43 lines
1.2 KiB
Solidity
43 lines
1.2 KiB
Solidity
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// SPDX-License-Identifier: MIT
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pragma solidity 0.6.12;
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/**
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* @dev Wrappers over Solidity's arithmetic operations with added overflow
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* checks.
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*
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* note that this is a stripped down version of open zeppelin's safemath
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* https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/math/SafeMath.sol
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*/
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contract SafeMath {
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/**
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* @dev Returns the subtraction of two unsigned integers, reverting on
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* overflow (when the result is negative).
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*
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* Counterpart to Solidity's `-` operator.
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*
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* Requirements:
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* - Subtraction cannot overflow.
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*/
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function sub(uint256 a, uint256 b) internal pure returns (uint256) {
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return _sub(a, b, "SafeMath: subtraction overflow");
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}
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/**
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* @dev Returns the subtraction of two unsigned integers, reverting with custom message on
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* overflow (when the result is negative).
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*
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* Counterpart to Solidity's `-` operator.
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*
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* Requirements:
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* - Subtraction cannot overflow.
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*/
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function _sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
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require(b <= a, errorMessage);
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uint256 c = a - b;
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return c;
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}
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}
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