Package org.jcsp.util

Class OverWriteOldestBuffer<T>

    • Field Summary

      Fields 
      Modifier and Type Field Description
      private T[] buffer
      The storage for the buffered Objects
      private int counter
      The number of Objects 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 < buffer.length)
      private boolean valueWrittenWhileFull  
    • Constructor Summary

      Constructors 
      Constructor Description
      OverWriteOldestBuffer​(int size)
      Construct a new OverWriteOldestBuffer with the specified size.
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      java.lang.Object clone()
      Returns a new (and EMPTY) OverWriteOldestBuffer with the same creation parameters as this one.
      void endGet()
      This ends an extended rendezvous by the reader.
      T get()
      Returns the oldest Object from the OverWriteOldestBuffer and removes it.
      int getState()
      Returns the current state of the OverWriteOldestBuffer.
      void put​(T value)
      Puts a new Object into the OverWriteOldestBuffer.
      void removeAll()
      Deletes all items in the buffer, leaving it empty.
      T startGet()
      Begins an extended rendezvous by the reader.
      • Methods inherited from class java.lang.Object

        equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Field Detail

      • buffer

        private final T[] buffer
        The storage for the buffered Objects
      • counter

        private int counter
        The number of Objects 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 < buffer.length)
      • valueWrittenWhileFull

        private boolean valueWrittenWhileFull
    • Constructor Detail

      • OverWriteOldestBuffer

        public OverWriteOldestBuffer​(int size)
        Construct a new OverWriteOldestBuffer with the specified size.
        Parameters:
        size - the number of Objects the OverWriteOldestBuffer can store.
        Throws:
        BufferSizeError - 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 Detail

      • get

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

        Pre-condition: getState must not currently return EMPTY.

        Specified by:
        get in interface ChannelDataStore<T>
        Returns:
        the oldest Object from the OverWriteOldestBuffer
      • startGet

        public T 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 ChannelDataStore<T>
        Returns:
        The oldest value in the buffer at this time
        See Also:
        ChannelDataStore.endGet()
      • put

        public void put​(T value)
        Puts a new Object into the OverWriteOldestBuffer.

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

        Specified by:
        put in interface ChannelDataStore<T>
        Parameters:
        value - the Object to put into the OverWriteOldestBuffer
      • getState

        public int getState()
        Returns the current state of the OverWriteOldestBuffer.
        Specified by:
        getState in interface ChannelDataStore<T>
        Returns:
        the current state of the OverWriteOldestBuffer (EMPTY or NONEMPTYFULL)
      • clone

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

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

        Specified by:
        clone in interface ChannelDataStore<T>
        Overrides:
        clone in class java.lang.Object
        Returns:
        the cloned instance of this OverWriteOldestBuffer.