// Offset should always be aligned to b.shardSize
		// Can never happen unless there are programmer bugs
		return 0, errUnexpected
	}
	if b.rc == nil {
		// For the first ReadAt() call we need to open the stream for reading.
		b.currOffset = offset
		streamOffset := (offset/b.shardSize)*int64(b.h.Size()) + offset
		if len(b.data) == 0 && b.tillOffset != streamOffset {