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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:		prlock.h
     37 ** Description:	API to basic locking functions of NSPR.
     38 **
     39 **
     40 ** NSPR provides basic locking mechanisms for thread synchronization.  Locks
     41 ** are lightweight resource contention controls that prevent multiple threads
     42 ** from accessing something (code/data) simultaneously.
     43 **/
     44 
     45 #ifndef prlock_h___
     46 #define prlock_h___
     47 
     48 #include "prtypes.h"
     49 
     50 PR_BEGIN_EXTERN_C
     51 
     52 /**********************************************************************/
     53 /************************* TYPES AND CONSTANTS ************************/
     54 /**********************************************************************/
     55 
     56 /*
     57  * PRLock --
     58  *
     59  *     NSPR represents the lock as an opaque entity to the client of the
     60  *	   API.  All routines operate on a pointer to this opaque entity.
     61  */
     62 
     63 typedef struct PRLock PRLock;
     64 
     65 /**********************************************************************/
     66 /****************************** FUNCTIONS *****************************/
     67 /**********************************************************************/
     68 
     69 /***********************************************************************
     70 ** FUNCTION:    PR_NewLock
     71 ** DESCRIPTION:
     72 **  Returns a pointer to a newly created opaque lock object.
     73 ** INPUTS:      void
     74 ** OUTPUTS:     void
     75 ** RETURN:      PRLock*
     76 **   If the lock can not be created because of resource constraints, NULL
     77 **   is returned.
     78 **
     79 ***********************************************************************/
     80 NSPR_API(PRLock*) PR_NewLock(void);
     81 
     82 /***********************************************************************
     83 ** FUNCTION:    PR_DestroyLock
     84 ** DESCRIPTION:
     85 **  Destroys a given opaque lock object.
     86 ** INPUTS:      PRLock *lock
     87 **              Lock to be freed.
     88 ** OUTPUTS:     void
     89 ** RETURN:      None
     90 ***********************************************************************/
     91 NSPR_API(void) PR_DestroyLock(PRLock *lock);
     92 
     93 /***********************************************************************
     94 ** FUNCTION:    PR_Lock
     95 ** DESCRIPTION:
     96 **  Lock a lock.
     97 ** INPUTS:      PRLock *lock
     98 **              Lock to locked.
     99 ** OUTPUTS:     void
    100 ** RETURN:      None
    101 ***********************************************************************/
    102 NSPR_API(void) PR_Lock(PRLock *lock);
    103 
    104 /***********************************************************************
    105 ** FUNCTION:    PR_Unlock
    106 ** DESCRIPTION:
    107 **  Unlock a lock.  Unlocking an unlocked lock has undefined results.
    108 ** INPUTS:      PRLock *lock
    109 **              Lock to unlocked.
    110 ** OUTPUTS:     void
    111 ** RETURN:      PR_STATUS
    112 **              Returns PR_FAILURE if the caller does not own the lock.
    113 ***********************************************************************/
    114 NSPR_API(PRStatus) PR_Unlock(PRLock *lock);
    115 
    116 PR_END_EXTERN_C
    117 
    118 #endif /* prlock_h___ */
    119