Function write_coverage 

pub unsafe fn write_coverage(
    afl_cmp_area: *mut u8,
    base_idx: usize,
    a: &[u8],
    b: &[u8],
    n: usize,
)

Record coverage information for the comparison between slices a and b. The coverage information is written to the coverage bitmap pointed to by afl_cmp_area, starting at base_idx.

Note that if n > cmp::CMP_MAX_LEN coverage information is only collected on the first CMP_MAX_LEN bytes of the comparison.