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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/*
** File: nsrwlock.h
** Description: API to basic reader-writer lock functions of NSS.
** These locks allow re-entry from writers but not readers. That is,
** If I hold the write lock, I can ask for it and get it again.
** If I hold the write lock, I can also ask for and get a read lock.
** I can then release the locks in any order (read or write).
** If I hold a read lock, I must not ask for another read lock or
** the write lock.
** I must release each lock type as many times as I acquired it.
**
** For deadlock detection, locks should be ranked, and no lock may be aquired
** while I hold a lock of higher rank number.
** If you don't want that feature, always use NSS_RWLOCK_RANK_NONE.
** Lock name is for debugging, and is optional (may be NULL)
**/
#ifndef nssrwlk_h___
#define nssrwlk_h___
#include "utilrename.h"
#include "prtypes.h"
#include "nssrwlkt.h"
#define NSS_RWLOCK_RANK_NONE 0
/* SEC_BEGIN_PROTOS */
PR_BEGIN_EXTERN_C
/***********************************************************************
** FUNCTION: NSSRWLock_New
** DESCRIPTION:
** Returns a pointer to a newly created reader-writer lock object.
** INPUTS: Lock rank
** Lock name
** OUTPUTS: void
** RETURN: NSSRWLock*
** If the lock cannot be created because of resource constraints, NULL
** is returned.
**
***********************************************************************/
extern NSSRWLock *NSSRWLock_New(PRUint32 lock_rank, const char *lock_name);
/***********************************************************************
** FUNCTION: NSSRWLock_AtomicCreate
** DESCRIPTION:
** Given the address of a NULL pointer to a NSSRWLock,
** atomically initializes that pointer to a newly created NSSRWLock.
** Returns the value placed into that pointer, or NULL.
**
** INPUTS: address of NSRWLock pointer
** Lock rank
** Lock name
** OUTPUTS: NSSRWLock*
** RETURN: NSSRWLock*
** If the lock cannot be created because of resource constraints,
** the pointer will be left NULL.
**
***********************************************************************/
extern NSSRWLock *
nssRWLock_AtomicCreate(NSSRWLock **prwlock,
PRUint32 lock_rank,
const char *lock_name);
/***********************************************************************
** FUNCTION: NSSRWLock_Destroy
** DESCRIPTION:
** Destroys a given RW lock object.
** INPUTS: NSSRWLock *lock - Lock to be freed.
** OUTPUTS: void
** RETURN: None
***********************************************************************/
extern void NSSRWLock_Destroy(NSSRWLock *lock);
/***********************************************************************
** FUNCTION: NSSRWLock_LockRead
** DESCRIPTION:
** Apply a read lock (non-exclusive) on a RWLock
** INPUTS: NSSRWLock *lock - Lock to be read-locked.
** OUTPUTS: void
** RETURN: None
***********************************************************************/
extern void NSSRWLock_LockRead(NSSRWLock *lock);
/***********************************************************************
** FUNCTION: NSSRWLock_LockWrite
** DESCRIPTION:
** Apply a write lock (exclusive) on a RWLock
** INPUTS: NSSRWLock *lock - Lock to write-locked.
** OUTPUTS: void
** RETURN: None
***********************************************************************/
extern void NSSRWLock_LockWrite(NSSRWLock *lock);
/***********************************************************************
** FUNCTION: NSSRWLock_UnlockRead
** DESCRIPTION:
** Release a Read lock. Unlocking an unlocked lock has undefined results.
** INPUTS: NSSRWLock *lock - Lock to unlocked.
** OUTPUTS: void
** RETURN: void
***********************************************************************/
extern void NSSRWLock_UnlockRead(NSSRWLock *lock);
/***********************************************************************
** FUNCTION: NSSRWLock_UnlockWrite
** DESCRIPTION:
** Release a Write lock. Unlocking an unlocked lock has undefined results.
** INPUTS: NSSRWLock *lock - Lock to unlocked.
** OUTPUTS: void
** RETURN: void
***********************************************************************/
extern void NSSRWLock_UnlockWrite(NSSRWLock *lock);
/***********************************************************************
** FUNCTION: NSSRWLock_HaveWriteLock
** DESCRIPTION:
** Tells caller whether the current thread holds the write lock, or not.
** INPUTS: NSSRWLock *lock - Lock to test.
** OUTPUTS: void
** RETURN: PRBool PR_TRUE IFF the current thread holds the write lock.
***********************************************************************/
extern PRBool NSSRWLock_HaveWriteLock(NSSRWLock *rwlock);
/* SEC_END_PROTOS */
PR_END_EXTERN_C
#endif /* nsrwlock_h___ */
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