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      1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
      2 /*
      3  * The contents of this file are subject to the Mozilla Public
      4  * License Version 1.1 (the "License"); you may not use this file
      5  * except in compliance with the License. You may obtain a copy of
      6  * the License at http://www.mozilla.org/MPL/
      7  *
      8  * Software distributed under the License is distributed on an "AS
      9  * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
     10  * implied. See the License for the specific language governing
     11  * rights and limitations under the License.
     12  *
     13  * The Original Code is the Netscape Portable Runtime (NSPR).
     14  *
     15  * The Initial Developer of the Original Code is Netscape
     16  * Communications Corporation.  Portions created by Netscape are
     17  * Copyright (C) 1998-2000 Netscape Communications Corporation.  All
     18  * Rights Reserved.
     19  *
     20  * Contributor(s):
     21  *
     22  * Alternatively, the contents of this file may be used under the
     23  * terms of the GNU General Public License Version 2 or later (the
     24  * "GPL"), in which case the provisions of the GPL are applicable
     25  * instead of those above.  If you wish to allow use of your
     26  * version of this file only under the terms of the GPL and not to
     27  * allow others to use your version of this file under the MPL,
     28  * indicate your decision by deleting the provisions above and
     29  * replace them with the notice and other provisions required by
     30  * the GPL.  If you do not delete the provisions above, a recipient
     31  * may use your version of this file under either the MPL or the
     32  * GPL.
     33  */
     34 
     35 /*
     36 ** File:		prrwlock.h
     37 ** Description:	API to basic reader-writer lock functions of NSPR.
     38 **
     39 **/
     40 
     41 #ifndef prrwlock_h___
     42 #define prrwlock_h___
     43 
     44 #include "prtypes.h"
     45 
     46 PR_BEGIN_EXTERN_C
     47 
     48 /*
     49  * PRRWLock --
     50  *
     51  *	The reader writer lock, PRRWLock, is an opaque object to the clients
     52  *	of NSPR.  All routines operate on a pointer to this opaque entity.
     53  */
     54 
     55 
     56 typedef struct PRRWLock PRRWLock;
     57 
     58 #define	PR_RWLOCK_RANK_NONE	0
     59 
     60 
     61 /***********************************************************************
     62 ** FUNCTION:    PR_NewRWLock
     63 ** DESCRIPTION:
     64 **  Returns a pointer to a newly created reader-writer lock object.
     65 ** INPUTS:      Lock rank
     66 **				Lock name
     67 ** OUTPUTS:     void
     68 ** RETURN:      PRRWLock*
     69 **   If the lock cannot be created because of resource constraints, NULL
     70 **   is returned.
     71 **
     72 ***********************************************************************/
     73 NSPR_API(PRRWLock*) PR_NewRWLock(PRUint32 lock_rank, const char *lock_name);
     74 
     75 /***********************************************************************
     76 ** FUNCTION:    PR_DestroyRWLock
     77 ** DESCRIPTION:
     78 **  Destroys a given RW lock object.
     79 ** INPUTS:      PRRWLock *lock - Lock to be freed.
     80 ** OUTPUTS:     void
     81 ** RETURN:      None
     82 ***********************************************************************/
     83 NSPR_API(void) PR_DestroyRWLock(PRRWLock *lock);
     84 
     85 /***********************************************************************
     86 ** FUNCTION:    PR_RWLock_Rlock
     87 ** DESCRIPTION:
     88 **  Apply a read lock (non-exclusive) on a RWLock
     89 ** INPUTS:      PRRWLock *lock - Lock to be read-locked.
     90 ** OUTPUTS:     void
     91 ** RETURN:      None
     92 ***********************************************************************/
     93 NSPR_API(void) PR_RWLock_Rlock(PRRWLock *lock);
     94 
     95 /***********************************************************************
     96 ** FUNCTION:    PR_RWLock_Wlock
     97 ** DESCRIPTION:
     98 **  Apply a write lock (exclusive) on a RWLock
     99 ** INPUTS:      PRRWLock *lock - Lock to write-locked.
    100 ** OUTPUTS:     void
    101 ** RETURN:      None
    102 ***********************************************************************/
    103 NSPR_API(void) PR_RWLock_Wlock(PRRWLock *lock);
    104 
    105 /***********************************************************************
    106 ** FUNCTION:    PR_RWLock_Unlock
    107 ** DESCRIPTION:
    108 **  Release a RW lock. Unlocking an unlocked lock has undefined results.
    109 ** INPUTS:      PRRWLock *lock - Lock to unlocked.
    110 ** OUTPUTS:     void
    111 ** RETURN:      void
    112 ***********************************************************************/
    113 NSPR_API(void) PR_RWLock_Unlock(PRRWLock *lock);
    114 
    115 PR_END_EXTERN_C
    116 
    117 #endif /* prrwlock_h___ */
    118