ok = false // Not all io.Seeker can really seek
		}
	}
	if !ok {
		return io.Copy(w, struct{ io.Reader }{sr})
	}

	var writeLastByte bool
	pos0 := sr.pos
	for sr.logicalRemaining() > 0 && !writeLastByte && err == nil {
		var nf int64 // Size of fragment
		holeStart, holeEnd := sr.sp[0].Offset, sr.sp[0].endOffset()
		if sr.pos < holeStart { // In a data fragment