Sprout/sprout/net/endian.hpp

/*=============================================================================
  Copyright (c) 2011-2015 Bolero MURAKAMI
  https://github.com/bolero-MURAKAMI/Sprout

  Copyright (c) 2015 Chris KAY
  https://github.com/cjkay-cpp-utils/Sprout

  Distributed under the Boost Software License, Version 1.0. (See accompanying
  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
=============================================================================*/
#ifndef SPROUT_NET_ENDIAN_HPP
#define SPROUT_NET_ENDIAN_HPP

#include <cstdint>
#include <sprout/config.hpp>
#include <boost/detail/endian.hpp>

namespace sprout {
    namespace net {
        namespace detail {
            /*
             * lshift_by
             * Left shift 'val' by 'n' bytes
             */
            template<typename T>
            SPROUT_CONSTEXPR T lshift_by(T val, std::uint_fast8_t n) {
                return val << (n * 8);
            }

            /*
             * rshift_by
             * Right shift 'val' by 'n' bytes
             */
            template<typename T>
            SPROUT_CONSTEXPR T rshift_by(T val, std::uint_fast8_t n) {
                return val >> (n * 8);
            }

            /*
             * mask_t
             * Mask 'n'th byte
             */
            template<typename T>
            SPROUT_CONSTEXPR T mask_at(std::uint_fast8_t n) {
                return sprout::net::detail::lshift_by(T(0xFF), n);
            }

            /*
             * byte_at
             * Get 'n'th byte from 'val'
             */
            template<typename T>
            SPROUT_CONSTEXPR T byte_at(T val, std::uint_fast8_t n) {
                return sprout::net::detail::rshift_by((val & sprout::net::detail::mask_at<T>(n)), n);
            }

            /*
             * replace_at
             * Replace, in 'val', 'n'th byte with 'byte_val'
             */
            template<typename T>
            SPROUT_CONSTEXPR T replace_at(T val, std::uint8_t byte_val, std::uint_fast8_t n) {
                return (val & ~sprout::net::detail::mask_at<T>(n)) | sprout::net::detail::lshift_by(T(byte_val), n);
            }

            /*
             * copy
             * Copy, in 'val', byte at index 'from' to byte at index 'to'
             */
            template<typename T>
            SPROUT_CONSTEXPR T copy(T val, std::uint_fast8_t from, std::uint_fast8_t to) {
                return sprout::net::detail::replace_at(val, sprout::net::detail::byte_at(val, from), to);
            }

            /*
             * swap
             * Swap, in 'val', byte at index 'n1' with byte at index 'n2'
             */
            template<typename T>
            SPROUT_CONSTEXPR T swap(T val, std::uint_fast8_t n1, std::uint_fast8_t n2) {
                return sprout::net::detail::replace_at(sprout::net::detail::copy(val, n1, n2), sprout::net::detail::byte_at(val, n2), n1);
            }

            /*
             * reverse_impl
             * Swap, in 'val', byte at index 'n1' with byte at index 'n2' in 'val', increment n1, decrement n2 until n1 > n2
             */
            template<typename T>
            SPROUT_CONSTEXPR T reverse_impl(T val, std::uint_fast8_t n1, std::uint_fast8_t n2) {
                return n1 > n2 ? val : sprout::net::detail::reverse_impl(swap(val, n1, n2), n1 + 1, n2 - 1);
            }

            /*
             * reverse
             * Reverse 'val'
             */
            template<typename T>
            SPROUT_CONSTEXPR T reverse(T val) {
                return sprout::net::detail::reverse_impl(val, 0, sizeof(T) - 1);
            }

            /*
             * reverse_words_impl
             * Swap, in 'val', byte at index 'n' - 1 with byte at index 'n' - 2, decrement n by 2 until n == 0
             */
            template<typename T>
            SPROUT_CONSTEXPR T reverse_words_impl(T val, std::uint_fast8_t n) {
                return n == 0 ? val : sprout::net::detail::reverse_words_impl(swap(val, n - 1, n - 2), n - 2);
            }

            /*
             * reverse_words
             * Reverse each word in 'val'
             */
            template<typename T>
            SPROUT_CONSTEXPR T reverse_words(T val) {
                return sprout::net::detail::reverse_words_impl(val, sizeof(T));
            }
        }   // namespace detail

        // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3620.pdf
        // template<>
        // constexpr unsigned-integral hton(unsigned-integral host)
        template<typename T>
        SPROUT_CONSTEXPR T hton SPROUT_PREVENT_MACRO_SUBSTITUTION (T host) {
#if defined(BOOST_BIG_ENDIAN)
            return host;
#elif defined(BOOST_LITTLE_ENDIAN)
            return sprout::net::detail::reverse(host);
#elif defined(BOOST_PDP_ENDIAN)
            return sprout::net::detail::reverse_words(host);
#endif
        }

        // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3620.pdf
        // template<>
        // constexpr unsigned-integral ntoh(unsigned-integral net)
        template<typename T>
        SPROUT_CONSTEXPR T ntoh SPROUT_PREVENT_MACRO_SUBSTITUTION (T net) {
#if defined(BOOST_BIG_ENDIAN)
            return net;
#elif defined(BOOST_LITTLE_ENDIAN)
            return sprout::net::detail::reverse(net);
#elif defined(BOOST_PDP_ENDIAN)
            return sprout::net::detail::reverse_words(host);
#endif
        }

        // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3620.pdf
        // uint32_t htonl(uint32_t host32)
        SPROUT_CONSTEXPR std::uint32_t htonl SPROUT_PREVENT_MACRO_SUBSTITUTION (std::uint32_t host32) {
            return sprout::net::hton SPROUT_PREVENT_MACRO_SUBSTITUTION (host32);
        }

        // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3620.pdf
        // uint16_t htons(uint16_t host16)
        SPROUT_CONSTEXPR std::uint16_t htons SPROUT_PREVENT_MACRO_SUBSTITUTION (std::uint16_t host16) {
            return sprout::net::hton SPROUT_PREVENT_MACRO_SUBSTITUTION (host16);
        }

        // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3620.pdf
        // uint32_t ntohl(uint32_t net32)
        SPROUT_CONSTEXPR std::uint32_t ntohl SPROUT_PREVENT_MACRO_SUBSTITUTION (std::uint32_t net32) {
            return sprout::net::ntoh SPROUT_PREVENT_MACRO_SUBSTITUTION (net32);
        }

        // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3620.pdf
        // uint16_t ntohs(uint32_t net16)
        SPROUT_CONSTEXPR std::uint16_t ntohs SPROUT_PREVENT_MACRO_SUBSTITUTION (std::uint16_t net16) {
            return sprout::net::ntoh SPROUT_PREVENT_MACRO_SUBSTITUTION (net16);
        }
    }   //namespace net
}	// namespace sprout

#endif	// #ifndef SPROUT_NET_ENDIAN_HPP