and a PipedOutputStream. PipedInputStreams and PipedOutputStreams don't support the mark operation, don't allow you to control buffer sizes that they use, and have a more complicated API that requires instantiating two classes and connecting them.

This class is thread safe.

Since:
ostermillerutils 1.00.00
See Also:
CircularCharBuffer, CircularObjectBuffer

Nested Class Summary
protected  class CircularByteBuffer.CircularByteBufferInputStream
          Class for reading from a circular byte buffer.
protected  class CircularByteBuffer.CircularByteBufferOutputStream
          Class for writing to a circular byte buffer.
 
Field Summary
protected  boolean blockingWrite
          True if a write to a full buffer should block until the buffer has room, false if the write method should throw an IOException
protected  byte[] buffer
          The circular buffer.
protected  java.io.InputStream in
          The InputStream that can empty this buffer.
protected  boolean infinite
          If this buffer is infinite (should resize itself when full)
static int INFINITE_SIZE
          A buffer that will grow as things are added.
protected  boolean inputStreamClosed
          true if the close() method has been called on the InputStream
protected  int markPosition
          Index of the first saved byte.
protected  int markSize
          Number of bytes that have to be saved to support mark() and reset() on the InputStream.
protected  java.io.OutputStream out
          The OutputStream that can fill this buffer.
protected  boolean outputStreamClosed
          true if the close() method has been called on the OutputStream
protected  int readPosition
          Index of the first byte available to be read.
protected  int writePosition
          Index of the first byte available to be written.
 
Constructor Summary
CircularByteBuffer()
          Create a new buffer with a default capacity.
CircularByteBuffer(boolean blockingWrite)
          Create a new buffer with a default capacity and given blocking behavior.
CircularByteBuffer(int size)
          Create a new buffer with given capacity.
CircularByteBuffer(int size, boolean blockingWrite)
          Create a new buffer with the given capacity and blocking behavior.
 
Method Summary
 void clear()
          Make this buffer ready for reuse.
 int getAvailable()
          Get number of bytes that are available to be read.
 java.io.InputStream getInputStream()
          Retrieve a InputStream that can be used to empty this buffer.
 java.io.OutputStream getOutputStream()
          Retrieve a OutputStream that can be used to fill this buffer.
 int getSize()
          Get the capacity of this buffer.
 int getSpaceLeft()
          Get the number of bytes this buffer has free for writing.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

INFINITE_SIZE

public static final int INFINITE_SIZE
A buffer that will grow as things are added.

Since:
ostermillerutils 1.00.00
See Also:
Constant Field Values

buffer

protected byte[] buffer
The circular buffer.

The actual capacity of the buffer is one less than the actual length of the buffer so that an empty and a full buffer can be distinguished. An empty buffer will have the markPostion and the writePosition equal to each other. A full buffer will have the writePosition one less than the markPostion.

There are three important indexes into the buffer: The readPosition, the writePosition, and the markPosition. If the InputStream has never been marked, the readPosition and the markPosition should always be the same. The bytes available to be read go from the readPosition to the writePosition, wrapping around the end of the buffer. The space available for writing goes from the write position to one less than the markPosition, wrapping around the end of the buffer. The bytes that have been saved to support a reset() of the InputStream go from markPosition to readPosition, wrapping around the end of the buffer.

Since:
ostermillerutils 1.00.00

readPosition

protected volatile int readPosition
Index of the first byte available to be read.

Since:
ostermillerutils 1.00.00

writePosition

protected volatile int writePosition
Index of the first byte available to be written.

Since:
ostermillerutils 1.00.00

markPosition

protected volatile int markPosition
Index of the first saved byte. (To support stream marking.)

Since:
ostermillerutils 1.00.00

markSize

protected volatile int markSize
Number of bytes that have to be saved to support mark() and reset() on the InputStream.

Since:
ostermillerutils 1.00.00

infinite

protected volatile boolean infinite
If this buffer is infinite (should resize itself when full)

Since:
ostermillerutils 1.00.00

blockingWrite

protected boolean blockingWrite
True if a write to a full buffer should block until the buffer has room, false if the write method should throw an IOException

Since:
ostermillerutils 1.00.00

in

protected java.io.InputStream in
The InputStream that can empty this buffer.

Since:
ostermillerutils 1.00.00

inputStreamClosed

protected boolean inputStreamClosed
true if the close() method has been called on the InputStream

Since:
ostermillerutils 1.00.00

out

protected java.io.OutputStream out
The OutputStream that can fill this buffer.

Since:
ostermillerutils 1.00.00

outputStreamClosed

protected boolean outputStreamClosed
true if the close() method has been called on the OutputStream

Since:
ostermillerutils 1.00.00
Constructor Detail

CircularByteBuffer

public CircularByteBuffer()
Create a new buffer with a default capacity. Writing to a full buffer will block until space is available rather than throw an exception.

Since:
ostermillerutils 1.00.00

CircularByteBuffer

public CircularByteBuffer(int size)
Create a new buffer with given capacity. Writing to a full buffer will block until space is available rather than throw an exception.

Note that the buffer may reserve some bytes for special purposes and capacity number of bytes may not be able to be written to the buffer.

Note that if the buffer is of INFINITE_SIZE it will neither block or throw exceptions, but rather grow without bound.

Parameters:
size - desired capacity of the buffer in bytes or CircularByteBuffer.INFINITE_SIZE.
Since:
ostermillerutils 1.00.00

CircularByteBuffer

public CircularByteBuffer(boolean blockingWrite)
Create a new buffer with a default capacity and given blocking behavior.

Parameters:
blockingWrite - true writing to a full buffer should block until space is available, false if an exception should be thrown instead.
Since:
ostermillerutils 1.00.00

CircularByteBuffer

public CircularByteBuffer(int size,
                          boolean blockingWrite)
Create a new buffer with the given capacity and blocking behavior.

Note that the buffer may reserve some bytes for special purposes and capacity number of bytes may not be able to be written to the buffer.

Note that if the buffer is of INFINITE_SIZE it will neither block or throw exceptions, but rather grow without bound.

Parameters:
size - desired capacity of the buffer in bytes or CircularByteBuffer.INFINITE_SIZE.
blockingWrite - true writing to a full buffer should block until space is available, false if an exception should be thrown instead.
Since:
ostermillerutils 1.00.00
Method Detail

clear

public void clear()
Make this buffer ready for reuse. The contents of the buffer will be cleared and the streams associated with this buffer will be reopened if they had been closed.

Since:
ostermillerutils 1.00.00

getOutputStream

public java.io.OutputStream getOutputStream()
Retrieve a OutputStream that can be used to fill this buffer.

Write methods may throw a BufferOverflowException if the buffer is not large enough. A large enough buffer size must be chosen so that this does not happen or the caller must be prepared to catch the exception and try again once part of the buffer has been consumed.

Returns:
the producer for this buffer.
Since:
ostermillerutils 1.00.00

getInputStream

public java.io.InputStream getInputStream()
Retrieve a InputStream that can be used to empty this buffer.

This InputStream supports marks at the expense of the buffer size.

Returns:
the consumer for this buffer.
Since:
ostermillerutils 1.00.00

getAvailable

public int getAvailable()
Get number of bytes that are available to be read.

Note that the number of bytes available plus the number of bytes free may not add up to the capacity of this buffer, as the buffer may reserve some space for other purposes.

Returns:
the size in bytes of this buffer
Since:
ostermillerutils 1.00.00

getSpaceLeft

public int getSpaceLeft()
Get the number of bytes this buffer has free for writing.

Note that the number of bytes available plus the number of bytes free may not add up to the capacity of this buffer, as the buffer may reserve some space for other purposes.

Returns:
the available space in bytes of this buffer
Since:
ostermillerutils 1.00.00

getSize

public int getSize()
Get the capacity of this buffer.

Note that the number of bytes available plus the number of bytes free may not add up to the capacity of this buffer, as the buffer may reserve some space for other purposes.

Returns:
the size in bytes of this buffer
Since:
ostermillerutils 1.00.00