Function read_op 

pub fn read_op<R: Read>(
    reader: &mut R,
    cur_d_addr: &mut u64,
    cur_o_addr: &mut u64,
    is_interleaved: bool,
) -> Result<Op>

Reads an operation from the reader at the given position.

• reader - The reader to read from.
• cur_d_addr - The last used copy dictionary address.
• cur_o_addr - The last used copy output address.
• is_interleaved - If the format is interleaved.

If this is segregated format, the Add ops will just be initialized to all zeros in the bytes field. The caller will need to fill in the bytes later.