Class OverWritingBufferInt

java.lang.Object
org.jcsp.util.ints.OverWritingBufferInt
All Implemented Interfaces:
Serializable, Cloneable, ChannelDataStoreInt
public class OverWritingBufferInt extends Object implements ChannelDataStoreInt, Serializable
This is used to create a buffered integer channel that always accepts input, overwriting its last entered data if full.

Description

OverWritingBufferInt is an implementation of ChannelDataStoreInt that yields a FIFO buffered semantics for a channel. When empty, the channel blocks readers. When full, a writer will overwrite the latest item written to the channel. See the static construction methods of Channel (Channel.one2oneInt(org.jcsp.util.ints.ChannelDataStoreInt) etc.).

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

See Also:

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    private final int[]
    buffer
    The storage for the buffered ints
    private int
    counter
    The number of ints stored in the Buffer
    private int
    firstIndex
    The index of the oldest element (when counter > 0)
    private int
    lastIndex
    The index of the next free element (when counter invalid input: '<' buffer.length)
    private boolean
    valueWrittenWhileFull
     

    Fields inherited from interface ChannelDataStoreInt

    EMPTY, FULL, NONEMPTYFULL

  • Constructor Summary

    Constructors
    Constructor
    Description
    OverWritingBufferInt(int size)
    Construct a new OverWritingBufferInt with the specified size.

  • Method Summary

    Modifier and Type
    Method
    Description
    Object
    clone()
    Returns a new (and EMPTY) OverWritingBufferInt with the same creation parameters as this one.
    void
    endGet()
    See startGet() for a description of the semantics of this method.
    int
    get()
    Returns the oldest int from the OverWritingBufferInt and removes it.
    int
    getState()
    Returns the current state of the OverWritingBufferInt.
    void
    put(int value)
    Puts a new int into the OverWritingBufferInt.
    void
    removeAll()
     
    int
    startGet()
    Begins an extended rendezvous by the reader.

    Methods inherited from class Object

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

  • Field Details

    • buffer

      private final int[] buffer
      The storage for the buffered ints

    • counter

      private int counter
      The number of ints stored in the Buffer

    • firstIndex

      private int firstIndex
      The index of the oldest element (when counter > 0)

    • lastIndex

      private int lastIndex
      The index of the next free element (when counter invalid input: '<' buffer.length)

    • valueWrittenWhileFull

      private boolean valueWrittenWhileFull

  • Constructor Details

    • OverWritingBufferInt

      public OverWritingBufferInt(int size)
      Construct a new OverWritingBufferInt with the specified size.
      Parameters:
      size - the number of ints the OverWritingBufferInt can store.
      Throws:
      BufferIntSizeError - if size is zero or negative. Note: no action should be taken to try/catch this exception - application code generating it is in error and needs correcting.

  • Method Details

    • get

      public int get()
      Returns the oldest int from the OverWritingBufferInt and removes it.

      Pre-condition: getState must not currently return EMPTY.

      Specified by:
      get in interface ChannelDataStoreInt
      Returns:
      the oldest int from the OverWritingBufferInt

    • startGet

      public int startGet()
      Begins an extended rendezvous by the reader. The semantics of an extended rendezvous on an overwrite-newest buffer are slightly complicated, but hopefully intuitive. If the buffer is of size 2 or larger, the semantics are as follows. Beginning an extended rendezvous will return the oldest value in the buffer, but not remove it. If the writer writes to the buffer during the rendezvous, it will grow the buffer and end up overwriting the newest value as normal. At the end of the extended rendezvous, the oldest value is removed. If the buffer is of size 1, the semantics are identical to those of an OverWriteOldestBuffer. For a complete description, refer to the documentation for the OverWriteOldestBuffer.startGet() method.
      Specified by:
      startGet in interface ChannelDataStoreInt
      Returns:
      The oldest value in the buffer at this time
      See Also:

    • endGet

      public void endGet()
      See startGet() for a description of the semantics of this method.
      Specified by:
      endGet in interface ChannelDataStoreInt
      See Also:

    • put

      public void put(int value)
      Puts a new int into the OverWritingBufferInt.

      If OverWritingBufferInt is full, the last item previously put into the buffer will be overwritten.

      Specified by:
      put in interface ChannelDataStoreInt
      Parameters:
      value - the int to put into the OverWritingBufferInt

    • getState

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

    • clone

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

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

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

    • removeAll

      public void removeAll()
      Specified by:
      removeAll in interface ChannelDataStoreInt