/** BEGIN COPYRIGHT BLOCK
 * Copyright 2001 Sun Microsystems, Inc.
 * Portions copyright 1999, 2001-2003 Netscape Communications Corporation.
 * All rights reserved.
 * END COPYRIGHT BLOCK **/
/*
 * fsmutex: Mutexes that are filesystem-based so they're available from more
 * than one process and address space
 * 
 * Rob McCool
 */


#ifndef FSMUTEX_H
#define FSMUTEX_H

#include "netsite.h"

typedef void * FSMUTEX;


/* ------------------------------ Prototypes ------------------------------ */

NSPR_BEGIN_EXTERN_C

/* 
   Flags to fsmutex_init. 

   FSMUTEX_VISIBLE makes a filesystem mutex which can be opened by other
   programs or processes.

   FSMUTEX_NEEDCRIT specifies that the fsmutex_lock and fsmutex_unlock 
   functions should also use a critical section to ensure that more than
   one thread does not acquire the mutex at a time. If this flag is not 
   specified, it is up to the caller to ensure that only thread within a 
   process tries to acquire the lock at any given time.
 */
#define FSMUTEX_VISIBLE 0x01
#define FSMUTEX_NEEDCRIT 0x02


/*
   fsmutex_init creates a new filesystem-based mutex. The resulting mutex
   is part of the filesystem. The name and number parameters are used to
   create a name for the mutex. If the FSMUTEX_VISIBLE flag is specified, 
   the mutex will be left in the filesystem for other programs and processes
   to access. If a mutex with the given name/number combination already
   exists, the calling process is allowed access to it. If the mutex does
   not already exist, the mutex is created.

   Returns NULL on failure, a void pointer to a fsmutex structure otherwise.
   This fsmutex structure is local to the current process.
 */
NSAPI_PUBLIC FSMUTEX fsmutex_init(char *name, int number, int flags);

/* 
   Sets the ownership of the underlying filesystem object to the given
   uid and gid. Only effective if the server is running as root.
 */
#ifdef XP_UNIX
#include <unistd.h>
#ifdef __sony
#include <sys/types.h>
#endif
NSAPI_PUBLIC void fsmutex_setowner(FSMUTEX fsm, uid_t uid, gid_t gid);
#endif



/*
   fsmutex_terminate deletes a filesystem-based mutex. A mutex will only
   be deleted when every process which has an open pointer to the mutex 
   calls this function.
 */
NSAPI_PUBLIC void fsmutex_terminate(FSMUTEX id);

/*
   fsmutex_lock attempts to acquire the given filesystem-based mutex. If 
   another process is holding the mutex, or if the FSMUTEX_NEEDCRIT flag
   was passed to fsmutex_init and another thread in the current process is 
   holding the mutex, then the calling thread will block until the mutex
   is available.
 */
NSAPI_PUBLIC void fsmutex_lock(FSMUTEX id);

/*
   fsmutex_unlock releases a filesystem-based mutex previously acquired
   by fsmutex_lock.
 */
NSAPI_PUBLIC void fsmutex_unlock(FSMUTEX id);

NSPR_END_EXTERN_C

#endif