another faster version

[ericlagergren]

This is very so slightly faster:

var pow10tab = [16]uint32{
	1,
	10,
	100,
	1000,
	10000,
	100000,
	1000000,
	10000000,
	100000000,
	1000000000,
}

func length(x uint32) int {
        x |= 1
	r := ((bits.Len32(x) + 1) * 1233) >> 12
	if x < pow10tab[r&15] {
		return r
	}
	return r + 1
}

I'm seeing ~0.9752 ns/op instead of ~1 ns/op.

[josharian]

Thanks! I need to do a bit of benchmarking and incorporate the latest from https://commaok.xyz/post/lookup_tables/, at which point I'll include this as a contender.