Source.Python/addons/source-python/Python3/asyncio/locks.py at main · CookStar/Source.Python · GitHub

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"""Synchronization primitives."""

__all__ = ['Lock', 'Event', 'Condition', 'Semaphore', 'BoundedSemaphore']

import collections

from . import compat

from . import events

from . import futures

from .coroutines import coroutine

class _ContextManager:

"""Context manager.

This enables the following idiom for acquiring and releasing a

lock around a block:

with (yield from lock):

<block>

while failing loudly when accidentally using:

with lock:

<block>

"""

def __init__(self, lock):

self._lock = lock

def __enter__(self):

# We have no use for the "as ..." clause in the with

# statement for locks.

return None

def __exit__(self, *args):

try:

self._lock.release()

finally:

self._lock = None # Crudely prevent reuse.

class _ContextManagerMixin:

def __enter__(self):

raise RuntimeError(

'"yield from" should be used as context manager expression')

def __exit__(self, *args):

# This must exist because __enter__ exists, even though that

# always raises; that's how the with-statement works.

pass

@coroutine

def __iter__(self):

# This is not a coroutine. It is meant to enable the idiom:

# with (yield from lock):

# <block>

# as an alternative to:

# yield from lock.acquire()

# try:

# <block>

# finally:

# lock.release()

yield from self.acquire()

return _ContextManager(self)

if compat.PY35:

def __await__(self):

# To make "with await lock" work.

yield from self.acquire()

return _ContextManager(self)

@coroutine

def __aenter__(self):

yield from self.acquire()

# We have no use for the "as ..." clause in the with

# statement for locks.

return None

@coroutine

def __aexit__(self, exc_type, exc, tb):

self.release()

class Lock(_ContextManagerMixin):

"""Primitive lock objects.

A primitive lock is a synchronization primitive that is not owned

by a particular coroutine when locked. A primitive lock is in one

of two states, 'locked' or 'unlocked'.

It is created in the unlocked state. It has two basic methods,

acquire() and release(). When the state is unlocked, acquire()

changes the state to locked and returns immediately. When the

state is locked, acquire() blocks until a call to release() in

another coroutine changes it to unlocked, then the acquire() call

resets it to locked and returns. The release() method should only

be called in the locked state; it changes the state to unlocked

and returns immediately. If an attempt is made to release an

unlocked lock, a RuntimeError will be raised.

When more than one coroutine is blocked in acquire() waiting for

the state to turn to unlocked, only one coroutine proceeds when a

release() call resets the state to unlocked; first coroutine which

is blocked in acquire() is being processed.

acquire() is a coroutine and should be called with 'yield from'.

Locks also support the context management protocol. '(yield from lock)'

should be used as the context manager expression.

Usage:

lock = Lock()

...

yield from lock

try:

...

finally:

lock.release()

Context manager usage:

lock = Lock()

...

with (yield from lock):

...

Lock objects can be tested for locking state:

if not lock.locked():

yield from lock

else:

# lock is acquired

...

"""

def __init__(self, *, loop=None):

self._waiters = collections.deque()

self._locked = False

if loop is not None:

self._loop = loop

else:

self._loop = events.get_event_loop()

def __repr__(self):

res = super().__repr__()

extra = 'locked' if self._locked else 'unlocked'

if self._waiters:

extra = '{},waiters:{}'.format(extra, len(self._waiters))

return '<{} [{}]>'.format(res[1:-1], extra)

def locked(self):

"""Return True if lock is acquired."""

return self._locked

@coroutine

def acquire(self):

"""Acquire a lock.

This method blocks until the lock is unlocked, then sets it to

locked and returns True.

"""

if not self._locked and all(w.cancelled() for w in self._waiters):

self._locked = True

return True

fut = self._loop.create_future()

self._waiters.append(fut)

try:

yield from fut

self._locked = True

return True

finally:

self._waiters.remove(fut)

def release(self):

"""Release a lock.

When the lock is locked, reset it to unlocked, and return.

If any other coroutines are blocked waiting for the lock to become

unlocked, allow exactly one of them to proceed.

When invoked on an unlocked lock, a RuntimeError is raised.

There is no return value.

"""

if self._locked:

self._locked = False

# Wake up the first waiter who isn't cancelled.

for fut in self._waiters:

if not fut.done():

fut.set_result(True)

break

else:

raise RuntimeError('Lock is not acquired.')

class Event:

"""Asynchronous equivalent to threading.Event.

Class implementing event objects. An event manages a flag that can be set

to true with the set() method and reset to false with the clear() method.

The wait() method blocks until the flag is true. The flag is initially

false.

"""

def __init__(self, *, loop=None):

self._waiters = collections.deque()

self._value = False

if loop is not None:

self._loop = loop

else:

self._loop = events.get_event_loop()

def __repr__(self):

res = super().__repr__()

extra = 'set' if self._value else 'unset'

if self._waiters:

extra = '{},waiters:{}'.format(extra, len(self._waiters))

return '<{} [{}]>'.format(res[1:-1], extra)

def is_set(self):

"""Return True if and only if the internal flag is true."""

return self._value

def set(self):

"""Set the internal flag to true. All coroutines waiting for it to

become true are awakened. Coroutine that call wait() once the flag is

true will not block at all.

"""

if not self._value:

self._value = True

for fut in self._waiters:

if not fut.done():

fut.set_result(True)

def clear(self):

"""Reset the internal flag to false. Subsequently, coroutines calling

wait() will block until set() is called to set the internal flag

to true again."""

self._value = False

@coroutine

def wait(self):

"""Block until the internal flag is true.

If the internal flag is true on entry, return True

immediately. Otherwise, block until another coroutine calls

set() to set the flag to true, then return True.

"""

if self._value:

return True

fut = self._loop.create_future()

self._waiters.append(fut)

try:

yield from fut

return True

finally:

self._waiters.remove(fut)

class Condition(_ContextManagerMixin):

"""Asynchronous equivalent to threading.Condition.

This class implements condition variable objects. A condition variable

allows one or more coroutines to wait until they are notified by another

coroutine.

A new Lock object is created and used as the underlying lock.

"""

def __init__(self, lock=None, *, loop=None):

if loop is not None:

self._loop = loop

else:

self._loop = events.get_event_loop()

if lock is None:

lock = Lock(loop=self._loop)

elif lock._loop is not self._loop:

raise ValueError("loop argument must agree with lock")

self._lock = lock

# Export the lock's locked(), acquire() and release() methods.

self.locked = lock.locked

self.acquire = lock.acquire

self.release = lock.release

self._waiters = collections.deque()

def __repr__(self):

res = super().__repr__()

extra = 'locked' if self.locked() else 'unlocked'

if self._waiters:

extra = '{},waiters:{}'.format(extra, len(self._waiters))

return '<{} [{}]>'.format(res[1:-1], extra)

@coroutine

def wait(self):

"""Wait until notified.

If the calling coroutine has not acquired the lock when this

method is called, a RuntimeError is raised.

This method releases the underlying lock, and then blocks

until it is awakened by a notify() or notify_all() call for

the same condition variable in another coroutine. Once

awakened, it re-acquires the lock and returns True.

"""

if not self.locked():

raise RuntimeError('cannot wait on un-acquired lock')

self.release()

try:

fut = self._loop.create_future()

self._waiters.append(fut)

try:

yield from fut

return True

finally:

self._waiters.remove(fut)

finally:

# Must reacquire lock even if wait is cancelled

while True:

try:

yield from self.acquire()

break

except futures.CancelledError:

pass

@coroutine

def wait_for(self, predicate):

"""Wait until a predicate becomes true.

The predicate should be a callable which result will be

interpreted as a boolean value. The final predicate value is

the return value.

"""

result = predicate()

while not result:

yield from self.wait()

result = predicate()

return result

def notify(self, n=1):

"""By default, wake up one coroutine waiting on this condition, if any.

If the calling coroutine has not acquired the lock when this method

is called, a RuntimeError is raised.

This method wakes up at most n of the coroutines waiting for the

condition variable; it is a no-op if no coroutines are waiting.

Note: an awakened coroutine does not actually return from its

wait() call until it can reacquire the lock. Since notify() does

not release the lock, its caller should.

"""

if not self.locked():

raise RuntimeError('cannot notify on un-acquired lock')

idx = 0

for fut in self._waiters:

if idx >= n:

break

if not fut.done():

idx += 1

fut.set_result(False)

def notify_all(self):

"""Wake up all threads waiting on this condition. This method acts

like notify(), but wakes up all waiting threads instead of one. If the

calling thread has not acquired the lock when this method is called,

a RuntimeError is raised.

"""

self.notify(len(self._waiters))

class Semaphore(_ContextManagerMixin):

"""A Semaphore implementation.

A semaphore manages an internal counter which is decremented by each

acquire() call and incremented by each release() call. The counter

can never go below zero; when acquire() finds that it is zero, it blocks,

waiting until some other thread calls release().

Semaphores also support the context management protocol.

The optional argument gives the initial value for the internal

counter; it defaults to 1. If the value given is less than 0,

ValueError is raised.

"""

def __init__(self, value=1, *, loop=None):

if value < 0:

raise ValueError("Semaphore initial value must be >= 0")

self._value = value

self._waiters = collections.deque()

if loop is not None:

self._loop = loop

else:

self._loop = events.get_event_loop()

def __repr__(self):

res = super().__repr__()

extra = 'locked' if self.locked() else 'unlocked,value:{}'.format(

self._value)

if self._waiters:

extra = '{},waiters:{}'.format(extra, len(self._waiters))

return '<{} [{}]>'.format(res[1:-1], extra)

def _wake_up_next(self):

while self._waiters:

waiter = self._waiters.popleft()

if not waiter.done():

waiter.set_result(None)

return

def locked(self):

"""Returns True if semaphore can not be acquired immediately."""

return self._value == 0

@coroutine

def acquire(self):

"""Acquire a semaphore.

If the internal counter is larger than zero on entry,

decrement it by one and return True immediately. If it is

zero on entry, block, waiting until some other coroutine has

called release() to make it larger than 0, and then return

True.

"""

while self._value <= 0:

fut = self._loop.create_future()

self._waiters.append(fut)

try:

yield from fut

except:

# See the similar code in Queue.get.

fut.cancel()

if self._value > 0 and not fut.cancelled():

self._wake_up_next()

raise

self._value -= 1

return True

def release(self):

"""Release a semaphore, incrementing the internal counter by one.

When it was zero on entry and another coroutine is waiting for it to

become larger than zero again, wake up that coroutine.

"""

self._value += 1

self._wake_up_next()

class BoundedSemaphore(Semaphore):

"""A bounded semaphore implementation.

This raises ValueError in release() if it would increase the value

above the initial value.

"""

def __init__(self, value=1, *, loop=None):

self._bound_value = value

super().__init__(value, loop=loop)

def release(self):

if self._value >= self._bound_value:

raise ValueError('BoundedSemaphore released too many times')

super().release()

Source.Python/addons/source-python/Python3/asyncio/locks.py at main · CookStar/Source.Python · GitHub

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