AICondition is like AIThreadSafeSimpleDC (it is derived from it),
and wraps some variable, protecting it with a builtin mutex.
While in a statemachine, one can call wait(condition) to make
the state machine go idle, and call condition.signal() to
wake it (or another) up again.
While normally a condition variable is used as follows:
condition.lock();
while (!whatwerewaitingfor)
{
condition.wait();
}
// Here the condition is guaranteed to be true and we're
// still in the critical area of the mutex.
condition.unlock();
where the thread blocks in wait(), the statemachine actually
returns CPU to the thread (the AIEngine), so there is no
while loop involved, and our wait() doesn't even unlock
the mutex: that happens because the state machine returns:
condition_wat condition_w(condition); // Lock condition.
if (!condition_w->whatwerewaitingfor()) // The variable(s) involved can only be accessed when condition is locked.
{
wait(condition); // Causes the state machine to go idle. This does not block.
break; // Leave scope (unlock condition) and return to the mainloop - but as idle state machine.
}
// Here the condition is guaranteed to be true and we're
// still in the critical area of the condition variable.
In this case, when condition.signal() is called, the thread
doesn't return from wait() with a locked mutex - but the
statemachine executes the same state again, and enters from
the top: locking the condition and doing the test again,
just like it would be when this was a while loop.
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