package lock import ( "sync" "github.com/pkg/errors" ) // Mutex holds a single mutex and whether it has been allocated. type Mutex struct { id uint32 lock sync.Mutex allocated bool } // ID retrieves the ID of the mutex func (m *Mutex) ID() uint32 { return m.id } // Lock locks the mutex func (m *Mutex) Lock() { m.lock.Lock() } // Unlock unlocks the mutex func (m *Mutex) Unlock() { m.lock.Unlock() } // Free deallocates the mutex to allow its reuse func (m *Mutex) Free() error { m.allocated = false return nil } // InMemoryManager is a lock manager that allocates and retrieves local-only // locks - that is, they are not multiprocess. This lock manager is intended // purely for unit and integration testing and should not be used in production // deployments. type InMemoryManager struct { locks []*Mutex numLocks uint32 localLock sync.Mutex } // NewInMemoryManager creates a new in-memory lock manager with the given number // of locks. func NewInMemoryManager(numLocks uint32) (Manager, error) { if numLocks == 0 { return nil, errors.Errorf("must provide a non-zero number of locks!") } manager := new(InMemoryManager) manager.numLocks = numLocks manager.locks = make([]*Mutex, numLocks) var i uint32 for i = 0; i < numLocks; i++ { lock := new(Mutex) lock.id = i manager.locks[i] = lock } return manager, nil } // AllocateLock allocates a lock from the manager. func (m *InMemoryManager) AllocateLock() (Locker, error) { m.localLock.Lock() defer m.localLock.Unlock() for _, lock := range m.locks { if !lock.allocated { lock.allocated = true return lock, nil } } return nil, errors.Errorf("all locks have been allocated") } // RetrieveLock retrieves a lock from the manager. func (m *InMemoryManager) RetrieveLock(id uint32) (Locker, error) { if id >= m.numLocks { return nil, errors.Errorf("given lock ID %d is too large - this manager only supports lock indexes up to %d", id, m.numLocks-1) } return m.locks[id], nil } // FreeAllLocks frees all locks. // This function is DANGEROUS. Please read the full comment in locks.go before // trying to use it. func (m *InMemoryManager) FreeAllLocks() error { for _, lock := range m.locks { lock.allocated = false } return nil }