bpo-38045: Improve the performance of _decompose() in enum.py (GH-16483)
* Improve the performance of _decompose() in enum.py Co-Authored-By: Brandt Bucher <brandtbucher@gmail.com>
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Lib/enum.py
33
Lib/enum.py
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@ -861,28 +861,20 @@ def _decompose(flag, value):
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# _decompose is only called if the value is not named
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not_covered = value
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negative = value < 0
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# issue29167: wrap accesses to _value2member_map_ in a list to avoid race
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# conditions between iterating over it and having more pseudo-
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# members added to it
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if negative:
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# only check for named flags
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flags_to_check = [
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(m, v)
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for v, m in list(flag._value2member_map_.items())
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if m.name is not None
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]
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else:
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# check for named flags and powers-of-two flags
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flags_to_check = [
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(m, v)
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for v, m in list(flag._value2member_map_.items())
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if m.name is not None or _power_of_two(v)
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]
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members = []
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for member, member_value in flags_to_check:
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for member in flag:
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member_value = member.value
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if member_value and member_value & value == member_value:
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members.append(member)
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not_covered &= ~member_value
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if not negative:
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tmp = not_covered
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while tmp:
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flag_value = 2 ** _high_bit(tmp)
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if flag_value in flag._value2member_map_:
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members.append(flag._value2member_map_[flag_value])
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not_covered &= ~flag_value
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tmp &= ~flag_value
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if not members and value in flag._value2member_map_:
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members.append(flag._value2member_map_[value])
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members.sort(key=lambda m: m._value_, reverse=True)
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@ -890,8 +882,3 @@ def _decompose(flag, value):
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# we have the breakdown, don't need the value member itself
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members.pop(0)
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return members, not_covered
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def _power_of_two(value):
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if value < 1:
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return False
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return value == 2 ** _high_bit(value)
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@ -0,0 +1 @@
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Improve the performance of :func:`enum._decompose` in :mod:`enum`. Patch by hongweipeng.
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