bit.h

// Copyright (c) Electronic Arts Inc. All rights reserved.
 
#ifndef EASTL_BIT_H
#define EASTL_BIT_H
 
#include <EASTL/internal/config.h>
 
#if defined(EA_PRAGMA_ONCE_SUPPORTED)
    #pragma once
#endif
 
#include <EASTL/internal/memory_base.h>
#include <EASTL/type_traits.h>
#include <string.h> // memcpy
 
namespace eastl
{
    // eastl::bit_cast
    // Obtains a value of type To by reinterpreting the object representation of 'from'.
    // Every bit in the value representation of the returned To object is equal to the
    // corresponding bit in the object representation of 'from'.
    //
    // In order for bit_cast to be constexpr, the compiler needs to explicitly support
    // it by providing the __builtin_bit_cast builtin. If that builtin is not available,
    // then we memcpy into aligned storage at runtime and return that instead.
    //
    // Both types To and From must be equal in size, and must be trivially copyable.
 
    #if defined(EASTL_CONSTEXPR_BIT_CAST_SUPPORTED) && EASTL_CONSTEXPR_BIT_CAST_SUPPORTED
 
        template<typename To, typename From,
            typename = eastl::enable_if_t<
                sizeof(To) == sizeof(From)
                && eastl::is_trivially_copyable<To>::value
                && eastl::is_trivially_copyable<From>::value
            >
        >
        EA_CONSTEXPR To bit_cast(const From& from) EA_NOEXCEPT
        {
            return __builtin_bit_cast(To, from);
        }
 
    #else
 
        template<typename To, typename From,
            typename = eastl::enable_if_t<
                sizeof(To) == sizeof(From)
                && eastl::is_trivially_copyable<To>::value
                && eastl::is_trivially_copyable<From>::value
            >
        >
        inline To bit_cast(const From& from) EA_NOEXCEPT
        {
            typename eastl::aligned_storage<sizeof(To), alignof(To)>::type to;
            ::memcpy(eastl::addressof(to), eastl::addressof(from), sizeof(To));
            return reinterpret_cast<To&>(to);
        }
 
    #endif // EASTL_CONSTEXPR_BIT_CAST_SUPPORTED
 
} // namespace eastl
 
#endif // EASTL_BIT_H