text: // Copyright (c) 2011-2016 The Cryptonote developers
  // Copyright (c) 2014-2017 XDN-project developers
  // Distributed under the MIT/X11 software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #pragma once
  
  #include <limits>
  #include <sstream>
  #include <string>
  #include <type_traits>
  #include <utility>
  
  namespace Tools {
  
      template<typename OutputIt, typename T>
      typename std::enable_if<std::is_integral<T>::value && std::is_unsigned<T>::value, void>::type
      write_varint(OutputIt &&dest, T i) {
          while (i >= 0x80) {
              *dest++ = (static_cast<char>(i) & 0x7f) | 0x80;
              i >>= 7;
          }
          *dest++ = static_cast<char>(i);
      }
  
      template<typename t_type>
      std::string get_varint_data(const t_type& v)
      {
        std::stringstream ss;
        write_varint(std::ostreambuf_iterator<char>(ss), v);
        return ss.str();
      }
  
      template<int bits, typename InputIt, typename T>
      typename std::enable_if<std::is_integral<T>::value && std::is_unsigned<T>::value && 0 <= bits && bits <= std::numeric_limits<T>::digits, int>::type
      read_varint(InputIt &&first, InputIt &&last, T &i) {
          int read = 0;
          i = 0;
          for (int shift = 0;; shift += 7) {
              if (first == last) {
                  return read; // End of input.
              }
              unsigned char byte = *first++;
              ++read;
              if (shift + 7 >= bits && byte >= 1 << (bits - shift)) {
                  return -1; // Overflow.
              }
              if (byte == 0 && shift != 0) {
                  return -2; // Non-canonical representation.
              }
              i |= static_cast<T>(byte & 0x7f) << shift;
              if ((byte & 0x80) == 0) {
                  break;
              }
          }
          return read;
      }
  
      template<typename InputIt, typename T>
      int read_varint(InputIt &&first, InputIt &&last, T &i) {
          return read_varint<std::numeric_limits<T>::digits, InputIt, T>(std::move(first), std::move(last), i);
      }
  }
  