atomic_rbuf.go
func (b *AtomicFixedSizeRingBuf) Readable() int {
	b.tex.Lock()
	defer b.tex.Unlock()
	return b.readable
}
func (b *AtomicFixedSizeRingBuf) Readable() int {
	b.tex.Lock()
	defer b.tex.Unlock()
	return b.readable
}
// Readable() returns the number of bytes available for reading.