WiderMathTest.sol

pragma solidity ^0.7.0;

contract WiderMathTest {
    function fullMul(uint256 x, uint256 y)
        public
        pure
        returns (uint256 l, uint256 h)
    {
        uint256 mm = mulmod(x, y, uint256(-1));
        l = x * y;
        h = mm - l;
        if (mm < l) h -= 1;
    }
    
    function mulDiv(
        uint256 x,
        uint256 y,
        uint256 z
    ) public pure returns (uint256) {
        (uint256 l, uint256 h) = fullMul(x, y);
        require(h < z);
        uint256 mm = mulmod(x, y, z);
        if (mm > l) h -= 1;
        l -= mm;
        uint256 pow2 = z & -z;
        z /= pow2;
        l /= pow2;
        l += h * ((-pow2) / pow2 + 1);
        uint256 r = 1;
        r *= 2 - z * r;
        r *= 2 - z * r;
        r *= 2 - z * r;
        r *= 2 - z * r;
        r *= 2 - z * r;
        r *= 2 - z * r;
        r *= 2 - z * r;
        r *= 2 - z * r;
        return l * r;
    }
}