"sync"
	"sync/atomic"
)

// Inspired from Golang sync.Once but it is only marked
// initialized when the provided function returns nil.

// Init represents the structure.
type Init struct {
	done uint32
	m    sync.Mutex
}

// Do is similar to sync.Once.Do - makes one successful
// call to the function. ie, it invokes the function
// if it is not successful yet.
func (l *Init) Do(f func() error) error {

	doTestParallelReaders(1, 4)
	doTestParallelReaders(3, 4)
	doTestParallelReaders(4, 2)
}

// Borrowed from rwmutex_test.go
func reader(resource string, numIterations int, activity *int32, cdone chan bool) {
	rwm := NewDRWMutex(ds, resource)
	for range numIterations {
		if rwm.GetRLock(context.Background(), nil, id, source, Options{Timeout: time.Second}) {
			n := atomic.AddInt32(activity, 1)

	id, err := hex.DecodeString(keyHex[:8])
	if err != nil {
		return err
	}
	key, err := hex.DecodeString(keyHex[8:])
	if err != nil {
		return err
	}
	// Verify that CRC is ok.
	want := binary.LittleEndian.Uint32(id)
	got := crc32.ChecksumIEEE(key)
	if want != got {
		return fmt.Errorf("Invalid key checksum, want %x, got %x", want, got)
	}

	stream, err := sio.AES_256_GCM.Stream(key)
	if err != nil {
		return err
	}

	}
	info.Used = info.Total - info.Free
	return info, nil
}

// GetDriveStats returns IO stats of the drive by its major:minor
func GetDriveStats(major, minor uint32) (iostats IOStats, err error) {
	return IOStats{}, errors.New("operation unsupported")

	Size    int64     `json:"size"`    // Size of the object `xl.meta`.
	ModTime time.Time `json:"modTime"` // ModTime of the object `xl.meta`.
	Name    string    `json:"name"`
	Dir     bool      `json:"dir"`
	Mode    uint32    `json:"mode"`
}

// ErasureInfo holds erasure coding and bitrot related information.
type ErasureInfo struct {
	// Algorithm is the string representation of erasure-coding-algorithm
	Algorithm string `json:"algorithm"`

	}
	info.Used = info.Total - info.Free
	return info, nil
}

// GetDriveStats returns IO stats of the drive by its major:minor
func GetDriveStats(major, minor uint32) (iostats IOStats, err error) {
	return IOStats{}, errors.New("operation unsupported")

	Weight   int         `json:"weight,omitempty"`
	Text     string      `json:"text,omitempty"`
	Mail     bool        `json:"mail,omitempty"` // Be an MX record. Priority becomes Preference.
	TTL      uint32      `json:"ttl,omitempty"`

	// Holds info about when the entry was created first.
	CreationDate time.Time `json:"creationDate"`

	// When a SRV record with a "Host: IP-address" is added, we synthesize

		if b, ok := v.(bool); ok {
			return b
		}
	}
	wpath, _ := windows.UTF16PtrFromString(path)
	wvolume := make([]uint16, len(path)+1)

	if err := windows.GetVolumePathName(wpath, &wvolume[0], uint32(len(wvolume))); err != nil {
		mountPointCache.Store(path, false)
		return false
	}

	switch windows.GetDriveType(&wvolume[0]) {

		ReadOnly
	}

	type Author struct {
		ID    string
		Name  string
		Email string
	}

	type HNPost struct {
		BasePost
		Author  `gorm:"EmbeddedPrefix:user_"` // Embedded struct
		Upvotes int32
	}

	type EngadgetPost struct {
		BasePost BasePost `gorm:"Embedded"`
		Author   *Author  `gorm:"Embedded;EmbeddedPrefix:author_"` // Embedded struct
		ImageUrl string
	}

	}
	info.Used = info.Total - info.Free
	return info, nil
}

// GetDriveStats returns IO stats of the drive by its major:minor
func GetDriveStats(major, minor uint32) (iostats IOStats, err error) {
	return IOStats{}, errors.New("operation unsupported")