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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef MOZILLA_AUTO_MAPPABLE_H
#define MOZILLA_AUTO_MAPPABLE_H
// Here be dragons.
#include <functional>
#include <tuple>
namespace mozilla {
template <class T>
size_t StdHash(const T& t) {
return std::hash<T>()(t);
}
//-
// From Boost:
// https://www.boost.org/doc/libs/1_37_0/doc/html/hash/reference.html#boost.hash_combine
inline size_t HashCombine(size_t seed, const size_t hash) {
seed ^= hash + 0x9e3779b9 + (seed << 6) + (seed >> 2);
return seed;
}
// -
namespace detail {
template <class... Args, size_t... Ids>
size_t StdHashTupleN(const std::tuple<Args...>& tup,
const std::index_sequence<Ids...>&) {
size_t seed = 0;
for (const auto& hash : {StdHash(std::get<Ids>(tup))...}) {
seed = HashCombine(seed, hash);
}
return seed;
}
} // namespace detail
// -
template <class T>
struct StdHashMembers {
size_t operator()(const T& t) const {
const auto members = t.Members();
return StdHash(members);
}
};
// -
#define MOZ_MIXIN_DERIVE_CMP_OP_BY_MEMBERS(OP, T) \
bool operator OP(const T& rhs) const { return Members() OP rhs.Members(); }
#define MOZ_MIXIN_DERIVE_CMP_OPS_BY_MEMBERS(T) \
MOZ_MIXIN_DERIVE_CMP_OP_BY_MEMBERS(==, T) \
MOZ_MIXIN_DERIVE_CMP_OP_BY_MEMBERS(!=, T) \
MOZ_MIXIN_DERIVE_CMP_OP_BY_MEMBERS(<, T) \
MOZ_MIXIN_DERIVE_CMP_OP_BY_MEMBERS(<=, T) \
MOZ_MIXIN_DERIVE_CMP_OP_BY_MEMBERS(>, T) \
MOZ_MIXIN_DERIVE_CMP_OP_BY_MEMBERS(>=, T)
template <class T>
struct DeriveCmpOpMembers {
private:
auto Members() const { return reinterpret_cast<const T*>(this)->Members(); }
public:
MOZ_MIXIN_DERIVE_CMP_OPS_BY_MEMBERS(T)
};
} // namespace mozilla
template <class... Args>
struct std::hash<std::tuple<Args...>> {
size_t operator()(const std::tuple<Args...>& t) const {
return mozilla::detail::StdHashTupleN(
t, std::make_index_sequence<sizeof...(Args)>());
}
};
#endif // MOZILLA_AUTO_MAPPABLE_H
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