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// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// Part of the BastionOS freestanding C++ standard library.
//
// Basic hash specializations for integral types, pointers, and bool.
//
//===----------------------------------------------------------------------===//
#ifndef _LIBBASTION_FUNCTIONAL_HASH_H
#define _LIBBASTION_FUNCTIONAL_HASH_H
#include <__config>
#include <cstddef>
#include <cstdint>
_LIBBASTION_BEGIN_NAMESPACE_STD
// Primary template — disabled.
template<class _Tp>
struct hash;
namespace __detail {
// FNV-1a for types larger than size_t would be overkill in a kernel.
// Identity hash for integers, cast-to-size_t for pointers.
inline constexpr size_t __hash_integral(size_t __val) noexcept {
// Mix bits for better distribution — based on splitmix64.
__val ^= __val >> 30;
__val *= 0xbf58476d1ce4e5b9ULL;
__val ^= __val >> 27;
__val *= 0x94d049bb133111ebULL;
__val ^= __val >> 31;
return __val;
}
} // namespace __detail
// Macro for integral type specializations.
#define _LIBBASTION_HASH_INTEGRAL(_Type) \
template<> \
struct hash<_Type> { \
_LIBBASTION_NODISCARD size_t operator()(_Type __val) const noexcept { \
return __detail::__hash_integral(static_cast<size_t>(__val)); \
} \
};
_LIBBASTION_HASH_INTEGRAL(bool)
_LIBBASTION_HASH_INTEGRAL(char)
_LIBBASTION_HASH_INTEGRAL(signed char)
_LIBBASTION_HASH_INTEGRAL(unsigned char)
_LIBBASTION_HASH_INTEGRAL(char8_t)
_LIBBASTION_HASH_INTEGRAL(char16_t)
_LIBBASTION_HASH_INTEGRAL(char32_t)
_LIBBASTION_HASH_INTEGRAL(wchar_t)
_LIBBASTION_HASH_INTEGRAL(short)
_LIBBASTION_HASH_INTEGRAL(unsigned short)
_LIBBASTION_HASH_INTEGRAL(int)
_LIBBASTION_HASH_INTEGRAL(unsigned int)
_LIBBASTION_HASH_INTEGRAL(long)
_LIBBASTION_HASH_INTEGRAL(unsigned long)
_LIBBASTION_HASH_INTEGRAL(long long)
_LIBBASTION_HASH_INTEGRAL(unsigned long long)
#undef _LIBBASTION_HASH_INTEGRAL
// Pointer specialization
template<class _Tp>
struct hash<_Tp*> {
_LIBBASTION_NODISCARD size_t operator()(_Tp* __ptr) const noexcept {
return __detail::__hash_integral(reinterpret_cast<size_t>(__ptr));
}
};
// nullptr_t
template<>
struct hash<nullptr_t> {
_LIBBASTION_NODISCARD size_t operator()(nullptr_t) const noexcept {
return 0;
}
};
_LIBBASTION_END_NAMESPACE_STD
#endif // _LIBBASTION_FUNCTIONAL_HASH_H
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