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prlock.h
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00001 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
00002 /* ***** BEGIN LICENSE BLOCK *****
00003  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
00004  *
00005  * The contents of this file are subject to the Mozilla Public License Version
00006  * 1.1 (the "License"); you may not use this file except in compliance with
00007  * the License. You may obtain a copy of the License at
00008  * http://www.mozilla.org/MPL/
00009  *
00010  * Software distributed under the License is distributed on an "AS IS" basis,
00011  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
00012  * for the specific language governing rights and limitations under the
00013  * License.
00014  *
00015  * The Original Code is the Netscape Portable Runtime (NSPR).
00016  *
00017  * The Initial Developer of the Original Code is
00018  * Netscape Communications Corporation.
00019  * Portions created by the Initial Developer are Copyright (C) 1998-2000
00020  * the Initial Developer. All Rights Reserved.
00021  *
00022  * Contributor(s):
00023  *
00024  * Alternatively, the contents of this file may be used under the terms of
00025  * either the GNU General Public License Version 2 or later (the "GPL"), or
00026  * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
00027  * in which case the provisions of the GPL or the LGPL are applicable instead
00028  * of those above. If you wish to allow use of your version of this file only
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00030  * use your version of this file under the terms of the MPL, indicate your
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00032  * and other provisions required by the GPL or the LGPL. If you do not delete
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00035  *
00036  * ***** END LICENSE BLOCK ***** */
00037 
00038 /*
00039 ** File:             prlock.h
00040 ** Description:      API to basic locking functions of NSPR.
00041 **
00042 **
00043 ** NSPR provides basic locking mechanisms for thread synchronization.  Locks 
00044 ** are lightweight resource contention controls that prevent multiple threads 
00045 ** from accessing something (code/data) simultaneously.
00046 **/
00047 
00048 #ifndef prlock_h___
00049 #define prlock_h___
00050 
00051 #include "prtypes.h"
00052 
00053 PR_BEGIN_EXTERN_C
00054 
00055 /**********************************************************************/
00056 /************************* TYPES AND CONSTANTS ************************/
00057 /**********************************************************************/
00058 
00059 /*
00060  * PRLock --
00061  *
00062  *     NSPR represents the lock as an opaque entity to the client of the
00063  *        API.  All routines operate on a pointer to this opaque entity.
00064  */
00065 
00066 typedef struct PRLock PRLock;
00067 
00068 /**********************************************************************/
00069 /****************************** FUNCTIONS *****************************/
00070 /**********************************************************************/
00071 
00072 /***********************************************************************
00073 ** FUNCTION:    PR_NewLock
00074 ** DESCRIPTION:
00075 **  Returns a pointer to a newly created opaque lock object.
00076 ** INPUTS:      void
00077 ** OUTPUTS:     void
00078 ** RETURN:      PRLock*
00079 **   If the lock can not be created because of resource constraints, NULL
00080 **   is returned.
00081 **  
00082 ***********************************************************************/
00083 NSPR_API(PRLock*) PR_NewLock(void);
00084 
00085 /***********************************************************************
00086 ** FUNCTION:    PR_DestroyLock
00087 ** DESCRIPTION:
00088 **  Destroys a given opaque lock object.
00089 ** INPUTS:      PRLock *lock
00090 **              Lock to be freed.
00091 ** OUTPUTS:     void
00092 ** RETURN:      None
00093 ***********************************************************************/
00094 NSPR_API(void) PR_DestroyLock(PRLock *lock);
00095 
00096 /***********************************************************************
00097 ** FUNCTION:    PR_Lock
00098 ** DESCRIPTION:
00099 **  Lock a lock.
00100 ** INPUTS:      PRLock *lock
00101 **              Lock to locked.
00102 ** OUTPUTS:     void
00103 ** RETURN:      None
00104 ***********************************************************************/
00105 NSPR_API(void) PR_Lock(PRLock *lock);
00106 
00107 /***********************************************************************
00108 ** FUNCTION:    PR_Unlock
00109 ** DESCRIPTION:
00110 **  Unlock a lock.  Unlocking an unlocked lock has undefined results.
00111 ** INPUTS:      PRLock *lock
00112 **              Lock to unlocked.
00113 ** OUTPUTS:     void
00114 ** RETURN:      PR_STATUS
00115 **              Returns PR_FAILURE if the caller does not own the lock.
00116 ***********************************************************************/
00117 NSPR_API(PRStatus) PR_Unlock(PRLock *lock);
00118 
00119 PR_END_EXTERN_C
00120 
00121 #endif /* prlock_h___ */