Returns the current count of a barrier.
mp
barrier-count barrier => result
barrier
A barrier.
result
A positive fixnum, or nil .
nil
The function barrier-count returns the current count of the barrier barrier , or nil for a disabled barrier.
barrier-count
The count value can be changed by barrier-unblock, barrier-enable, barrier-disable or barrier-change-count.
barrier-change-count barrier-disable barrier-enable barrier-unblock
