Contract Source Code:

pragma solidity ^0.5.16;

import "./ComptrollerInterface.sol";
import "./CTokenInterfaces.sol";
import "./ErrorReporter.sol";
import "./Exponential.sol";
import "./EIP20Interface.sol";
import "./EIP20NonStandardInterface.sol";
import "./InterestRateModel.sol";

/**
 * @title Compound's CToken Contract
 * @notice Abstract base for CTokens
 * @author Compound
 */
contract CToken is CTokenInterface, Exponential, TokenErrorReporter {
    /**
     * @notice Initialize the money market
     * @param comptroller_ The address of the Comptroller
     * @param interestRateModel_ The address of the interest rate model
     * @param initialExchangeRateMantissa_ The initial exchange rate, scaled by 1e18
     * @param name_ EIP-20 name of this token
     * @param symbol_ EIP-20 symbol of this token
     * @param decimals_ EIP-20 decimal precision of this token
     */
    function initialize(
        ComptrollerInterface comptroller_,
        InterestRateModel interestRateModel_,
        uint256 initialExchangeRateMantissa_,
        string memory name_,
        string memory symbol_,
        uint8 decimals_
    ) public {
        require(msg.sender == admin, "admin only");
        require(accrualBlockNumber == 0 && borrowIndex == 0, "initialized");

        // Set initial exchange rate
        initialExchangeRateMantissa = initialExchangeRateMantissa_;
        require(initialExchangeRateMantissa > 0, "invalid exchange rate");

        // Set the comptroller
        uint256 err = _setComptroller(comptroller_);
        require(err == uint256(Error.NO_ERROR), "set comptroller failed");

        // Initialize block number and borrow index (block number mocks depend on comptroller being set)
        accrualBlockNumber = getBlockNumber();
        borrowIndex = mantissaOne;

        // Set the interest rate model (depends on block number / borrow index)
        err = _setInterestRateModelFresh(interestRateModel_);
        require(err == uint256(Error.NO_ERROR), "set IRM failed");

        name = name_;
        symbol = symbol_;
        decimals = decimals_;

        // The counter starts true to prevent changing it from zero to non-zero (i.e. smaller cost/refund)
        _notEntered = true;
    }

    /**
     * @notice Transfer `amount` tokens from `msg.sender` to `dst`
     * @param dst The address of the destination account
     * @param amount The number of tokens to transfer
     * @return Whether or not the transfer succeeded
     */
    function transfer(address dst, uint256 amount) external nonReentrant returns (bool) {
        return transferTokens(msg.sender, msg.sender, dst, amount) == uint256(Error.NO_ERROR);
    }

    /**
     * @notice Transfer `amount` tokens from `src` to `dst`
     * @param src The address of the source account
     * @param dst The address of the destination account
     * @param amount The number of tokens to transfer
     * @return Whether or not the transfer succeeded
     */
    function transferFrom(
        address src,
        address dst,
        uint256 amount
    ) external nonReentrant returns (bool) {
        return transferTokens(msg.sender, src, dst, amount) == uint256(Error.NO_ERROR);
    }

    /**
     * @notice Approve `spender` to transfer up to `amount` from `src`
     * @dev This will overwrite the approval amount for `spender`
     *  and is subject to issues noted [here](https://eips.ethereum.org/EIPS/eip-20#approve)
     * @param spender The address of the account which may transfer tokens
     * @param amount The number of tokens that are approved (-1 means infinite)
     * @return Whether or not the approval succeeded
     */
    function approve(address spender, uint256 amount) external returns (bool) {
        address src = msg.sender;
        transferAllowances[src][spender] = amount;
        emit Approval(src, spender, amount);
        return true;
    }

    /**
     * @notice Get the current allowance from `owner` for `spender`
     * @param owner The address of the account which owns the tokens to be spent
     * @param spender The address of the account which may transfer tokens
     * @return The number of tokens allowed to be spent (-1 means infinite)
     */
    function allowance(address owner, address spender) external view returns (uint256) {
        return transferAllowances[owner][spender];
    }

    /**
     * @notice Get the token balance of the `owner`
     * @param owner The address of the account to query
     * @return The number of tokens owned by `owner`
     */
    function balanceOf(address owner) external view returns (uint256) {
        return accountTokens[owner];
    }

    /**
     * @notice Get the underlying balance of the `owner`
     * @dev This also accrues interest in a transaction
     * @param owner The address of the account to query
     * @return The amount of underlying owned by `owner`
     */
    function balanceOfUnderlying(address owner) external returns (uint256) {
        Exp memory exchangeRate = Exp({mantissa: exchangeRateCurrent()});
        return mul_ScalarTruncate(exchangeRate, accountTokens[owner]);
    }

    /**
     * @notice Get a snapshot of the account's balances, and the cached exchange rate
     * @dev This is used by comptroller to more efficiently perform liquidity checks.
     * @param account Address of the account to snapshot
     * @return (possible error, token balance, borrow balance, exchange rate mantissa)
     */
    function getAccountSnapshot(address account)
        external
        view
        returns (
            uint256,
            uint256,
            uint256,
            uint256
        )
    {
        uint256 cTokenBalance = getCTokenBalanceInternal(account);
        uint256 borrowBalance = borrowBalanceStoredInternal(account);
        uint256 exchangeRateMantissa = exchangeRateStoredInternal();

        return (uint256(Error.NO_ERROR), cTokenBalance, borrowBalance, exchangeRateMantissa);
    }

    /**
     * @dev Function to simply retrieve block number
     *  This exists mainly for inheriting test contracts to stub this result.
     */
    function getBlockNumber() internal view returns (uint256) {
        return block.timestamp;
    }

    /**
     * @notice Returns the current per-block borrow interest rate for this cToken
     * @return The borrow interest rate per block, scaled by 1e18
     */
    function borrowRatePerBlock() external view returns (uint256) {
        return interestRateModel.getBorrowRate(getCashPrior(), totalBorrows, totalReserves);
    }

    /**
     * @notice Returns the current per-block supply interest rate for this cToken
     * @return The supply interest rate per block, scaled by 1e18
     */
    function supplyRatePerBlock() external view returns (uint256) {
        return interestRateModel.getSupplyRate(getCashPrior(), totalBorrows, totalReserves, reserveFactorMantissa);
    }

    /**
     * @notice Returns the estimated per-block borrow interest rate for this cToken after some change
     * @return The borrow interest rate per block, scaled by 1e18
     */
    function estimateBorrowRatePerBlockAfterChange(uint256 change, bool repay) external view returns (uint256) {
        uint256 cashPriorNew;
        uint256 totalBorrowsNew;

        if (repay) {
            cashPriorNew = add_(getCashPrior(), change);
            totalBorrowsNew = sub_(totalBorrows, change);
        } else {
            cashPriorNew = sub_(getCashPrior(), change);
            totalBorrowsNew = add_(totalBorrows, change);
        }
        return interestRateModel.getBorrowRate(cashPriorNew, totalBorrowsNew, totalReserves);
    }

    /**
     * @notice Returns the estimated per-block supply interest rate for this cToken after some change
     * @return The supply interest rate per block, scaled by 1e18
     */
    function estimateSupplyRatePerBlockAfterChange(uint256 change, bool repay) external view returns (uint256) {
        uint256 cashPriorNew;
        uint256 totalBorrowsNew;

        if (repay) {
            cashPriorNew = add_(getCashPrior(), change);
            totalBorrowsNew = sub_(totalBorrows, change);
        } else {
            cashPriorNew = sub_(getCashPrior(), change);
            totalBorrowsNew = add_(totalBorrows, change);
        }

        return interestRateModel.getSupplyRate(cashPriorNew, totalBorrowsNew, totalReserves, reserveFactorMantissa);
    }

    /**
     * @notice Returns the current total borrows plus accrued interest
     * @return The total borrows with interest
     */
    function totalBorrowsCurrent() external nonReentrant returns (uint256) {
        accrueInterest();
        return totalBorrows;
    }

    /**
     * @notice Accrue interest to updated borrowIndex and then calculate account's borrow balance using the updated borrowIndex
     * @param account The address whose balance should be calculated after updating borrowIndex
     * @return The calculated balance
     */
    function borrowBalanceCurrent(address account) external nonReentrant returns (uint256) {
        accrueInterest();
        return borrowBalanceStored(account);
    }

    /**
     * @notice Return the borrow balance of account based on stored data
     * @param account The address whose balance should be calculated
     * @return The calculated balance
     */
    function borrowBalanceStored(address account) public view returns (uint256) {
        return borrowBalanceStoredInternal(account);
    }

    /**
     * @notice Return the borrow balance of account based on stored data
     * @param account The address whose balance should be calculated
     * @return the calculated balance or 0 if error code is non-zero
     */
    function borrowBalanceStoredInternal(address account) internal view returns (uint256) {
        /* Get borrowBalance and borrowIndex */
        BorrowSnapshot storage borrowSnapshot = accountBorrows[account];

        /* If borrowBalance = 0 then borrowIndex is likely also 0.
         * Rather than failing the calculation with a division by 0, we immediately return 0 in this case.
         */
        if (borrowSnapshot.principal == 0) {
            return 0;
        }

        /* Calculate new borrow balance using the interest index:
         *  recentBorrowBalance = borrower.borrowBalance * market.borrowIndex / borrower.borrowIndex
         */
        uint256 principalTimesIndex = mul_(borrowSnapshot.principal, borrowIndex);
        uint256 result = div_(principalTimesIndex, borrowSnapshot.interestIndex);
        return result;
    }

    /**
     * @notice Accrue interest then return the up-to-date exchange rate
     * @return Calculated exchange rate scaled by 1e18
     */
    function exchangeRateCurrent() public nonReentrant returns (uint256) {
        accrueInterest();
        return exchangeRateStored();
    }

    /**
     * @notice Calculates the exchange rate from the underlying to the CToken
     * @dev This function does not accrue interest before calculating the exchange rate
     * @return Calculated exchange rate scaled by 1e18
     */
    function exchangeRateStored() public view returns (uint256) {
        return exchangeRateStoredInternal();
    }

    /**
     * @notice Calculates the exchange rate from the underlying to the CToken
     * @dev This function does not accrue interest before calculating the exchange rate
     * @return calculated exchange rate scaled by 1e18
     */
    function exchangeRateStoredInternal() internal view returns (uint256) {
        uint256 _totalSupply = totalSupply;
        if (_totalSupply == 0) {
            /*
             * If there are no tokens minted:
             *  exchangeRate = initialExchangeRate
             */
            return initialExchangeRateMantissa;
        } else {
            /*
             * Otherwise:
             *  exchangeRate = (totalCash + totalBorrows - totalReserves) / totalSupply
             */
            uint256 totalCash = getCashPrior();
            uint256 cashPlusBorrowsMinusReserves = sub_(add_(totalCash, totalBorrows), totalReserves);
            uint256 exchangeRate = div_(cashPlusBorrowsMinusReserves, Exp({mantissa: _totalSupply}));
            return exchangeRate;
        }
    }

    /**
     * @notice Get cash balance of this cToken in the underlying asset
     * @return The quantity of underlying asset owned by this contract
     */
    function getCash() external view returns (uint256) {
        return getCashPrior();
    }

    /**
     * @notice Applies accrued interest to total borrows and reserves
     * @dev This calculates interest accrued from the last checkpointed block
     *   up to the current block and writes new checkpoint to storage.
     */
    function accrueInterest() public returns (uint256) {
        /* Remember the initial block number */
        uint256 currentBlockNumber = getBlockNumber();
        uint256 accrualBlockNumberPrior = accrualBlockNumber;

        /* Short-circuit accumulating 0 interest */
        if (accrualBlockNumberPrior == currentBlockNumber) {
            return uint256(Error.NO_ERROR);
        }

        /* Read the previous values out of storage */
        uint256 cashPrior = getCashPrior();
        uint256 borrowsPrior = totalBorrows;
        uint256 reservesPrior = totalReserves;
        uint256 borrowIndexPrior = borrowIndex;

        /* Calculate the current borrow interest rate */
        uint256 borrowRateMantissa = interestRateModel.getBorrowRate(cashPrior, borrowsPrior, reservesPrior);
        require(borrowRateMantissa <= borrowRateMaxMantissa, "borrow rate too high");

        /* Calculate the number of blocks elapsed since the last accrual */
        uint256 blockDelta = sub_(currentBlockNumber, accrualBlockNumberPrior);

        /*
         * Calculate the interest accumulated into borrows and reserves and the new index:
         *  simpleInterestFactor = borrowRate * blockDelta
         *  interestAccumulated = simpleInterestFactor * totalBorrows
         *  totalBorrowsNew = interestAccumulated + totalBorrows
         *  totalReservesNew = interestAccumulated * reserveFactor + totalReserves
         *  borrowIndexNew = simpleInterestFactor * borrowIndex + borrowIndex
         */

        Exp memory simpleInterestFactor = mul_(Exp({mantissa: borrowRateMantissa}), blockDelta);
        uint256 interestAccumulated = mul_ScalarTruncate(simpleInterestFactor, borrowsPrior);
        uint256 totalBorrowsNew = add_(interestAccumulated, borrowsPrior);
        uint256 totalReservesNew = mul_ScalarTruncateAddUInt(
            Exp({mantissa: reserveFactorMantissa}),
            interestAccumulated,
            reservesPrior
        );
        uint256 borrowIndexNew = mul_ScalarTruncateAddUInt(simpleInterestFactor, borrowIndexPrior, borrowIndexPrior);

        /////////////////////////
        // EFFECTS & INTERACTIONS
        // (No safe failures beyond this point)

        /* We write the previously calculated values into storage */
        accrualBlockNumber = currentBlockNumber;
        borrowIndex = borrowIndexNew;
        totalBorrows = totalBorrowsNew;
        totalReserves = totalReservesNew;

        /* We emit an AccrueInterest event */
        emit AccrueInterest(cashPrior, interestAccumulated, borrowIndexNew, totalBorrowsNew);

        return uint256(Error.NO_ERROR);
    }

    /**
     * @notice Sender supplies assets into the market and receives cTokens in exchange
     * @dev Accrues interest whether or not the operation succeeds, unless reverted
     * @param mintAmount The amount of the underlying asset to supply
     * @param isNative The amount is in native or not
     * @return (uint, uint) An error code (0=success, otherwise a failure, see ErrorReporter.sol), and the actual mint amount.
     */
    function mintInternal(uint256 mintAmount, bool isNative) internal nonReentrant returns (uint256, uint256) {
        accrueInterest();
        // mintFresh emits the actual Mint event if successful and logs on errors, so we don't need to
        return mintFresh(msg.sender, mintAmount, isNative);
    }

    /**
     * @notice Sender redeems cTokens in exchange for the underlying asset
     * @dev Accrues interest whether or not the operation succeeds, unless reverted
     * @param redeemTokens The number of cTokens to redeem into underlying
     * @param isNative The amount is in native or not
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function redeemInternal(uint256 redeemTokens, bool isNative) internal nonReentrant returns (uint256) {
        accrueInterest();
        // redeemFresh emits redeem-specific logs on errors, so we don't need to
        return redeemFresh(msg.sender, redeemTokens, 0, isNative);
    }

    /**
     * @notice Sender redeems cTokens in exchange for a specified amount of underlying asset
     * @dev Accrues interest whether or not the operation succeeds, unless reverted
     * @param redeemAmount The amount of underlying to receive from redeeming cTokens
     * @param isNative The amount is in native or not
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function redeemUnderlyingInternal(uint256 redeemAmount, bool isNative) internal nonReentrant returns (uint256) {
        accrueInterest();
        // redeemFresh emits redeem-specific logs on errors, so we don't need to
        return redeemFresh(msg.sender, 0, redeemAmount, isNative);
    }

    /**
     * @notice Sender borrows assets from the protocol to their own address
     * @param borrowAmount The amount of the underlying asset to borrow
     * @param isNative The amount is in native or not
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function borrowInternal(uint256 borrowAmount, bool isNative) internal nonReentrant returns (uint256) {
        accrueInterest();
        // borrowFresh emits borrow-specific logs on errors, so we don't need to
        return borrowFresh(msg.sender, borrowAmount, isNative);
    }

    struct BorrowLocalVars {
        MathError mathErr;
        uint256 accountBorrows;
        uint256 accountBorrowsNew;
        uint256 totalBorrowsNew;
    }

    /**
     * @notice Users borrow assets from the protocol to their own address
     * @param borrowAmount The amount of the underlying asset to borrow
     * @param isNative The amount is in native or not
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function borrowFresh(
        address payable borrower,
        uint256 borrowAmount,
        bool isNative
    ) internal returns (uint256) {
        /* Fail if borrow not allowed */
        require(comptroller.borrowAllowed(address(this), borrower, borrowAmount) == 0, "rejected");

        /* Verify market's block number equals current block number */
        require(accrualBlockNumber == getBlockNumber(), "market is stale");

        /* Reverts if protocol has insufficient cash */
        require(getCashPrior() >= borrowAmount, "insufficient cash");

        BorrowLocalVars memory vars;

        /*
         * We calculate the new borrower and total borrow balances, failing on overflow:
         *  accountBorrowsNew = accountBorrows + borrowAmount
         *  totalBorrowsNew = totalBorrows + borrowAmount
         */
        vars.accountBorrows = borrowBalanceStoredInternal(borrower);
        vars.accountBorrowsNew = add_(vars.accountBorrows, borrowAmount);
        vars.totalBorrowsNew = add_(totalBorrows, borrowAmount);

        /////////////////////////
        // EFFECTS & INTERACTIONS
        // (No safe failures beyond this point)

        /* We write the previously calculated values into storage */
        accountBorrows[borrower].principal = vars.accountBorrowsNew;
        accountBorrows[borrower].interestIndex = borrowIndex;
        totalBorrows = vars.totalBorrowsNew;

        /*
         * We invoke doTransferOut for the borrower and the borrowAmount.
         *  Note: The cToken must handle variations between ERC-20 and ETH underlying.
         *  On success, the cToken borrowAmount less of cash.
         *  doTransferOut reverts if anything goes wrong, since we can't be sure if side effects occurred.
         */
        doTransferOut(borrower, borrowAmount, isNative);

        /* We emit a Borrow event */
        emit Borrow(borrower, borrowAmount, vars.accountBorrowsNew, vars.totalBorrowsNew);

        /* We call the defense hook */
        comptroller.borrowVerify(address(this), borrower, borrowAmount);

        return uint256(Error.NO_ERROR);
    }

    /**
     * @notice Sender repays their own borrow
     * @param repayAmount The amount to repay
     * @param isNative The amount is in native or not
     * @return (uint, uint) An error code (0=success, otherwise a failure, see ErrorReporter.sol), and the actual repayment amount.
     */
    function repayBorrowInternal(uint256 repayAmount, bool isNative) internal nonReentrant returns (uint256, uint256) {
        accrueInterest();
        // repayBorrowFresh emits repay-borrow-specific logs on errors, so we don't need to
        return repayBorrowFresh(msg.sender, msg.sender, repayAmount, isNative);
    }

    /**
     * @notice Sender repays a borrow belonging to borrower
     * @param borrower the account with the debt being payed off
     * @param repayAmount The amount to repay
     * @param isNative The amount is in native or not
     * @return (uint, uint) An error code (0=success, otherwise a failure, see ErrorReporter.sol), and the actual repayment amount.
     */
    function repayBorrowBehalfInternal(
        address borrower,
        uint256 repayAmount,
        bool isNative
    ) internal nonReentrant returns (uint256, uint256) {
        accrueInterest();
        // repayBorrowFresh emits repay-borrow-specific logs on errors, so we don't need to
        return repayBorrowFresh(msg.sender, borrower, repayAmount, isNative);
    }

    struct RepayBorrowLocalVars {
        Error err;
        MathError mathErr;
        uint256 repayAmount;
        uint256 borrowerIndex;
        uint256 accountBorrows;
        uint256 accountBorrowsNew;
        uint256 totalBorrowsNew;
        uint256 actualRepayAmount;
    }

    /**
     * @notice Borrows are repaid by another user (possibly the borrower).
     * @param payer the account paying off the borrow
     * @param borrower the account with the debt being payed off
     * @param repayAmount the amount of underlying tokens being returned
     * @param isNative The amount is in native or not
     * @return (uint, uint) An error code (0=success, otherwise a failure, see ErrorReporter.sol), and the actual repayment amount.
     */
    function repayBorrowFresh(
        address payer,
        address borrower,
        uint256 repayAmount,
        bool isNative
    ) internal returns (uint256, uint256) {
        /* Fail if repayBorrow not allowed */
        require(comptroller.repayBorrowAllowed(address(this), payer, borrower, repayAmount) == 0, "rejected");

        /* Verify market's block number equals current block number */
        require(accrualBlockNumber == getBlockNumber(), "market is stale");

        RepayBorrowLocalVars memory vars;

        /* We remember the original borrowerIndex for verification purposes */
        vars.borrowerIndex = accountBorrows[borrower].interestIndex;

        /* We fetch the amount the borrower owes, with accumulated interest */
        vars.accountBorrows = borrowBalanceStoredInternal(borrower);

        /* If repayAmount == -1, repayAmount = accountBorrows */
        if (repayAmount == uint256(-1)) {
            vars.repayAmount = vars.accountBorrows;
        } else {
            vars.repayAmount = repayAmount;
        }

        /////////////////////////
        // EFFECTS & INTERACTIONS
        // (No safe failures beyond this point)

        /*
         * We call doTransferIn for the payer and the repayAmount
         *  Note: The cToken must handle variations between ERC-20 and ETH underlying.
         *  On success, the cToken holds an additional repayAmount of cash.
         *  doTransferIn reverts if anything goes wrong, since we can't be sure if side effects occurred.
         *   it returns the amount actually transferred, in case of a fee.
         */
        vars.actualRepayAmount = doTransferIn(payer, vars.repayAmount, isNative);

        /*
         * We calculate the new borrower and total borrow balances, failing on underflow:
         *  accountBorrowsNew = accountBorrows - actualRepayAmount
         *  totalBorrowsNew = totalBorrows - actualRepayAmount
         */
        vars.accountBorrowsNew = sub_(vars.accountBorrows, vars.actualRepayAmount);
        vars.totalBorrowsNew = sub_(totalBorrows, vars.actualRepayAmount);

        /* We write the previously calculated values into storage */
        accountBorrows[borrower].principal = vars.accountBorrowsNew;
        accountBorrows[borrower].interestIndex = borrowIndex;
        totalBorrows = vars.totalBorrowsNew;

        /* We emit a RepayBorrow event */
        emit RepayBorrow(payer, borrower, vars.actualRepayAmount, vars.accountBorrowsNew, vars.totalBorrowsNew);

        /* We call the defense hook */
        comptroller.repayBorrowVerify(address(this), payer, borrower, vars.actualRepayAmount, vars.borrowerIndex);

        return (uint256(Error.NO_ERROR), vars.actualRepayAmount);
    }

    /**
     * @notice The sender liquidates the borrowers collateral.
     *  The collateral seized is transferred to the liquidator.
     * @param borrower The borrower of this cToken to be liquidated
     * @param repayAmount The amount of the underlying borrowed asset to repay
     * @param cTokenCollateral The market in which to seize collateral from the borrower
     * @param isNative The amount is in native or not
     * @return (uint, uint) An error code (0=success, otherwise a failure, see ErrorReporter.sol), and the actual repayment amount.
     */
    function liquidateBorrowInternal(
        address borrower,
        uint256 repayAmount,
        CTokenInterface cTokenCollateral,
        bool isNative
    ) internal nonReentrant returns (uint256, uint256) {
        accrueInterest();
        require(cTokenCollateral.accrueInterest() == uint256(Error.NO_ERROR), "accrue interest failed");

        // liquidateBorrowFresh emits borrow-specific logs on errors, so we don't need to
        return liquidateBorrowFresh(msg.sender, borrower, repayAmount, cTokenCollateral, isNative);
    }

    struct LiquidateBorrowLocalVars {
        uint256 repayBorrowError;
        uint256 actualRepayAmount;
        uint256 amountSeizeError;
        uint256 seizeTokens;
    }

    /**
     * @notice The liquidator liquidates the borrowers collateral.
     *  The collateral seized is transferred to the liquidator.
     * @param borrower The borrower of this cToken to be liquidated
     * @param liquidator The address repaying the borrow and seizing collateral
     * @param cTokenCollateral The market in which to seize collateral from the borrower
     * @param repayAmount The amount of the underlying borrowed asset to repay
     * @param isNative The amount is in native or not
     * @return (uint, uint) An error code (0=success, otherwise a failure, see ErrorReporter.sol), and the actual repayment amount.
     */
    function liquidateBorrowFresh(
        address liquidator,
        address borrower,
        uint256 repayAmount,
        CTokenInterface cTokenCollateral,
        bool isNative
    ) internal returns (uint256, uint256) {
        /* Fail if liquidate not allowed */
        require(
            comptroller.liquidateBorrowAllowed(
                address(this),
                address(cTokenCollateral),
                liquidator,
                borrower,
                repayAmount
            ) == 0,
            "rejected"
        );

        /* Verify market's block number equals current block number */
        require(accrualBlockNumber == getBlockNumber(), "market is stale");

        /* Verify cTokenCollateral market's block number equals current block number */
        require(cTokenCollateral.accrualBlockNumber() == getBlockNumber(), "market is stale");

        /* Fail if borrower = liquidator */
        require(borrower != liquidator, "invalid account pair");

        /* Fail if repayAmount = 0 or repayAmount = -1 */
        require(repayAmount > 0 && repayAmount != uint256(-1), "invalid amount");

        LiquidateBorrowLocalVars memory vars;

        /* Fail if repayBorrow fails */
        (vars.repayBorrowError, vars.actualRepayAmount) = repayBorrowFresh(liquidator, borrower, repayAmount, isNative);
        require(vars.repayBorrowError == uint256(Error.NO_ERROR), "repay borrow failed");

        /////////////////////////
        // EFFECTS & INTERACTIONS
        // (No safe failures beyond this point)

        /* We calculate the number of collateral tokens that will be seized */
        (vars.amountSeizeError, vars.seizeTokens) = comptroller.liquidateCalculateSeizeTokens(
            address(this),
            address(cTokenCollateral),
            vars.actualRepayAmount
        );
        require(vars.amountSeizeError == uint256(Error.NO_ERROR), "calculate seize amount failed");

        /* Revert if borrower collateral token balance < seizeTokens */
        require(cTokenCollateral.balanceOf(borrower) >= vars.seizeTokens, "seize too much");

        // If this is also the collateral, run seizeInternal to avoid re-entrancy, otherwise make an external call
        uint256 seizeError;
        if (address(cTokenCollateral) == address(this)) {
            seizeError = seizeInternal(address(this), liquidator, borrower, vars.seizeTokens);
        } else {
            seizeError = cTokenCollateral.seize(liquidator, borrower, vars.seizeTokens);
        }

        /* Revert if seize tokens fails (since we cannot be sure of side effects) */
        require(seizeError == uint256(Error.NO_ERROR), "token seizure failed");

        /* We emit a LiquidateBorrow event */
        emit LiquidateBorrow(liquidator, borrower, vars.actualRepayAmount, address(cTokenCollateral), vars.seizeTokens);

        /* We call the defense hook */
        comptroller.liquidateBorrowVerify(
            address(this),
            address(cTokenCollateral),
            liquidator,
            borrower,
            vars.actualRepayAmount,
            vars.seizeTokens
        );

        return (uint256(Error.NO_ERROR), vars.actualRepayAmount);
    }

    /**
     * @notice Transfers collateral tokens (this market) to the liquidator.
     * @dev Will fail unless called by another cToken during the process of liquidation.
     *  Its absolutely critical to use msg.sender as the borrowed cToken and not a parameter.
     * @param liquidator The account receiving seized collateral
     * @param borrower The account having collateral seized
     * @param seizeTokens The number of cTokens to seize
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function seize(
        address liquidator,
        address borrower,
        uint256 seizeTokens
    ) external nonReentrant returns (uint256) {
        return seizeInternal(msg.sender, liquidator, borrower, seizeTokens);
    }

    /*** Admin Functions ***/

    /**
     * @notice Begins transfer of admin rights. The newPendingAdmin must call `_acceptAdmin` to finalize the transfer.
     * @dev Admin function to begin change of admin. The newPendingAdmin must call `_acceptAdmin` to finalize the transfer.
     * @param newPendingAdmin New pending admin.
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function _setPendingAdmin(address payable newPendingAdmin) external returns (uint256) {
        // Check caller = admin
        if (msg.sender != admin) {
            return fail(Error.UNAUTHORIZED, FailureInfo.SET_PENDING_ADMIN_OWNER_CHECK);
        }

        // Save current value, if any, for inclusion in log
        address oldPendingAdmin = pendingAdmin;

        // Store pendingAdmin with value newPendingAdmin
        pendingAdmin = newPendingAdmin;

        // Emit NewPendingAdmin(oldPendingAdmin, newPendingAdmin)
        emit NewPendingAdmin(oldPendingAdmin, newPendingAdmin);

        return uint256(Error.NO_ERROR);
    }

    /**
     * @notice Accepts transfer of admin rights. msg.sender must be pendingAdmin
     * @dev Admin function for pending admin to accept role and update admin
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function _acceptAdmin() external returns (uint256) {
        // Check caller is pendingAdmin and pendingAdmin ≠ address(0)
        if (msg.sender != pendingAdmin || msg.sender == address(0)) {
            return fail(Error.UNAUTHORIZED, FailureInfo.ACCEPT_ADMIN_PENDING_ADMIN_CHECK);
        }

        // Save current values for inclusion in log
        address oldAdmin = admin;
        address oldPendingAdmin = pendingAdmin;

        // Store admin with value pendingAdmin
        admin = pendingAdmin;

        // Clear the pending value
        pendingAdmin = address(0);

        emit NewAdmin(oldAdmin, admin);
        emit NewPendingAdmin(oldPendingAdmin, pendingAdmin);

        return uint256(Error.NO_ERROR);
    }

    /**
     * @notice Sets a new comptroller for the market
     * @dev Admin function to set a new comptroller
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function _setComptroller(ComptrollerInterface newComptroller) public returns (uint256) {
        // Check caller is admin
        if (msg.sender != admin) {
            return fail(Error.UNAUTHORIZED, FailureInfo.SET_COMPTROLLER_OWNER_CHECK);
        }

        ComptrollerInterface oldComptroller = comptroller;
        // Ensure invoke comptroller.isComptroller() returns true
        require(newComptroller.isComptroller(), "not comptroller");

        // Set market's comptroller to newComptroller
        comptroller = newComptroller;

        // Emit NewComptroller(oldComptroller, newComptroller)
        emit NewComptroller(oldComptroller, newComptroller);

        return uint256(Error.NO_ERROR);
    }

    /**
     * @notice accrues interest and sets a new reserve factor for the protocol using _setReserveFactorFresh
     * @dev Admin function to accrue interest and set a new reserve factor
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function _setReserveFactor(uint256 newReserveFactorMantissa) external nonReentrant returns (uint256) {
        accrueInterest();
        // _setReserveFactorFresh emits reserve-factor-specific logs on errors, so we don't need to.
        return _setReserveFactorFresh(newReserveFactorMantissa);
    }

    /**
     * @notice Sets a new reserve factor for the protocol (*requires fresh interest accrual)
     * @dev Admin function to set a new reserve factor
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function _setReserveFactorFresh(uint256 newReserveFactorMantissa) internal returns (uint256) {
        // Check caller is admin
        if (msg.sender != admin) {
            return fail(Error.UNAUTHORIZED, FailureInfo.SET_RESERVE_FACTOR_ADMIN_CHECK);
        }

        // Verify market's block number equals current block number
        if (accrualBlockNumber != getBlockNumber()) {
            return fail(Error.MARKET_NOT_FRESH, FailureInfo.SET_RESERVE_FACTOR_FRESH_CHECK);
        }

        // Check newReserveFactor ≤ maxReserveFactor
        if (newReserveFactorMantissa > reserveFactorMaxMantissa) {
            return fail(Error.BAD_INPUT, FailureInfo.SET_RESERVE_FACTOR_BOUNDS_CHECK);
        }

        uint256 oldReserveFactorMantissa = reserveFactorMantissa;
        reserveFactorMantissa = newReserveFactorMantissa;

        emit NewReserveFactor(oldReserveFactorMantissa, newReserveFactorMantissa);

        return uint256(Error.NO_ERROR);
    }

    /**
     * @notice Accrues interest and reduces reserves by transferring from msg.sender
     * @param addAmount Amount of addition to reserves
     * @param isNative The amount is in native or not
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function _addReservesInternal(uint256 addAmount, bool isNative) internal nonReentrant returns (uint256) {
        accrueInterest();
        // _addReservesFresh emits reserve-addition-specific logs on errors, so we don't need to.
        (uint256 error, ) = _addReservesFresh(addAmount, isNative);
        return error;
    }

    /**
     * @notice Add reserves by transferring from caller
     * @dev Requires fresh interest accrual
     * @param addAmount Amount of addition to reserves
     * @param isNative The amount is in native or not
     * @return (uint, uint) An error code (0=success, otherwise a failure (see ErrorReporter.sol for details)) and the actual amount added, net token fees
     */
    function _addReservesFresh(uint256 addAmount, bool isNative) internal returns (uint256, uint256) {
        // totalReserves + actualAddAmount
        uint256 totalReservesNew;
        uint256 actualAddAmount;

        // We fail gracefully unless market's block number equals current block number
        if (accrualBlockNumber != getBlockNumber()) {
            return (fail(Error.MARKET_NOT_FRESH, FailureInfo.ADD_RESERVES_FRESH_CHECK), actualAddAmount);
        }

        /////////////////////////
        // EFFECTS & INTERACTIONS
        // (No safe failures beyond this point)

        /*
         * We call doTransferIn for the caller and the addAmount
         *  Note: The cToken must handle variations between ERC-20 and ETH underlying.
         *  On success, the cToken holds an additional addAmount of cash.
         *  doTransferIn reverts if anything goes wrong, since we can't be sure if side effects occurred.
         *  it returns the amount actually transferred, in case of a fee.
         */

        actualAddAmount = doTransferIn(msg.sender, addAmount, isNative);

        totalReservesNew = add_(totalReserves, actualAddAmount);

        // Store reserves[n+1] = reserves[n] + actualAddAmount
        totalReserves = totalReservesNew;

        /* Emit NewReserves(admin, actualAddAmount, reserves[n+1]) */
        emit ReservesAdded(msg.sender, actualAddAmount, totalReservesNew);

        /* Return (NO_ERROR, actualAddAmount) */
        return (uint256(Error.NO_ERROR), actualAddAmount);
    }

    /**
     * @notice Accrues interest and reduces reserves by transferring to admin
     * @param reduceAmount Amount of reduction to reserves
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function _reduceReserves(uint256 reduceAmount) external nonReentrant returns (uint256) {
        accrueInterest();
        // _reduceReservesFresh emits reserve-reduction-specific logs on errors, so we don't need to.
        return _reduceReservesFresh(reduceAmount);
    }

    /**
     * @notice Reduces reserves by transferring to admin
     * @dev Requires fresh interest accrual
     * @param reduceAmount Amount of reduction to reserves
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function _reduceReservesFresh(uint256 reduceAmount) internal returns (uint256) {
        // totalReserves - reduceAmount
        uint256 totalReservesNew;

        // Check caller is admin
        if (msg.sender != admin) {
            return fail(Error.UNAUTHORIZED, FailureInfo.REDUCE_RESERVES_ADMIN_CHECK);
        }

        // We fail gracefully unless market's block number equals current block number
        if (accrualBlockNumber != getBlockNumber()) {
            return fail(Error.MARKET_NOT_FRESH, FailureInfo.REDUCE_RESERVES_FRESH_CHECK);
        }

        // Fail gracefully if protocol has insufficient underlying cash
        if (getCashPrior() < reduceAmount) {
            return fail(Error.TOKEN_INSUFFICIENT_CASH, FailureInfo.REDUCE_RESERVES_CASH_NOT_AVAILABLE);
        }

        // Check reduceAmount ≤ reserves[n] (totalReserves)
        if (reduceAmount > totalReserves) {
            return fail(Error.BAD_INPUT, FailureInfo.REDUCE_RESERVES_VALIDATION);
        }

        /////////////////////////
        // EFFECTS & INTERACTIONS
        // (No safe failures beyond this point)

        totalReservesNew = sub_(totalReserves, reduceAmount);

        // Store reserves[n+1] = reserves[n] - reduceAmount
        totalReserves = totalReservesNew;

        // doTransferOut reverts if anything goes wrong, since we can't be sure if side effects occurred.
        // Restrict reducing reserves in wrapped token. Implementations except `CWrappedNative` won't use parameter `isNative`.
        doTransferOut(admin, reduceAmount, false);

        emit ReservesReduced(admin, reduceAmount, totalReservesNew);

        return uint256(Error.NO_ERROR);
    }

    /**
     * @notice accrues interest and updates the interest rate model using _setInterestRateModelFresh
     * @dev Admin function to accrue interest and update the interest rate model
     * @param newInterestRateModel the new interest rate model to use
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function _setInterestRateModel(InterestRateModel newInterestRateModel) public returns (uint256) {
        accrueInterest();
        // _setInterestRateModelFresh emits interest-rate-model-update-specific logs on errors, so we don't need to.
        return _setInterestRateModelFresh(newInterestRateModel);
    }

    /**
     * @notice updates the interest rate model (*requires fresh interest accrual)
     * @dev Admin function to update the interest rate model
     * @param newInterestRateModel the new interest rate model to use
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function _setInterestRateModelFresh(InterestRateModel newInterestRateModel) internal returns (uint256) {
        // Used to store old model for use in the event that is emitted on success
        InterestRateModel oldInterestRateModel;

        // Check caller is admin
        if (msg.sender != admin) {
            return fail(Error.UNAUTHORIZED, FailureInfo.SET_INTEREST_RATE_MODEL_OWNER_CHECK);
        }

        // We fail gracefully unless market's block number equals current block number
        if (accrualBlockNumber != getBlockNumber()) {
            return fail(Error.MARKET_NOT_FRESH, FailureInfo.SET_INTEREST_RATE_MODEL_FRESH_CHECK);
        }

        // Track the market's current interest rate model
        oldInterestRateModel = interestRateModel;

        // Ensure invoke newInterestRateModel.isInterestRateModel() returns true
        require(newInterestRateModel.isInterestRateModel(), "invalid IRM");

        // Set the interest rate model to newInterestRateModel
        interestRateModel = newInterestRateModel;

        // Emit NewMarketInterestRateModel(oldInterestRateModel, newInterestRateModel)
        emit NewMarketInterestRateModel(oldInterestRateModel, newInterestRateModel);

        return uint256(Error.NO_ERROR);
    }

    /*** Safe Token ***/

    /**
     * @notice Gets balance of this contract in terms of the underlying
     * @dev This excludes the value of the current message, if any
     * @return The quantity of underlying owned by this contract
     */
    function getCashPrior() internal view returns (uint256);

    /**
     * @dev Performs a transfer in, reverting upon failure. Returns the amount actually transferred to the protocol, in case of a fee.
     *  This may revert due to insufficient balance or insufficient allowance.
     */
    function doTransferIn(
        address from,
        uint256 amount,
        bool isNative
    ) internal returns (uint256);

    /**
     * @dev Performs a transfer out, ideally returning an explanatory error code upon failure rather than reverting.
     *  If caller has not called checked protocol's balance, may revert due to insufficient cash held in the contract.
     *  If caller has checked protocol's balance, and verified it is >= amount, this should not revert in normal conditions.
     */
    function doTransferOut(
        address payable to,
        uint256 amount,
        bool isNative
    ) internal;

    /**
     * @notice Transfer `tokens` tokens from `src` to `dst` by `spender`
     * @dev Called by both `transfer` and `transferFrom` internally
     */
    function transferTokens(
        address spender,
        address src,
        address dst,
        uint256 tokens
    ) internal returns (uint256);

    /**
     * @notice Get the account's cToken balances
     */
    function getCTokenBalanceInternal(address account) internal view returns (uint256);

    /**
     * @notice User supplies assets into the market and receives cTokens in exchange
     * @dev Assumes interest has already been accrued up to the current block
     */
    function mintFresh(
        address minter,
        uint256 mintAmount,
        bool isNative
    ) internal returns (uint256, uint256);

    /**
     * @notice User redeems cTokens in exchange for the underlying asset
     * @dev Assumes interest has already been accrued up to the current block
     */
    function redeemFresh(
        address payable redeemer,
        uint256 redeemTokensIn,
        uint256 redeemAmountIn,
        bool isNative
    ) internal returns (uint256);

    /**
     * @notice Transfers collateral tokens (this market) to the liquidator.
     * @dev Called only during an in-kind liquidation, or by liquidateBorrow during the liquidation of another CToken.
     *  Its absolutely critical to use msg.sender as the seizer cToken and not a parameter.
     */
    function seizeInternal(
        address seizerToken,
        address liquidator,
        address borrower,
        uint256 seizeTokens
    ) internal returns (uint256);

    /*** Reentrancy Guard ***/

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     */
    modifier nonReentrant() {
        require(_notEntered, "re-entered");
        _notEntered = false;
        _;
        _notEntered = true; // get a gas-refund post-Istanbul
    }
}

pragma solidity ^0.5.16;

import "./ComptrollerInterface.sol";
import "./InterestRateModel.sol";
import "./ERC3156FlashBorrowerInterface.sol";

contract CTokenStorage {
    /**
     * @dev Guard variable for re-entrancy checks
     */
    bool internal _notEntered;

    /**
     * @notice EIP-20 token name for this token
     */
    string public name;

    /**
     * @notice EIP-20 token symbol for this token
     */
    string public symbol;

    /**
     * @notice EIP-20 token decimals for this token
     */
    uint8 public decimals;

    /**
     * @notice Maximum borrow rate that can ever be applied (.0005% / block)
     */

    uint256 internal constant borrowRateMaxMantissa = 0.0005e16;

    /**
     * @notice Maximum fraction of interest that can be set aside for reserves
     */
    uint256 internal constant reserveFactorMaxMantissa = 1e18;

    /**
     * @notice Administrator for this contract
     */
    address payable public admin;

    /**
     * @notice Pending administrator for this contract
     */
    address payable public pendingAdmin;

    /**
     * @notice Contract which oversees inter-cToken operations
     */
    ComptrollerInterface public comptroller;

    /**
     * @notice Model which tells what the current interest rate should be
     */
    InterestRateModel public interestRateModel;

    /**
     * @notice Initial exchange rate used when minting the first CTokens (used when totalSupply = 0)
     */
    uint256 internal initialExchangeRateMantissa;

    /**
     * @notice Fraction of interest currently set aside for reserves
     */
    uint256 public reserveFactorMantissa;

    /**
     * @notice Block number that interest was last accrued at
     */
    uint256 public accrualBlockNumber;

    /**
     * @notice Accumulator of the total earned interest rate since the opening of the market
     */
    uint256 public borrowIndex;

    /**
     * @notice Total amount of outstanding borrows of the underlying in this market
     */
    uint256 public totalBorrows;

    /**
     * @notice Total amount of reserves of the underlying held in this market
     */
    uint256 public totalReserves;

    /**
     * @notice Total number of tokens in circulation
     */
    uint256 public totalSupply;

    /**
     * @notice Official record of token balances for each account
     */
    mapping(address => uint256) internal accountTokens;

    /**
     * @notice Approved token transfer amounts on behalf of others
     */
    mapping(address => mapping(address => uint256)) internal transferAllowances;

    /**
     * @notice Container for borrow balance information
     * @member principal Total balance (with accrued interest), after applying the most recent balance-changing action
     * @member interestIndex Global borrowIndex as of the most recent balance-changing action
     */
    struct BorrowSnapshot {
        uint256 principal;
        uint256 interestIndex;
    }

    /**
     * @notice Mapping of account addresses to outstanding borrow balances
     */
    mapping(address => BorrowSnapshot) internal accountBorrows;
}

contract CErc20Storage {
    /**
     * @notice Underlying asset for this CToken
     */
    address public underlying;

    /**
     * @notice Implementation address for this contract
     */
    address public implementation;
}

contract CSupplyCapStorage {
    /**
     * @notice Internal cash counter for this CToken. Should equal underlying.balanceOf(address(this)) for CERC20.
     */
    uint256 public internalCash;
}

contract CCollateralCapStorage {
    /**
     * @notice Total number of tokens used as collateral in circulation.
     */
    uint256 public totalCollateralTokens;

    /**
     * @notice Record of token balances which could be treated as collateral for each account.
     *         If collateral cap is not set, the value should be equal to accountTokens.
     */
    mapping(address => uint256) public accountCollateralTokens;

    /**
     * @notice Check if accountCollateralTokens have been initialized.
     */
    mapping(address => bool) public isCollateralTokenInit;

    /**
     * @notice Collateral cap for this CToken, zero for no cap.
     */
    uint256 public collateralCap;
}

/*** Interface ***/

contract CTokenInterface is CTokenStorage {
    /**
     * @notice Indicator that this is a CToken contract (for inspection)
     */
    bool public constant isCToken = true;

    /*** Market Events ***/

    /**
     * @notice Event emitted when interest is accrued
     */
    event AccrueInterest(uint256 cashPrior, uint256 interestAccumulated, uint256 borrowIndex, uint256 totalBorrows);

    /**
     * @notice Event emitted when tokens are minted
     */
    event Mint(address minter, uint256 mintAmount, uint256 mintTokens);

    /**
     * @notice Event emitted when tokens are redeemed
     */
    event Redeem(address redeemer, uint256 redeemAmount, uint256 redeemTokens);

    /**
     * @notice Event emitted when underlying is borrowed
     */
    event Borrow(address borrower, uint256 borrowAmount, uint256 accountBorrows, uint256 totalBorrows);

    /**
     * @notice Event emitted when a borrow is repaid
     */
    event RepayBorrow(
        address payer,
        address borrower,
        uint256 repayAmount,
        uint256 accountBorrows,
        uint256 totalBorrows
    );

    /**
     * @notice Event emitted when a borrow is liquidated
     */
    event LiquidateBorrow(
        address liquidator,
        address borrower,
        uint256 repayAmount,
        address cTokenCollateral,
        uint256 seizeTokens
    );

    /*** Admin Events ***/

    /**
     * @notice Event emitted when pendingAdmin is changed
     */
    event NewPendingAdmin(address oldPendingAdmin, address newPendingAdmin);

    /**
     * @notice Event emitted when pendingAdmin is accepted, which means admin is updated
     */
    event NewAdmin(address oldAdmin, address newAdmin);

    /**
     * @notice Event emitted when comptroller is changed
     */
    event NewComptroller(ComptrollerInterface oldComptroller, ComptrollerInterface newComptroller);

    /**
     * @notice Event emitted when interestRateModel is changed
     */
    event NewMarketInterestRateModel(InterestRateModel oldInterestRateModel, InterestRateModel newInterestRateModel);

    /**
     * @notice Event emitted when the reserve factor is changed
     */
    event NewReserveFactor(uint256 oldReserveFactorMantissa, uint256 newReserveFactorMantissa);

    /**
     * @notice Event emitted when the reserves are added
     */
    event ReservesAdded(address benefactor, uint256 addAmount, uint256 newTotalReserves);

    /**
     * @notice Event emitted when the reserves are reduced
     */
    event ReservesReduced(address admin, uint256 reduceAmount, uint256 newTotalReserves);

    /**
     * @notice EIP20 Transfer event
     */
    event Transfer(address indexed from, address indexed to, uint256 amount);

    /**
     * @notice EIP20 Approval event
     */
    event Approval(address indexed owner, address indexed spender, uint256 amount);

    /**
     * @notice Failure event
     */
    event Failure(uint256 error, uint256 info, uint256 detail);

    /*** User Interface ***/

    function transfer(address dst, uint256 amount) external returns (bool);

    function transferFrom(
        address src,
        address dst,
        uint256 amount
    ) external returns (bool);

    function approve(address spender, uint256 amount) external returns (bool);

    function allowance(address owner, address spender) external view returns (uint256);

    function balanceOf(address owner) external view returns (uint256);

    function balanceOfUnderlying(address owner) external returns (uint256);

    function getAccountSnapshot(address account)
        external
        view
        returns (
            uint256,
            uint256,
            uint256,
            uint256
        );

    function borrowRatePerBlock() external view returns (uint256);

    function supplyRatePerBlock() external view returns (uint256);

    function totalBorrowsCurrent() external returns (uint256);

    function borrowBalanceCurrent(address account) external returns (uint256);

    function borrowBalanceStored(address account) public view returns (uint256);

    function exchangeRateCurrent() public returns (uint256);

    function exchangeRateStored() public view returns (uint256);

    function getCash() external view returns (uint256);

    function accrueInterest() public returns (uint256);

    function seize(
        address liquidator,
        address borrower,
        uint256 seizeTokens
    ) external returns (uint256);

    /*** Admin Functions ***/

    function _setPendingAdmin(address payable newPendingAdmin) external returns (uint256);

    function _acceptAdmin() external returns (uint256);

    function _setComptroller(ComptrollerInterface newComptroller) public returns (uint256);

    function _setReserveFactor(uint256 newReserveFactorMantissa) external returns (uint256);

    function _reduceReserves(uint256 reduceAmount) external returns (uint256);

    function _setInterestRateModel(InterestRateModel newInterestRateModel) public returns (uint256);
}

contract CErc20Interface is CErc20Storage {
    /*** User Interface ***/

    function mint(uint256 mintAmount) external returns (uint256);

    function redeem(uint256 redeemTokens) external returns (uint256);

    function redeemUnderlying(uint256 redeemAmount) external returns (uint256);

    function borrow(uint256 borrowAmount) external returns (uint256);

    function repayBorrow(uint256 repayAmount) external returns (uint256);

    function repayBorrowBehalf(address borrower, uint256 repayAmount) external returns (uint256);

    function liquidateBorrow(
        address borrower,
        uint256 repayAmount,
        CTokenInterface cTokenCollateral
    ) external returns (uint256);

    function _addReserves(uint256 addAmount) external returns (uint256);
}

contract CCapableErc20Interface is CErc20Interface, CSupplyCapStorage {
    /**
     * @notice Flash loan fee ratio
     */
    uint256 public constant flashFeeBips = 9;

    /*** Market Events ***/

    /**
     * @notice Event emitted when a flashloan occurred
     */
    event Flashloan(address indexed receiver, uint256 amount, uint256 totalFee, uint256 reservesFee);

    /*** User Interface ***/

    function gulp() external;
}

contract CWrappedNativeInterface is CCapableErc20Interface {
    /*** User Interface ***/

    function mintNative() external payable returns (uint256);

    function redeemNative(uint256 redeemTokens) external returns (uint256);

    function redeemUnderlyingNative(uint256 redeemAmount) external returns (uint256);

    function borrowNative(uint256 borrowAmount) external returns (uint256);

    function repayBorrowNative() external payable returns (uint256);

    function repayBorrowBehalfNative(address borrower) external payable returns (uint256);

    function liquidateBorrowNative(address borrower, CTokenInterface cTokenCollateral)
        external
        payable
        returns (uint256);

    function flashLoan(
        ERC3156FlashBorrowerInterface receiver,
        address initiator,
        uint256 amount,
        bytes calldata data
    ) external returns (bool);

    function _addReservesNative() external payable returns (uint256);

    function collateralCap() external view returns (uint256);

    function totalCollateralTokens() external view returns (uint256);
}

contract CCollateralCapErc20Interface is CCapableErc20Interface, CCollateralCapStorage {
    /*** Admin Events ***/

    /**
     * @notice Event emitted when collateral cap is set
     */
    event NewCollateralCap(address token, uint256 newCap);

    /**
     * @notice Event emitted when user collateral is changed
     */
    event UserCollateralChanged(address account, uint256 newCollateralTokens);

    /*** User Interface ***/

    function registerCollateral(address account) external returns (uint256);

    function unregisterCollateral(address account) external;

    function flashLoan(
        ERC3156FlashBorrowerInterface receiver,
        address initiator,
        uint256 amount,
        bytes calldata data
    ) external returns (bool);

    /*** Admin Functions ***/

    function _setCollateralCap(uint256 newCollateralCap) external;
}

contract CDelegatorInterface {
    /**
     * @notice Emitted when implementation is changed
     */
    event NewImplementation(address oldImplementation, address newImplementation);

    /**
     * @notice Called by the admin to update the implementation of the delegator
     * @param implementation_ The address of the new implementation for delegation
     * @param allowResign Flag to indicate whether to call _resignImplementation on the old implementation
     * @param becomeImplementationData The encoded bytes data to be passed to _becomeImplementation
     */
    function _setImplementation(
        address implementation_,
        bool allowResign,
        bytes memory becomeImplementationData
    ) public;
}

contract CDelegateInterface {
    /**
     * @notice Called by the delegator on a delegate to initialize it for duty
     * @dev Should revert if any issues arise which make it unfit for delegation
     * @param data The encoded bytes data for any initialization
     */
    function _becomeImplementation(bytes memory data) public;

    /**
     * @notice Called by the delegator on a delegate to forfeit its responsibility
     */
    function _resignImplementation() public;
}

/*** External interface ***/

/**
 * @title Flash loan receiver interface
 */
interface IFlashloanReceiver {
    function executeOperation(
        address sender,
        address underlying,
        uint256 amount,
        uint256 fee,
        bytes calldata params
    ) external;
}

pragma solidity ^0.5.16;

import "./CToken.sol";
import "./ERC3156FlashBorrowerInterface.sol";
import "./ERC3156FlashLenderInterface.sol";

/**
 * @title Wrapped native token interface
 */
interface WrappedNativeInterface {
    function deposit() external payable;

    function withdraw(uint256 wad) external;
}

/**
 * @title Zeno's CWrappedNative Contract
 * @notice CTokens which wrap the native token
 * @author Zeno
 */
contract CWrappedNative is CToken, CWrappedNativeInterface {
    /**
     * @notice Initialize the new money market
     * @param underlying_ The address of the underlying asset
     * @param comptroller_ The address of the Comptroller
     * @param interestRateModel_ The address of the interest rate model
     * @param initialExchangeRateMantissa_ The initial exchange rate, scaled by 1e18
     * @param name_ ERC-20 name of this token
     * @param symbol_ ERC-20 symbol of this token
     * @param decimals_ ERC-20 decimal precision of this token
     */
    function initialize(
        address underlying_,
        ComptrollerInterface comptroller_,
        InterestRateModel interestRateModel_,
        uint256 initialExchangeRateMantissa_,
        string memory name_,
        string memory symbol_,
        uint8 decimals_
    ) public {
        // CToken initialize does the bulk of the work
        super.initialize(comptroller_, interestRateModel_, initialExchangeRateMantissa_, name_, symbol_, decimals_);

        // Set underlying and sanity check it
        underlying = underlying_;
        EIP20Interface(underlying).totalSupply();
        WrappedNativeInterface(underlying);
    }

    /*** User Interface ***/

    /**
     * @notice Sender supplies assets into the market and receives cTokens in exchange
     * @dev Accrues interest whether or not the operation succeeds, unless reverted
     *  Keep return in the function signature for backward compatibility
     * @param mintAmount The amount of the underlying asset to supply
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function mint(uint256 mintAmount) external returns (uint256) {
        (uint256 err, ) = mintInternal(mintAmount, false);
        require(err == 0, "mint failed");
    }

    /**
     * @notice Sender supplies assets into the market and receives cTokens in exchange
     * @dev Accrues interest whether or not the operation succeeds, unless reverted
     *  Keep return in the function signature for consistency
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function mintNative() external payable returns (uint256) {
        (uint256 err, ) = mintInternal(msg.value, true);
        require(err == 0, "mint native failed");
    }

    /**
     * @notice Sender redeems cTokens in exchange for the underlying asset
     * @dev Accrues interest whether or not the operation succeeds, unless reverted
     *  Keep return in the function signature for backward compatibility
     * @param redeemTokens The number of cTokens to redeem into underlying
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function redeem(uint256 redeemTokens) external returns (uint256) {
        require(redeemInternal(redeemTokens, false) == 0, "redeem failed");
    }

    /**
     * @notice Sender redeems cTokens in exchange for the underlying asset
     * @dev Accrues interest whether or not the operation succeeds, unless reverted
     *  Keep return in the function signature for consistency
     * @param redeemTokens The number of cTokens to redeem into underlying
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function redeemNative(uint256 redeemTokens) external returns (uint256) {
        require(redeemInternal(redeemTokens, true) == 0, "redeem native failed");
    }

    /**
     * @notice Sender redeems cTokens in exchange for a specified amount of underlying asset
     * @dev Accrues interest whether or not the operation succeeds, unless reverted
     *  Keep return in the function signature for backward compatibility
     * @param redeemAmount The amount of underlying to redeem
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function redeemUnderlying(uint256 redeemAmount) external returns (uint256) {
        require(redeemUnderlyingInternal(redeemAmount, false) == 0, "redeem underlying failed");
    }

    /**
     * @notice Sender redeems cTokens in exchange for a specified amount of underlying asset
     * @dev Accrues interest whether or not the operation succeeds, unless reverted
     *  Keep return in the function signature for consistency
     * @param redeemAmount The amount of underlying to redeem
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function redeemUnderlyingNative(uint256 redeemAmount) external returns (uint256) {
        require(redeemUnderlyingInternal(redeemAmount, true) == 0, "redeem underlying native failed");
    }

    /**
     * @notice Sender borrows assets from the protocol to their own address
     * @dev Accrues interest whether or not the operation succeeds, unless reverted
     *  Keep return in the function signature for backward compatibility
     * @param borrowAmount The amount of the underlying asset to borrow
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function borrow(uint256 borrowAmount) external returns (uint256) {
        require(borrowInternal(borrowAmount, false) == 0, "borrow failed");
    }

    /**
     * @notice Sender borrows assets from the protocol to their own address
     * @dev Accrues interest whether or not the operation succeeds, unless reverted
     *  Keep return in the function signature for consistency
     * @param borrowAmount The amount of the underlying asset to borrow
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function borrowNative(uint256 borrowAmount) external returns (uint256) {
        require(borrowInternal(borrowAmount, true) == 0, "borrow native failed");
    }

    /**
     * @notice Sender repays their own borrow
     * @dev Accrues interest whether or not the operation succeeds, unless reverted
     *  Keep return in the function signature for backward compatibility
     * @param repayAmount The amount to repay
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function repayBorrow(uint256 repayAmount) external returns (uint256) {
        (uint256 err, ) = repayBorrowInternal(repayAmount, false);
        require(err == 0, "repay failed");
    }

    /**
     * @notice Sender repays their own borrow
     * @dev Accrues interest whether or not the operation succeeds, unless reverted
     *  Keep return in the function signature for consistency
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function repayBorrowNative() external payable returns (uint256) {
        (uint256 err, ) = repayBorrowInternal(msg.value, true);
        require(err == 0, "repay native failed");
    }

    /**
     * @notice Sender repays a borrow belonging to borrower
     * @param borrower the account with the debt being payed off
     * @param repayAmount The amount to repay
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function repayBorrowBehalf(address borrower, uint256 repayAmount) external returns (uint256) {
        (uint256 err, ) = repayBorrowBehalfInternal(borrower, repayAmount, false);
        require(err == 0, "repay behalf failed");
    }

    /**
     * @notice Sender repays a borrow belonging to borrower
     * @param borrower the account with the debt being payed off
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function repayBorrowBehalfNative(address borrower) external payable returns (uint256) {
        (uint256 err, ) = repayBorrowBehalfInternal(borrower, msg.value, true);
        require(err == 0, "repay behalf native failed");
    }

    /**
     * @notice The sender liquidates the borrowers collateral.
     *  The collateral seized is transferred to the liquidator.
     * @dev Accrues interest whether or not the operation succeeds, unless reverted
     *  Keep return in the function signature for backward compatibility
     * @param borrower The borrower of this cToken to be liquidated
     * @param repayAmount The amount of the underlying borrowed asset to repay
     * @param cTokenCollateral The market in which to seize collateral from the borrower
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function liquidateBorrow(
        address borrower,
        uint256 repayAmount,
        CTokenInterface cTokenCollateral
    ) external returns (uint256) {
        (uint256 err, ) = liquidateBorrowInternal(borrower, repayAmount, cTokenCollateral, false);
        require(err == 0, "liquidate borrow failed");
    }

    /**
     * @notice The sender liquidates the borrowers collateral.
     *  The collateral seized is transferred to the liquidator.
     * @dev Accrues interest whether or not the operation succeeds, unless reverted
     *  Keep return in the function signature for consistency
     * @param borrower The borrower of this cToken to be liquidated
     * @param cTokenCollateral The market in which to seize collateral from the borrower
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function liquidateBorrowNative(address borrower, CTokenInterface cTokenCollateral)
        external
        payable
        returns (uint256)
    {
        (uint256 err, ) = liquidateBorrowInternal(borrower, msg.value, cTokenCollateral, true);
        require(err == 0, "liquidate borrow native failed");
    }

    /**
     * @notice Absorb excess cash into reserves.
     */
    function gulp() external nonReentrant {
        uint256 cashOnChain = getCashOnChain();
        uint256 cashPrior = getCashPrior();

        uint256 excessCash = sub_(cashOnChain, cashPrior);
        totalReserves = add_(totalReserves, excessCash);
        internalCash = cashOnChain;
    }

    /**
     * @dev The amount of currency available to be lent.
     * @param token The loan currency.
     * @return The amount of `token` that can be borrowed.
     */
    function maxFlashLoan(address token) external view returns (uint256) {
        uint256 amount = 0;
        if (
            token == underlying &&
            ComptrollerInterfaceExtension(address(comptroller)).flashloanAllowed(address(this), address(0), amount, "")
        ) {
            amount = getCashPrior();
        }
        return amount;
    }

    /**
     * @notice Get the flash loan fees
     * @param token The loan currency. Must match the address of this contract's underlying.
     * @param amount amount of token to borrow
     * @return The amount of `token` to be charged for the loan, on top of the returned principal.
     */
    function flashFee(address token, uint256 amount) external view returns (uint256) {
        require(token == underlying, "unsupported currency");
        require(
            ComptrollerInterfaceExtension(address(comptroller)).flashloanAllowed(address(this), address(0), amount, ""),
            "flashloan is paused"
        );
        return _flashFee(token, amount);
    }

    /**
     * @notice Flash loan funds to a given account.
     * @param receiver The receiver address for the funds
     * @param token The loan currency. Must match the address of this contract's underlying.
     * @param amount The amount of the funds to be loaned
     * @param data The other data
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function flashLoan(
        ERC3156FlashBorrowerInterface receiver,
        address token,
        uint256 amount,
        bytes calldata data
    ) external nonReentrant returns (bool) {
        require(amount > 0, "invalid flashloan amount");
        require(token == underlying, "unsupported currency");
        accrueInterest();
        require(
            ComptrollerInterfaceExtension(address(comptroller)).flashloanAllowed(
                address(this),
                address(receiver),
                amount,
                data
            ),
            "flashloan is paused"
        );
        uint256 cashOnChainBefore = getCashOnChain();
        uint256 cashBefore = getCashPrior();
        require(cashBefore >= amount, "insufficient cash");

        // 1. calculate fee, 1 bips = 1/10000
        uint256 totalFee = _flashFee(token, amount);

        // 2. transfer fund to receiver
        doTransferOut(address(uint160(address(receiver))), amount, false);

        // 3. update totalBorrows
        totalBorrows = add_(totalBorrows, amount);

        // 4. execute receiver's callback function
        require(
            receiver.onFlashLoan(msg.sender, underlying, amount, totalFee, data) ==
                keccak256("ERC3156FlashBorrowerInterface.onFlashLoan"),
            "IERC3156: Callback failed"
        );

        // 5. take amount + fee from receiver, then check balance
        uint256 repaymentAmount = add_(amount, totalFee);
        doTransferIn(address(receiver), repaymentAmount, false);

        uint256 cashOnChainAfter = getCashOnChain();

        require(cashOnChainAfter == add_(cashOnChainBefore, totalFee), "inconsistent balance");

        // 6. update reserves and internal cash and totalBorrows
        uint256 reservesFee = mul_ScalarTruncate(Exp({mantissa: reserveFactorMantissa}), totalFee);
        totalReserves = add_(totalReserves, reservesFee);
        internalCash = add_(cashBefore, totalFee);
        totalBorrows = sub_(totalBorrows, amount);

        emit Flashloan(address(receiver), amount, totalFee, reservesFee);
        return true;
    }

    /**
     * @notice Get the flash loan fees
     * @param token The loan currency. Must match the address of this contract's underlying.
     * @param amount amount of token to borrow
     * @return The amount of `token` to be charged for the loan, on top of the returned principal.
     */
    function _flashFee(address token, uint256 amount) internal view returns (uint256) {
        return div_(mul_(amount, flashFeeBips), 10000);
    }

    /**
     * @dev CWrappedNative doesn't have the collateral cap functionality. Return the supply cap for
     * interface consistency.
     * @return the supply cap of this market
     */
    function collateralCap() external view returns (uint256) {
        return ComptrollerInterfaceExtension(address(comptroller)).supplyCaps(address(this));
    }

    /**
     * @dev CWrappedNative doesn't have the collateral cap functionality. Return the total supply for
     * interface consistency.
     * @return the total supply of this market
     */
    function totalCollateralTokens() external view returns (uint256) {
        return totalSupply;
    }

    function() external payable {
        require(msg.sender == underlying, "only wrapped native contract could send native token");
    }

    /**
     * @notice The sender adds to reserves.
     * @dev Accrues interest whether or not the operation succeeds, unless reverted
     *  Keep return in the function signature for backward compatibility
     * @param addAmount The amount fo underlying token to add as reserves
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function _addReserves(uint256 addAmount) external returns (uint256) {
        require(_addReservesInternal(addAmount, false) == 0, "add reserves failed");
    }

    /**
     * @notice The sender adds to reserves.
     * @dev Accrues interest whether or not the operation succeeds, unless reverted
     *  Keep return in the function signature for consistency
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function _addReservesNative() external payable returns (uint256) {
        require(_addReservesInternal(msg.value, true) == 0, "add reserves failed");
    }

    /*** Safe Token ***/

    /**
     * @notice Gets internal balance of this contract in terms of the underlying.
     *  It excludes balance from direct transfer.
     * @dev This excludes the value of the current message, if any
     * @return The quantity of underlying tokens owned by this contract
     */
    function getCashPrior() internal view returns (uint256) {
        return internalCash;
    }

    /**
     * @notice Gets total balance of this contract in terms of the underlying
     * @dev This excludes the value of the current message, if any
     * @return The quantity of underlying tokens owned by this contract
     */
    function getCashOnChain() internal view returns (uint256) {
        EIP20Interface token = EIP20Interface(underlying);
        return token.balanceOf(address(this));
    }

    /**
     * @dev Similar to EIP20 transfer, except it handles a False result from `transferFrom` and reverts in that case.
     *      This will revert due to insufficient balance or insufficient allowance.
     *      This function returns the actual amount received,
     *      which may be less than `amount` if there is a fee attached to the transfer.
     *
     *      Note: This wrapper safely handles non-standard ERC-20 tokens that do not return a value.
     *            See here: https://medium.com/coinmonks/missing-return-value-bug-at-least-130-tokens-affected-d67bf08521ca
     */
    function doTransferIn(
        address from,
        uint256 amount,
        bool isNative
    ) internal returns (uint256) {
        if (isNative) {
            // Sanity checks
            require(msg.sender == from, "sender mismatch");
            require(msg.value == amount, "value mismatch");

            // Convert received native token to wrapped token
            WrappedNativeInterface(underlying).deposit.value(amount)();
            internalCash = add_(internalCash, amount);
            return amount;
        } else {
            EIP20NonStandardInterface token = EIP20NonStandardInterface(underlying);
            uint256 balanceBefore = EIP20Interface(underlying).balanceOf(address(this));
            token.transferFrom(from, address(this), amount);

            bool success;
            assembly {
                switch returndatasize()
                case 0 {
                    // This is a non-standard ERC-20
                    success := not(0) // set success to true
                }
                case 32 {
                    // This is a compliant ERC-20
                    returndatacopy(0, 0, 32)
                    success := mload(0) // Set `success = returndata` of external call
                }
                default {
                    // This is an excessively non-compliant ERC-20, revert.
                    revert(0, 0)
                }
            }
            require(success, "transfer failed");

            // Calculate the amount that was *actually* transferred
            uint256 balanceAfter = EIP20Interface(underlying).balanceOf(address(this));
            uint256 transferredIn = sub_(balanceAfter, balanceBefore);
            internalCash = add_(internalCash, transferredIn);
            return transferredIn;
        }
    }

    /**
     * @dev Similar to EIP20 transfer, except it handles a False success from `transfer` and returns an explanatory
     *      error code rather than reverting. If caller has not called checked protocol's balance, this may revert due to
     *      insufficient cash held in this contract. If caller has checked protocol's balance prior to this call, and verified
     *      it is >= amount, this should not revert in normal conditions.
     *
     *      Note: This wrapper safely handles non-standard ERC-20 tokens that do not return a value.
     *            See here: https://medium.com/coinmonks/missing-return-value-bug-at-least-130-tokens-affected-d67bf08521ca
     */
    function doTransferOut(
        address payable to,
        uint256 amount,
        bool isNative
    ) internal {
        // Update the internal cash.
        internalCash = sub_(internalCash, amount);
        if (isNative) {
            // Convert wrapped token to native token
            WrappedNativeInterface(underlying).withdraw(amount);
            /* Send the Ether, with minimal gas and revert on failure */
            to.transfer(amount);
        } else {
            EIP20NonStandardInterface token = EIP20NonStandardInterface(underlying);
            token.transfer(to, amount);

            bool success;
            assembly {
                switch returndatasize()
                case 0 {
                    // This is a non-standard ERC-20
                    success := not(0) // set success to true
                }
                case 32 {
                    // This is a complaint ERC-20
                    returndatacopy(0, 0, 32)
                    success := mload(0) // Set `success = returndata` of external call
                }
                default {
                    // This is an excessively non-compliant ERC-20, revert.
                    revert(0, 0)
                }
            }
            require(success, "transfer failed");
        }
    }

    /**
     * @notice Transfer `tokens` tokens from `src` to `dst` by `spender`
     * @dev Called by both `transfer` and `transferFrom` internally
     * @param spender The address of the account performing the transfer
     * @param src The address of the source account
     * @param dst The address of the destination account
     * @param tokens The number of tokens to transfer
     * @return Whether or not the transfer succeeded
     */
    function transferTokens(
        address spender,
        address src,
        address dst,
        uint256 tokens
    ) internal returns (uint256) {
        /* Fail if transfer not allowed */
        require(comptroller.transferAllowed(address(this), src, dst, tokens) == 0, "rejected");

        /* Do not allow self-transfers */
        require(src != dst, "bad input");

        /* Get the allowance, infinite for the account owner */
        uint256 startingAllowance = 0;
        if (spender == src) {
            startingAllowance = uint256(-1);
        } else {
            startingAllowance = transferAllowances[src][spender];
        }

        /* Do the calculations, checking for {under,over}flow */
        accountTokens[src] = sub_(accountTokens[src], tokens);
        accountTokens[dst] = add_(accountTokens[dst], tokens);

        /* Eat some of the allowance (if necessary) */
        if (startingAllowance != uint256(-1)) {
            transferAllowances[src][spender] = sub_(startingAllowance, tokens);
        }

        /* We emit a Transfer event */
        emit Transfer(src, dst, tokens);

        comptroller.transferVerify(address(this), src, dst, tokens);

        return uint256(Error.NO_ERROR);
    }

    /**
     * @notice Get the account's cToken balances
     * @param account The address of the account
     */
    function getCTokenBalanceInternal(address account) internal view returns (uint256) {
        return accountTokens[account];
    }

    struct MintLocalVars {
        uint256 exchangeRateMantissa;
        uint256 mintTokens;
        uint256 actualMintAmount;
    }

    /**
     * @notice User supplies assets into the market and receives cTokens in exchange
     * @dev Assumes interest has already been accrued up to the current block
     * @param minter The address of the account which is supplying the assets
     * @param mintAmount The amount of the underlying asset to supply
     * @param isNative The amount is in native or not
     * @return (uint, uint) An error code (0=success, otherwise a failure, see ErrorReporter.sol), and the actual mint amount.
     */
    function mintFresh(
        address minter,
        uint256 mintAmount,
        bool isNative
    ) internal returns (uint256, uint256) {
        /* Fail if mint not allowed */
        require(comptroller.mintAllowed(address(this), minter, mintAmount) == 0, "rejected");

        /*
         * Return if mintAmount is zero.
         * Put behind `mintAllowed` for accruing potential COMP rewards.
         */
        if (mintAmount == 0) {
            return (uint256(Error.NO_ERROR), 0);
        }

        /* Verify market's block number equals current block number */
        require(accrualBlockNumber == getBlockNumber(), "market is stale");

        MintLocalVars memory vars;

        vars.exchangeRateMantissa = exchangeRateStoredInternal();

        /////////////////////////
        // EFFECTS & INTERACTIONS
        // (No safe failures beyond this point)

        /*
         *  We call `doTransferIn` for the minter and the mintAmount.
         *  Note: The cToken must handle variations between ERC-20 and ETH underlying.
         *  `doTransferIn` reverts if anything goes wrong, since we can't be sure if
         *  side-effects occurred. The function returns the amount actually transferred,
         *  in case of a fee. On success, the cToken holds an additional `actualMintAmount`
         *  of cash.
         */
        vars.actualMintAmount = doTransferIn(minter, mintAmount, isNative);

        /*
         * We get the current exchange rate and calculate the number of cTokens to be minted:
         *  mintTokens = actualMintAmount / exchangeRate
         */
        vars.mintTokens = div_ScalarByExpTruncate(vars.actualMintAmount, Exp({mantissa: vars.exchangeRateMantissa}));

        /*
         * We calculate the new total supply of cTokens and minter token balance, checking for overflow:
         *  totalSupply = totalSupply + mintTokens
         *  accountTokens[minter] = accountTokens[minter] + mintTokens
         */
        totalSupply = add_(totalSupply, vars.mintTokens);
        accountTokens[minter] = add_(accountTokens[minter], vars.mintTokens);

        /* We emit a Mint event, and a Transfer event */
        emit Mint(minter, vars.actualMintAmount, vars.mintTokens);
        emit Transfer(address(this), minter, vars.mintTokens);

        /* We call the defense hook */
        comptroller.mintVerify(address(this), minter, vars.actualMintAmount, vars.mintTokens);

        return (uint256(Error.NO_ERROR), vars.actualMintAmount);
    }

    struct RedeemLocalVars {
        uint256 exchangeRateMantissa;
        uint256 redeemTokens;
        uint256 redeemAmount;
        uint256 totalSupplyNew;
        uint256 accountTokensNew;
    }

    /**
     * @notice User redeems cTokens in exchange for the underlying asset
     * @dev Assumes interest has already been accrued up to the current block. Only one of redeemTokensIn or redeemAmountIn may be non-zero and it would do nothing if both are zero.
     * @param redeemer The address of the account which is redeeming the tokens
     * @param redeemTokensIn The number of cTokens to redeem into underlying
     * @param redeemAmountIn The number of underlying tokens to receive from redeeming cTokens
     * @param isNative The amount is in native or not
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function redeemFresh(
        address payable redeemer,
        uint256 redeemTokensIn,
        uint256 redeemAmountIn,
        bool isNative
    ) internal returns (uint256) {
        require(redeemTokensIn == 0 || redeemAmountIn == 0, "bad input");

        RedeemLocalVars memory vars;

        /* exchangeRate = invoke Exchange Rate Stored() */
        vars.exchangeRateMantissa = exchangeRateStoredInternal();

        /* If redeemTokensIn > 0: */
        if (redeemTokensIn > 0) {
            /*
             * We calculate the exchange rate and the amount of underlying to be redeemed:
             *  redeemTokens = redeemTokensIn
             *  redeemAmount = redeemTokensIn x exchangeRateCurrent
             */
            vars.redeemTokens = redeemTokensIn;
            vars.redeemAmount = mul_ScalarTruncate(Exp({mantissa: vars.exchangeRateMantissa}), redeemTokensIn);
        } else {
            /*
             * We get the current exchange rate and calculate the amount to be redeemed:
             *  redeemTokens = redeemAmountIn / exchangeRate
             *  redeemAmount = redeemAmountIn
             */
            vars.redeemTokens = div_ScalarByExpTruncate(redeemAmountIn, Exp({mantissa: vars.exchangeRateMantissa}));
            vars.redeemAmount = redeemAmountIn;
        }

        /* Fail if redeem not allowed */
        require(comptroller.redeemAllowed(address(this), redeemer, vars.redeemTokens) == 0, "rejected");

        /*
         * Return if redeemTokensIn and redeemAmountIn are zero.
         * Put behind `redeemAllowed` for accruing potential COMP rewards.
         */
        if (redeemTokensIn == 0 && redeemAmountIn == 0) {
            return uint256(Error.NO_ERROR);
        }

        /* Verify market's block number equals current block number */
        require(accrualBlockNumber == getBlockNumber(), "market is stale");

        /*
         * We calculate the new total supply and redeemer balance, checking for underflow:
         *  totalSupplyNew = totalSupply - redeemTokens
         *  accountTokensNew = accountTokens[redeemer] - redeemTokens
         */
        vars.totalSupplyNew = sub_(totalSupply, vars.redeemTokens);
        vars.accountTokensNew = sub_(accountTokens[redeemer], vars.redeemTokens);

        /* Reverts if protocol has insufficient cash */
        require(getCashPrior() >= vars.redeemAmount, "insufficient cash");

        /////////////////////////
        // EFFECTS & INTERACTIONS
        // (No safe failures beyond this point)

        /* We write previously calculated values into storage */
        totalSupply = vars.totalSupplyNew;
        accountTokens[redeemer] = vars.accountTokensNew;

        /*
         * We invoke doTransferOut for the redeemer and the redeemAmount.
         *  Note: The cToken must handle variations between ERC-20 and ETH underlying.
         *  On success, the cToken has redeemAmount less of cash.
         *  doTransferOut reverts if anything goes wrong, since we can't be sure if side effects occurred.
         */
        doTransferOut(redeemer, vars.redeemAmount, isNative);

        /* We emit a Transfer event, and a Redeem event */
        emit Transfer(redeemer, address(this), vars.redeemTokens);
        emit Redeem(redeemer, vars.redeemAmount, vars.redeemTokens);

        /* We call the defense hook */
        comptroller.redeemVerify(address(this), redeemer, vars.redeemAmount, vars.redeemTokens);

        return uint256(Error.NO_ERROR);
    }

    /**
     * @notice Transfers collateral tokens (this market) to the liquidator.
     * @dev Called only during an in-kind liquidation, or by liquidateBorrow during the liquidation of another CToken.
     *  Its absolutely critical to use msg.sender as the seizer cToken and not a parameter.
     * @param seizerToken The contract seizing the collateral (i.e. borrowed cToken)
     * @param liquidator The account receiving seized collateral
     * @param borrower The account having collateral seized
     * @param seizeTokens The number of cTokens to seize
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function seizeInternal(
        address seizerToken,
        address liquidator,
        address borrower,
        uint256 seizeTokens
    ) internal returns (uint256) {
        /* Fail if seize not allowed */
        require(
            comptroller.seizeAllowed(address(this), seizerToken, liquidator, borrower, seizeTokens) == 0,
            "rejected"
        );

        /*
         * Return if seizeTokens is zero.
         * Put behind `seizeAllowed` for accruing potential COMP rewards.
         */
        if (seizeTokens == 0) {
            return uint256(Error.NO_ERROR);
        }

        /* Fail if borrower = liquidator */
        require(borrower != liquidator, "invalid account pair");

        /*
         * We calculate the new borrower and liquidator token balances, failing on underflow/overflow:
         *  borrowerTokensNew = accountTokens[borrower] - seizeTokens
         *  liquidatorTokensNew = accountTokens[liquidator] + seizeTokens
         */
        accountTokens[borrower] = sub_(accountTokens[borrower], seizeTokens);
        accountTokens[liquidator] = add_(accountTokens[liquidator], seizeTokens);

        /* Emit a Transfer event */
        emit Transfer(borrower, liquidator, seizeTokens);

        /* We call the defense hook */
        comptroller.seizeVerify(address(this), seizerToken, liquidator, borrower, seizeTokens);

        return uint256(Error.NO_ERROR);
    }
}

pragma solidity ^0.5.16;

import "./CWrappedNative.sol";

/**
 * @title Zeno's CWrappedNativeDelegate Contract
 * @notice CTokens which wrap an EIP-20 underlying and are delegated to
 * @author Zeno
 */
contract CWrappedNativeDelegate is CWrappedNative {
    /**
     * @notice Construct an empty delegate
     */
    constructor() public {}

    /**
     * @notice Called by the delegator on a delegate to initialize it for duty
     * @param data The encoded bytes data for any initialization
     */
    function _becomeImplementation(bytes memory data) public {
        // Shh -- currently unused
        data;

        require(msg.sender == admin, "admin only");

        // Set CToken version in comptroller and convert native token to wrapped token.
        ComptrollerInterfaceExtension(address(comptroller)).updateCTokenVersion(
            address(this),
            ComptrollerV1Storage.Version.WRAPPEDNATIVE
        );
        uint256 balance = address(this).balance;
        if (balance > 0) {
            WrappedNativeInterface(underlying).deposit.value(balance)();
        }

        // Set internal cash when becoming implementation
        internalCash = getCashOnChain();
    }

    /**
     * @notice Called by the delegator on a delegate to forfeit its responsibility
     */
    function _resignImplementation() public {
        // Shh -- we don't ever want this hook to be marked pure
        if (false) {
            implementation = address(0);
        }

        require(msg.sender == admin, "admin only");
    }
}

pragma solidity ^0.5.16;

/**
 * @title Careful Math
 * @author Compound
 * @notice Derived from OpenZeppelin's SafeMath library
 *         https://github.com/OpenZeppelin/openzeppelin-solidity/blob/master/contracts/math/SafeMath.sol
 */
contract CarefulMath {
    /**
     * @dev Possible error codes that we can return
     */
    enum MathError {
        NO_ERROR,
        DIVISION_BY_ZERO,
        INTEGER_OVERFLOW,
        INTEGER_UNDERFLOW
    }

    /**
     * @dev Multiplies two numbers, returns an error on overflow.
     */
    function mulUInt(uint256 a, uint256 b) internal pure returns (MathError, uint256) {
        if (a == 0) {
            return (MathError.NO_ERROR, 0);
        }

        uint256 c = a * b;

        if (c / a != b) {
            return (MathError.INTEGER_OVERFLOW, 0);
        } else {
            return (MathError.NO_ERROR, c);
        }
    }

    /**
     * @dev Integer division of two numbers, truncating the quotient.
     */
    function divUInt(uint256 a, uint256 b) internal pure returns (MathError, uint256) {
        if (b == 0) {
            return (MathError.DIVISION_BY_ZERO, 0);
        }

        return (MathError.NO_ERROR, a / b);
    }

    /**
     * @dev Subtracts two numbers, returns an error on overflow (i.e. if subtrahend is greater than minuend).
     */
    function subUInt(uint256 a, uint256 b) internal pure returns (MathError, uint256) {
        if (b <= a) {
            return (MathError.NO_ERROR, a - b);
        } else {
            return (MathError.INTEGER_UNDERFLOW, 0);
        }
    }

    /**
     * @dev Adds two numbers, returns an error on overflow.
     */
    function addUInt(uint256 a, uint256 b) internal pure returns (MathError, uint256) {
        uint256 c = a + b;

        if (c >= a) {
            return (MathError.NO_ERROR, c);
        } else {
            return (MathError.INTEGER_OVERFLOW, 0);
        }
    }

    /**
     * @dev add a and b and then subtract c
     */
    function addThenSubUInt(
        uint256 a,
        uint256 b,
        uint256 c
    ) internal pure returns (MathError, uint256) {
        (MathError err0, uint256 sum) = addUInt(a, b);

        if (err0 != MathError.NO_ERROR) {
            return (err0, 0);
        }

        return subUInt(sum, c);
    }
}

pragma solidity ^0.5.16;

import "./CToken.sol";
import "./ComptrollerStorage.sol";

contract ComptrollerInterface {
    /// @notice Indicator that this is a Comptroller contract (for inspection)
    bool public constant isComptroller = true;

    /*** Assets You Are In ***/

    function enterMarkets(address[] calldata cTokens) external returns (uint256[] memory);

    function exitMarket(address cToken) external returns (uint256);

    /*** Policy Hooks ***/

    function mintAllowed(
        address cToken,
        address minter,
        uint256 mintAmount
    ) external returns (uint256);

    function mintVerify(
        address cToken,
        address minter,
        uint256 mintAmount,
        uint256 mintTokens
    ) external;

    function redeemAllowed(
        address cToken,
        address redeemer,
        uint256 redeemTokens
    ) external returns (uint256);

    function redeemVerify(
        address cToken,
        address redeemer,
        uint256 redeemAmount,
        uint256 redeemTokens
    ) external;

    function borrowAllowed(
        address cToken,
        address borrower,
        uint256 borrowAmount
    ) external returns (uint256);

    function borrowVerify(
        address cToken,
        address borrower,
        uint256 borrowAmount
    ) external;

    function repayBorrowAllowed(
        address cToken,
        address payer,
        address borrower,
        uint256 repayAmount
    ) external returns (uint256);

    function repayBorrowVerify(
        address cToken,
        address payer,
        address borrower,
        uint256 repayAmount,
        uint256 borrowerIndex
    ) external;

    function liquidateBorrowAllowed(
        address cTokenBorrowed,
        address cTokenCollateral,
        address liquidator,
        address borrower,
        uint256 repayAmount
    ) external returns (uint256);

    function liquidateBorrowVerify(
        address cTokenBorrowed,
        address cTokenCollateral,
        address liquidator,
        address borrower,
        uint256 repayAmount,
        uint256 seizeTokens
    ) external;

    function seizeAllowed(
        address cTokenCollateral,
        address cTokenBorrowed,
        address liquidator,
        address borrower,
        uint256 seizeTokens
    ) external returns (uint256);

    function seizeVerify(
        address cTokenCollateral,
        address cTokenBorrowed,
        address liquidator,
        address borrower,
        uint256 seizeTokens
    ) external;

    function transferAllowed(
        address cToken,
        address src,
        address dst,
        uint256 transferTokens
    ) external returns (uint256);

    function transferVerify(
        address cToken,
        address src,
        address dst,
        uint256 transferTokens
    ) external;

    /*** Liquidity/Liquidation Calculations ***/

    function liquidateCalculateSeizeTokens(
        address cTokenBorrowed,
        address cTokenCollateral,
        uint256 repayAmount
    ) external view returns (uint256, uint256);
}

interface ComptrollerInterfaceExtension {
    function checkMembership(address account, CToken cToken) external view returns (bool);

    function updateCTokenVersion(address cToken, ComptrollerV1Storage.Version version) external;

    function flashloanAllowed(
        address cToken,
        address receiver,
        uint256 amount,
        bytes calldata params
    ) external view returns (bool);

    function getAccountLiquidity(address account)
        external
        view
        returns (
            uint256,
            uint256,
            uint256
        );

    function supplyCaps(address market) external view returns (uint256);
}

pragma solidity ^0.5.16;

import "./CToken.sol";
import "./PriceOracle/PriceOracle.sol";

contract UnitrollerAdminStorage {
    /**
     * @notice Administrator for this contract
     */
    address public admin;

    /**
     * @notice Pending administrator for this contract
     */
    address public pendingAdmin;

    /**
     * @notice Active brains of Unitroller
     */
    address public comptrollerImplementation;

    /**
     * @notice Pending brains of Unitroller
     */
    address public pendingComptrollerImplementation;
}

contract ComptrollerV1Storage is UnitrollerAdminStorage {
    /**
     * @notice Oracle which gives the price of any given asset
     */
    PriceOracle public oracle;

    /**
     * @notice Multiplier used to calculate the maximum repayAmount when liquidating a borrow
     */
    uint256 public closeFactorMantissa;

    /**
     * @notice Multiplier representing the discount on collateral that a liquidator receives
     */
    uint256 public liquidationIncentiveMantissa;

    /**
     * @notice Per-account mapping of "assets you are in"
     */
    mapping(address => CToken[]) public accountAssets;

    enum Version {
        VANILLA,
        COLLATERALCAP,
        WRAPPEDNATIVE
    }

    struct Market {
        /// @notice Whether or not this market is listed
        bool isListed;
        /**
         * @notice Multiplier representing the most one can borrow against their collateral in this market.
         *  For instance, 0.9 to allow borrowing 90% of collateral value.
         *  Must be between 0 and 1, and stored as a mantissa.
         */
        uint256 collateralFactorMantissa;
        /// @notice Per-market mapping of "accounts in this asset"
        mapping(address => bool) accountMembership;
        /// @notice CToken version
        Version version;
    }

    /**
     * @notice Official mapping of cTokens -> Market metadata
     * @dev Used e.g. to determine if a market is supported
     */
    mapping(address => Market) public markets;

    /**
     * @notice The Guardian can pause certain actions as a safety mechanism.
     *  Actions which allow users to remove their own assets cannot be paused.
     *  Liquidation / seizing / transfer can only be paused globally, not by market.
     */
    address public guardian;
    bool public _mintGuardianPaused;
    bool public _borrowGuardianPaused;
    bool public transferGuardianPaused;
    bool public seizeGuardianPaused;
    mapping(address => bool) public mintGuardianPaused;
    mapping(address => bool) public borrowGuardianPaused;
    mapping(address => bool) public flashloanGuardianPaused;

    /// @notice A list of all markets
    CToken[] public allMarkets;

    /// @notice The borrowCapGuardian can set borrowCaps to any number for any market. Lowering the borrow cap could disable borrowing on the given market.
    /// @dev This storage is deprecated.
    address public borrowCapGuardian;

    /// @notice Borrow caps enforced by borrowAllowed for each cToken address. Defaults to zero which corresponds to unlimited borrowing.
    mapping(address => uint256) public borrowCaps;

    /// @notice The supplyCapGuardian can set supplyCaps to any number for any market. Lowering the supply cap could disable supplying to the given market.
    /// @dev This storage is deprecated.
    address public supplyCapGuardian;

    /// @notice Supply caps enforced by mintAllowed for each cToken address. Defaults to zero which corresponds to unlimited supplying.
    mapping(address => uint256) public supplyCaps;

    /// @notice creditLimits allowed specific protocols to borrow and repay specific markets without collateral.
    mapping(address => mapping(address => uint256)) public creditLimits;

    /// @notice liquidityMining the liquidity mining module that handles the LM rewards distribution.
    address public liquidityMining;

    /// @notice isMarketSoftDelisted records the market which has been soft delisted by us.
    mapping(address => bool) public isMarketSoftDelisted;

    /// @notice creditLimitManager is the role who is in charge of increasing the credit limit.
    address public creditLimitManager;

    /// @notice A list of all soft delisted markets
    address[] public softDelistedMarkets;
}

pragma solidity ^0.5.16;

/**
 * @title ERC 20 Token Standard Interface
 *  https://eips.ethereum.org/EIPS/eip-20
 */
interface EIP20Interface {
    function name() external view returns (string memory);

    function symbol() external view returns (string memory);

    function decimals() external view returns (uint8);

    /**
     * @notice Get the total number of tokens in circulation
     * @return The supply of tokens
     */
    function totalSupply() external view returns (uint256);

    /**
     * @notice Gets the balance of the specified address
     * @param owner The address from which the balance will be retrieved
     * @return The balance
     */
    function balanceOf(address owner) external view returns (uint256 balance);

    /**
     * @notice Transfer `amount` tokens from `msg.sender` to `dst`
     * @param dst The address of the destination account
     * @param amount The number of tokens to transfer
     * @return Whether or not the transfer succeeded
     */
    function transfer(address dst, uint256 amount) external returns (bool success);

    /**
     * @notice Transfer `amount` tokens from `src` to `dst`
     * @param src The address of the source account
     * @param dst The address of the destination account
     * @param amount The number of tokens to transfer
     * @return Whether or not the transfer succeeded
     */
    function transferFrom(
        address src,
        address dst,
        uint256 amount
    ) external returns (bool success);

    /**
     * @notice Approve `spender` to transfer up to `amount` from `src`
     * @dev This will overwrite the approval amount for `spender`
     *  and is subject to issues noted [here](https://eips.ethereum.org/EIPS/eip-20#approve)
     * @param spender The address of the account which may transfer tokens
     * @param amount The number of tokens that are approved (-1 means infinite)
     * @return Whether or not the approval succeeded
     */
    function approve(address spender, uint256 amount) external returns (bool success);

    /**
     * @notice Get the current allowance from `owner` for `spender`
     * @param owner The address of the account which owns the tokens to be spent
     * @param spender The address of the account which may transfer tokens
     * @return The number of tokens allowed to be spent (-1 means infinite)
     */
    function allowance(address owner, address spender) external view returns (uint256 remaining);

    event Transfer(address indexed from, address indexed to, uint256 amount);
    event Approval(address indexed owner, address indexed spender, uint256 amount);
}

pragma solidity ^0.5.16;

/**
 * @title EIP20NonStandardInterface
 * @dev Version of ERC20 with no return values for `transfer` and `transferFrom`
 *  See https://medium.com/coinmonks/missing-return-value-bug-at-least-130-tokens-affected-d67bf08521ca
 */
interface EIP20NonStandardInterface {
    /**
     * @notice Get the total number of tokens in circulation
     * @return The supply of tokens
     */
    function totalSupply() external view returns (uint256);

    /**
     * @notice Gets the balance of the specified address
     * @param owner The address from which the balance will be retrieved
     * @return The balance
     */
    function balanceOf(address owner) external view returns (uint256 balance);

    ///
    /// !!!!!!!!!!!!!!
    /// !!! NOTICE !!! `transfer` does not return a value, in violation of the ERC-20 specification
    /// !!!!!!!!!!!!!!
    ///

    /**
     * @notice Transfer `amount` tokens from `msg.sender` to `dst`
     * @param dst The address of the destination account
     * @param amount The number of tokens to transfer
     */
    function transfer(address dst, uint256 amount) external;

    ///
    /// !!!!!!!!!!!!!!
    /// !!! NOTICE !!! `transferFrom` does not return a value, in violation of the ERC-20 specification
    /// !!!!!!!!!!!!!!
    ///

    /**
     * @notice Transfer `amount` tokens from `src` to `dst`
     * @param src The address of the source account
     * @param dst The address of the destination account
     * @param amount The number of tokens to transfer
     */
    function transferFrom(
        address src,
        address dst,
        uint256 amount
    ) external;

    /**
     * @notice Approve `spender` to transfer up to `amount` from `src`
     * @dev This will overwrite the approval amount for `spender`
     *  and is subject to issues noted [here](https://eips.ethereum.org/EIPS/eip-20#approve)
     * @param spender The address of the account which may transfer tokens
     * @param amount The number of tokens that are approved
     * @return Whether or not the approval succeeded
     */
    function approve(address spender, uint256 amount) external returns (bool success);

    /**
     * @notice Get the current allowance from `owner` for `spender`
     * @param owner The address of the account which owns the tokens to be spent
     * @param spender The address of the account which may transfer tokens
     * @return The number of tokens allowed to be spent
     */
    function allowance(address owner, address spender) external view returns (uint256 remaining);

    event Transfer(address indexed from, address indexed to, uint256 amount);
    event Approval(address indexed owner, address indexed spender, uint256 amount);
}

pragma solidity ^0.5.16;

interface ERC3156FlashBorrowerInterface {
    /**
     * @dev Receive a flash loan.
     * @param initiator The initiator of the loan.
     * @param token The loan currency.
     * @param amount The amount of tokens lent.
     * @param fee The additional amount of tokens to repay.
     * @param data Arbitrary data structure, intended to contain user-defined parameters.
     * @return The keccak256 hash of "ERC3156FlashBorrower.onFlashLoan"
     */
    function onFlashLoan(
        address initiator,
        address token,
        uint256 amount,
        uint256 fee,
        bytes calldata data
    ) external returns (bytes32);
}

pragma solidity ^0.5.16;
import "./ERC3156FlashBorrowerInterface.sol";

interface ERC3156FlashLenderInterface {
    /**
     * @dev The amount of currency available to be lent.
     * @param token The loan currency.
     * @return The amount of `token` that can be borrowed.
     */
    function maxFlashLoan(address token) external view returns (uint256);

    /**
     * @dev The fee to be charged for a given loan.
     * @param token The loan currency.
     * @param amount The amount of tokens lent.
     * @return The amount of `token` to be charged for the loan, on top of the returned principal.
     */
    function flashFee(address token, uint256 amount) external view returns (uint256);

    /**
     * @dev Initiate a flash loan.
     * @param receiver The receiver of the tokens in the loan, and the receiver of the callback.
     * @param token The loan currency.
     * @param amount The amount of tokens lent.
     * @param data Arbitrary data structure, intended to contain user-defined parameters.
     */
    function flashLoan(
        ERC3156FlashBorrowerInterface receiver,
        address token,
        uint256 amount,
        bytes calldata data
    ) external returns (bool);
}

pragma solidity ^0.5.16;

contract ComptrollerErrorReporter {
    enum Error {
        NO_ERROR,
        UNAUTHORIZED,
        COMPTROLLER_MISMATCH,
        INSUFFICIENT_SHORTFALL,
        INSUFFICIENT_LIQUIDITY,
        INVALID_CLOSE_FACTOR,
        INVALID_COLLATERAL_FACTOR,
        INVALID_LIQUIDATION_INCENTIVE,
        MARKET_NOT_ENTERED, // no longer possible
        MARKET_NOT_LISTED,
        MARKET_ALREADY_LISTED,
        MATH_ERROR,
        NONZERO_BORROW_BALANCE,
        PRICE_ERROR,
        REJECTION,
        SNAPSHOT_ERROR,
        TOO_MANY_ASSETS,
        TOO_MUCH_REPAY
    }

    enum FailureInfo {
        ACCEPT_ADMIN_PENDING_ADMIN_CHECK,
        ACCEPT_PENDING_IMPLEMENTATION_ADDRESS_CHECK,
        EXIT_MARKET_BALANCE_OWED,
        EXIT_MARKET_REJECTION,
        SET_CLOSE_FACTOR_OWNER_CHECK,
        SET_CLOSE_FACTOR_VALIDATION,
        SET_COLLATERAL_FACTOR_OWNER_CHECK,
        SET_COLLATERAL_FACTOR_NO_EXISTS,
        SET_COLLATERAL_FACTOR_VALIDATION,
        SET_COLLATERAL_FACTOR_WITHOUT_PRICE,
        SET_IMPLEMENTATION_OWNER_CHECK,
        SET_LIQUIDATION_INCENTIVE_OWNER_CHECK,
        SET_LIQUIDATION_INCENTIVE_VALIDATION,
        SET_MAX_ASSETS_OWNER_CHECK,
        SET_PENDING_ADMIN_OWNER_CHECK,
        SET_PENDING_IMPLEMENTATION_OWNER_CHECK,
        SET_PRICE_ORACLE_OWNER_CHECK,
        SUPPORT_MARKET_EXISTS,
        SUPPORT_MARKET_OWNER_CHECK,
        SET_PAUSE_GUARDIAN_OWNER_CHECK
    }

    /**
     * @dev `error` corresponds to enum Error; `info` corresponds to enum FailureInfo, and `detail` is an arbitrary
     * contract-specific code that enables us to report opaque error codes from upgradeable contracts.
     **/
    event Failure(uint256 error, uint256 info, uint256 detail);

    /**
     * @dev use this when reporting a known error from the money market or a non-upgradeable collaborator
     */
    function fail(Error err, FailureInfo info) internal returns (uint256) {
        emit Failure(uint256(err), uint256(info), 0);

        return uint256(err);
    }

    /**
     * @dev use this when reporting an opaque error from an upgradeable collaborator contract
     */
    function failOpaque(
        Error err,
        FailureInfo info,
        uint256 opaqueError
    ) internal returns (uint256) {
        emit Failure(uint256(err), uint256(info), opaqueError);

        return uint256(err);
    }
}

contract TokenErrorReporter {
    enum Error {
        NO_ERROR,
        UNAUTHORIZED,
        BAD_INPUT,
        COMPTROLLER_REJECTION,
        COMPTROLLER_CALCULATION_ERROR,
        INTEREST_RATE_MODEL_ERROR,
        INVALID_ACCOUNT_PAIR,
        INVALID_CLOSE_AMOUNT_REQUESTED,
        INVALID_COLLATERAL_FACTOR,
        MATH_ERROR,
        MARKET_NOT_FRESH,
        MARKET_NOT_LISTED,
        TOKEN_INSUFFICIENT_ALLOWANCE,
        TOKEN_INSUFFICIENT_BALANCE,
        TOKEN_INSUFFICIENT_CASH,
        TOKEN_TRANSFER_IN_FAILED,
        TOKEN_TRANSFER_OUT_FAILED
    }

    /*
     * Note: FailureInfo (but not Error) is kept in alphabetical order
     *       This is because FailureInfo grows significantly faster, and
     *       the order of Error has some meaning, while the order of FailureInfo
     *       is entirely arbitrary.
     */
    enum FailureInfo {
        ACCEPT_ADMIN_PENDING_ADMIN_CHECK,
        ACCRUE_INTEREST_BORROW_RATE_CALCULATION_FAILED,
        BORROW_ACCRUE_INTEREST_FAILED,
        BORROW_CASH_NOT_AVAILABLE,
        BORROW_FRESHNESS_CHECK,
        BORROW_MARKET_NOT_LISTED,
        BORROW_COMPTROLLER_REJECTION,
        LIQUIDATE_ACCRUE_BORROW_INTEREST_FAILED,
        LIQUIDATE_ACCRUE_COLLATERAL_INTEREST_FAILED,
        LIQUIDATE_COLLATERAL_FRESHNESS_CHECK,
        LIQUIDATE_COMPTROLLER_REJECTION,
        LIQUIDATE_COMPTROLLER_CALCULATE_AMOUNT_SEIZE_FAILED,
        LIQUIDATE_CLOSE_AMOUNT_IS_UINT_MAX,
        LIQUIDATE_CLOSE_AMOUNT_IS_ZERO,
        LIQUIDATE_FRESHNESS_CHECK,
        LIQUIDATE_LIQUIDATOR_IS_BORROWER,
        LIQUIDATE_REPAY_BORROW_FRESH_FAILED,
        LIQUIDATE_SEIZE_COMPTROLLER_REJECTION,
        LIQUIDATE_SEIZE_LIQUIDATOR_IS_BORROWER,
        LIQUIDATE_SEIZE_TOO_MUCH,
        MINT_ACCRUE_INTEREST_FAILED,
        MINT_COMPTROLLER_REJECTION,
        MINT_FRESHNESS_CHECK,
        MINT_TRANSFER_IN_FAILED,
        MINT_TRANSFER_IN_NOT_POSSIBLE,
        REDEEM_ACCRUE_INTEREST_FAILED,
        REDEEM_COMPTROLLER_REJECTION,
        REDEEM_FRESHNESS_CHECK,
        REDEEM_TRANSFER_OUT_NOT_POSSIBLE,
        REDUCE_RESERVES_ACCRUE_INTEREST_FAILED,
        REDUCE_RESERVES_ADMIN_CHECK,
        REDUCE_RESERVES_CASH_NOT_AVAILABLE,
        REDUCE_RESERVES_FRESH_CHECK,
        REDUCE_RESERVES_VALIDATION,
        REPAY_BEHALF_ACCRUE_INTEREST_FAILED,
        REPAY_BORROW_ACCRUE_INTEREST_FAILED,
        REPAY_BORROW_COMPTROLLER_REJECTION,
        REPAY_BORROW_FRESHNESS_CHECK,
        REPAY_BORROW_TRANSFER_IN_NOT_POSSIBLE,
        SET_COLLATERAL_FACTOR_OWNER_CHECK,
        SET_COLLATERAL_FACTOR_VALIDATION,
        SET_COMPTROLLER_OWNER_CHECK,
        SET_INTEREST_RATE_MODEL_ACCRUE_INTEREST_FAILED,
        SET_INTEREST_RATE_MODEL_FRESH_CHECK,
        SET_INTEREST_RATE_MODEL_OWNER_CHECK,
        SET_MAX_ASSETS_OWNER_CHECK,
        SET_ORACLE_MARKET_NOT_LISTED,
        SET_PENDING_ADMIN_OWNER_CHECK,
        SET_RESERVE_FACTOR_ACCRUE_INTEREST_FAILED,
        SET_RESERVE_FACTOR_ADMIN_CHECK,
        SET_RESERVE_FACTOR_FRESH_CHECK,
        SET_RESERVE_FACTOR_BOUNDS_CHECK,
        TRANSFER_COMPTROLLER_REJECTION,
        TRANSFER_NOT_ALLOWED,
        ADD_RESERVES_ACCRUE_INTEREST_FAILED,
        ADD_RESERVES_FRESH_CHECK,
        ADD_RESERVES_TRANSFER_IN_NOT_POSSIBLE
    }

    /**
     * @dev `error` corresponds to enum Error; `info` corresponds to enum FailureInfo, and `detail` is an arbitrary
     * contract-specific code that enables us to report opaque error codes from upgradeable contracts.
     **/
    event Failure(uint256 error, uint256 info, uint256 detail);

    /**
     * @dev use this when reporting a known error from the money market or a non-upgradeable collaborator
     */
    function fail(Error err, FailureInfo info) internal returns (uint256) {
        emit Failure(uint256(err), uint256(info), 0);

        return uint256(err);
    }

    /**
     * @dev use this when reporting an opaque error from an upgradeable collaborator contract
     */
    function failOpaque(
        Error err,
        FailureInfo info,
        uint256 opaqueError
    ) internal returns (uint256) {
        emit Failure(uint256(err), uint256(info), opaqueError);

        return uint256(err);
    }
}

pragma solidity ^0.5.16;

import "./CarefulMath.sol";

/**
 * @title Exponential module for storing fixed-precision decimals
 * @author Compound
 * @notice Exp is a struct which stores decimals with a fixed precision of 18 decimal places.
 *         Thus, if we wanted to store the 5.1, mantissa would store 5.1e18. That is:
 *         `Exp({mantissa: 5100000000000000000})`.
 */
contract Exponential is CarefulMath {
    uint256 constant expScale = 1e18;
    uint256 constant doubleScale = 1e36;
    uint256 constant halfExpScale = expScale / 2;
    uint256 constant mantissaOne = expScale;

    struct Exp {
        uint256 mantissa;
    }

    struct Double {
        uint256 mantissa;
    }

    /**
     * @dev Creates an exponential from numerator and denominator values.
     *      Note: Returns an error if (`num` * 10e18) > MAX_INT,
     *            or if `denom` is zero.
     */
    function getExp(uint256 num, uint256 denom) internal pure returns (MathError, Exp memory) {
        (MathError err0, uint256 scaledNumerator) = mulUInt(num, expScale);
        if (err0 != MathError.NO_ERROR) {
            return (err0, Exp({mantissa: 0}));
        }

        (MathError err1, uint256 rational) = divUInt(scaledNumerator, denom);
        if (err1 != MathError.NO_ERROR) {
            return (err1, Exp({mantissa: 0}));
        }

        return (MathError.NO_ERROR, Exp({mantissa: rational}));
    }

    /**
     * @dev Adds two exponentials, returning a new exponential.
     */
    function addExp(Exp memory a, Exp memory b) internal pure returns (MathError, Exp memory) {
        (MathError error, uint256 result) = addUInt(a.mantissa, b.mantissa);

        return (error, Exp({mantissa: result}));
    }

    /**
     * @dev Subtracts two exponentials, returning a new exponential.
     */
    function subExp(Exp memory a, Exp memory b) internal pure returns (MathError, Exp memory) {
        (MathError error, uint256 result) = subUInt(a.mantissa, b.mantissa);

        return (error, Exp({mantissa: result}));
    }

    /**
     * @dev Multiply an Exp by a scalar, returning a new Exp.
     */
    function mulScalar(Exp memory a, uint256 scalar) internal pure returns (MathError, Exp memory) {
        (MathError err0, uint256 scaledMantissa) = mulUInt(a.mantissa, scalar);
        if (err0 != MathError.NO_ERROR) {
            return (err0, Exp({mantissa: 0}));
        }

        return (MathError.NO_ERROR, Exp({mantissa: scaledMantissa}));
    }

    /**
     * @dev Multiply an Exp by a scalar, then truncate to return an unsigned integer.
     */
    function mulScalarTruncate(Exp memory a, uint256 scalar) internal pure returns (MathError, uint256) {
        (MathError err, Exp memory product) = mulScalar(a, scalar);
        if (err != MathError.NO_ERROR) {
            return (err, 0);
        }

        return (MathError.NO_ERROR, truncate(product));
    }

    /**
     * @dev Multiply an Exp by a scalar, truncate, then add an to an unsigned integer, returning an unsigned integer.
     */
    function mulScalarTruncateAddUInt(
        Exp memory a,
        uint256 scalar,
        uint256 addend
    ) internal pure returns (MathError, uint256) {
        (MathError err, Exp memory product) = mulScalar(a, scalar);
        if (err != MathError.NO_ERROR) {
            return (err, 0);
        }

        return addUInt(truncate(product), addend);
    }

    /**
     * @dev Multiply an Exp by a scalar, then truncate to return an unsigned integer.
     */
    function mul_ScalarTruncate(Exp memory a, uint256 scalar) internal pure returns (uint256) {
        Exp memory product = mul_(a, scalar);
        return truncate(product);
    }

    /**
     * @dev Multiply an Exp by a scalar, truncate, then add an to an unsigned integer, returning an unsigned integer.
     */
    function mul_ScalarTruncateAddUInt(
        Exp memory a,
        uint256 scalar,
        uint256 addend
    ) internal pure returns (uint256) {
        Exp memory product = mul_(a, scalar);
        return add_(truncate(product), addend);
    }

    /**
     * @dev Divide an Exp by a scalar, returning a new Exp.
     */
    function divScalar(Exp memory a, uint256 scalar) internal pure returns (MathError, Exp memory) {
        (MathError err0, uint256 descaledMantissa) = divUInt(a.mantissa, scalar);
        if (err0 != MathError.NO_ERROR) {
            return (err0, Exp({mantissa: 0}));
        }

        return (MathError.NO_ERROR, Exp({mantissa: descaledMantissa}));
    }

    /**
     * @dev Divide a scalar by an Exp, returning a new Exp.
     */
    function divScalarByExp(uint256 scalar, Exp memory divisor) internal pure returns (MathError, Exp memory) {
        /*
          We are doing this as:
          getExp(mulUInt(expScale, scalar), divisor.mantissa)

          How it works:
          Exp = a / b;
          Scalar = s;
          `s / (a / b)` = `b * s / a` and since for an Exp `a = mantissa, b = expScale`
        */
        (MathError err0, uint256 numerator) = mulUInt(expScale, scalar);
        if (err0 != MathError.NO_ERROR) {
            return (err0, Exp({mantissa: 0}));
        }
        return getExp(numerator, divisor.mantissa);
    }

    /**
     * @dev Divide a scalar by an Exp, then truncate to return an unsigned integer.
     */
    function divScalarByExpTruncate(uint256 scalar, Exp memory divisor) internal pure returns (MathError, uint256) {
        (MathError err, Exp memory fraction) = divScalarByExp(scalar, divisor);
        if (err != MathError.NO_ERROR) {
            return (err, 0);
        }

        return (MathError.NO_ERROR, truncate(fraction));
    }

    /**
     * @dev Divide a scalar by an Exp, returning a new Exp.
     */
    function div_ScalarByExp(uint256 scalar, Exp memory divisor) internal pure returns (Exp memory) {
        /*
          We are doing this as:
          getExp(mulUInt(expScale, scalar), divisor.mantissa)

          How it works:
          Exp = a / b;
          Scalar = s;
          `s / (a / b)` = `b * s / a` and since for an Exp `a = mantissa, b = expScale`
        */
        uint256 numerator = mul_(expScale, scalar);
        return Exp({mantissa: div_(numerator, divisor)});
    }

    /**
     * @dev Divide a scalar by an Exp, then truncate to return an unsigned integer.
     */
    function div_ScalarByExpTruncate(uint256 scalar, Exp memory divisor) internal pure returns (uint256) {
        Exp memory fraction = div_ScalarByExp(scalar, divisor);
        return truncate(fraction);
    }

    /**
     * @dev Multiplies two exponentials, returning a new exponential.
     */
    function mulExp(Exp memory a, Exp memory b) internal pure returns (MathError, Exp memory) {
        (MathError err0, uint256 doubleScaledProduct) = mulUInt(a.mantissa, b.mantissa);
        if (err0 != MathError.NO_ERROR) {
            return (err0, Exp({mantissa: 0}));
        }

        // We add half the scale before dividing so that we get rounding instead of truncation.
        //  See "Listing 6" and text above it at https://accu.org/index.php/journals/1717
        // Without this change, a result like 6.6...e-19 will be truncated to 0 instead of being rounded to 1e-18.
        (MathError err1, uint256 doubleScaledProductWithHalfScale) = addUInt(halfExpScale, doubleScaledProduct);
        if (err1 != MathError.NO_ERROR) {
            return (err1, Exp({mantissa: 0}));
        }

        (MathError err2, uint256 product) = divUInt(doubleScaledProductWithHalfScale, expScale);
        // The only error `div` can return is MathError.DIVISION_BY_ZERO but we control `expScale` and it is not zero.
        assert(err2 == MathError.NO_ERROR);

        return (MathError.NO_ERROR, Exp({mantissa: product}));
    }

    /**
     * @dev Multiplies two exponentials given their mantissas, returning a new exponential.
     */
    function mulExp(uint256 a, uint256 b) internal pure returns (MathError, Exp memory) {
        return mulExp(Exp({mantissa: a}), Exp({mantissa: b}));
    }

    /**
     * @dev Multiplies three exponentials, returning a new exponential.
     */
    function mulExp3(
        Exp memory a,
        Exp memory b,
        Exp memory c
    ) internal pure returns (MathError, Exp memory) {
        (MathError err, Exp memory ab) = mulExp(a, b);
        if (err != MathError.NO_ERROR) {
            return (err, ab);
        }
        return mulExp(ab, c);
    }

    /**
     * @dev Divides two exponentials, returning a new exponential.
     *     (a/scale) / (b/scale) = (a/scale) * (scale/b) = a/b,
     *  which we can scale as an Exp by calling getExp(a.mantissa, b.mantissa)
     */
    function divExp(Exp memory a, Exp memory b) internal pure returns (MathError, Exp memory) {
        return getExp(a.mantissa, b.mantissa);
    }

    /**
     * @dev Truncates the given exp to a whole number value.
     *      For example, truncate(Exp{mantissa: 15 * expScale}) = 15
     */
    function truncate(Exp memory exp) internal pure returns (uint256) {
        // Note: We are not using careful math here as we're performing a division that cannot fail
        return exp.mantissa / expScale;
    }

    /**
     * @dev Checks if first Exp is less than second Exp.
     */
    function lessThanExp(Exp memory left, Exp memory right) internal pure returns (bool) {
        return left.mantissa < right.mantissa;
    }

    /**
     * @dev Checks if left Exp <= right Exp.
     */
    function lessThanOrEqualExp(Exp memory left, Exp memory right) internal pure returns (bool) {
        return left.mantissa <= right.mantissa;
    }

    /**
     * @dev returns true if Exp is exactly zero
     */
    function isZeroExp(Exp memory value) internal pure returns (bool) {
        return value.mantissa == 0;
    }

    function safe224(uint256 n, string memory errorMessage) internal pure returns (uint224) {
        require(n < 2**224, errorMessage);
        return uint224(n);
    }

    function safe32(uint256 n, string memory errorMessage) internal pure returns (uint32) {
        require(n < 2**32, errorMessage);
        return uint32(n);
    }

    function add_(Exp memory a, Exp memory b) internal pure returns (Exp memory) {
        return Exp({mantissa: add_(a.mantissa, b.mantissa)});
    }

    function add_(Double memory a, Double memory b) internal pure returns (Double memory) {
        return Double({mantissa: add_(a.mantissa, b.mantissa)});
    }

    function add_(uint256 a, uint256 b) internal pure returns (uint256) {
        return add_(a, b, "addition overflow");
    }

    function add_(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, errorMessage);
        return c;
    }

    function sub_(Exp memory a, Exp memory b) internal pure returns (Exp memory) {
        return Exp({mantissa: sub_(a.mantissa, b.mantissa)});
    }

    function sub_(Double memory a, Double memory b) internal pure returns (Double memory) {
        return Double({mantissa: sub_(a.mantissa, b.mantissa)});
    }

    function sub_(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub_(a, b, "subtraction underflow");
    }

    function sub_(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        return a - b;
    }

    function mul_(Exp memory a, Exp memory b) internal pure returns (Exp memory) {
        return Exp({mantissa: mul_(a.mantissa, b.mantissa) / expScale});
    }

    function mul_(Exp memory a, uint256 b) internal pure returns (Exp memory) {
        return Exp({mantissa: mul_(a.mantissa, b)});
    }

    function mul_(uint256 a, Exp memory b) internal pure returns (uint256) {
        return mul_(a, b.mantissa) / expScale;
    }

    function mul_(Double memory a, Double memory b) internal pure returns (Double memory) {
        return Double({mantissa: mul_(a.mantissa, b.mantissa) / doubleScale});
    }

    function mul_(Double memory a, uint256 b) internal pure returns (Double memory) {
        return Double({mantissa: mul_(a.mantissa, b)});
    }

    function mul_(uint256 a, Double memory b) internal pure returns (uint256) {
        return mul_(a, b.mantissa) / doubleScale;
    }

    function mul_(uint256 a, uint256 b) internal pure returns (uint256) {
        return mul_(a, b, "multiplication overflow");
    }

    function mul_(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        if (a == 0 || b == 0) {
            return 0;
        }
        uint256 c = a * b;
        require(c / a == b, errorMessage);
        return c;
    }

    function div_(Exp memory a, Exp memory b) internal pure returns (Exp memory) {
        return Exp({mantissa: div_(mul_(a.mantissa, expScale), b.mantissa)});
    }

    function div_(Exp memory a, uint256 b) internal pure returns (Exp memory) {
        return Exp({mantissa: div_(a.mantissa, b)});
    }

    function div_(uint256 a, Exp memory b) internal pure returns (uint256) {
        return div_(mul_(a, expScale), b.mantissa);
    }

    function div_(Double memory a, Double memory b) internal pure returns (Double memory) {
        return Double({mantissa: div_(mul_(a.mantissa, doubleScale), b.mantissa)});
    }

    function div_(Double memory a, uint256 b) internal pure returns (Double memory) {
        return Double({mantissa: div_(a.mantissa, b)});
    }

    function div_(uint256 a, Double memory b) internal pure returns (uint256) {
        return div_(mul_(a, doubleScale), b.mantissa);
    }

    function div_(uint256 a, uint256 b) internal pure returns (uint256) {
        return div_(a, b, "divide by zero");
    }

    function div_(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a / b;
    }

    function fraction(uint256 a, uint256 b) internal pure returns (Double memory) {
        return Double({mantissa: div_(mul_(a, doubleScale), b)});
    }

    // implementation from https://github.com/Uniswap/uniswap-lib/commit/99f3f28770640ba1bb1ff460ac7c5292fb8291a0
    // original implementation: https://github.com/abdk-consulting/abdk-libraries-solidity/blob/master/ABDKMath64x64.sol#L687
    function sqrt(uint256 x) internal pure returns (uint256) {
        if (x == 0) return 0;
        uint256 xx = x;
        uint256 r = 1;

        if (xx >= 0x100000000000000000000000000000000) {
            xx >>= 128;
            r <<= 64;
        }
        if (xx >= 0x10000000000000000) {
            xx >>= 64;
            r <<= 32;
        }
        if (xx >= 0x100000000) {
            xx >>= 32;
            r <<= 16;
        }
        if (xx >= 0x10000) {
            xx >>= 16;
            r <<= 8;
        }
        if (xx >= 0x100) {
            xx >>= 8;
            r <<= 4;
        }
        if (xx >= 0x10) {
            xx >>= 4;
            r <<= 2;
        }
        if (xx >= 0x8) {
            r <<= 1;
        }

        r = (r + x / r) >> 1;
        r = (r + x / r) >> 1;
        r = (r + x / r) >> 1;
        r = (r + x / r) >> 1;
        r = (r + x / r) >> 1;
        r = (r + x / r) >> 1;
        r = (r + x / r) >> 1; // Seven iterations should be enough
        uint256 r1 = x / r;
        return (r < r1 ? r : r1);
    }
}

pragma solidity ^0.5.16;

/**
 * @title Compound's InterestRateModel Interface
 * @author Compound
 */
contract InterestRateModel {
    /// @notice Indicator that this is an InterestRateModel contract (for inspection)
    bool public constant isInterestRateModel = true;

    /**
     * @notice Calculates the current borrow interest rate per block
     * @param cash The total amount of cash the market has
     * @param borrows The total amount of borrows the market has outstanding
     * @param reserves The total amount of reserves the market has
     * @return The borrow rate per block (as a percentage, and scaled by 1e18)
     */
    function getBorrowRate(
        uint256 cash,
        uint256 borrows,
        uint256 reserves
    ) external view returns (uint256);

    /**
     * @notice Calculates the current supply interest rate per block
     * @param cash The total amount of cash the market has
     * @param borrows The total amount of borrows the market has outstanding
     * @param reserves The total amount of reserves the market has
     * @param reserveFactorMantissa The current reserve factor the market has
     * @return The supply rate per block (as a percentage, and scaled by 1e18)
     */
    function getSupplyRate(
        uint256 cash,
        uint256 borrows,
        uint256 reserves,
        uint256 reserveFactorMantissa
    ) external view returns (uint256);
}

pragma solidity ^0.5.16;

import "../CToken.sol";

contract PriceOracle {
    /**
     * @notice Get the underlying price of a cToken asset
     * @param cToken The cToken to get the underlying price of
     * @return The underlying asset price mantissa (scaled by 1e18).
     *  Zero means the price is unavailable.
     */
    function getUnderlyingPrice(CToken cToken) external view returns (uint256);
}