// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
/**
* @title SignedSafeMath
* @dev Signed math operations with safety checks that revert on error.
*/
library SignedSafeMath {
int256 constant private _INT256_MIN = -2**255;
/**
* @dev Returns the multiplication of two signed integers, reverting on
* overflow.
*
* Counterpart to Solidity's `*` operator.
*
* Requirements:
*
* - Multiplication cannot overflow.
*/
function mul(int256 a, int256 b) internal pure returns (int256) {
// 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;
}
require(!(a == -1 && b == _INT256_MIN), "SignedSafeMath: multiplication overflow");
int256 c = a * b;
require(c / a == b, "SignedSafeMath: multiplication overflow");
return c;
}
/**
* @dev Returns the integer division of two signed 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(int256 a, int256 b) internal pure returns (int256) {
require(b != 0, "SignedSafeMath: division by zero");
require(!(b == -1 && a == _INT256_MIN), "SignedSafeMath: division overflow");
int256 c = a / b;
return c;
}
/**
* @dev Returns the subtraction of two signed integers, reverting on
* overflow.
*
* Counterpart to Solidity's `-` operator.
*
* Requirements:
*
* - Subtraction cannot overflow.
*/
function sub(int256 a, int256 b) internal pure returns (int256) {
int256 c = a - b;
require((b >= 0 && c <= a) || (b < 0 && c > a), "SignedSafeMath: subtraction overflow");
return c;
}
/**
* @dev Returns the addition of two signed integers, reverting on
* overflow.
*
* Counterpart to Solidity's `+` operator.
*
* Requirements:
*
* - Addition cannot overflow.
*/
function add(int256 a, int256 b) internal pure returns (int256) {
int256 c = a + b;
require((b >= 0 && c >= a) || (b < 0 && c < a), "SignedSafeMath: addition overflow");
return c;
}
}