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# Copyright (C) 2018 Bloomberg LP
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2 of the License, or (at your option) any later version.
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# Lesser General Public License for more details.
# You should have received a copy of the GNU Lesser General Public
# License along with this library. If not, see <>.
# Authors:
# Tristan Van Berkom <>
# Jim MacArthur <>
# Benjamin Schubert <>
# MetaFastEnum()
# This is a reemplementation of MetaEnum, in order to get a faster implementation of Enum.
# Enum turns out to be very slow and would add a noticeable slowdown when we try to add them to the codebase.
# We therefore reimplement a subset of the `Enum` functionality that keeps it compatible with normal `Enum`.
# That way, any place in the code base that access a `FastEnum`, can normally also accept an `Enum`. The reverse
# is not correct, since we only implement a subset of `Enum`.
class MetaFastEnum(type):
def __new__(mcs, name, bases, dct):
if name == "FastEnum":
return type.__new__(mcs, name, bases, dct)
assert len(bases) == 1, "Multiple inheritance with Fast enums is not currently supported."
dunder_values = {}
normal_values = {}
parent_keys = bases[0].__dict__.keys()
assert "__class__" not in dct.keys(), "Overriding '__class__' is not allowed on 'FastEnum' classes"
for key, value in dct.items():
if key.startswith("__") and key.endswith("__"):
dunder_values[key] = value
assert key not in parent_keys, "Overriding 'FastEnum.{}' is not allowed. ".format(key)
normal_values[key] = value
kls = type.__new__(mcs, name, bases, dunder_values)
mcs.set_values(kls, normal_values)
return kls
def set_values(mcs, kls, data):
value_to_entry = {}
assert len(set(data.values())) == len(data.values()), "Values for {} are not unique".format(kls)
assert len(set(type(value) for value in data.values())) <= 1, \
"Values of {} are of heterogeneous types".format(kls)
for key, value in data.items():
new_value = object.__new__(kls)
object.__setattr__(new_value, "value", value)
object.__setattr__(new_value, "name", key)
type.__setattr__(kls, key, new_value)
value_to_entry[value] = new_value
type.__setattr__(kls, "_value_to_entry", value_to_entry)
def __repr__(self):
return "<fastenum '{}'>".format(self.__name__)
def __setattr__(self, key, value):
raise AttributeError("Adding new values dynamically is not supported")
def __iter__(self):
return iter(self._value_to_entry.values())