pub unsafe extern "C" fn Hacl_Bignum64_sub(
    len: u32,
    a: *mut u64,
    b: *mut u64,
    res: *mut u64
) -> u64
Expand description

Write a - b mod 2 ^ (64 * len) in res.

This functions returns the carry.

The arguments a, b and the outparam res are meant to be len limbs in size, i.e. uint64_t[len]