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openflow/usr/include/nss/nssrwlk.h

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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 are re-entrant reader writer locks; 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).
+**  I must release each lock type as many times as I acquired it.
+**  Otherwise, these are normal reader/writer locks.
+**
+** 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___ */