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85 lines
2.5 KiB
85 lines
2.5 KiB
6 years ago
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from .compat import threading
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import weakref
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class NameRegistry(object):
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"""Generates and return an object, keeping it as a
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singleton for a certain identifier for as long as its
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strongly referenced.
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e.g.::
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class MyFoo(object):
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"some important object."
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def __init__(self, identifier):
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self.identifier = identifier
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registry = NameRegistry(MyFoo)
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# thread 1:
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my_foo = registry.get("foo1")
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# thread 2
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my_foo = registry.get("foo1")
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Above, ``my_foo`` in both thread #1 and #2 will
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be *the same object*. The constructor for
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``MyFoo`` will be called once, passing the
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identifier ``foo1`` as the argument.
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When thread 1 and thread 2 both complete or
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otherwise delete references to ``my_foo``, the
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object is *removed* from the :class:`.NameRegistry` as
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a result of Python garbage collection.
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:param creator: A function that will create a new
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value, given the identifier passed to the :meth:`.NameRegistry.get`
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method.
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"""
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_locks = weakref.WeakValueDictionary()
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_mutex = threading.RLock()
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def __init__(self, creator):
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"""Create a new :class:`.NameRegistry`.
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"""
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self._values = weakref.WeakValueDictionary()
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self._mutex = threading.RLock()
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self.creator = creator
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def get(self, identifier, *args, **kw):
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"""Get and possibly create the value.
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:param identifier: Hash key for the value.
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If the creation function is called, this identifier
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will also be passed to the creation function.
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:param \*args, \**kw: Additional arguments which will
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also be passed to the creation function if it is
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called.
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"""
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try:
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if identifier in self._values:
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return self._values[identifier]
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else:
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return self._sync_get(identifier, *args, **kw)
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except KeyError:
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return self._sync_get(identifier, *args, **kw)
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def _sync_get(self, identifier, *args, **kw):
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self._mutex.acquire()
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try:
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try:
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if identifier in self._values:
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return self._values[identifier]
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else:
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self._values[identifier] = value = self.creator(identifier, *args, **kw)
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return value
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except KeyError:
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self._values[identifier] = value = self.creator(identifier, *args, **kw)
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return value
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finally:
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self._mutex.release()
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