Function digit_row 

pub fn digit_row(i: b6) -> b9

Row of digit i’s first entry pair within a key’s 512-row table.

Rows hold two entries each. Radix-32 digits 0..39 have 16 entries (8 rows), so digit i starts at row 8i; radix-16 digits 39..54 have 8 entries (4 rows) and start after the 312 rows of the radix-32 digits.