What is the Windows XP equivalent of inet_pton or InetPton?

Question

I need to determine whether a particular string is a valid IPv4 or IPv6 address literal. If I understand correctly, the correct way to do this on POSIX systems is to use inet_pton to convert it into a network address structure and see if it succeeds. Windows Vista and later have InetPton which does essentially the same thing. But as far as I can tell, Windows XP doesn't declare either of those, and I need to be able to do this correctly on XP. So, the question is what system function to use to do this?

Worst case, I can write a function to parse it myself, but I'd prefer a standard, system function which has therefore been thoroughly tested and properly handles all corner cases and whatnot. It's already bad enough that Microsoft couldn't just declare inet_pton like everyone else and went with InetPton for their newer OSes.

Answer 1

In windows XP you can use these functions:

#include <stdlib.h>
#include <string.h>
#include <stdio.h>

#include <winsock2.h>
#include <ws2tcpip.h>


int inet_pton(int af, const char *src, void *dst)
{
  struct sockaddr_storage ss;
  int size = sizeof(ss);
  char src_copy[INET6_ADDRSTRLEN+1];

  ZeroMemory(&ss, sizeof(ss));
  /* stupid non-const API */
  strncpy (src_copy, src, INET6_ADDRSTRLEN+1);
  src_copy[INET6_ADDRSTRLEN] = 0;

  if (WSAStringToAddress(src_copy, af, NULL, (struct sockaddr *)&ss, &size) == 0) {
    switch(af) {
      case AF_INET:
    *(struct in_addr *)dst = ((struct sockaddr_in *)&ss)->sin_addr;
    return 1;
      case AF_INET6:
    *(struct in6_addr *)dst = ((struct sockaddr_in6 *)&ss)->sin6_addr;
    return 1;
    }
  }
  return 0;
}

const char *inet_ntop(int af, const void *src, char *dst, socklen_t size)
{
  struct sockaddr_storage ss;
  unsigned long s = size;

  ZeroMemory(&ss, sizeof(ss));
  ss.ss_family = af;

  switch(af) {
    case AF_INET:
      ((struct sockaddr_in *)&ss)->sin_addr = *(struct in_addr *)src;
      break;
    case AF_INET6:
      ((struct sockaddr_in6 *)&ss)->sin6_addr = *(struct in6_addr *)src;
      break;
    default:
      return NULL;
  }
  /* cannot direclty use &size because of strict aliasing rules */
  return (WSAAddressToString((struct sockaddr *)&ss, sizeof(ss), NULL, dst, &s) == 0)?
          dst : NULL;
}

That's it. Link with ws2_32 library.