The Locking Group contain the API for using the various lock types: exclusive, partition, and shared. More...

Macros
#define	MDBM_LOCKMODE_UNKNOWN 0xFFFFFFFF
	Returned by mdbm_get_lockmode for an unknown lock mode (MDBM V2). More...

#define	MDBM_LOCKMODE_UNKNOWN 0xFFFFFFFF
	Returned by mdbm_get_lockmode for an unknown lock mode (MDBM V2). More...

Functions
int	mdbm_islocked (MDBM *db)
	Returns whether or not MDBM is locked by another process or thread (thread: V3 only). More...

int	mdbm_isowned (MDBM *db)
	Returns whether or not MDBM is currently locked (owned) by the calling process. More...

uint32_t	mdbm_get_lockmode (MDBM *db)
	Gets the MDBM's lock mode. More...

int	mdbm_lock (MDBM *db)
	Locks the database for exclusive access by the caller. More...

int	mdbm_unlock (MDBM *db)
	Unlocks the database, releasing exclusive or shared access by the caller. More...

int	mdbm_trylock (MDBM *db)
	Attempts to exclusively lock an MDBM. More...

int	mdbm_plock (MDBM db, const datum key, int flags)
	Locks a specific partition in the database for exclusive access by the caller. More...

int	mdbm_punlock (MDBM db, const datum key, int flags)
	Unlocks a specific partition in the database, releasing exclusive access by the caller. More...

int	mdbm_tryplock (MDBM db, const datum key, int flags)
	Tries to locks a specific partition in the database for exclusive access by the caller. More...

int	mdbm_lock_shared (MDBM *db)
	Locks the database for shared access by readers, excluding access to writers. More...

int	mdbm_trylock_shared (MDBM *db)
	Locks the database for shared access by readers, excluding access to writers. More...

int	mdbm_lock_smart (MDBM db, const datum key, int flags)
	Perform either partition, shared or exclusive locking based on the locking-related flags supplied to mdbm_open. More...

int	mdbm_trylock_smart (MDBM db, const datum key, int flags)
	Attempts to lock an MDBM based on the locking flags supplied to mdbm_open. More...

int	mdbm_unlock_smart (MDBM db, const datum key, int flags)
	Unlock an MDBM based on the locking flags supplied to mdbm_open. More...

int	mdbm_lock_reset (const char *dbfilename, int flags)
	Resets the global lock ownership state of a database. More...

int	mdbm_delete_lockfiles (const char *dbname)
	Removes all lockfiles associated with an MDBM file. More...

Detailed Description

The Locking Group contain the API for using the various lock types: exclusive, partition, and shared.

Macro Definition Documentation

#define MDBM_LOCKMODE_UNKNOWN 0xFFFFFFFF

Returned by mdbm_get_lockmode for an unknown lock mode (MDBM V2).

#define MDBM_LOCKMODE_UNKNOWN 0xFFFFFFFF

Returned by mdbm_get_lockmode for an unknown lock mode (MDBM V2).

Function Documentation

int mdbm_islocked ( MDBM * db )

Returns whether or not MDBM is locked by another process or thread (thread: V3 only).

Parameters

[in,out] db Database handle

Returns: Locked status

Return values

0	Database is not locked
1	Database is locked

int mdbm_isowned ( MDBM * db )

Returns whether or not MDBM is currently locked (owned) by the calling process.

Owned MDBMs have multiple nested locks in place.

Parameters

[in,out] db Database handle

Returns: Owned status

Return values

0	Database is not owned
1	Database is owned

uint32_t mdbm_get_lockmode ( MDBM * db )

Gets the MDBM's lock mode.

Parameters

[in,out] db Database handle

Returns: Lock mode

Return values

0	- Exclusive locking
MDBM_OPEN_NOLOCK	- No locking
MDBM_PARTITIONED_LOCKS	- Partitioned locking
MDBM_RW_LOCKS	- Shared (read-write) locking

int mdbm_lock ( MDBM * db )

Locks the database for exclusive access by the caller.

The lock is nestable, so a caller already holding the lock may call mdbm_lock again as long as an equal number of calls to mdbm_unlock are made to release the lock.

Parameters

[in,out] db Database handle

Returns: Lock status

Return values

-1	Error, and errno is set. Typically, an error occurs if the database has been corrupted.
1	Success, exclusive lock was acquired

int mdbm_unlock ( MDBM * db )

Unlocks the database, releasing exclusive or shared access by the caller.

If the caller has called mdbm_lock or mdbm_lock_shared multiple times in a row, an equal number of unlock calls are required. See mdbm_lock and mdbm_lock_shared for usage.

Parameters

[in,out] db Database to be unlocked

Returns: Lock status

Return values

-1	Error, and errno is set. Typically, an error occurs if the database has been corrupted, or the process/thread does not own the lock.
1	Success, exclusive lock was released

int mdbm_trylock ( MDBM * db )

Attempts to exclusively lock an MDBM.

Parameters

[in,out] db Database handle

Returns: Lock status

Return values

-1	Error, and errno is set
1	Success, exclusive lock was acquired

int mdbm_plock	(	MDBM *	db,
		const datum *	key,
		int	flags
	)

Locks a specific partition in the database for exclusive access by the caller.

The lock is nestable, so a caller already holding the lock may call mdbm_plock again as long as an equal number of calls to mdbm_punlock are made to release the lock.

Parameters

[in,out]	db	Database to be locked.
[in]	key	Key to be hashed to determine page to lock
[in]	flags	Ignored.

Returns: Lock status

Return values

-1	Error, and errno is set. Typically, an error occurs if the database has been corrupted.
1	Success, partition lock was acquired

int mdbm_punlock	(	MDBM *	db,
		const datum *	key,
		int	flags
	)

Unlocks a specific partition in the database, releasing exclusive access by the caller.

If the caller has called mdbm_plock multiple times in a row, an equal number of unlock calls are required. See mdbm_plock for usage.

Parameters

[in,out]	db	Database to be unlocked
[in]	key	Ignored.
[in]	flags	Ignored.

Returns: Lock status

Return values

-1	Error, and errno is set. Typically, an error occurs if the database has been corrupted, or mdbm_plock is called without holding the lock
1	Success, partition lock was released

int mdbm_tryplock	(	MDBM *	db,
		const datum *	key,
		int	flags
	)

Tries to locks a specific partition in the database for exclusive access by the caller.

The lock is nestable, so a caller already holding the lock may call mdbm_plock again as long as an equal number of calls to mdbm_punlock are made to release the lock. See mdbm_plock for usage.

Parameters

[in,out]	db	Database to be unlocked
[in]	key	Key to be hashed to determine page to lock
[in]	flags	Ignored.

Returns: Lock status

Return values

-1	Error, and errno is set. Partition is not locked. Typically, an error occurs if the database has been corrupted.
1	Success, partition lock was acquired

int mdbm_lock_shared ( MDBM * db )

Locks the database for shared access by readers, excluding access to writers.

This is multiple-readers, one writer (MROW) locking. The database must be opened with the MDBM_RW_LOCKS flag to enable shared locks. Use mdbm_unlock to release a shared lock.

Write access (ex. mdbm_store and mdbm_delete) must not be done in the context of a shared lock. Write access must be done in the context of an exclusive lock (mdbm_lock and mdbm_unlock).

The lock is nestable, so a caller already holding the lock may call mdbm_lock_shared again as long as an equal number of calls to mdbm_unlock are made to release the lock.

Parameters

[in,out] db Database handle

Returns: Lock status

Return values

-1	Error, and errno is set. Typically, an error occurs if the database has been corrupted.
1	Success, shared lock was acquired

int mdbm_trylock_shared ( MDBM * db )

Locks the database for shared access by readers, excluding access to writers.

This is the non-blocking version of mdbm_lock_shared

This is MROW locking. The database must be opened with the MDBM_RW_LOCKS flag to enable shared locks.

Write access (ex. mdbm_store and mdbm_delete) must not be done in the context of a shared lock. Write access must be done in the context of an exclusive lock (mdbm_lock and mdbm_unlock).

Parameters

[in,out] db Database handle

Returns: Lock status

Return values

-1	Error, and errno is set. Typically, an error occurs if the database has been corrupted, or the database is already exclusively locked.
1	Success, shared lock was acquired

int mdbm_lock_smart	(	MDBM *	db,
		const datum *	key,
		int	flags
	)

Perform either partition, shared or exclusive locking based on the locking-related flags supplied to mdbm_open.

Parameters

[in,out]	db	Database handle
[in]	key	Key to be hashed to determine which page to lock (if needed)
[in]	flags	MDBM_O_RDWR means lock to perform a write

Returns: Lock status

Return values

-1	Error, and errno is set. Typically, an error occurs if the database has been corrupted.
1	Success, smart lock was acquired, or db was opened with MDBM_OPEN_NOLOCK.

int mdbm_trylock_smart	(	MDBM *	db,
		const datum *	key,
		int	flags
	)

Attempts to lock an MDBM based on the locking flags supplied to mdbm_open.

Parameters

[in,out]	db	Database handle
[in]	key	Key to be hashed to determine page to lock (if needed)
[in]	flags	MDBM_O_RDWR means lock to perform a write.

Returns: Lock status

Return values

-1	Error, and errno is set
1	Success, smart lock was acquired, or db was opened with MDBM_OPEN_NOLOCK.

int mdbm_unlock_smart	(	MDBM *	db,
		const datum *	key,
		int	flags
	)

Unlock an MDBM based on the locking flags supplied to mdbm_open.

Parameters

[in,out]	db	Database handle
[in]	key	Key to be hashed to determine page to lock (if needed)
[in]	flags	Reserved for future use

Returns: Lock status

Return values

-1	Error, and errno is set
1	Success, smart lock was released, or db was opened with MDBM_OPEN_NOLOCK.

int mdbm_lock_reset	(	const char *	dbfilename,
		int	flags
	)

Resets the global lock ownership state of a database.

USE THIS FUNCTION WITH EXTREME CAUTION! The global lock ownership state of an MDBM is visible to other processes and is reset system-wide. Resetting a lock state while other threads/processes are accessing this database might cause those operations to fail.

Parameters

[in]	dbfilename	Database file name
[in]	flags	Reserved for future use, and must be 0.

Returns: Lock reset status

Return values

-1	Error, and errno is set
0	Success

int mdbm_delete_lockfiles ( const char * dbname )

Removes all lockfiles associated with an MDBM file.

USE THIS FUNCTION WITH EXTREME CAUTION! NOTE: This is only intended to clean-up lockfiles when removing an MDBM file. This function can only be used when all processes that access the MDBM whose locks are being deleted are not running. Calling it on an MDBM still in use will cause corruption and undefined behavior. Deleting lockfiles resets lock ownership and locking mode (exclusive/partition/shared).

Parameters

[in] dbname Full path of MDBM file

Returns: Lockfile deletion status

Return values

-1	Error, and errno is set
0	Success

Macros

Functions

Detailed Description

Macro Definition Documentation

Function Documentation