/*

 * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

#include "precompiled.hpp"

#include "iphlp_interface.hpp"

#include "runtime/os.hpp"

// IPHLP API

typedef DWORD(WINAPI *GetIfTable2_Fn)(PMIB_IF_TABLE2*);

typedef DWORD(WINAPI *FreeMibTable_Fn)(PVOID);

// IPHLP statics

GetIfTable2_Fn IphlpDll::_GetIfTable2 = NULL;

FreeMibTable_Fn IphlpDll::_FreeMibTable = NULL;

LONG IphlpDll::_critical_section = 0;

LONG IphlpDll::_initialized = 0;

LONG IphlpDll::_iphlp_reference_count = 0;

HMODULE IphlpDll::_hModule = NULL;

void IphlpDll::initialize(void) {

  _hModule = os::win32::load_Windows_dll("iphlpapi.dll", NULL, 0);

  if (NULL == _hModule) {

    return;

  }

  // The 'A' at the end means the ANSI (not the UNICODE) vesions of the methods

  _GetIfTable2 = (GetIfTable2_Fn)::GetProcAddress(_hModule, "GetIfTable2");

  _FreeMibTable = (FreeMibTable_Fn)::GetProcAddress(_hModule, "FreeMibTable");

  // interlock is used for fencing

  InterlockedExchange(&_initialized, 1);

}

bool IphlpDll::IphlpDetach(void) {

  LONG prev_ref_count = InterlockedExchangeAdd(&_iphlp_reference_count, -1);

  BOOL ret = false;

  if (1 == prev_ref_count) {

    if (_initialized && _hModule != NULL) {

      ret = FreeLibrary(_hModule);

      if (ret) {

        _hModule = NULL;

        _GetIfTable2 = NULL;

        _FreeMibTable = NULL;

        InterlockedExchange(&_initialized, 0);

      }

    }

  }

  return ret != 0;

}

bool IphlpDll::IphlpAttach(void) {

  InterlockedExchangeAdd(&_iphlp_reference_count, 1);

  if (1 == _initialized) {

    return true;

  }

  while (InterlockedCompareExchange(&_critical_section, 1, 0) == 1);

  if (0 == _initialized) {

    initialize();

  }

  while (InterlockedCompareExchange(&_critical_section, 0, 1) == 0);

  return (_GetIfTable2 != NULL && _FreeMibTable != NULL);

}

DWORD IphlpDll::GetIfTable2(PMIB_IF_TABLE2* Table) {

  assert(_initialized && _GetIfTable2 != NULL,

         "IphlpAttach() not yet called");

  return _GetIfTable2(Table);

}

DWORD IphlpDll::FreeMibTable(PVOID Memory) {

  assert(_initialized && _FreeMibTable != NULL,

         "IphlpAttach() not yet called");

  return _FreeMibTable(Memory);

}