/* GNU mailutils - a suite of utilities for electronic mail
   Copyright (C) 1999, 2000 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Library Public License as published by
   the Free Software Foundation; either version 2, 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 Library General Public License for more details.

   You should have received a copy of the GNU Library General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */

/* Tell GLIBC that we want UNIX98 pthread_rwlock_xx() functions.  */
#define _XOPEN_SOURCE   500
/* Tell QNX/Neutrino to define pthread_rwlock_xx() functions.  */
#define _QNX_SOURCE
#define _POSIX_C_SOURCE 199506
#ifdef HAVE_CONFIG_H
#  include <config.h>
#endif

#ifdef WITH_PTHREAD
#  ifdef HAVE_PTHREAD_H
#    include <pthread.h>
#  endif
#endif
#include <errno.h>
#include <stdlib.h>

#include <monitor0.h>


#ifdef WITH_PTHREAD
pthread_mutex_t monitor_lock = PTHREAD_MUTEX_INITIALIZER;
#  define STATIC_LOCK(m) pthread_mutex_lock(m)
#  define STATIC_UNLOCK(m) pthread_mutex_unlock(m)
#else
#  define STATIC_LOCK(m) 0
#  define STATIC_UNLOCK(m) 0
int monitor_lock;
#endif

union _p_lock
{
#ifdef WITH_PTHREAD
#  ifdef HAVE_PTHREAD_RWLOCK_INIT
     pthread_rwlock_t mutex;
#  else
     pthread_mutex_t mutex;
#  endif
#else
  int dummy;
#endif
};

typedef union _p_lock *p_lock_t;
static int  monitor_pthread_create (p_lock_t *);
static void monitor_pthread_destroy (p_lock_t *);
static int monitor_pthread_rdlock (p_lock_t);
static int monitor_pthread_wrlock (p_lock_t);
static int monitor_pthread_unlock (p_lock_t);

/* The idea was to have a general/portable object monitor_t.
   The monitor_t object could have different implementation (on the fly ?)
   of locking.  Also the rest of the library would not have to know about
   different threading implementation.  So far we've pretty much hardcoded
   the concrete implementation of monitor on pthread and read/write locks,
   but changing to a different concrete implementation will not be hard if
   the need arise.
   For static initializers we take a small penality and since we have
   a global static lock.
 */

int
monitor_create (monitor_t *pmonitor, int flags, void *owner)
{
  monitor_t monitor;

  if (pmonitor == NULL)
    return EINVAL;

  monitor = calloc (1, sizeof (*monitor));
  if (monitor == NULL)
    return ENOMEM;

  if (flags == MU_MONITOR_PTHREAD)
    {
      int status = monitor_pthread_create ((p_lock_t *)&(monitor->data));
      if (status != 0)
	{
	  free (monitor);
	  return status;
	}
    }
  monitor->owner = owner;
  monitor->allocated = 1;
  monitor->flags = flags;
  *pmonitor = monitor;
  return 0;
}

void *
monitor_get_owner (monitor_t monitor)
{
  return (monitor == NULL) ? NULL : monitor->owner;
}

void
monitor_destroy (monitor_t *pmonitor, void *owner)
{
  if (pmonitor && *pmonitor)
    {
      monitor_t monitor = *pmonitor;
      if (monitor->owner == owner)
	{
	  if (monitor->flags == MU_MONITOR_PTHREAD)
	    monitor_pthread_destroy ((p_lock_t *)&(monitor->data));
	}
      free (monitor);
      *pmonitor = NULL;
    }
}

int
monitor_rdlock (monitor_t monitor)
{
  if (monitor)
    {
      if (!monitor->allocated)
	{
	  int status = STATIC_LOCK (&monitor_lock);
	  if (monitor->data == NULL)
	    {
	      if (monitor->flags == MU_MONITOR_PTHREAD)
		status = monitor_pthread_create ((p_lock_t*)&(monitor->data));
	      if (status != 0)
		{
		  STATIC_UNLOCK (&monitor_lock);
		  return status;
		}
	    }
	  monitor->allocated = 1;
	  STATIC_UNLOCK (&monitor_lock);
	}
      if (monitor->flags == MU_MONITOR_PTHREAD)
	return monitor_pthread_rdlock ((p_lock_t)monitor->data);
    }
  return 0;
}

int
monitor_wrlock  (monitor_t monitor)
{
  if (monitor)
    {
      if (!monitor->allocated)
	{
	  int status = STATIC_LOCK (&monitor_lock);
	  if (monitor->data == NULL)
	    {
	      if (monitor->flags == MU_MONITOR_PTHREAD)
		status = monitor_pthread_create ((p_lock_t *)&(monitor->data));
	      if (status != 0)
		{
		  STATIC_UNLOCK (&monitor_lock);
		  return status;
		}
	    }
	  monitor->allocated = 1;
	  STATIC_UNLOCK (&monitor_lock);
	}
      if (monitor->flags == MU_MONITOR_PTHREAD)
	return monitor_pthread_wrlock ((p_lock_t)monitor->data);
    }
  return 0;
}

int
monitor_unlock (monitor_t monitor)
{
  if (monitor)
    {
      if (monitor->flags == MU_MONITOR_PTHREAD)
	return monitor_pthread_unlock ((p_lock_t)monitor->data);
    }
  return 0;
}

int
monitor_wait (monitor_t monitor)
{
  (void)monitor;
  return ENOSYS;
}

int
monitor_notify (monitor_t monitor)
{
  (void)monitor;
  return ENOSYS;
}


/* Concrete Implementation of pthread base on rwlocks.  */

#ifdef WITH_PTHREAD
#  ifdef HAVE_PTHREAD_RWLOCK_INIT
#    define RWLOCK_INIT(rwl, attr)  pthread_rwlock_init (rwl, attr)
#    define RWLOCK_DESTROY(rwl)     pthread_rwlock_destroy (rwl)
#    define RWLOCK_RDLOCK(rwl)      pthread_rwlock_rdlock (rwl)
#    define RWLOCK_TRYRDLOCK(rwl)   pthread_rwlock_tryrdlock (rwl)
#    define RWLOCK_WRLOCK(rwl)      pthread_rwlock_wrlock (rwl)
#    define RWLOCK_TRYWRLOCK(rwl)   pthread_rwlock_trywrlock (rwl)
#    define RWLOCK_UNLOCK(rwl)      pthread_rwlock_unlock (rwl)
#  else
#    define RWLOCK_INIT(rwl, attr)  pthread_mutex_init (rwl, attr)
#    define RWLOCK_DESTROY(rwl)     pthread_mutex_destroy (rwl)
#    define RWLOCK_RDLOCK(rwl)      pthread_mutex_lock (rwl)
#    define RWLOCK_TRYRDLOCK(rwl)   pthread_mutex_trylock (rwl)
#    define RWLOCK_WRLOCK(rwl)      pthread_mutex_lock (rwl)
#    define RWLOCK_TRYWRLOCK(rwl)   pthread_mutex_trylock (rwl)
#    define RWLOCK_UNLOCK(rwl)      pthread_mutex_unlock (rwl)
#  endif
#else
#  define RWLOCK_INIT(rwl, attr)    0
#  define RWLOCK_DESTROY(rwl)       0
#  define RWLOCK_RDLOCK(rwl)        0
#  define RWLOCK_TRYRDLOCK(rwl)     0
#  define RWLOCK_WRLOCK(rwl)        0
#  define RWLOCK_TRYWRLOCK(rwl)     0
#  define RWLOCK_UNLOCK(rwl)        0
#  define flockfile(arg)            0
#  define funlockfile(arg)          0
#endif



static int
monitor_pthread_create (p_lock_t *plock)
{
  int status;
  p_lock_t lock = calloc (1, sizeof (*lock));
  if (lock == NULL)
    return ENOMEM;
  status = RWLOCK_INIT (&(lock->mutex), NULL);
  if (status != 0)
    {
      free (lock);
      return status;
    }
  *plock = lock;
  return 0;
}

static void
monitor_pthread_destroy (p_lock_t *plock)
{
  p_lock_t lock = *plock;
  if (lock)
    {
      RWLOCK_DESTROY (&(lock->mutex));
      free (lock);
    }
  *plock = NULL;
}

static int
monitor_pthread_rdlock (p_lock_t lock)
{
  return RWLOCK_RDLOCK (&(lock->mutex));
}

static int
monitor_pthread_wrlock (p_lock_t lock)
{
  return RWLOCK_WRLOCK (&(lock->mutex));
}

static int
monitor_pthread_unlock (p_lock_t lock)
{
  return RWLOCK_UNLOCK (&(lock->mutex));
}