/**
* Acquire the protected resource with reading privileges. Many readers can access the protected
* resource at the same time, but no writer can access it while at least one reader is present.
* The locking is recursive (i.e. the same thread can acquire the lock multiple times, but must
* unlock it a matching number of times to actually free the protected resource).
*/
public synchronized void readLock() {
while (currentWriter != null) {
// Someone is writing the resource --> Go to sleep
try {
wait();
} catch (InterruptedException ie) {
if (logger.isLoggable(Logger.WARNING))
logger.log(Logger.WARNING, "Unexpected interruption. " + ie.getMessage());
}
}
readersCnt++;
}
/**
* Acquire the protected resource with writing privileges. Only one writer at a time can access
* the protected resource, and no readers can access it at the same time. The locking is recursive
* (i.e. the same thread can acquire the lock multiple times, but must unlock it a matching number
* of times to actually free the protected resource).
*/
public synchronized void writeLock() {
Thread me = Thread.currentThread();
while ((currentWriter != null && currentWriter != me) || readersCnt > 0) {
// Someone (not me) is writing the resource OR
// There are one or more Threads reading the resource
// --> Go to sleep
try {
wait();
} catch (InterruptedException ie) {
if (logger.isLoggable(Logger.WARNING))
logger.log(Logger.WARNING, "Unexpected interruption. " + ie.getMessage());
}
}
writeLockDepth++;
if (writeLockDepth == 1) {
currentWriter = me;
onWriteStart();
}
}