Venus.io

1ragma solidity ^0.5.16;
2​
3/**
4  * @title Careful Math
5  * @author Venus
6  * @notice Derived from OpenZeppelin's SafeMath library
7  *         https://github.com/OpenZeppelin/openzeppelin-solidity/blob/master/contracts/math/SafeMath.sol
8  */
9contract CarefulMath {
10​
11    /*
12     * @dev Possible error codes that we can return
13     */
14    enum MathError {
15        NO_ERROR,
16        DIVISION_BY_ZERO,
17        INTEGER_OVERFLOW,
18        INTEGER_UNDERFLOW
19    }
20​
21    /*
22    * @dev Multiplies two numbers, returns an error on overflow.
23    */
24    function mulUInt(uint a, uint b) internal pure returns (MathError, uint) {
25        if (a == 0) {
26            return (MathError.NO_ERROR, 0);
27        }
28​
29        uint c = a * b;
30​
31        if (c / a != b) {
32            return (MathError.INTEGER_OVERFLOW, 0);
33        } else {
34            return (MathError.NO_ERROR, c);
35        }
36    }
37​
38    /**
39    * @dev Integer division of two numbers, truncating the quotient.
40    */
41    function divUInt(uint a, uint b) internal pure returns (MathError, uint) {
42        if (b == 0) {
43            return (MathError.DIVISION_BY_ZERO, 0);
44        }
45​
46        return (MathError.NO_ERROR, a / b);
47    }
48​
49    /**
50    * @dev Subtracts two numbers, returns an error on overflow (i.e. if subtrahend is greater than minuend).
51    */
52    function subUInt(uint a, uint b) internal pure returns (MathError, uint) {
53        if (b <= a) {
54            return (MathError.NO_ERROR, a - b);
55        } else {
56            return (MathError.INTEGER_UNDERFLOW, 0);
57        }
58    }
59​
60    /**
61    * @dev Adds two numbers, returns an error on overflow.
62    */
63    function addUInt(uint a, uint b) internal pure returns (MathError, uint) {
64        uint c = a + b;
65​
66        if (c >= a) {
67            return (MathError.NO_ERROR, c);
68        } else {
69            return (MathError.INTEGER_OVERFLOW, 0);
70        }
71    }
72​
73    /**
74    * @dev add a and b and then subtract c
75    */
76    function addThenSubUInt(uint a, uint b, uint c) internal pure returns (MathError, uint) {
77        (MathError err0, uint sum) = addUInt(a, b);
78​
79        if (err0 != MathError.NO_ERROR) {
80            return (err0, 0);
81        }
82​
83        return subUInt(sum, c);

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