/**
* Executes the code in this actor. This actor uses a CDO construct when it is waiting to be used
* by either of the philosophers next to it. Once one of the philosophers is using it, this actor
* waits to receive a message that the philosopher is finished eating (using it). It is a good
* example of using a CDO. This process continues executing until a TerminateProcessException is
* thrown.
*
* @exception IllegalActionException If an error occurs during executing the process.
* @exception TerminateProcessException If the process termination is requested by the director.
*/
public void fire() throws IllegalActionException {
super.fire();
try {
boolean guard = true;
boolean continueCDO = true;
ConditionalBranch[] branches = new ConditionalBranch[2];
Token t = new IntToken(0);
while (continueCDO) {
// step 1
branches[0] = new ConditionalSend(guard, leftOut, 0, 0, t);
branches[1] = new ConditionalSend(guard, rightOut, 0, 1, t);
// step 2
int successfulBranch = chooseBranch(branches);
// step 3
if (successfulBranch == 0) {
// Wait for philosopher on left to finish eating.
leftIn.get(0);
} else if (successfulBranch == 1) {
// Wait for philosopher on right to finish eating.
rightIn.get(0);
} else if (successfulBranch == -1) {
// all guards false so exit CDO
continueCDO = false;
} else {
throw new IllegalActionException(
getName() + ": " + "invalid branch id returned during execution " + "of CDO.");
}
}
} catch (NoTokenException ex) {
throw new IllegalActionException(getName() + ": cannot " + "get token.");
}
}
/**
* If there are available resources, then perform a conditional branch on any <i>release</i> input
* or <i>grant</i> output. If the selected branch is a release input, then add the provided token
* to the end of the resource pool. If it is a grant output, then remove the first element from
* the resource pool and send it to the output. If there are no available resources, then perform
* a conditional branch only on the release inputs.
*
* @exception IllegalActionException If an error occurs during executing the process.
* @exception TerminateProcessException If the process termination is requested by the director.
*/
public void fire() throws IllegalActionException {
super.fire();
if (_debugging) {
_debug("Resources available: " + _pool);
}
int numberOfConditionals = release.getWidth();
if (_pool.size() > 0) {
numberOfConditionals += grant.getWidth();
}
ConditionalBranch[] branches = new ConditionalBranch[numberOfConditionals];
for (int i = 0; i < release.getWidth(); i++) {
// The branch has channel i and ID i.
branches[i] = new ConditionalReceive(release, i, i);
if (_debugging && _VERBOSE_DEBUGGING) {
branches[i].addDebugListener(this);
}
}
if (_pool.size() > 0) {
Token token = (Token) _pool.get(0);
for (int i = release.getWidth(); i < numberOfConditionals; i++) {
int channel = i - release.getWidth();
branches[i] = new ConditionalSend(grant, channel, i, token);
if (_debugging && _VERBOSE_DEBUGGING) {
branches[i].addDebugListener(this);
}
}
}
int successfulBranch = chooseBranch(branches);
if (_debugging && _VERBOSE_DEBUGGING) {
for (int i = 0; i < branches.length; i++) {
branches[i].removeDebugListener(this);
}
}
if (successfulBranch < 0) {
_branchEnabled = false;
} else if (successfulBranch < release.getWidth()) {
// Rendezvous occurred with a release input.
_branchEnabled = true;
Token received = branches[successfulBranch].getToken();
_pool.add(received);
if (_debugging) {
_debug("Resource released on channel " + successfulBranch + ": " + received);
}
} else {
// Rendezvous occurred with a grant output.
_branchEnabled = true;
if (_debugging) {
_debug(
"Resource granted on channel "
+ (successfulBranch - release.getWidth())
+ ": "
+ _pool.get(0));
}
_pool.remove(0);
}
}
/**
* Override the base class to reset the resource pool to match the specified initialPool value.
*
* @param attribute The attribute that changed.
* @exception IllegalActionException If the change is not acceptable to this container (not thrown
* in this base class).
*/
public void attributeChanged(Attribute attribute) throws IllegalActionException {
if (attribute == initialPool) {
ArrayToken pool = (ArrayToken) initialPool.getToken();
// Reset the pool.
_pool.clear();
// Copy the tokens into the pool.
for (int i = 0; i < pool.length(); i++) {
_pool.add(pool.getElement(i));
}
} else {
super.attributeChanged(attribute);
}
}
/**
* Return true unless none of the branches were enabled in the most recent invocation of fire().
*
* @return True if another iteration can occur.
*/
public boolean postfire() {
super.postfire();
return _branchEnabled;
}