aave-protocol-v2/contracts/libraries/WadRayMath.sol

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// SPDX-License-Identifier: agpl-3.0
pragma solidity ^0.6.8;
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import '@openzeppelin/contracts/math/SafeMath.sol';
/**
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* @title WadRayMath library
* @author Aave
* @dev Provides mul and div function for wads (decimal numbers with 18 digits precision) and rays (decimals with 27 digits)
**/
library WadRayMath {
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using SafeMath for uint256;
uint256 internal constant WAD = 1e18;
uint256 internal constant halfWAD = WAD / 2;
uint256 internal constant RAY = 1e27;
uint256 internal constant halfRAY = RAY / 2;
uint256 internal constant WAD_RAY_RATIO = 1e9;
/**
* @return one ray, 1e27
**/
function ray() internal pure returns (uint256) {
return RAY;
}
/**
* @return one wad, 1e18
**/
function wad() internal pure returns (uint256) {
return WAD;
}
/**
* @return half ray, 1e27/2
**/
function halfRay() internal pure returns (uint256) {
return halfRAY;
}
/**
* @return half ray, 1e18/2
**/
function halfWad() internal pure returns (uint256) {
return halfWAD;
}
/**
* @dev multiplies two wad, rounding half up to the nearest wad
* @param a wad
* @param b wad
* @return the result of a*b, in wad
**/
function wadMul(uint256 a, uint256 b) internal pure returns (uint256) {
return halfWAD.add(a.mul(b)).div(WAD);
}
/**
* @dev divides two wad, rounding half up to the nearest wad
* @param a wad
* @param b wad
* @return the result of a/b, in wad
**/
function wadDiv(uint256 a, uint256 b) internal pure returns (uint256) {
uint256 halfB = b / 2;
return halfB.add(a.mul(WAD)).div(b);
}
/**
* @dev multiplies two ray, rounding half up to the nearest ray
* @param a ray
* @param b ray
* @return the result of a*b, in ray
**/
function rayMul(uint256 a, uint256 b) internal pure returns (uint256) {
return halfRAY.add(a.mul(b)).div(RAY);
}
/**
* @dev divides two ray, rounding half up to the nearest ray
* @param a ray
* @param b ray
* @return the result of a/b, in ray
**/
function rayDiv(uint256 a, uint256 b) internal pure returns (uint256) {
uint256 halfB = b / 2;
return halfB.add(a.mul(RAY)).div(b);
}
/**
* @dev casts ray down to wad
* @param a ray
* @return a casted to wad, rounded half up to the nearest wad
**/
function rayToWad(uint256 a) internal pure returns (uint256) {
uint256 halfRatio = WAD_RAY_RATIO / 2;
return halfRatio.add(a).div(WAD_RAY_RATIO);
}
/**
* @dev convert wad up to ray
* @param a wad
* @return a converted in ray
**/
function wadToRay(uint256 a) internal pure returns (uint256) {
return a.mul(WAD_RAY_RATIO);
}
}