inline int getaddrinfo_emulation()

in demo_example/asio/asio/detail/impl/socket_ops.ipp [3335:3534]

• 170 lines of code
• 42 McCabe index (conditional complexity)

inline int getaddrinfo_emulation(const char* host, const char* service,
    const addrinfo_type* hintsp, addrinfo_type** result)
{
  // Set up linked list of addrinfo structures.
  addrinfo_type* aihead = 0;
  addrinfo_type** ainext = &aihead;
  char* canon = 0;

  // Supply default hints if not specified by caller.
  addrinfo_type hints = addrinfo_type();
  hints.ai_family = ASIO_OS_DEF(AF_UNSPEC);
  if (hintsp)
    hints = *hintsp;

  // If the resolution is not specifically for AF_INET6, remove the AI_V4MAPPED
  // and AI_ALL flags.
#if defined(AI_V4MAPPED)
  if (hints.ai_family != ASIO_OS_DEF(AF_INET6))
    hints.ai_flags &= ~AI_V4MAPPED;
#endif
#if defined(AI_ALL)
  if (hints.ai_family != ASIO_OS_DEF(AF_INET6))
    hints.ai_flags &= ~AI_ALL;
#endif

  // Basic error checking.
  int rc = gai_echeck(host, service, hints.ai_flags, hints.ai_family,
      hints.ai_socktype, hints.ai_protocol);
  if (rc != 0)
  {
    freeaddrinfo_emulation(aihead);
    return rc;
  }

  gai_search search[2];
  int search_count = gai_nsearch(host, &hints, search);
  for (gai_search* sptr = search; sptr < search + search_count; ++sptr)
  {
    // Check for IPv4 dotted decimal string.
    in4_addr_type inaddr;
    asio::error_code ec;
    if (socket_ops::inet_pton(ASIO_OS_DEF(AF_INET),
          sptr->host, &inaddr, 0, ec) == 1)
    {
      if (hints.ai_family != ASIO_OS_DEF(AF_UNSPEC)
          && hints.ai_family != ASIO_OS_DEF(AF_INET))
      {
        freeaddrinfo_emulation(aihead);
        gai_free(canon);
        return EAI_FAMILY;
      }
      if (sptr->family == ASIO_OS_DEF(AF_INET))
      {
        rc = gai_aistruct(&ainext, &hints, &inaddr, ASIO_OS_DEF(AF_INET));
        if (rc != 0)
        {
          freeaddrinfo_emulation(aihead);
          gai_free(canon);
          return rc;
        }
      }
      continue;
    }

    // Check for IPv6 hex string.
    in6_addr_type in6addr;
    if (socket_ops::inet_pton(ASIO_OS_DEF(AF_INET6),
          sptr->host, &in6addr, 0, ec) == 1)
    {
      if (hints.ai_family != ASIO_OS_DEF(AF_UNSPEC)
          && hints.ai_family != ASIO_OS_DEF(AF_INET6))
      {
        freeaddrinfo_emulation(aihead);
        gai_free(canon);
        return EAI_FAMILY;
      }
      if (sptr->family == ASIO_OS_DEF(AF_INET6))
      {
        rc = gai_aistruct(&ainext, &hints, &in6addr,
            ASIO_OS_DEF(AF_INET6));
        if (rc != 0)
        {
          freeaddrinfo_emulation(aihead);
          gai_free(canon);
          return rc;
        }
      }
      continue;
    }

    // Look up hostname.
    hostent hent;
    char hbuf[8192] = "";
    hostent* hptr = socket_ops::gethostbyname(sptr->host,
        sptr->family, &hent, hbuf, sizeof(hbuf), hints.ai_flags, ec);
    if (hptr == 0)
    {
      if (search_count == 2)
      {
        // Failure is OK if there are multiple searches.
        continue;
      }
      freeaddrinfo_emulation(aihead);
      gai_free(canon);
      if (ec == asio::error::host_not_found)
        return EAI_NONAME;
      if (ec == asio::error::host_not_found_try_again)
        return EAI_AGAIN;
      if (ec == asio::error::no_recovery)
        return EAI_FAIL;
      if (ec == asio::error::no_data)
        return EAI_NONAME;
      return EAI_NONAME;
    }

    // Check for address family mismatch if one was specified.
    if (hints.ai_family != ASIO_OS_DEF(AF_UNSPEC)
        && hints.ai_family != hptr->h_addrtype)
    {
      freeaddrinfo_emulation(aihead);
      gai_free(canon);
      socket_ops::freehostent(hptr);
      return EAI_FAMILY;
    }

    // Save canonical name first time.
    if (host != 0 && host[0] != '\0' && hptr->h_name && hptr->h_name[0]
        && (hints.ai_flags & AI_CANONNAME) && canon == 0)
    {
      std::size_t canon_len = strlen(hptr->h_name) + 1;
      canon = gai_alloc<char>(canon_len);
      if (canon == 0)
      {
        freeaddrinfo_emulation(aihead);
        socket_ops::freehostent(hptr);
        return EAI_MEMORY;
      }
      gai_strcpy(canon, hptr->h_name, canon_len);
    }

    // Create an addrinfo structure for each returned address.
    for (char** ap = hptr->h_addr_list; *ap; ++ap)
    {
      rc = gai_aistruct(&ainext, &hints, *ap, hptr->h_addrtype);
      if (rc != 0)
      {
        freeaddrinfo_emulation(aihead);
        gai_free(canon);
        socket_ops::freehostent(hptr);
        return EAI_FAMILY;
      }
    }

    socket_ops::freehostent(hptr);
  }

  // Check if we found anything.
  if (aihead == 0)
  {
    gai_free(canon);
    return EAI_NONAME;
  }

  // Return canonical name in first entry.
  if (host != 0 && host[0] != '\0' && (hints.ai_flags & AI_CANONNAME))
  {
    if (canon)
    {
      aihead->ai_canonname = canon;
      canon = 0;
    }
    else
    {
      std::size_t canonname_len = strlen(search[0].host) + 1;
      aihead->ai_canonname = gai_alloc<char>(canonname_len);
      if (aihead->ai_canonname == 0)
      {
        freeaddrinfo_emulation(aihead);
        return EAI_MEMORY;
      }
      gai_strcpy(aihead->ai_canonname, search[0].host, canonname_len);
    }
  }
  gai_free(canon);

  // Process the service name.
  if (service != 0 && service[0] != '\0')
  {
    rc = gai_serv(aihead, &hints, service);
    if (rc != 0)
    {
      freeaddrinfo_emulation(aihead);
      return rc;
    }
  }

  // Return result to caller.
  *result = aihead;
  return 0;
}