dundee/gdu

package analyze

import "sync"

// A WaitGroup waits for a collection of goroutines to finish.
// In contrast to sync.WaitGroup Add method can be called from a goroutine.
type WaitGroup struct {
    wait   sync.Mutex
    value  int
    access sync.Mutex
}

// Init prepares the WaitGroup for usage, locks
func (s *WaitGroup) Init() *WaitGroup {
    s.wait.Lock()
    return s
}

// Add increments value
func (s *WaitGroup) Add(value int) {
    s.access.Lock()
    s.value += value
    s.access.Unlock()
}

// Done decrements the value by one, if value is 0, lock is released
func (s *WaitGroup) Done() {
    s.access.Lock()
    s.value--
    s.check()
    s.access.Unlock()
}

// Wait blocks until value is 0
func (s *WaitGroup) Wait() {
    s.access.Lock()
    isValue := s.value > 0
    s.access.Unlock()
    if isValue {
        s.wait.Lock()
    }
}

func (s *WaitGroup) check() {
    if s.value == 0 {
        s.wait.TryLock()
        s.wait.Unlock()
    }
}