Contract Name:

WhitePaperInterestRateModel

Contract Source Code:

File 1 of 1 : WhitePaperInterestRateModel

// File: contracts/InterestRateModel.sol
pragma solidity ^0.5.16;
/**
* @title Aquarius's InterestRateModel Interface
* @author Aquarius
*/
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(uint cash, uint borrows, uint reserves) external view returns (uint);
/**
* @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(uint cash, uint borrows, uint reserves, uint reserveFactorMantissa) external view returns (uint);
}
// File: contracts/SafeMath.sol
pragma solidity ^0.5.16;
// From https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/math/Math.sol
// Subject to the MIT license.
/**
* @dev Wrappers over Solidity's arithmetic operations with added overflow
* checks.
*
* Arithmetic operations in Solidity wrap on overflow. This can easily result
* in bugs, because programmers usually assume that an overflow raises an
* error, which is the standard behavior in high level programming languages.
* `SafeMath` restores this intuition by reverting the transaction when an
* operation overflows.
*
* Using this library instead of the unchecked operations eliminates an entire
* class of bugs, so it's recommended to use it always.
*/
library SafeMath {
/**
* @dev Returns the addition of two unsigned integers, reverting on overflow.
*
* Counterpart to Solidity's `+` operator.
*
* Requirements:
* - Addition cannot overflow.
*/
function add(uint256 a, uint256 b) internal pure returns (uint256) {
uint256 c = a + b;
require(c >= a, "SafeMath: addition overflow");
return c;
}
/**
* @dev Returns the addition of two unsigned integers, reverting with custom message on overflow.
*
* Counterpart to Solidity's `+` operator.
*
* Requirements:
* - Addition cannot overflow.
*/
function add(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
uint256 c = a + b;
require(c >= a, errorMessage);
return c;
}
/**
* @dev Returns the subtraction of two unsigned integers, reverting on underflow (when the result is negative).
*
* Counterpart to Solidity's `-` operator.
*
* Requirements:
* - Subtraction cannot underflow.
*/
function sub(uint256 a, uint256 b) internal pure returns (uint256) {
return sub(a, b, "SafeMath: subtraction underflow");
}
/**
* @dev Returns the subtraction of two unsigned integers, reverting with custom message on underflow (when the result is negative).
*
* Counterpart to Solidity's `-` operator.
*
* Requirements:
* - Subtraction cannot underflow.
*/
function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
require(b <= a, errorMessage);
uint256 c = a - b;
return c;
}
/**
* @dev Returns the multiplication of two unsigned integers, reverting on overflow.
*
* Counterpart to Solidity's `*` operator.
*
* Requirements:
* - Multiplication cannot overflow.
*/
function mul(uint256 a, uint256 b) internal pure returns (uint256) {
// Gas optimization: this is cheaper than requiring 'a' not being zero, but the
// benefit is lost if 'b' is also tested.
// See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
if (a == 0) {
return 0;
}
uint256 c = a * b;
require(c / a == b, "SafeMath: multiplication overflow");
return c;
}
/**
* @dev Returns the multiplication of two unsigned integers, reverting on overflow.
*
* Counterpart to Solidity's `*` operator.
*
* Requirements:
* - Multiplication cannot overflow.
*/
function mul(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
// Gas optimization: this is cheaper than requiring 'a' not being zero, but the
// benefit is lost if 'b' is also tested.
// See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
if (a == 0) {
return 0;
}
uint256 c = a * b;
require(c / a == b, errorMessage);
return c;
}
/**
* @dev Returns the integer division of two unsigned integers.
* Reverts on division by zero. The result is rounded towards zero.
*
* Counterpart to Solidity's `/` operator. Note: this function uses a
* `revert` opcode (which leaves remaining gas untouched) while Solidity
* uses an invalid opcode to revert (consuming all remaining gas).
*
* Requirements:
* - The divisor cannot be zero.
*/
function div(uint256 a, uint256 b) internal pure returns (uint256) {
return div(a, b, "SafeMath: division by zero");
}
/**
* @dev Returns the integer division of two unsigned integers.
* Reverts with custom message on division by zero. The result is rounded towards zero.
*
* Counterpart to Solidity's `/` operator. Note: this function uses a
* `revert` opcode (which leaves remaining gas untouched) while Solidity
* uses an invalid opcode to revert (consuming all remaining gas).
*
* Requirements:
* - The divisor cannot be zero.
*/
function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
// Solidity only automatically asserts when dividing by 0
require(b > 0, errorMessage);
uint256 c = a / b;
// assert(a == b * c + a % b); // There is no case in which this doesn't hold
return c;
}
/**
* @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
* Reverts when dividing by zero.
*
* Counterpart to Solidity's `%` operator. This function uses a `revert`
* opcode (which leaves remaining gas untouched) while Solidity uses an
* invalid opcode to revert (consuming all remaining gas).
*
* Requirements:
* - The divisor cannot be zero.
*/
function mod(uint256 a, uint256 b) internal pure returns (uint256) {
return mod(a, b, "SafeMath: modulo by zero");
}
/**
* @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
* Reverts with custom message when dividing by zero.
*
* Counterpart to Solidity's `%` operator. This function uses a `revert`
* opcode (which leaves remaining gas untouched) while Solidity uses an
* invalid opcode to revert (consuming all remaining gas).
*
* Requirements:
* - The divisor cannot be zero.
*/
function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
require(b != 0, errorMessage);
return a % b;
}
}
// File: contracts/WhitePaperInterestRateModel.sol
pragma solidity ^0.5.16;
/**
* @title Aquarius's WhitePaperInterestRateModel Contract
* @author Aquarius
* @notice The parameterized model described in section 2.4 of the original Aquarius Protocol whitepaper
*/
contract WhitePaperInterestRateModel is InterestRateModel {
using SafeMath for uint;
event NewInterestParams(uint baseRatePerBlock, uint multiplierPerBlock);
/**
* @notice The approximate number of blocks per year that is assumed by the interest rate model
*/
uint public constant blocksPerYear = 15512500;
/**
* @notice The multiplier of utilization rate that gives the slope of the interest rate
*/
uint public multiplierPerBlock;
/**
* @notice The base interest rate which is the y-intercept when utilization rate is 0
*/
uint public baseRatePerBlock;
/**
* @notice Construct an interest rate model
* @param baseRatePerYear The approximate target base APR, as a mantissa (scaled by 1e18)
* @param multiplierPerYear The rate of increase in interest rate wrt utilization (scaled by 1e18)
*/
constructor(uint baseRatePerYear, uint multiplierPerYear) public {
baseRatePerBlock = baseRatePerYear.div(blocksPerYear);
multiplierPerBlock = multiplierPerYear.div(blocksPerYear);
emit NewInterestParams(baseRatePerBlock, multiplierPerBlock);
}
/**
* @notice Calculates the utilization rate of the market: `borrows / (cash + borrows - reserves)`
* @param cash The amount of cash in the market
* @param borrows The amount of borrows in the market
* @param reserves The amount of reserves in the market (currently unused)
* @return The utilization rate as a mantissa between [0, 1e18]
*/
function utilizationRate(uint cash, uint borrows, uint reserves) public pure returns (uint) {
// Utilization rate is 0 when there are no borrows
if (borrows == 0) {
return 0;
}
return borrows.mul(1e18).div(cash.add(borrows).sub(reserves));
}
/**
* @notice Calculates the current borrow rate per block, with the error code expected by the market
* @param cash The amount of cash in the market
* @param borrows The amount of borrows in the market
* @param reserves The amount of reserves in the market
* @return The borrow rate percentage per block as a mantissa (scaled by 1e18)
*/
function getBorrowRate(uint cash, uint borrows, uint reserves) public view returns (uint) {
uint ur = utilizationRate(cash, borrows, reserves);
return ur.mul(multiplierPerBlock).div(1e18).add(baseRatePerBlock);
}
/**
* @notice Calculates the current supply rate per block
* @param cash The amount of cash in the market
* @param borrows The amount of borrows in the market
* @param reserves The amount of reserves in the market
* @param reserveFactorMantissa The current reserve factor for the market
* @return The supply rate percentage per block as a mantissa (scaled by 1e18)
*/
function getSupplyRate(uint cash, uint borrows, uint reserves, uint reserveFactorMantissa) public view returns (uint) {
uint oneMinusReserveFactor = uint(1e18).sub(reserveFactorMantissa);
uint borrowRate = getBorrowRate(cash, borrows, reserves);
uint rateToPool = borrowRate.mul(oneMinusReserveFactor).div(1e18);
return utilizationRate(cash, borrows, reserves).mul(rateToPool).div(1e18);
}
}