Package org.jcsp.util

Class OverWriteOldestBuffer<T>

    • 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 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 Object
        Returns:
        the cloned instance of this OverWriteOldestBuffer.