A C library for asynchronous DNS requests (grpc依赖)
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/* 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;
fpGetAdaptersAddresses_t ares_fpGetAdaptersAddresses = 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;
}
ares_fpGetAdaptersAddresses = (fpGetAdaptersAddresses_t)
GetProcAddress(hnd_iphlpapi, "GetAdaptersAddresses");
if (!ares_fpGetAdaptersAddresses)
{
/* This can happen on clients before WinXP, I don't
think it should be an error, unless we don't want to
support Windows 2000 anymore */
}
/*
* 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)
{
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_initialized)
return;
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;
}