Refactor the Nat464Xlat function for simplicity.
This makes the code easier to understand by making state
transitions more explicit. It also makes it easier to address a
TODO to turn the class into a StateMachine.
This should be an exact no-op refactoring. The current cases
covered by the code (all mutually exclusive) are:
1. requiresClat && !isPrefixDiscoveryStarted
Action: startPrefixDiscovery()
Equivalent to IDLE && requiresClat, because
isPrefixDiscoveryStarted returns true for every state except
IDLE.
2. requiresClat && isPrefixDiscoveryStarted && shouldStartClat
Action: start()
Equivalent to DISCOVERING && shouldStartClat,
because isPrefixDiscoveryStarted is true in DISCOVERING,
STARTING, and RUNNING, but start() does nothing if mState is
STARTING or RUNNING.
3. requiresClat && isPrefixDiscoveryStarted && !shouldStartClat
Action: stop()
Equivalent to (STARTING or RUNNING) && !shouldStartClat,
because isPrefixDiscoveryStarted is true in DISCOVERING,
STARTING, and RUNNING, but stop() does nothing if mState is
not STARTING or RUNNING.
4. !requiresClat && isStarted
Action: stop()
Equivalent to (STARTING or RUNNING) && !requiresClat,
because isStarted() is only true in STARTING and RUNNING.
5. !requiresClat && !isStarted && isPrefixDiscoveryStarted
Action: leaveStartedState()
Equivalent to DISCOVERING && !requiresClat, because
the only state with isPrefixDiscoveryStarted and !isStarted
is DISCOVERING.
Also, simplify case #5. In this case, calling leaveStartedState
is superfluous, because in the DISCOVERING state:
- There is no need to call unregisterObserver, since the observer
is only registered when entering STARTING and is unregistered
when going back to DISCOVERING or IDLE.
- mIface and mBaseIface don't need to be set to null because they
are only set to non-null when entering STARTING and nulled out
when going back to DISCOVERING or IDLE.
Bug: 126113090
Bug: 150648313
Test: covered by existing ConnectivityServiceTest and Nat464XlatTest
Change-Id: Ice536bcb269cc8b040c6e7a72c15d0bc8b5bd235
1 file changed