OpenVPNAdapter/Sources/OpenVPN3/openvpn/buffer/buffmt.hpp

//    OpenVPN -- An application to securely tunnel IP networks
//               over a single port, with support for SSL/TLS-based
//               session authentication and key exchange,
//               packet encryption, packet authentication, and
//               packet compression.
//
//    Copyright (C) 2012-2022 OpenVPN Inc.
//
//    This program is free software: you can redistribute it and/or modify
//    it under the terms of the GNU Affero General Public License Version 3
//    as published by the Free Software Foundation.
//
//    This program is distributed in the hope that it will be useful,
//    but WITHOUT ANY WARRANTY; without even the implied warranty of
//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//    GNU Affero General Public License for more details.
//
//    You should have received a copy of the GNU Affero General Public License
//    along with this program in the COPYING file.
//    If not, see <http://www.gnu.org/licenses/>.

#pragma once

#include <utility>
#include <type_traits>

#include <openvpn/common/exception.hpp>
#include <openvpn/buffer/buffer.hpp>
#include <openvpn/common/hexstr.hpp>

namespace openvpn {
  namespace BufferFormat {

    template <typename T>
    class UnsignedDecimal
    {
    public:
      static void write(Buffer& buf, T value)
      {
	UnsignedDecimal dec(std::move(value));
	char ret[max_length()];
	for (size_t i = sizeof(ret); i --> 0;)
	  {
	    ret[i] = dec.next();
	    if (dec.is_zero())
	      {
		buf.write(ret + i, sizeof(ret) - i);
		return;
	      }
	  }
	throw Exception("BufferFormat::UnsignedDecimal::write: overflow");
      }

      static constexpr size_t max_length()
      {
	return sizeof(T) * 3;
      }

    private:
      UnsignedDecimal(T&& value)
	: value_(std::move(value))
      {
	static_assert(std::is_unsigned<T>::value, "UnsignedDecimal: unsigned type required");
      }

      char next()
      {
	T d = value_ / T(10);
	T r = value_ % T(10);
	value_ = d;
	return '0' + r;
      }

      bool is_zero() const
      {
	return !value_;
      }

      T value_;
    };

    template <typename T>
    class Hex
    {
    public:
      static void write(Buffer& buf, T value)
      {
	Hex hex(std::move(value));
	char ret[max_length()];
	for (size_t i = sizeof(ret); i --> 0;)
	  {
	    ret[i] = hex.next();
	    if (hex.is_zero())
	      {
		buf.write(ret + i, sizeof(ret) - i);
		return;
	      }
	  }
	throw Exception("BufferFormat::Hex::write: overflow");
      }

      static constexpr size_t max_length()
      {
	return sizeof(T) * 2;
      }

    private:
      Hex(T&& value)
	: value_(std::move(value))
      {
	static_assert(std::is_unsigned<T>::value, "BufferFormat::Hex: unsigned type required");
      }

      char next()
      {
	T d = value_ / T(16);
	T r = value_ % T(16);
	value_ = d;
	return render_hex_char(r);
      }

      bool is_zero() const
      {
	return !value_;
      }

      T value_;
    };

  }
}