Method Lock

vfs.go:2182–2229

(elock sqlite3vfs.LockType)

}

func (f *VFSFile) Lock(elock sqlite3vfs.LockType) error {
	f.logger.Debug("locking file", "lock", elock)

	f.mu.Lock()
	defer f.mu.Unlock()

	if elock < f.lockType {
		return fmt.Errorf("invalid lock downgrade: current=%s target=%s", f.lockType, elock)
	}

	if elock >= sqlite3vfs.LockReserved {
		// Wait for any disable operation to complete before allowing RESERVED lock.
		// This prevents new write transactions from starting during disable.
		for f.disabling {
			f.logger.Debug("waiting for disable to complete before acquiring RESERVED lock")
			f.cond.Wait()
		}

		// Reject write-intent locks when writes are disabled. Since we always
		// report OpenReadWrite to SQLite (to support cold enable), SQLite may
		// attempt write transactions even when writes are logically disabled.
		if !f.writeEnabled {
			return sqlite3vfs.ReadOnlyError
		}
	}

	if f.writeEnabled && elock >= sqlite3vfs.LockReserved && !f.inTransaction {
		if f.vfs != nil {
			f.vfs.writeMu.Lock()
			if f.vfs.writeFile != nil && f.vfs.writeFile != f {
				f.vfs.writeMu.Unlock()
				return sqlite3vfs.BusyError
			}
			f.vfs.writeFile = f
			if f.vfs.lastSyncedTXID > f.expectedTXID && len(f.dirty) == 0 {
				f.expectedTXID = f.vfs.lastSyncedTXID
				f.pendingTXID = f.vfs.lastSyncedTXID + 1
				f.pos = ltx.Pos{TXID: f.expectedTXID}
			}
			f.vfs.writeMu.Unlock()
		}
		f.inTransaction = true
		f.logger.Debug("transaction started", "expectedTXID", f.expectedTXID)
	}

	f.lockType = elock
	return nil
}

func (f *VFSFile) Unlock(elock sqlite3vfs.LockType) error {
	f.logger.Debug("unlocking file", "lock", elock)