Method CreateGroup

windowgroup.go:43–74

CreateGroup returns a window group for the given thread ID. If one does not already exist, it will be created. The group will have its counter incremented as a result of this call. It is the caller's responsibility to call Done when finished with the group.

(threadID uint32)

// It is the caller's responsibility to call Done when finished with the
// group.
func (m *windowGroupManager) CreateGroup(threadID uint32) *WindowGroup {
	// Fast path with read lock
	m.mutex.RLock()
	if m.groups != nil {
		if group := m.groups[threadID]; group != nil {
			m.mutex.RUnlock()
			group.Add(1)
			return group
		}
	}
	m.mutex.RUnlock()

	// Slow path with write lock
	m.mutex.Lock()
	if m.groups == nil {
		m.groups = make(map[uint32]*WindowGroup)
	} else {
		if group := m.groups[threadID]; group != nil {
			// Another caller raced with our lock and beat us
			m.mutex.Unlock()
			group.Add(1)
			return group
		}
	}

	group := newWindowGroup(threadID, m.removeGroup)
	group.Add(1)
	m.groups[threadID] = group
	m.mutex.Unlock()

	return group
}

// removeGroup is called by window groups to remove themselves from
// the manager.