doneCh := make(chan struct{})
	defer close(doneCh)
	if err := ps.Subscribe(MaskAll, ch1, doneCh, nil); err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if err := ps.Subscribe(MaskAll, ch2, doneCh, nil); err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	ps.Lock()
	defer ps.Unlock()

	if len(ps.subs) != 2 || ps.NumSubscribers(MaskAll) != 2 || ps.Subscribers() != 2 {
		t.Fatalf("expected 2 subscribers")
	}
}

package pubsub

import (
	"math"
	"math/bits"
)

// Mask allows filtering by a bitset mask.
type Mask uint64

const (
	// MaskAll is the mask for all entries.
	MaskAll Mask = math.MaxUint64
)

// MaskFromMaskable extracts mask from an interface.
func MaskFromMaskable(m Maskable) Mask {
	return Mask(m.Mask())
}

// Contains returns whether *all* flags in other is present in t.
func (t Mask) Contains(other Mask) bool {

// If data is not xlv2, it is returned in full.
func readXLMetaNoData(r io.Reader, size int64) ([]byte, error) {
	initial := size
	hasFull := true
	if initial > metaDataReadDefault {
		initial = metaDataReadDefault
		hasFull = false
	}

	buf := metaDataPoolGet()[:initial]
	_, err := io.ReadFull(r, buf)
	if err != nil {
		return nil, fmt.Errorf("readXLMetaNoData(io.ReadFull): %w", err)