forked from OSchip/llvm-project
59 lines
1.7 KiB
Python
59 lines
1.7 KiB
Python
# ====================================================================
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# Provides a with-style resource handler for optionally-None resources
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# ====================================================================
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class optional_with(object):
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# pylint: disable=too-few-public-methods
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# This is a wrapper - it is not meant to provide any extra methods.
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"""Provides a wrapper for objects supporting "with", allowing None.
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This lets a user use the "with object" syntax for resource usage
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(e.g. locks) even when the wrapped with object is None.
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e.g.
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wrapped_lock = optional_with(thread.Lock())
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with wrapped_lock:
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# Do something while the lock is obtained.
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pass
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might_be_none = None
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wrapped_none = optional_with(might_be_none)
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with wrapped_none:
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# This code here still works.
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pass
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This prevents having to write code like this when
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a lock is optional:
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if lock:
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lock.acquire()
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try:
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code_fragment_always_run()
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finally:
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if lock:
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lock.release()
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And I'd posit it is safer, as it becomes impossible to
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forget the try/finally using optional_with(), since
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the with syntax can be used.
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"""
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def __init__(self, wrapped_object):
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self.wrapped_object = wrapped_object
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def __enter__(self):
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if self.wrapped_object is not None:
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return self.wrapped_object.__enter__()
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else:
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return self
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def __exit__(self, the_type, value, traceback):
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if self.wrapped_object is not None:
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return self.wrapped_object.__exit__(the_type, value, traceback)
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else:
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# Don't suppress any exceptions
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return False
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