/**
* Close this PersistentStore without destroying its contents
*
* @throws IOException If file system access errors are encountered
*/
public void close() throws IOException {
try {
// Using write lock because we want an exclusive lock
mutatorLock.writeLock();
updateCount = 0;
// Don't need to sync on this because
// mutatorLock.writeLock() gives us an exclusive lock
log.close();
} finally {
// Using write lock because we want an exclusive lock
mutatorLock.writeUnlock();
}
}
/**
* Block until we can acquire a non-exclusive mutator lock on the servers 's persistent state.
* This lock should be acquired in a <code>try</code> block and a <code>releaseMutatorLock</code>
* call should be placed in a <code>finally</code> block.
*/
public void acquireMutatorLock() {
// Do we already hold a lock?
Long lockStateVal = lockState.get();
if (lockStateVal == null) lockStateVal = zero;
final long longVal = lockStateVal;
if (longVal == 0) {
// No, this thread currently does not hold a lock,
// grab non-exclusive lock (which for mutatorLock is a
// read lock)
mutatorLock.readLock();
}
// Ether way, bump the lock count and update our thread state
lockState.set(longVal + 1);
}
/** Release one level of mutator locks if this thread holds at lease one. */
public void releaseMutatorLock() {
Long lockStateVal = lockState.get();
if (lockStateVal == null) lockStateVal = zero;
final long longVal = lockStateVal;
if (longVal == 0)
// No lock to release, return
return;
if (longVal == 1) {
// Last one on stack release lock
// Using read lock because we want a non-exclusive lock
mutatorLock.readUnlock();
lockStateVal = zero;
} else {
lockStateVal = longVal - 1;
}
lockState.set(lockStateVal);
}