Class AcknowledgementsBuffer

java.lang.Object
org.jcsp.net.AcknowledgementsBuffer
All Implemented Interfaces:
Serializable, Cloneable, ChannelDataStore
class AcknowledgementsBuffer extends Object implements ChannelDataStore, Serializable
This is used to create a buffered object channel that always accepts and never loses any input.

Description

AcknowledgementsBuffer is an implementation of ChannelDataStore that yields a FIFO buffered semantics for a channel. When empty, the channel blocks readers. However, its capacity is infinite (expanding to whatever is needed so far as the underlying memory system will permit). So, it never gets full and blocks a writer. See the static
invalid reference 
create
methods of One2OneChannel etc.

The getState method returns EMPTY or NONEMPTYFULL, but never FULL.

An initial size for the buffer can be specified during construction.

This buffer will save memory by changing multiple ChannelMessage.Ack messages into AcknowledgementsBuffer.Acks.

See Also:

  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    (package private) static class 
    AcknowledgementsBuffer.Acks
    Compressed form of one or more acknowledgements.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    private AcknowledgementsBuffer.Acks
    acks
    The Acks which is currently in the buffer.
    private Object[]
    buffer
    The storage for the buffered Objects
    private int
    counter
    The number of Objects stored in the InfiniteBuffer
    private static final int
    DEFAULT_SIZE
    The default size of the buffer
    private int
    firstIndex
    The index of the first element
    private int
    initialSize
    The initial size of the buffer
    private int
    lastIndex
    The index of the last element

    Fields inherited from interface ChannelDataStore

    EMPTY, FULL, NONEMPTYFULL

  • Constructor Summary

    Constructors
    Constructor
    Description
    AcknowledgementsBuffer()
    Construct a new InfiniteBuffer with the default size (of 8).
    AcknowledgementsBuffer(int initialSize)
    Construct a new AcknowledgementsBuffer with the specified initial size.

  • Method Summary

    Modifier and Type
    Method
    Description
    Object
    clone()
    Returns a new (and EMPTY) AcknowledgementsBuffer with the same creation parameters as this one.
    void
    endGet()
    Ends an extended read on the buffer.
    Object
    get()
    Returns the oldest Object from the InfiniteBuffer and removes it.
    int
    getState()
    Returns the current state of the AcknowledgementsBuffer.
    void
    put(Object value)
    Puts a new Object into the InfiniteBuffer.
    void
    removeAll()
    Deletes all items in the buffer, leaving it empty.
    Object
    startGet()
    Begins an extended read on the buffer, returning the data for the extended read.

    Methods inherited from class Object

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

  • Field Details

    • DEFAULT_SIZE

      private static final int DEFAULT_SIZE
      The default size of the buffer
      See Also:

    • initialSize

      private int initialSize
      The initial size of the buffer

    • buffer

      private Object[] buffer
      The storage for the buffered Objects

    • counter

      private int counter
      The number of Objects stored in the InfiniteBuffer

    • firstIndex

      private int firstIndex
      The index of the first element

    • lastIndex

      private int lastIndex
      The index of the last element

    • acks

      private AcknowledgementsBuffer.Acks acks
      The Acks which is currently in the buffer.

  • Constructor Details

    • AcknowledgementsBuffer

      AcknowledgementsBuffer()
      Construct a new InfiniteBuffer with the default size (of 8).

    • AcknowledgementsBuffer

      AcknowledgementsBuffer(int initialSize)
      Construct a new AcknowledgementsBuffer with the specified initial size.
      Parameters:
      initialSize - the number of Objects the AcknowledgementsBuffer can initially store

  • Method Details

    • get

      public Object get()
      Returns the oldest Object from the InfiniteBuffer and removes it.

      Pre-condition: getState must not currently return EMPTY.

      Specified by:
      get in interface ChannelDataStore
      Returns:
      the oldest Object from the InfiniteBuffer

    • startGet

      public Object startGet()
      Description copied from interface: ChannelDataStore
      Begins an extended read on the buffer, returning the data for the extended read.

      Pre-condition: getState must not currently return EMPTY.

      The exact behaviour of this method depends on your buffer. When a process performs an extended rendezvous on a buffered channel, it will first call this method, then the ChannelDataStore.endGet() method.

      A FIFO buffer would implement this method as returning the value from the front of the buffer and the next call would remove the value. An overflowing buffer would do the same.

      However, for an overwriting buffer it is more complex. Refer to the documentation for OverWritingBuffer.startGet() and OverWriteOldestBuffer.startGet() for details

      Specified by:
      startGet in interface ChannelDataStore
      Returns:
      The object to be read from the channel at the beginning of the extended rendezvous
      See Also:

    • endGet

      public void endGet()
      Description copied from interface: ChannelDataStore
      Ends an extended read on the buffer. The channels guarantee that this method will be called exactly once after each startGet call. During the period between startGet and endGet, it is possible that put will be called, but not get.
      Specified by:
      endGet in interface ChannelDataStore
      See Also:

    • put

      public void put(Object value)
      Puts a new Object into the InfiniteBuffer.

      Implementation note: if InfiniteBuffer is full, a new internal buffer with double the capacity is constructed and the old data copied across.

      Specified by:
      put in interface ChannelDataStore
      Parameters:
      value - the Object to put into the InfiniteBuffer

    • getState

      public int getState()
      Returns the current state of the AcknowledgementsBuffer.
      Specified by:
      getState in interface ChannelDataStore
      Returns:
      the current state of the AcknowledgementsBuffer (EMPTY or NONEMPTYFULL)

    • clone

      public Object clone()
      Returns a new (and EMPTY) AcknowledgementsBuffer with the same creation parameters as this one.

      Note: Only the initial size and structure of the AcknowledgementsBuffer is cloned, not any stored data.

      Specified by:
      clone in interface ChannelDataStore
      Overrides:
      clone in class Object
      Returns:
      the cloned instance of this AcknowledgementsBuffer.

    • removeAll

      public void removeAll()
      Description copied from interface: ChannelDataStore
      Deletes all items in the buffer, leaving it empty.
      Specified by:
      removeAll in interface ChannelDataStore