Instead of transforming between return value and callback, pass
the wrapped callback on to the invoked function as the last argument.
This eliminates the need for multiple invokeWithArgument overloads
and permits invoked functions to be asynchronous.
Thread<T> is a generic thread management object that starts a thread, creates an object T in that thread and calls its .start() function. When the Thread<T> object is destructed (which must happen in the thread that created it), it'll call the object's .stop() function, and wait for thread termination. The .stop() function must somehow get the thread to terminate. Note that object T's constructor/destructor/start()/stop() must be protected/private, and Thread<T> must be declared as a friend class. All public functions may be called from any thread and are exposed through operator->().
RunLoop encapsulates a libuv runloop and has a facility of dispatching function objects to the thread. It can be used either as a worker thread class by itself, or it can be derived from. This commit converts SQLiteCache to derive from RunLoop and removes the custom code used previously for managing the cache thread.
- catch SQLite exceptions and report them
- failed statements are ignored, we're really just caching here, so if it fails we're handling it gracefully elsewhere
- handle cases where the database file goes away after we opened it
- handle cases where the schema wasn't created after the database file was opened successfully
- add tests
