fastLog10

assert(fastLog10(1UL) == 0);
assert(fastLog10(9UL) == 0);
assert(fastLog10(11UL) == 1);
assert(fastLog10(99UL) == 1);
// TODO: assert(fastLog10(111UL) == 2);
assert(fastLog10(999UL) == 2);
assert(fastLog10(1_111UL) == 3);
assert(fastLog10(9_999UL) == 3);
assert(fastLog10(11_111UL) == 4);
assert(fastLog10(99_999UL) == 4);
assert(fastLog10(999_999_999UL) == 8);
assert(fastLog10(1_000_000_000UL) == 9);
assert(fastLog10(10_000_000_000UL) == 10);
assert(fastLog10(100_000_000_000UL) == 11);
assert(fastLog10(1_000_000_000_000UL) == 12);
assert(fastLog10(10_000_000_000_000UL) == 13);
assert(fastLog10(100_000_000_000_000UL) == 14);
assert(fastLog10(1_000_000_000_000_000UL) == 15);
assert(fastLog10(10_000_000_000_000_000UL) == 16);
assert(fastLog10(100_000_000_000_000_000UL) == 17);
assert(fastLog10(1_000_000_000_000_000_000UL) == 18);
assert(fastLog10(10_000_000_000_000_000_000UL) == 19);