Package org.jcsp.lang

Class One2OneChannelIntImpl

  • All Implemented Interfaces:
    ChannelInternalsInt, One2OneChannelInt
    class One2OneChannelIntImpl
extends java.lang.Object
implements ChannelInternalsInt, One2OneChannelInt
    This implements a one-to-one integer channel.

    Description

    One2OneChannelIntImpl implements a one-to-one integer channel. Multiple readers or multiple writers are not allowed -- these are catered for by Any2OneChannelIntImpl, One2AnyChannelIntImpl or Any2AnyChannelIntImpl.

    The reading process may ALT on this channel. The writing process is committed (i.e. it may not back off).

    The default semantics of the channel is that of CSP -- i.e. it is zero-buffered and fully synchronised. The reading process must wait for a matching writer and vice-versa.

    However, the static methods of Channel allow the creation of a channel with a plug-in driver conforming to the ChannelDataStoreInt interface. This allows a variety of different channel semantics to be introduced -- including buffered channels of user-defined capacity (including infinite), overwriting channels (with various overwriting policies) etc.. Standard examples are given in the org.jcsp.util.ints package, but careful users may write their own.

    See Also:
    Alternative, Any2OneChannelIntImpl, One2AnyChannelIntImpl, Any2AnyChannelIntImpl, ChannelDataStoreInt

    • Field Detail

      • rwMonitor

        private java.lang.Object rwMonitor
        The monitor synchronising reader and writer on this channel

      • hold

        private int hold
        The (invisible-to-users) buffer used to store the data for the channel

      • empty

        private boolean empty
        The synchronisation flag

      • alt

        private Alternative alt
        The Alternative class that controls the selection

      • spuriousWakeUp

        private boolean spuriousWakeUp
        Flag to deal with a spurious wakeup during a write

    • Constructor Detail

      • One2OneChannelIntImpl

        One2OneChannelIntImpl()

    • Method Detail

      • in

        public AltingChannelInputInt in()
        Returns the AltingChannelInputInt object to use for this channel. As One2OneChannelIntImpl implements AltingChannelInputInt itself, this method simply returns a reference to the object that it is called on.
        Specified by:
        in in interface One2OneChannelInt
        Returns:
        the AltingChannelInputInt object to use for this channel.

      • out

        public ChannelOutputInt out()
        Returns the ChannelOutputInt object to use for this channel. As One2OneChannelIntImpl implements ChannelOutputInt itself, this method simply returns a reference to the object that it is called on.
        Specified by:
        out in interface One2OneChannelInt
        Returns:
        the ChannelOutputInt object to use for this channel.

      • read

        public int read()
        Reads an int from the channel.
        Specified by:
        read in interface ChannelInternalsInt
        Returns:
        the integer read from the channel.

      • write

        public void write​(int value)
        Writes an int to the channel.
        Specified by:
        write in interface ChannelInternalsInt
        Parameters:
        value - the integer to write to the channel.

      • readerEnable

        public boolean readerEnable​(Alternative alt)
        turns on Alternative selection for the channel. Returns true if the channel has data that can be read immediately.

        Note: this method should only be called by the Alternative class

        Specified by:
        readerEnable in interface ChannelInternalsInt
        Parameters:
        alt - the Alternative class which will control the selection
        Returns:
        true if the channel has data that can be read, else false

      • readerDisable

        public boolean readerDisable()
        turns off Alternative selection for the channel. Returns true if the channel contained data that can be read.

        Note: this method should only be called by the Alternative class

        Specified by:
        readerDisable in interface ChannelInternalsInt
        Returns:
        true if the channel has data that can be read, else false

      • readerPending

        public boolean readerPending()
        Returns whether there is data pending on this channel.

        Note: if there is, it won't go away until you read it. But if there isn't, there may be some by the time you check the result of this method.

        This method is provided for convenience. Its functionality can be provided by Pri Alting the channel against a SKIP guard, although at greater run-time and syntactic cost. For example, the following code fragment: 

           if (c.pending ()) {
     int x = c.read ();
     ...  do something with x
   } else (
     ...  do something else
   }
        is equivalent to: 
           if (c_pending.priSelect () == 0) {
     int x = c.read ();
     ...  do something with x
   } else (
     ...  do something else
 }
        where earlier would have had to have been declared: 
         final Alternative c_pending =
   new Alternative (new Guard[] {c, new Skip ()});
        Specified by:
        readerPending in interface ChannelInternalsInt
        Returns:
        state of the channel.

      • create

        public static One2OneChannelInt[] create​(int n)
        Creates an array of One2OneChannelInts.
        Parameters:
        n - the number of channels to create in the array
        Returns:
        the array of One2OneChannelIntImpl

      • create

        public static One2OneChannelInt create​(ChannelDataStoreInt store)
        Creates a One2OneChannelIntImpl using the specified ChannelDataStoreInt.
        Returns:
        the One2OneChannelIntImpl

      • create

        public static One2OneChannelInt[] create​(int n,
                                         ChannelDataStoreInt store)
        Creates an array of One2OneChannelInts using the specified ChannelDataStoreInt.
        Parameters:
        n - the number of channels to create in the array
        Returns:
        the array of One2OneChannelIntImpl