/* Plain mutexes (native Windows implementation).

   Copyright (C) 2005-2020 Free Software Foundation, Inc.

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

   it under the terms of the GNU General Public License as published by

   the Free Software Foundation; either version 3, or (at your option)

   any later version.

   This program 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 for more details.

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

   along with this program; if not, see <https://www.gnu.org/licenses/>.  */

/* Written by Bruno Haible <bruno@clisp.org>, 2005.

   Based on GCC's gthr-win32.h.  */

#include <config.h>

/* Specification.  */

#include "windows-mutex.h"

#include <errno.h>

void

glwthread_mutex_init (glwthread_mutex_t *mutex)

{

  InitializeCriticalSection (&mutex->lock);

  mutex->guard.done = 1;

}

int

glwthread_mutex_lock (glwthread_mutex_t *mutex)

{

  if (!mutex->guard.done)

    {

      if (InterlockedIncrement (&mutex->guard.started) == 0)

        /* This thread is the first one to need this mutex.  Initialize it.  */

        glwthread_mutex_init (mutex);

      else

        {

          /* Don't let mutex->guard.started grow and wrap around.  */

          InterlockedDecrement (&mutex->guard.started);

          /* Yield the CPU while waiting for another thread to finish

             initializing this mutex.  */

          while (!mutex->guard.done)

            Sleep (0);

        }

    }

  EnterCriticalSection (&mutex->lock);

  return 0;

}

int

glwthread_mutex_trylock (glwthread_mutex_t *mutex)

{

  if (!mutex->guard.done)

    {

      if (InterlockedIncrement (&mutex->guard.started) == 0)

        /* This thread is the first one to need this mutex.  Initialize it.  */

        glwthread_mutex_init (mutex);

      else

        {

          /* Don't let mutex->guard.started grow and wrap around.  */

          InterlockedDecrement (&mutex->guard.started);

          /* Let another thread finish initializing this mutex, and let it also

             lock this mutex.  */

          return EBUSY;

        }

    }

  if (!TryEnterCriticalSection (&mutex->lock))

    return EBUSY;

  return 0;

}

int

glwthread_mutex_unlock (glwthread_mutex_t *mutex)

{

  if (!mutex->guard.done)

    return EINVAL;

  LeaveCriticalSection (&mutex->lock);

  return 0;

}

int

glwthread_mutex_destroy (glwthread_mutex_t *mutex)

{

  if (!mutex->guard.done)

    return EINVAL;

  DeleteCriticalSection (&mutex->lock);

  mutex->guard.done = 0;

  return 0;

}