byte_order.hpp

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/*
 
Copyright 2025 Matthew Tolman
 
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
 
   http://www.apache.org/licenses/LICENSE-2.0
 
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
 
*/
 
#ifndef MTSTD_BYTE_ORDER_HPP
#define MTSTD_BYTE_ORDER_HPP
 
#include <bit>


namespace mtcore {
  namespace endian {
    constexpr auto machine = std::endian::native;
    constexpr auto opposite = std::endian::native == std::endian::little ? std::endian::big : std::endian::little;
  }  // namespace endian

  constexpr u16 flip_endian_u16(const u16 bytes) { return bytes << 8 | ((bytes >> 8) & 0xFF); }

  constexpr char16_t flip_endian_ch16(const char16_t ch) {
    return static_cast<u16>(flip_endian_u16(static_cast<u16>(ch)));
  }

  constexpr u32 flip_endian_u32(const u32 bytes) {
    return bytes << 24 | ((bytes << 8) & 0xFF0000) | ((bytes >> 8) & 0xFF00) | ((bytes >> 24) & 0xFF);
  }

  constexpr char32_t flip_endian_ch32(const char32_t ch) {
    return static_cast<char32_t>(flip_endian_u32(static_cast<u32>(ch)));
  }

  template<typename T>
  constexpr auto flip_endian(const T bytes) {
    static_assert(std::same_as<u16, T> || std::same_as<char16_t, T> || std::same_as<u32, T> ||
                  std::same_as<char32_t, T>);
    if constexpr (std::is_same_v<u16, T>) {
      return flip_endian_u16(bytes);
    }
    else if constexpr (std::is_same_v<char16_t, T>) {
      return flip_endian_ch16(bytes);
    }
    else if constexpr (std::is_same_v<u32, T>) {
      return flip_endian_u32(bytes);
    }
    else {
      return flip_endian_ch32(bytes);
    }
  }
}  // namespace mtcore
 
#endif  // MTSTD_BYTE_ORDER_HPP