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| | class Semaphore
def initialize(resource_count = 0)
@available_resource_count = resource_count
@mutex = Mutex.new
@waiting_threads = []
end
def wait
make_thread_wait unless resource_is_available
end
def signal
schedule_waiting_thread if thread_is_waiting
end
def synchronize
self.wait
yield
ensure
self.signal
end
private
def resource_is_available
@mutex.synchronize do
return (@available_resource_count -= 1) >= 0
end
end
def make_thread_wait
@waiting_threads << Thread.current
Thread.stop
end
def thread_is_waiting
@mutex.synchronize do
return (@available_resource_count += 1) <= 0
end
end
def schedule_waiting_thread
thread = @waiting_threads.shift
thread.wakeup if thread
end
end
|