c-ares/ares_library_init.c

/* Copyright 1998 by the Massachusetts Institute of Technology.
 * Copyright (C) 2004-2009 by Daniel Stenberg
 *
 * Permission to use, copy, modify, and distribute this
 * software and its documentation for any purpose and without
 * fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright
 * notice and this permission notice appear in supporting
 * documentation, and that the name of M.I.T. not be used in
 * advertising or publicity pertaining to distribution of the
 * software without specific, written prior permission.
 * M.I.T. makes no representations about the suitability of
 * this software for any purpose.  It is provided "as is"
 * without express or implied warranty.
 */

#include "ares_setup.h"

#include "ares.h"
#include "ares_library_init.h"
#include "ares_private.h"

/* library-private global and unique instance vars */

#ifdef USE_WINSOCK
fpGetNetworkParams_t ares_fpGetNetworkParams = ZERO_NULL;
fpSystemFunction036_t ares_fpSystemFunction036 = ZERO_NULL;
#endif

/* library-private global vars with source visibility restricted to this file */

static unsigned int ares_initialized;
static int          ares_init_flags;

#ifdef USE_WINSOCK
static HMODULE hnd_iphlpapi;
static HMODULE hnd_advapi32;
#endif


static int ares_win32_init(void)
{
#ifdef USE_WINSOCK

  hnd_iphlpapi = 0;
  hnd_iphlpapi = LoadLibrary("iphlpapi.dll");
  if (!hnd_iphlpapi)
    return ARES_ELOADIPHLPAPI;

  ares_fpGetNetworkParams = (fpGetNetworkParams_t)
    GetProcAddress(hnd_iphlpapi, "GetNetworkParams");
  if (!ares_fpGetNetworkParams)
    {
      FreeLibrary(hnd_iphlpapi);
      return ARES_EADDRGETNETWORKPARAMS;
    }

  /*
   * When advapi32.dll is unavailable or advapi32.dll has no SystemFunction036,
   * also known as RtlGenRandom, which is the case for Windows versions prior
   * to WinXP then c-ares uses portable rand() function. Then don't error here.
   */

  hnd_advapi32 = 0;
  hnd_advapi32 = LoadLibrary("advapi32.dll");
  if (hnd_advapi32)
    {
      ares_fpSystemFunction036 = (fpSystemFunction036_t)
        GetProcAddress(hnd_advapi32, "SystemFunction036");
    }

#endif
  return ARES_SUCCESS;
}


static void ares_win32_cleanup(void)
{
#ifdef USE_WINSOCK
  if (hnd_advapi32)
    FreeLibrary(hnd_advapi32);
  if (hnd_iphlpapi)
    FreeLibrary(hnd_iphlpapi);
#endif
}


int ares_library_init(int flags)
{
  int res;

  if (ares_initialized)
    return ARES_SUCCESS;
  ares_initialized++;

  if (flags & ARES_LIB_INIT_WIN32)
    {
      res = ares_win32_init();
      if (res != ARES_SUCCESS)
        return res;
    }

  ares_init_flags = flags;

  return ARES_SUCCESS;
}


void ares_library_cleanup(void)
{
  if (!ares_initialized)
    return;
  ares_initialized--;

  if (ares_init_flags & ARES_LIB_INIT_WIN32)
    ares_win32_cleanup();

  ares_init_flags = ARES_LIB_INIT_NONE;
}


int ares_library_initialized(void)
{
#ifdef USE_WINSOCK
  if (!ares_initialized)
    return ARES_ENOTINITIALIZED;
#endif
  return ARES_SUCCESS;
}