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/gecko_api/include/nssrwlk.h

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  1/* ***** BEGIN LICENSE BLOCK *****
  2 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
  3 *
  4 * The contents of this file are subject to the Mozilla Public License Version
  5 * 1.1 (the "License"); you may not use this file except in compliance with
  6 * the License. You may obtain a copy of the License at
  7 * http://www.mozilla.org/MPL/
  8 *
  9 * Software distributed under the License is distributed on an "AS IS" basis,
 10 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 11 * for the specific language governing rights and limitations under the
 12 * License.
 13 *
 14 * The Original Code is the Netscape security libraries.
 15 *
 16 * The Initial Developer of the Original Code is
 17 * Netscape Communications Corporation.
 18 * Portions created by the Initial Developer are Copyright (C) 1994-2000
 19 * the Initial Developer. All Rights Reserved.
 20 *
 21 * Contributor(s):
 22 *
 23 * Alternatively, the contents of this file may be used under the terms of
 24 * either the GNU General Public License Version 2 or later (the "GPL"), or
 25 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 26 * in which case the provisions of the GPL or the LGPL are applicable instead
 27 * of those above. If you wish to allow use of your version of this file only
 28 * under the terms of either the GPL or the LGPL, and not to allow others to
 29 * use your version of this file under the terms of the MPL, indicate your
 30 * decision by deleting the provisions above and replace them with the notice
 31 * and other provisions required by the GPL or the LGPL. If you do not delete
 32 * the provisions above, a recipient may use your version of this file under
 33 * the terms of any one of the MPL, the GPL or the LGPL.
 34 *
 35 * ***** END LICENSE BLOCK ***** */
 36
 37/*
 38** File:		nsrwlock.h
 39** Description:	API to basic reader-writer lock functions of NSS.
 40**	These are re-entrant reader writer locks; that is,
 41**	If I hold the write lock, I can ask for it and get it again.
 42**	If I hold the write lock, I can also ask for and get a read lock.
 43**      I can then release the locks in any order (read or write).
 44**	I must release each lock type as many times as I acquired it.
 45**	Otherwise, these are normal reader/writer locks.
 46**
 47** For deadlock detection, locks should be ranked, and no lock may be aquired
 48** while I hold a lock of higher rank number.
 49** If you don't want that feature, always use NSS_RWLOCK_RANK_NONE.
 50** Lock name is for debugging, and is optional (may be NULL)
 51**/
 52
 53#ifndef nssrwlk_h___
 54#define nssrwlk_h___
 55
 56#include "utilrename.h"
 57#include "prtypes.h"
 58#include "nssrwlkt.h"
 59
 60#define	NSS_RWLOCK_RANK_NONE	0
 61
 62/* SEC_BEGIN_PROTOS */
 63PR_BEGIN_EXTERN_C
 64
 65/***********************************************************************
 66** FUNCTION:    NSSRWLock_New
 67** DESCRIPTION:
 68**  Returns a pointer to a newly created reader-writer lock object.
 69** INPUTS:      Lock rank
 70**		Lock name
 71** OUTPUTS:     void
 72** RETURN:      NSSRWLock*
 73**   If the lock cannot be created because of resource constraints, NULL
 74**   is returned.
 75**  
 76***********************************************************************/
 77PR_EXTERN(NSSRWLock*) NSSRWLock_New(PRUint32 lock_rank, const char *lock_name);
 78
 79/***********************************************************************
 80** FUNCTION:    NSSRWLock_AtomicCreate
 81** DESCRIPTION:
 82**  Given the address of a NULL pointer to a NSSRWLock, 
 83**  atomically initializes that pointer to a newly created NSSRWLock.
 84**  Returns the value placed into that pointer, or NULL.
 85**
 86** INPUTS:      address of NSRWLock pointer
 87**              Lock rank
 88**		Lock name
 89** OUTPUTS:     NSSRWLock*
 90** RETURN:      NSSRWLock*
 91**   If the lock cannot be created because of resource constraints, 
 92**   the pointer will be left NULL.
 93**  
 94***********************************************************************/
 95PR_EXTERN(NSSRWLock *)
 96nssRWLock_AtomicCreate( NSSRWLock  ** prwlock, 
 97			PRUint32      lock_rank, 
 98			const char *  lock_name);
 99
100/***********************************************************************
101** FUNCTION:    NSSRWLock_Destroy
102** DESCRIPTION:
103**  Destroys a given RW lock object.
104** INPUTS:      NSSRWLock *lock - Lock to be freed.
105** OUTPUTS:     void
106** RETURN:      None
107***********************************************************************/
108PR_EXTERN(void) NSSRWLock_Destroy(NSSRWLock *lock);
109
110/***********************************************************************
111** FUNCTION:    NSSRWLock_LockRead
112** DESCRIPTION:
113**  Apply a read lock (non-exclusive) on a RWLock
114** INPUTS:      NSSRWLock *lock - Lock to be read-locked.
115** OUTPUTS:     void
116** RETURN:      None
117***********************************************************************/
118PR_EXTERN(void) NSSRWLock_LockRead(NSSRWLock *lock);
119
120/***********************************************************************
121** FUNCTION:    NSSRWLock_LockWrite
122** DESCRIPTION:
123**  Apply a write lock (exclusive) on a RWLock
124** INPUTS:      NSSRWLock *lock - Lock to write-locked.
125** OUTPUTS:     void
126** RETURN:      None
127***********************************************************************/
128PR_EXTERN(void) NSSRWLock_LockWrite(NSSRWLock *lock);
129
130/***********************************************************************
131** FUNCTION:    NSSRWLock_UnlockRead
132** DESCRIPTION:
133**  Release a Read lock. Unlocking an unlocked lock has undefined results.
134** INPUTS:      NSSRWLock *lock - Lock to unlocked.
135** OUTPUTS:     void
136** RETURN:      void
137***********************************************************************/
138PR_EXTERN(void) NSSRWLock_UnlockRead(NSSRWLock *lock);
139
140/***********************************************************************
141** FUNCTION:    NSSRWLock_UnlockWrite
142** DESCRIPTION:
143**  Release a Write lock. Unlocking an unlocked lock has undefined results.
144** INPUTS:      NSSRWLock *lock - Lock to unlocked.
145** OUTPUTS:     void
146** RETURN:      void
147***********************************************************************/
148PR_EXTERN(void) NSSRWLock_UnlockWrite(NSSRWLock *lock);
149
150/***********************************************************************
151** FUNCTION:    NSSRWLock_HaveWriteLock
152** DESCRIPTION:
153**  Tells caller whether the current thread holds the write lock, or not.
154** INPUTS:      NSSRWLock *lock - Lock to test.
155** OUTPUTS:     void
156** RETURN:      PRBool	PR_TRUE IFF the current thread holds the write lock.
157***********************************************************************/
158
159PR_EXTERN(PRBool) NSSRWLock_HaveWriteLock(NSSRWLock *rwlock);
160
161/* SEC_END_PROTOS */
162PR_END_EXTERN_C
163
164#endif /* nsrwlock_h___ */