half.hpp

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// SPDX-License-Identifier: BSL-1.0
// SPDX-FileCopyrightText: Copyright (C) 2021 Tobias Hienzsch
 
#ifndef TETL_CFLOAT_HALF_HPP
#define TETL_CFLOAT_HALF_HPP
 
#include <etl/_bit/bit_cast.hpp>
#include <etl/_cstdint/uint_t.hpp>
 
namespace etl {
 
struct binary_t { };
 
inline constexpr auto binary = binary_t{};
 
struct half {
    using storage_type = etl::uint16_t;
 
    constexpr half() = default;
    constexpr half(binary_t /*tag*/, storage_type bits);
 
private:
    storage_type _bits{0};
};
 
[[nodiscard]] constexpr auto isfinite(half arg) noexcept -> bool;
[[nodiscard]] constexpr auto isinf(half arg) noexcept -> bool;
[[nodiscard]] constexpr auto isnan(half arg) noexcept -> bool;
[[nodiscard]] constexpr auto isnormal(half arg) noexcept -> bool;
[[nodiscard]] constexpr auto signbit(half arg) noexcept -> bool;
 
// IMPL
namespace detail {
inline constexpr etl::half::storage_type exp_mask{0b0111'1100'0000'0000};
inline constexpr etl::half::storage_type man_mask{0b0000'0011'1111'1111};
inline constexpr etl::half::storage_type inf_mask{0b0111'1111'1111'1111};
inline constexpr etl::half::storage_type sign_mask{0b1000'0000'0000'0000};
} // namespace detail
 
constexpr half::half(binary_t /*tag*/, half::storage_type bits)
    : _bits{bits}
{
    // [tobi] This needs to be here, or clang will complain about an unused
    // member. All free functions use bit_cast to access the underlying bits of
    // the half float, so no "getter" method exists.
    (void)_bits;
}
 
constexpr auto isfinite(half arg) noexcept -> bool
{
    using uint_t = half::storage_type;
    return (etl::bit_cast<uint_t>(arg) & detail::exp_mask) != detail::exp_mask;
}
 
constexpr auto isinf(half arg) noexcept -> bool
{
    using uint_t = half::storage_type;
    return (etl::bit_cast<uint_t>(arg) & detail::inf_mask) == detail::exp_mask;
}
 
constexpr auto isnan(half arg) noexcept -> bool
{
    using uint_t = half::storage_type;
    return (etl::bit_cast<uint_t>(arg) & detail::inf_mask) > detail::exp_mask;
}
 
constexpr auto isnormal(half arg) noexcept -> bool
{
    using uint_t    = half::storage_type;
    auto const mask = detail::exp_mask;
    auto const bits = etl::bit_cast<uint_t>(arg);
    return ((bits & mask) != 0) & ((bits & mask) != mask); // NOLINT
}
 
constexpr auto signbit(half arg) noexcept -> bool
{
    using uint_t = half::storage_type;
    return (etl::bit_cast<uint_t>(arg) & detail::sign_mask) != 0;
}
 
} // namespace etl
 
#endif // TETL_CFLOAT_HALF_HPP