MDEX 智能合约 getAmountsIn 方法

Question

function swapETHForExactTokens(uint amountOut, address[] calldata path, address to, uint deadline)
    external
    virtual
    override
    payable
    ensure(deadline)
    returns (uint[] memory amounts)
    {
        require(path[0] == WHT, 'MdexRouter: INVALID_PATH');
        amounts = IMdexFactory(factory).getAmountsIn(amountOut, path);
        require(amounts[0] <= msg.value, 'MdexRouter: EXCESSIVE_INPUT_AMOUNT');
        IWHT(WHT).deposit{value : amounts[0]}();
        assert(IWHT(WHT).transfer(pairFor(path[0], path[1]), amounts[0]));
        _swap(amounts, path, to);
        // refund dust eth, if any
        if (msg.value > amounts[0]) TransferHelper.safeTransferETH(msg.sender, msg.value - amounts[0]);
    }

amounts = IMdexFactory(factory).getAmountsIn(amountOut, path);
这个方法的数据是从哪里返回的 能自定义吗
合约地址 https://hecoinfo.com/address/...

Answer 1

是将 uniswalV2Library 的 getAmountsIn 方法写到了 factory 中,然后通过 factory 的接口计算返回.他是根据 x * y =k 的公式演变而来的 uniswap 的写法

uint numerator = reserveIn.mul(amountOut).mul(1000);
uint denominator = reserveOut.sub(amountOut).mul(997);
amountIn = (numerator / denominator).add(1);