128 lines
3.3 KiB
Python
128 lines
3.3 KiB
Python
"""Method decorator helpers."""
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import functools
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import weakref
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def warn_cache_none():
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from warnings import warn
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warn(
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"returning `None` from `cache(self)` is deprecated",
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DeprecationWarning,
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stacklevel=3,
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)
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def _condition(method, cache, key, lock, cond):
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pending = weakref.WeakKeyDictionary()
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def wrapper(self, *args, **kwargs):
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c = cache(self)
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if c is None:
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warn_cache_none()
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return method(self, *args, **kwargs)
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k = key(self, *args, **kwargs)
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with lock(self):
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p = pending.setdefault(self, set())
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cond(self).wait_for(lambda: k not in p)
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try:
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return c[k]
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except KeyError:
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p.add(k)
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try:
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v = method(self, *args, **kwargs)
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with lock(self):
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try:
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c[k] = v
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except ValueError:
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pass # value too large
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return v
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finally:
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with lock(self):
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pending[self].remove(k)
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cond(self).notify_all()
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def cache_clear(self):
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c = cache(self)
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if c is not None:
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with lock(self):
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c.clear()
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wrapper.cache_clear = cache_clear
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return wrapper
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def _locked(method, cache, key, lock):
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def wrapper(self, *args, **kwargs):
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c = cache(self)
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if c is None:
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warn_cache_none()
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return method(self, *args, **kwargs)
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k = key(self, *args, **kwargs)
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with lock(self):
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try:
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return c[k]
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except KeyError:
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pass # key not found
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v = method(self, *args, **kwargs)
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# in case of a race, prefer the item already in the cache
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with lock(self):
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try:
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return c.setdefault(k, v)
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except ValueError:
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return v # value too large
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def cache_clear(self):
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c = cache(self)
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if c is not None:
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with lock(self):
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c.clear()
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wrapper.cache_clear = cache_clear
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return wrapper
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def _unlocked(method, cache, key):
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def wrapper(self, *args, **kwargs):
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c = cache(self)
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if c is None:
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warn_cache_none()
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return method(self, *args, **kwargs)
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k = key(self, *args, **kwargs)
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try:
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return c[k]
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except KeyError:
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pass # key not found
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v = method(self, *args, **kwargs)
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try:
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c[k] = v
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except ValueError:
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pass # value too large
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return v
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def cache_clear(self):
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c = cache(self)
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if c is not None:
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c.clear()
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wrapper.cache_clear = cache_clear
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return wrapper
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def _wrapper(method, cache, key, lock=None, cond=None):
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if cond is not None and lock is not None:
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wrapper = _condition(method, cache, key, lock, cond)
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elif cond is not None:
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wrapper = _condition(method, cache, key, cond, cond)
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elif lock is not None:
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wrapper = _locked(method, cache, key, lock)
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else:
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wrapper = _unlocked(method, cache, key)
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wrapper.cache = cache
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wrapper.cache_key = key
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wrapper.cache_lock = lock if lock is not None else cond
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wrapper.cache_condition = cond
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return functools.update_wrapper(wrapper, method)
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