/* GNU Mailutils -- a suite of utilities for electronic mail
   Copyright (C) 1999, 2000, 2001, 2005, 2006, 2007, 2008, 2010, 2011
   Free Software Foundation, Inc.

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 3 of the License, or (at your option) any later version.

   This library 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General
   Public License along with this library.  If not, see 
   <http://www.gnu.org/licenses/>. */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <fcntl.h>
#include <utime.h>

#include <sys/param.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>

#include <mailutils/errno.h>
#include <mailutils/locker.h>
#include <mailutils/util.h>

#define LOCKFILE_ATTR           0644

/* First draft by Brian Edmond. */
/* For subsequent modifications, see the GNU mailutils ChangeLog. */

struct _mu_locker
{
  unsigned refcnt;             /* Number of times mu_locker_lock was called */
  enum mu_locker_mode mode;    /* Current locking mode (if refcnt > 0) */

  char *file;
  int flags;
  int expire_time;
  int retries;
  int retry_sleep;

  union lock_data {
    struct {
      char *dotlock;
      char *nfslock;
    } dot;
    
    struct {
      char *name;
    } external;
    
    struct {
      int fd;
    } kernel;
  } data;
};

#define MU_LOCKER_TYPE(l) MU_LOCKER_FLAG_TO_TYPE((l)->flags)

struct locker_tab
{
  int (*init) (mu_locker_t);
  void (*destroy) (mu_locker_t);
  int (*prelock) (mu_locker_t); 
  int (*lock) (mu_locker_t, enum mu_locker_mode);
  int (*unlock) (mu_locker_t);
};

static int init_dotlock (mu_locker_t);
static void destroy_dotlock (mu_locker_t);
static int lock_dotlock (mu_locker_t, enum mu_locker_mode);
static int unlock_dotlock (mu_locker_t);

static int init_external (mu_locker_t);
static void destroy_external (mu_locker_t);
static int lock_external (mu_locker_t, enum mu_locker_mode);
static int unlock_external (mu_locker_t);

static int init_kernel (mu_locker_t);
static int lock_kernel (mu_locker_t, enum mu_locker_mode);
static int unlock_kernel (mu_locker_t);

static int prelock_common (mu_locker_t);

static struct locker_tab locker_tab[] = {
  /* MU_LOCKER_TYPE_DOTLOCK */
  { init_dotlock, destroy_dotlock, prelock_common,
    lock_dotlock, unlock_dotlock },
  /* MU_LOCKER_TYPE_EXTERNAL */
  { init_external, destroy_external, prelock_common,
    lock_external, unlock_external },
  /* MU_LOCKER_TYPE_KERNEL */
  { init_kernel, NULL, NULL, lock_kernel, unlock_kernel },
  /* MU_LOCKER_TYPE_NULL */
  { NULL, NULL, NULL, NULL, NULL }
};

#define MU_LOCKER_NTYPES (sizeof (locker_tab) / sizeof (locker_tab[0]))


static int
stat_check (const char *file, int fd, int links)
{
  struct stat fn_stat;
  struct stat fd_stat;
  int err = 0;
  int localfd = -1;

  if (fd == -1)
    {
      localfd = open (file, O_RDONLY);
      
      if (localfd == -1)
	return errno;
      fd = localfd;
    }

  /* We should always be able to stat a valid fd, so this
     is an error condition. */
  if (lstat (file, &fn_stat) || fstat (fd, &fd_stat))
    err = errno;
  else
    {
      /* If the link and stat don't report the same info, or the
         file is a symlink, fail the locking. */
#define CHK(X) if(X) err = EINVAL

      CHK (!S_ISREG (fn_stat.st_mode));
      CHK (!S_ISREG (fd_stat.st_mode));
      CHK (fn_stat.st_nlink != links);
      CHK (fn_stat.st_dev != fd_stat.st_dev);
      CHK (fn_stat.st_ino != fd_stat.st_ino);
      CHK (fn_stat.st_mode != fd_stat.st_mode);
      CHK (fn_stat.st_nlink != fd_stat.st_nlink);
      CHK (fn_stat.st_uid != fd_stat.st_uid);
      CHK (fn_stat.st_gid != fd_stat.st_gid);
      CHK (fn_stat.st_rdev != fd_stat.st_rdev);

#undef CHK
    }
  if (localfd != -1)
    close (localfd);

  return err;
}

static int
check_file_permissions (const char *file)
{
  int fd = -1;
  int err = 0;

  if ((fd = open (file, O_RDONLY)) == -1)
    return errno == ENOENT ? 0 : errno;

  err = stat_check (file, fd, 1);
  close (fd);
  fd = -1;
  if (err)
    {
      if (err == EINVAL)
	err = MU_ERR_LOCK_BAD_FILE;
      return err;
    }

  return 0;
}

static int
prelock_common (mu_locker_t locker)
{
  /* Check if we are trying to lock a regular file, with a link count
     of 1, that we have permission to read, etc., or don't lock it. */
  return check_file_permissions (locker->file);
}


static int mu_locker_default_flags = MU_LOCKER_DEFAULT;
static time_t mu_locker_retry_timeout = MU_LOCKER_RETRY_SLEEP;
static size_t mu_locker_retry_count = MU_LOCKER_RETRIES;
static time_t mu_locker_expire_timeout = MU_LOCKER_EXPIRE_TIME;
static char *mu_locker_external_program = NULL;

int
mu_locker_set_default_flags (int flags, enum mu_locker_set_mode mode)
{
  switch (mode)
    {
    case mu_locker_assign:
      mu_locker_default_flags = flags;
      break;

    case mu_locker_set_bit:
      mu_locker_default_flags |= flags;
      break;

    case mu_locker_clear_bit:
      mu_locker_default_flags &= ~flags;
      break;

    default:
      return EINVAL;
    }
  return 0;
}

void
mu_locker_set_default_retry_timeout (time_t to)
{
  mu_locker_retry_timeout = to;
}

void
mu_locker_set_default_retry_count (size_t n)
{
  mu_locker_retry_count = n;
}

void
mu_locker_set_default_expire_timeout (time_t t)
{
  mu_locker_expire_timeout = t;
}

void
mu_locker_set_default_external_program (char *path)
{
  free (mu_locker_external_program);
  mu_locker_external_program = strdup (path);
}

int
mu_locker_mod_flags (mu_locker_t locker, int flags,
		     enum mu_locker_set_mode mode)
{
  unsigned otype, ntype;
  int new_flags;
  
  if (!locker)
    return MU_ERR_LOCKER_NULL;

  switch (mode)
    {
    case mu_locker_assign:
      new_flags = flags;
      break;

    case mu_locker_set_bit:
      new_flags = locker->flags | flags;
      break;

    case mu_locker_clear_bit:
      new_flags = locker->flags & ~flags;
      break;

    default:
      return EINVAL;
    }

  otype = MU_LOCKER_TYPE (locker);
  if (otype >= MU_LOCKER_NTYPES)
    return EINVAL;
  ntype = MU_LOCKER_FLAG_TO_TYPE (new_flags);
  if (ntype >= MU_LOCKER_NTYPES)
    return EINVAL;

  if (ntype != otype)
    {
      int rc;
      
      if (locker_tab[otype].destroy)
	locker_tab[otype].destroy (locker);
      locker->flags = new_flags;
      if (locker_tab[ntype].init)
	{
	  rc = locker_tab[ntype].init (locker);
	  if (rc)
	    locker->flags = MU_LOCKER_NULL;
	  return rc;
	}
    }
  else
    locker->flags = new_flags;

  return 0;
}

int
mu_locker_set_flags (mu_locker_t locker, int flags)
{
  return mu_locker_mod_flags (locker, flags, mu_locker_assign);
}

int
mu_locker_set_expire_time (mu_locker_t locker, int etime)
{
  if (!locker)
    return MU_ERR_LOCKER_NULL;

  if (etime <= 0)
    return EINVAL;

  locker->expire_time = etime;

  return 0;
}

int
mu_locker_set_retries (mu_locker_t locker, int retries)
{
  if (!locker)
    return MU_ERR_LOCKER_NULL;

  if (retries <= 0)
    return EINVAL;

  locker->retries = retries;

  return 0;
}

int
mu_locker_set_retry_sleep (mu_locker_t locker, int retry_sleep)
{
  if (!locker)
    return MU_ERR_LOCKER_NULL;

  if (retry_sleep <= 0)
    return EINVAL;

  locker->retry_sleep = retry_sleep;

  return 0;
}

int
mu_locker_set_external (mu_locker_t locker, const char* program)
{
  char* p = NULL;

  if (!locker)
    return MU_ERR_LOCKER_NULL;
  if (MU_LOCKER_TYPE (locker) != MU_LOCKER_TYPE_EXTERNAL)
    return EINVAL;
    
  /* program can be NULL */
  if (program != 0)
    {
      p = strdup (program);
      if (!p)
	return ENOMEM;
  }

  free (locker->data.external.name);
  locker->data.external.name = p;

  return 0;
}

int
mu_locker_get_flags (mu_locker_t locker, int *flags)
{
  if (!locker)
    return MU_ERR_LOCKER_NULL;

  if (!flags)
    return EINVAL;

  *flags = locker->flags;

  return 0;
}

int
mu_locker_get_expire_time (mu_locker_t locker, int *ptime)
{
  if (!locker)
    return MU_ERR_LOCKER_NULL;

  if (!ptime)
    return EINVAL;

  *ptime = locker->expire_time;

  return 0;
}

int
mu_locker_get_retries (mu_locker_t locker, int *retries)
{
  if (!locker)
    return MU_ERR_LOCKER_NULL;

  if (!retries)
    return EINVAL;

  *retries = locker->retries;

  return 0;
}

int
mu_locker_get_retry_sleep (mu_locker_t locker, int *retry_sleep)
{
  if (!locker)
    return MU_ERR_LOCKER_NULL;

  if (!retry_sleep)
    return EINVAL;

  *retry_sleep = locker->retry_sleep;

  return 0;
}

int
mu_locker_create (mu_locker_t *plocker, const char *fname, int flags)
{
  unsigned type;
  mu_locker_t l;
  char *filename;
  int err = 0;

  if (plocker == NULL)
    return MU_ERR_OUT_PTR_NULL;

  if (fname == NULL)
    return EINVAL;

  if ((err = mu_unroll_symlink (fname, &filename)))
    {
      if (err == ENOENT)
	{
	  /* Try the directory part.  If it unrolls successfully (i.e.
	     all its components exist), tuck the filename part back in
	     the resulting path and use it as the lock filename. */
	  char *p, *tmp = strdup (fname);
	  if (!tmp)
	    return ENOMEM;
	  p = strchr (tmp, '/');
	  if (!p)
	    filename = tmp;
	  else
	    {
	      err = mu_unroll_symlink (tmp, &filename);
	      free (tmp);
	      if (err)
		return err;
	      tmp = realloc (filename, strlen (filename) + strlen (p) + 1);
	      if (!tmp)
		{
		  free (filename);
		  return ENOMEM;
		}
	      strcat (tmp, p);
	      filename = tmp;
	    }
	}
      else
	return err;
    }

  l = calloc (1, sizeof (*l));

  if (l == NULL)
    {
      free (filename);
      return ENOMEM;
    }
  
  l->file = filename;
  
  if (l->file == NULL)
    {
      free (l);
      return ENOMEM;
    }

  if (strcmp (filename, "/dev/null") == 0)
    l->flags = MU_LOCKER_NULL;
  else if (flags)
    l->flags = flags;
  else
    l->flags = mu_locker_default_flags;

  l->expire_time = mu_locker_expire_timeout;
  l->retries = mu_locker_retry_count;
  l->retry_sleep = mu_locker_retry_timeout;

  type = MU_LOCKER_TYPE (l);

  if (type >= MU_LOCKER_NTYPES)
    {
      free (l->file);
      return EINVAL;
    }

  /* Initialize locker-type-specific data */
  err = locker_tab[type].init ? locker_tab[type].init (l) : 0;
  if (err)
    {
      mu_locker_destroy (&l);
      return err;
    }

  *plocker = l;

  return 0;
}

void
mu_locker_destroy (mu_locker_t *plocker)
{
  if (plocker && *plocker)
    {
      unsigned type = MU_LOCKER_TYPE (*plocker);
      if (type < MU_LOCKER_NTYPES)
	{
	  if (locker_tab[type].destroy)
	    locker_tab[type].destroy (*plocker);
	  free ((*plocker)->file);
	  free (*plocker);
	  *plocker = NULL;
	}
    }
}

int
_mu_locker_lock (mu_locker_t lock, enum mu_locker_mode mode)
{
  int rc;
  unsigned type;
  unsigned retries = 1;
  
  if (lock == NULL || (type = MU_LOCKER_TYPE (lock)) >= MU_LOCKER_NTYPES)
    return EINVAL;

  if (locker_tab[type].prelock && (rc = locker_tab[type].prelock (lock)))
    return rc;
  
  /* Is the lock already applied? */
  if (lock->refcnt > 0)
    {
      lock->refcnt++;
      if (mode == lock->mode)
	return 0;
    }

  lock->mode = mode;

  if (lock->flags & MU_LOCKER_RETRY)
    retries = lock->retries;

  if (locker_tab[type].lock)
    {
      while (retries--)
	{
	  rc = locker_tab[type].lock (lock, mode);
	  if (rc == EAGAIN && retries)
	    {
	      sleep (lock->retry_sleep);
	      continue;
	    }

	  if (rc == 0)
	    lock->refcnt++;

	  break;
	}
    }
  else
    rc = 0;
  
  return rc;
}

int
mu_locker_lock (mu_locker_t lock)
{
  return _mu_locker_lock (lock, mu_lck_exc);
}

int
mu_locker_unlock (mu_locker_t lock)
{
  int rc = 0;
  unsigned type;
  
  if (!lock)
    return MU_ERR_LOCKER_NULL;

  if (lock->refcnt == 0)
    return MU_ERR_LOCK_NOT_HELD;

  if ((rc = check_file_permissions (lock->file)))
    return rc;

  if (--lock->refcnt > 0)
    return 0;

  type = MU_LOCKER_TYPE (lock);
  if (locker_tab[type].unlock)
    rc = locker_tab[type].unlock (lock);
  else
    rc = 0;
  
  return rc;
}

int
mu_locker_remove_lock (mu_locker_t lock)
{
  if (!lock)
    return MU_ERR_LOCKER_NULL;

  /* Force the reference count to 1 to unlock the file. */
  lock->refcnt = 1;
  return mu_locker_unlock (lock);
}


#define DOTLOCK_SUFFIX ".lock"

/* expire a stale lock (if MU_LOCKER_PID or MU_LOCKER_TIME) */
static void
expire_stale_lock (mu_locker_t lock)
{
  int stale = 0;
  int fd = open (lock->data.dot.dotlock, O_RDONLY);
  if (fd == -1)
    return;

  /* Check to see if this process is still running.  */
  if (lock->flags & MU_LOCKER_PID)
    {
      char buf[16];
      pid_t pid;
      int nread = read (fd, buf, sizeof (buf) - 1);
      if (nread > 0)
	{
	  buf[nread] = '\0';
	  pid = strtol (buf, NULL, 10);
	  if (pid > 0)
	    {
	      /* Process is gone so we try to remove the lock. */
	      if (kill (pid, 0) == -1)
		stale = 1;
	    }
	  else
	    stale = 1;		/* Corrupted file, remove the lock. */
	}
    }
  
  /* Check to see if the lock expired.  */
  if (lock->flags & MU_LOCKER_TIME)
    {
      struct stat stbuf;

      fstat (fd, &stbuf);
      /* The lock has expired. */
      if ((time (NULL) - stbuf.st_mtime) > lock->expire_time)
	stale = 1;
    }

  close (fd);
  if (stale)
    unlink (lock->data.dot.dotlock);
}

static int
init_dotlock (mu_locker_t locker)
{
  char *tmp, *p;

  /* Make sure the spool directory is writable */
  tmp = strdup (locker->file);
  if (!tmp)
    return ENOMEM;

  strcpy (tmp, locker->file);
  p = strrchr (tmp, '/');
  if (!p)
    {
      free (tmp);
      tmp = strdup (".");
      if (!tmp)
	return ENOMEM;
    }
  else
    *p = 0; 

  if (access (tmp, W_OK))
    {
      /* Fallback to kernel locking */
      free (tmp);
      return mu_locker_set_flags (locker,
			   MU_LOCKER_KERNEL|MU_LOCKER_OPTIONS(locker->flags));
    }
  
  free (tmp);
  
  locker->data.dot.dotlock = malloc (strlen (locker->file)
				     + sizeof (DOTLOCK_SUFFIX));
  
  if (!locker->data.dot.dotlock)
    return ENOMEM;
  strcpy (locker->data.dot.dotlock, locker->file);
  strcat (locker->data.dot.dotlock, DOTLOCK_SUFFIX);

  return 0;
}

static void
destroy_dotlock (mu_locker_t locker)
{
  free (locker->data.dot.dotlock);
  free (locker->data.dot.nfslock);
}

static int
lock_dotlock (mu_locker_t locker, enum mu_locker_mode mode)
{
  int rc;
  char *host = NULL;
  char pid[11];		/* 10 is strlen(2^32 = 4294967296) */
  char now[11];
  size_t sz = 0;
  int err = 0;
  int fd;
    
  if (locker->data.dot.nfslock)
    {
      unlink (locker->data.dot.nfslock);
      free (locker->data.dot.nfslock);
      locker->data.dot.nfslock = NULL;
    }

  expire_stale_lock (locker);

  /* build the NFS hitching-post to the lock file */

  rc = mu_get_host_name (&host);
  if (rc)
    return rc;

  snprintf (now, sizeof (now), "%lu", (unsigned long) time (0));
  now[sizeof (now) - 1] = 0;

  snprintf (pid, sizeof (pid), "%lu", (unsigned long) getpid ());
  pid[sizeof (pid) - 1] = 0;
		  
  sz = strlen (locker->file) + 1 /* "." */
    + strlen (pid) + 1 /* "." */
    + strlen (now) + 1 /* "." */
    + strlen (host) + 1;
  
  locker->data.dot.nfslock = malloc (sz);
  
  if (!locker->data.dot.nfslock)
    {
      free (host);
      return ENOMEM;
    }

  snprintf (locker->data.dot.nfslock, sz, "%s.%s.%s.%s",
	    locker->file, pid, now, host);
  free (host);
  
  fd = open (locker->data.dot.nfslock,
	     O_WRONLY | O_CREAT | O_EXCL, LOCKFILE_ATTR);
  if (fd == -1)
    {
      if (errno == EEXIST)
	return EAGAIN;
      else
	return errno;
    }
  close (fd);
  
  /* Try to link to the lockfile. */
  if (link (locker->data.dot.nfslock, locker->data.dot.dotlock) == -1)
    {
      unlink (locker->data.dot.nfslock);
      if (errno == EEXIST)
	return MU_ERR_LOCK_CONFLICT;
      return errno;
    }

  if ((fd = open (locker->data.dot.dotlock, O_RDWR)) == -1)
    {
      unlink (locker->data.dot.nfslock);
      return errno;
    }
  
  err = stat_check (locker->data.dot.nfslock, fd, 2);
  if (err)
    {
      unlink (locker->data.dot.nfslock);
      if (err == EINVAL)
	return MU_ERR_LOCK_BAD_LOCK;
      return errno;
    }

  unlink (locker->data.dot.nfslock);

  /* FIXME: If no errors, we have the lock. */
  assert (locker->refcnt == 0);

  if (locker->flags & MU_LOCKER_PID)
    {
      char buf[16];
      sprintf (buf, "%ld", (long) getpid ());
      write (fd, buf, strlen (buf));
    }
  close (fd);
  return 0;
}

static int
unlock_dotlock (mu_locker_t locker)
{
  if (unlink (locker->data.dot.dotlock) == -1)
    {
      int err = errno;
      if (err == ENOENT)
	{
	  locker->refcnt = 0; /*FIXME?*/
	  err = MU_ERR_LOCK_NOT_HELD;
	  return err;
	}
      return err;
    }
  return 0;
}

int
mu_locker_touchlock (mu_locker_t lock)
{
  if (!lock)
    return MU_ERR_LOCKER_NULL;

  if (MU_LOCKER_TYPE (lock) != MU_LOCKER_TYPE_DOTLOCK)
    return 0;
  
  if (lock->refcnt > 0)
    return utime (lock->data.dot.dotlock, NULL);

  return MU_ERR_LOCK_NOT_HELD;
}


/* Kernel locking */
static int
init_kernel (mu_locker_t locker)
{
  return 0;
}

static int
lock_kernel (mu_locker_t locker, enum mu_locker_mode mode)
{
  int fd;
  struct flock fl;

  switch (mode)
    {
    case mu_lck_shr:
    case mu_lck_opt:
      mode = O_RDONLY;
      fl.l_type = F_RDLCK;
      break;

    case mu_lck_exc:
      mode = O_RDWR;
      fl.l_type = F_WRLCK;
      break;

    default:
      return EINVAL;
    }
  
  fd = open (locker->file, O_RDWR);
  if (fd == -1)
    return errno;
  locker->data.kernel.fd = fd;
  
  fl.l_whence = SEEK_SET;
  fl.l_start = 0;
  fl.l_len = 0; /* Lock entire file */
  if (fcntl (fd, F_SETLK, &fl))
    {
#ifdef EACCESS      
      if (errno == EACCESS)
	return EAGAIN;
#endif
      if (errno == EAGAIN)
	return EAGAIN;
      return errno;
    }
  return 0;
}

static int
unlock_kernel (mu_locker_t locker)
{
  struct flock fl;

  fl.l_type = F_UNLCK;
  fl.l_whence = SEEK_SET;
  fl.l_start = 0;
  fl.l_len = 0; /* Unlock entire file */
  if (fcntl (locker->data.kernel.fd, F_SETLK, &fl))
    {
#ifdef EACCESS
      if (errno == EACCESS)
	return EAGAIN;
#endif
      if (errno == EAGAIN)
	return EAGAIN;
      return errno;
    }
  close (locker->data.kernel.fd);
  return 0;
}

static int
init_external (mu_locker_t locker)
{
  if (!(locker->data.external.name = strdup (mu_locker_external_program ?
					     mu_locker_external_program :
					     MU_LOCKER_EXTERNAL_PROGRAM)))
    return ENOMEM;
  return 0;
}

static void
destroy_external (mu_locker_t locker)
{
  free (locker->data.external.name);
}

/*
  Estimate 1 decimal digit per 3 bits, + 1 for round off.
*/
#define DEC_DIGS_PER_INT (sizeof(int) * 8 / 3 + 1)

static int
external_locker (mu_locker_t l, int lock)
{
  int err = 0;
  char *av[6];
  int ac = 0;
  char aforce[3 + DEC_DIGS_PER_INT + 1];
  char aretry[3 + DEC_DIGS_PER_INT + 1];
  int status = 0;

  assert (l);
  assert (l->flags & MU_LOCKER_EXTERNAL);
  /* FIXME */
  assert (lock == !l->refcnt);
  /* lock is true, refcnt is 0 or lock is false and refcnt is 1 */

  av[ac++] = l->data.external.name ?
                   l->data.external.name : MU_LOCKER_EXTERNAL_PROGRAM;

  if (l->flags & MU_LOCKER_TIME)
    {
      snprintf (aforce, sizeof (aforce), "-f%d", l->expire_time);
      aforce[sizeof (aforce) - 1] = 0;
      av[ac++] = aforce;
    }
  
  if (l->flags & MU_LOCKER_RETRY)
    {
      snprintf (aretry, sizeof (aretry), "-r%d", l->retries);
      aretry[sizeof (aretry) - 1] = 0;
      av[ac++] = aretry;
    }

  if (!lock)
    av[ac++] = "-u";

  av[ac++] = l->file;

  av[ac++] = NULL;

  if ((err = mu_spawnvp (av[0], av, &status)))
    return err;

  if (!WIFEXITED (status))
    {
      err = MU_ERR_LOCK_EXT_KILLED;
    }
  else
    {
      switch (WEXITSTATUS (status))
	{
	case 127:
	  err = MU_ERR_LOCK_EXT_FAIL;
	  break;
	  
	case MU_DL_EX_OK:
	  err = 0;
	  l->refcnt = lock;
	  break;
	  
	case MU_DL_EX_NEXIST:
	  err = MU_ERR_LOCK_NOT_HELD;
	  break;
	  
	case MU_DL_EX_EXIST:
	  err = MU_ERR_LOCK_CONFLICT;
	  break;
	  
	case MU_DL_EX_PERM:
	  err = EPERM;
	  break;
	  
	default:
	case MU_DL_EX_ERROR:
	  err = MU_ERR_LOCK_EXT_ERR;
	  break;
	}
    }

  return err;
}

static int
lock_external (mu_locker_t locker, enum mu_locker_mode mode)
{
  return external_locker (locker, 1);
}

static int
unlock_external (mu_locker_t locker)
{
  return external_locker (locker, 0);
}