text: //
  // ip/impl/network_v4.ipp
  // ~~~~~~~~~~~~~~~~~~~~~~
  //
  // Copyright (c) 2003-2019 Christopher M. Kohlhoff (chris at kohlhoff dot com)
  // Copyright (c) 2014 Oliver Kowalke (oliver dot kowalke at gmail dot com)
  //
  // 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 BOOST_ASIO_IP_IMPL_NETWORK_V4_IPP
  #define BOOST_ASIO_IP_IMPL_NETWORK_V4_IPP
  
  #if defined(_MSC_VER) && (_MSC_VER >= 1200)
  # pragma once
  #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
  
  #include <boost/asio/detail/config.hpp>
  #include <climits>
  #include <cstdio>
  #include <cstdlib>
  #include <stdexcept>
  #include <boost/asio/error.hpp>
  #include <boost/asio/detail/throw_error.hpp>
  #include <boost/asio/detail/throw_exception.hpp>
  #include <boost/asio/ip/network_v4.hpp>
  
  #include <boost/asio/detail/push_options.hpp>
  
  namespace boost {
  namespace asio {
  namespace ip {
  
  network_v4::network_v4(const address_v4& addr, unsigned short prefix_len)
    : address_(addr),
      prefix_length_(prefix_len)
  {
    if (prefix_len > 32)
    {
      std::out_of_range ex("prefix length too large");
      boost::asio::detail::throw_exception(ex);
    }
  }
  
  network_v4::network_v4(const address_v4& addr, const address_v4& mask)
    : address_(addr),
      prefix_length_(0)
  {
    address_v4::bytes_type mask_bytes = mask.to_bytes();
    bool finished = false;
    for (std::size_t i = 0; i < mask_bytes.size(); ++i)
    {
      if (finished)
      {
        if (mask_bytes[i])
        {
          std::invalid_argument ex("non-contiguous netmask");
          boost::asio::detail::throw_exception(ex);
        }
        continue;
      }
      else
      {
        switch (mask_bytes[i])
        {
        case 255:
          prefix_length_ += 8;
          break;
        case 254: // prefix_length_ += 7
          prefix_length_ += 1;
        case 252: // prefix_length_ += 6
          prefix_length_ += 1;
        case 248: // prefix_length_ += 5
          prefix_length_ += 1;
        case 240: // prefix_length_ += 4
          prefix_length_ += 1;
        case 224: // prefix_length_ += 3
          prefix_length_ += 1;
        case 192: // prefix_length_ += 2
          prefix_length_ += 1;
        case 128: // prefix_length_ += 1
          prefix_length_ += 1;
        case 0:   // nbits += 0
          finished = true;
          break;
        default:
          std::out_of_range ex("non-contiguous netmask");
          boost::asio::detail::throw_exception(ex);
        }
      }
    }
  }
  
  address_v4 network_v4::netmask() const BOOST_ASIO_NOEXCEPT
  {
    uint32_t nmbits = 0xffffffff;
    if (prefix_length_ == 0)
      nmbits = 0;
    else
      nmbits = nmbits << (32 - prefix_length_);
    return address_v4(nmbits);
  }
  
  address_v4_range network_v4::hosts() const BOOST_ASIO_NOEXCEPT
  {
    return is_host()
      ? address_v4_range(address_, address_v4(address_.to_uint() + 1))
      : address_v4_range(address_v4(network().to_uint() + 1), broadcast());
  }
  
  bool network_v4::is_subnet_of(const network_v4& other) const
  {
    if (other.prefix_length_ >= prefix_length_)
      return false; // Only real subsets are allowed.
    const network_v4 me(address_, other.prefix_length_);
    return other.canonical() == me.canonical();
  }
  
  std::string network_v4::to_string() const
  {
    boost::system::error_code ec;
    std::string addr = to_string(ec);
    boost::asio::detail::throw_error(ec);
    return addr;
  }
  
  std::string network_v4::to_string(boost::system::error_code& ec) const
  {
    using namespace std; // For sprintf.
    ec = boost::system::error_code();
    char prefix_len[16];
  #if defined(BOOST_ASIO_HAS_SECURE_RTL)
    sprintf_s(prefix_len, sizeof(prefix_len), "/%u", prefix_length_);
  #else // defined(BOOST_ASIO_HAS_SECURE_RTL)
    sprintf(prefix_len, "/%u", prefix_length_);
  #endif // defined(BOOST_ASIO_HAS_SECURE_RTL)
    return address_.to_string() + prefix_len;
  }
  
  network_v4 make_network_v4(const char* str)
  {
    return make_network_v4(std::string(str));
  }
  
  network_v4 make_network_v4(const char* str, boost::system::error_code& ec)
  {
    return make_network_v4(std::string(str), ec);
  }
  
  network_v4 make_network_v4(const std::string& str)
  {
    boost::system::error_code ec;
    network_v4 net = make_network_v4(str, ec);
    boost::asio::detail::throw_error(ec);
    return net;
  }
  
  network_v4 make_network_v4(const std::string& str,
      boost::system::error_code& ec)
  {
    std::string::size_type pos = str.find_first_of("/");
  
    if (pos == std::string::npos)
    {
      ec = boost::asio::error::invalid_argument;
      return network_v4();
    }
  
    if (pos == str.size() - 1)
    {
      ec = boost::asio::error::invalid_argument;
      return network_v4();
    }
  
    std::string::size_type end = str.find_first_not_of("0123456789", pos + 1);
    if (end != std::string::npos)
    {
      ec = boost::asio::error::invalid_argument;
      return network_v4();
    }
  
    const address_v4 addr = make_address_v4(str.substr(0, pos), ec);
    if (ec)
      return network_v4();
  
    const int prefix_len = std::atoi(str.substr(pos + 1).c_str());
    if (prefix_len < 0 || prefix_len > 32)
    {
      ec = boost::asio::error::invalid_argument;
      return network_v4();
    }
  
    return network_v4(addr, static_cast<unsigned short>(prefix_len));
  }
  
  #if defined(BOOST_ASIO_HAS_STRING_VIEW)
  
  network_v4 make_network_v4(string_view str)
  {
    return make_network_v4(static_cast<std::string>(str));
  }
  
  network_v4 make_network_v4(string_view str,
      boost::system::error_code& ec)
  {
    return make_network_v4(static_cast<std::string>(str), ec);
  }
  
  #endif // defined(BOOST_ASIO_HAS_STRING_VIEW)
  
  } // namespace ip
  } // namespace asio
  } // namespace boost
  
  #include <boost/asio/detail/pop_options.hpp>
  
  #endif // BOOST_ASIO_IP_IMPL_NETWORK_V4_IPP
  