a9ef189a54
This patchs adds a header file, "core/enum.hh"; Code which includes this header file will be able to use an enumerated type as the key in a hash table. The header file implements a hash function for *all* enumerated types, by using the standard hash function of the underlying integer type.
29 lines
722 B
C++
29 lines
722 B
C++
/*
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* Copyright (C) 2015 Cloudius Systems, Ltd.
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*/
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#pragma once
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/*
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* This header file defines a hash function for all enum types, using the
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* standard hash function of the underlying type (such as int). This makes
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* it possible to use an enum type as a key for std::unordered_map, for
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* example.
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*/
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#include <type_traits>
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#include <functional>
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#include <cstddef>
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namespace std {
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template<typename T>
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class hash {
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using sfinae = typename std::enable_if<std::is_enum<T>::value, T>::type;
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public:
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std::size_t operator()(const T& e) const {
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using utype = typename std::underlying_type<T>::type;
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return std::hash<utype>()(static_cast<utype>(e));
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}
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};
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}
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