text: // Copyright (c) 2011-2017 The Cryptonote developers
  // Copyright (c) 2017-2018 The Circle Foundation & Conceal Devs
  // Copyright (c) 2018-2019 Conceal Network & Conceal Devs
  // Copyright (c) 2019-2020 The Wallet 2 Wallet Team
  // Distributed under the MIT/X11 software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #include "Ipv4Resolver.h"
  #include <cassert>
  #include <random>
  #include <stdexcept>
  
  #include <netdb.h>
  
  #include <System/Dispatcher.h>
  #include <System/ErrorMessage.h>
  #include <System/InterruptedException.h>
  #include <System/Ipv4Address.h>
  
  namespace System {
  
  Ipv4Resolver::Ipv4Resolver() : dispatcher(nullptr) {
  }
  
  Ipv4Resolver::Ipv4Resolver(Dispatcher& dispatcher) : dispatcher(&dispatcher) {
  }
  
  Ipv4Resolver::Ipv4Resolver(Ipv4Resolver&& other) : dispatcher(other.dispatcher) {
    if (dispatcher != nullptr) {
      other.dispatcher = nullptr;
    }
  }
  
  Ipv4Resolver::~Ipv4Resolver() {
  }
  
  Ipv4Resolver& Ipv4Resolver::operator=(Ipv4Resolver&& other) {
    dispatcher = other.dispatcher;
    if (dispatcher != nullptr) {
      other.dispatcher = nullptr;
    }
  
    return *this;
  }
  
  Ipv4Address Ipv4Resolver::resolve(const std::string& host) {
    assert(dispatcher != nullptr);
    if (dispatcher->interrupted()) {
      throw InterruptedException();
    }
  
    addrinfo hints = { 0, AF_INET, SOCK_STREAM, IPPROTO_TCP, 0, NULL, NULL, NULL };
    addrinfo* addressInfos;
    int result = getaddrinfo(host.c_str(), NULL, &hints, &addressInfos);
    if (result != 0) {
      throw std::runtime_error("Ipv4Resolver::resolve, getaddrinfo failed, " + errorMessage(result));
    }
    
    std::size_t count = 0;
    for (addrinfo* addressInfo = addressInfos; addressInfo != nullptr; addressInfo = addressInfo->ai_next) {
      ++count;
    }
  
    std::mt19937 generator{ std::random_device()() };
    std::size_t index = std::uniform_int_distribution<std::size_t>(0, count - 1)(generator);
    addrinfo* addressInfo = addressInfos;
    for (std::size_t i = 0; i < index; ++i) {
      addressInfo = addressInfo->ai_next;
    }
  
    Ipv4Address address(ntohl(reinterpret_cast<sockaddr_in*>(addressInfo->ai_addr)->sin_addr.s_addr));
    freeaddrinfo(addressInfo);
    return address;
  }
  
  }
  