Class OverWriteOldestBufferInt

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

Description

OverWriteOldestBufferInt 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 oldest item left unread in 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
    OverWriteOldestBufferInt(int size)
    Construct a new OverWriteOldestBufferInt with the specified size.

  • Method Summary

    Modifier and Type
    Method
    Description
    Object
    clone()
    Returns a new (and EMPTY) OverWriteOldestBufferInt 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 OverWriteOldestBufferInt and removes it.
    int
    getState()
    Returns the current state of the OverWriteOldestBufferInt.
    void
    put(int value)
    Puts a new int into the OverWriteOldestBufferInt.
    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

    • OverWriteOldestBufferInt

      public OverWriteOldestBufferInt(int size)
      Construct a new OverWriteOldestBufferInt with the specified size.
      Parameters:
      size - the number of ints the OverWriteOldestBufferInt 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 OverWriteOldestBufferInt and removes it.

      Pre-condition: getState must not currently return EMPTY.

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

    • startGet

      public int startGet()
      Begins an extended rendezvous by the reader. The semantics of an extended rendezvous on an overwrite-oldest buffer are slightly complicated, but hopefully intuitive. When a reader begins an extended rendezvous, the oldest value is returned from the buffer (as it would be for a call to get()). While an extended rendezvous is ongoing, the writer may (repeatedly) write to the buffer, without ever blocking. When the reader finishes an extended rendezvous, the following options are possible:
      • The writer has not written to the channel during the rendezvous. In this case, the value that was read at the start of the rendezvous is removed from the buffer.
      • The writer has written to the channel during the rendezvous, but has not over-written the value that was read at the start of the rendezvous. In this case, the value that was read at the start of the rendezvous is removed from the buffer.
      • The writer has written to the channel during the rendezvous, and has over-written (perhaps repeatedly) the value that was read at the start of the rendezvous. In this case, the value that was read at the start of the rendezvous is no longer in the buffer, and hence nothing is removed.
      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 OverWriteOldestBufferInt.

      If OverWriteOldestBufferInt is full, the oldest item left unread in the buffer will be overwritten.

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

    • getState

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

    • clone

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

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

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

    • removeAll

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