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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,92 @@ | ||
| #!/bin/python3 | ||
| # author: Jan Hybs | ||
| import threading | ||
| from time import monotonic as _time | ||
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| class ComplexSemaphore(object): | ||
| """This class implements semaphore objects. | ||
| Semaphores manage a counter representing the number of release() calls minus | ||
| the number of acquire() calls, plus an initial value. The acquire() method | ||
| blocks if necessary until it can return without making the counter | ||
| negative. If not given, value defaults to 1. | ||
| """ | ||
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| # After Tim Peters' semaphore class, but not quite the same (no maximum) | ||
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| def __init__(self, value=1): | ||
| if value < 0: | ||
| raise ValueError("semaphore initial value must be >= 0") | ||
| self._cond = threading.Condition(threading.Lock()) | ||
| self._value = value | ||
| self._limit = value | ||
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| def acquire(self, blocking=True, timeout=None, value=1): | ||
| """Acquire a semaphore, decrementing the internal counter by one. | ||
| When invoked without arguments: if the internal counter is larger than | ||
| zero on entry, decrement it by one and return immediately. If it is zero | ||
| on entry, block, waiting until some other thread has called release() to | ||
| make it larger than zero. This is done with proper interlocking so that | ||
| if multiple acquire() calls are blocked, release() will wake exactly one | ||
| of them up. The implementation may pick one at random, so the order in | ||
| which blocked threads are awakened should not be relied on. There is no | ||
| return value in this case. | ||
| When invoked with blocking set to true, do the same thing as when called | ||
| without arguments, and return true. | ||
| When invoked with blocking set to false, do not block. If a call without | ||
| an argument would block, return false immediately; otherwise, do the | ||
| same thing as when called without arguments, and return true. | ||
| When invoked with a timeout other than None, it will block for at | ||
| most timeout seconds. If acquire does not complete successfully in | ||
| that interval, return false. Return true otherwise. | ||
| The value parameter specifies how many units to take from the semaphore | ||
| default value is 1. | ||
| """ | ||
| if not blocking and timeout is not None: | ||
| raise ValueError("can't specify timeout for non-blocking acquire") | ||
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| if value > self._limit: | ||
| raise ValueError("can't aquire the lock because specified value is greater then max value") | ||
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| rc = False | ||
| endtime = None | ||
| with self._cond: | ||
| while self._value < value: | ||
| if not blocking: | ||
| break | ||
| if timeout is not None: | ||
| if endtime is None: | ||
| endtime = _time() + timeout | ||
| else: | ||
| timeout = endtime - _time() | ||
| if timeout <= 0: | ||
| break | ||
| self._cond.wait(timeout) | ||
| else: | ||
| self._value -= value | ||
| rc = True | ||
| return rc | ||
|
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| __enter__ = acquire | ||
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| def release(self, value=1): | ||
| """Release a semaphore, incrementing the internal counter by one. | ||
| When the counter is zero on entry and another thread is waiting for it | ||
| to become larger than zero again, wake up that thread. | ||
| """ | ||
| with self._cond: | ||
| self._value += value | ||
| self._cond.notify() | ||
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| def __exit__(self, t, v, tb): | ||
| self.release() |
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