Package org.jcsp.net

Class AcknowledgementsBuffer

  • All Implemented Interfaces:
    java.io.Serializable, java.lang.Cloneable, ChannelDataStore
    class AcknowledgementsBuffer
extends java.lang.Object
implements ChannelDataStore, java.io.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 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:
    InfiniteBuffer

    • Nested Class Summary

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

    • 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

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      java.lang.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.
      java.lang.Object get()
      Returns the oldest Object from the InfiniteBuffer and removes it.
      int getState()
      Returns the current state of the AcknowledgementsBuffer.
      void put​(java.lang.Object value)
      Puts a new Object into the InfiniteBuffer.
      void removeAll()
      Deletes all items in the buffer, leaving it empty.
      java.lang.Object startGet()
      Begins an extended read on the buffer, returning the data for the extended read.

      • Methods inherited from class java.lang.Object

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

    • Field Detail

      • DEFAULT_SIZE

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

      • initialSize

        private int initialSize
        The initial size of the buffer

      • buffer

        private java.lang.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

    • Constructor Detail

      • 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 Detail

      • get

        public java.lang.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 java.lang.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:
        ChannelDataStore.endGet()

      • put

        public void put​(java.lang.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 java.lang.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 java.lang.Object
        Returns:
        the cloned instance of this AcknowledgementsBuffer.