object elasticBuffer {
import scala.concurrent.pilib._;
/**
* Recursive type for channels that carry a "String" channel and
* an object of the type we define.
*/
class MetaChan extends Chan[Pair[Chan[String], MetaChan]];
def Buffer(put: Chan[String], get: Chan[String]): unit = {
/**
* An empty buffer cell, ready to pass on (o,r) to the left.
*/
def Bl(i:Chan[String], l: MetaChan,
o: Chan[String], r: MetaChan): unit =
choice (
l(Pair(o,r)) * (System.out.println("Removed one cell.")),
i * (inp => Cl(i, l, o, r, inp))
);
/**
* A buffer cell containing a value, ready to receive (o,r) from the right.
*/
def Cl(i: Chan[String], l: MetaChan,
o: Chan[String], r: MetaChan, content: String): unit =
choice (
o(content) * (Bl(i,l,o,r)),
i * (inp => Dl(i,l,o,r,content, inp)),
r * ( { case Pair(newo, newr) => Cl(i,l,newo,newr,content) })
);
/**
* Two joined buffer cells, of type Cl.
*/
def Dl(i: Chan[String], l: MetaChan,
o: Chan[String], r: MetaChan,
content: String, inp: String): unit = {
val newlr = new MetaChan;
val newio = new Chan[String];
spawn < Cl(i, l, newio, newlr, inp) | Cl(newio, newlr, o, r,content) >;
}
// l and r channels for the leftmost and rightmost cell, respectively.
val unused1 = new MetaChan;
val unused2 = new MetaChan;
Bl(put, unused1, get, unused2);
}
val random = new java.util.Random();
def Producer(n: int, put: Chan[String]): unit = {
Thread.sleep(1 + random.nextInt(1000));
val msg = "object " + n;
put.write(msg);
System.out.println("Producer gave " + msg);
Producer(n + 1, put)
}
def Consumer(get: Chan[String]): unit = {
Thread.sleep(1 + random.nextInt(1000));
val msg = get.read;
System.out.println("Consummer took " + msg);
Consumer(get)
}
def main(args: Array[String]): unit = {
val put = new Chan[String];
val get = new Chan[String];
spawn < Producer(0, put) | Consumer(get) | Buffer(put, get) >
}
}
