> how easily this could be extended to 64 bit integers? It's effectively: size_t logx = int_log2(x); uint32_t carry = ((uint64_t)x + tablo[logx]) >> 32;

> how easily this could be extended to 64 bit integers? It's effectively: size_t logx = int_log2(x); uint32_t carry = ((uint64_t)x + tablo[logx]) >> 32; return tabhi[logx] + carry; Assembly can do (from a equivalent start): mov rdx rax # save x xor eax eax add rdx [8*rcx+tablo] # set carry (would cmp be better?) adc al [1*rcx+tabhi] # result never exceeds 64/log(10) < 20