Function find_largest_pow10

native/thirdpart/json/json.hpp:13134–13188

! For n != 0, returns k, such that pow10 := 10^(k-1) <= n < 10^k. For n == 0, returns 1 and sets pow10 := 1. */

For n == 0, returns 1 and sets pow10 := 1.
*/
inline int find_largest_pow10(const std::uint32_t n, std::uint32_t& pow10)
{
    // LCOV_EXCL_START
    if (n >= 1000000000)
    {
        pow10 = 1000000000;
        return 10;
    }
    // LCOV_EXCL_STOP
    else if (n >= 100000000)
    {
        pow10 = 100000000;
        return  9;
    }
    else if (n >= 10000000)
    {
        pow10 = 10000000;
        return  8;
    }
    else if (n >= 1000000)
    {
        pow10 = 1000000;
        return  7;
    }
    else if (n >= 100000)
    {
        pow10 = 100000;
        return  6;
    }
    else if (n >= 10000)
    {
        pow10 = 10000;
        return  5;
    }
    else if (n >= 1000)
    {
        pow10 = 1000;
        return  4;
    }
    else if (n >= 100)
    {
        pow10 = 100;
        return  3;
    }
    else if (n >= 10)
    {
        pow10 = 10;
        return  2;
    }
    else
    {
        pow10 = 1;
        return 1;
    }
}

inline void grisu2_round(char* buf, int len, std::uint64_t dist, std::uint64_t delta,
                         std::uint64_t rest, std::uint64_t ten_k)