library UniswapV2OracleLibrary {
    using FixedPoint for *;
    // helper function that returns the current block timestamp within the range of uint32, i.e. [0, 2**32 - 1]
    function currentBlockTimestamp() internal view returns (uint32) {
        return uint32(block.timestamp % 2**32);
    }
    // produces the cumulative price using counterfactuals to save gas and avoid a call to sync.
    function currentCumulativePrices(address pair)
        internal
        view
        returns (
            uint256 ,
            uint256 ,
            uint32 
        )
    {
        uint32 blockTimestamp = currentBlockTimestamp();
        uint256 price0Cumulative = IUniswapV2Pair(pair).price0CumulativeLast();
        uint256 price1Cumulative = IUniswapV2Pair(pair).price1CumulativeLast();
        // if time has elapsed since the last update on the pair, mock the accumulated price values
        (uint112 reserve0, uint112 reserve1, uint32 blockTimestampLast) = IUniswapV2Pair(pair).getReserves();
        if (blockTimestampLast != blockTimestamp) {
            // subtraction overflow is desired
            uint32 timeElapsed = blockTimestamp - blockTimestampLast;
            // addition overflow is desired
            // counterfactual
            price0Cumulative += uint256(FixedPoint.fraction(reserve1, reserve0)._x) * timeElapsed;
            // counterfactual
            price1Cumulative += uint256(FixedPoint.fraction(reserve0, reserve1)._x) * timeElapsed;
        }
        return (price0Cumulative, price1Cumulative, blockTimestampLast);
    }
}
function currentCumulativePrices(address pair)
    internal
    view
    returns (
        uint256 ,
        uint256 ,
        uint32 
    )
{
    uint32 blockTimestamp = currentBlockTimestamp();
    uint256 price0Cumulative = IUniswapV2Pair(pair).price0CumulativeLast();
    uint256 price1Cumulative = IUniswapV2Pair(pair).price1CumulativeLast();
    // if time has elapsed since the last update on the pair, mock the accumulated price values
    (uint112 reserve0, uint112 reserve1, uint32 blockTimestampLast) = IUniswapV2Pair(pair).getReserves();
    if (blockTimestampLast != blockTimestamp) {
        // subtraction overflow is desired
        uint32 timeElapsed = blockTimestamp - blockTimestampLast;
        // addition overflow is desired
        // counterfactual
        price0Cumulative += uint256(FixedPoint.fraction(reserve1, reserve0)._x) * timeElapsed;
        // counterfactual
        price1Cumulative += uint256(FixedPoint.fraction(reserve0, reserve1)._x) * timeElapsed;
    }
    return (price0Cumulative, price1Cumulative, blockTimestampLast);
}

// produces the cumulative price using counterfactuals to save gas and avoid a call to sync.