Michael.W基于Foundry精读Openzeppelin第16期—

Michael.W基于Foundry精读Openzeppelin第16期——SignedSafeMath.sol

news2024/11/16 5:33:40

Michael.W基于Foundry精读Openzeppelin第16期——SignedSafeMath.sol

- - 0. 版本
  - - 0.1 SignedSafeMath.sol
  - 1. 目标合约
  - 2. 代码精读
  - - 2.1 mul(int256 a, int256 b)
    - 2.2 div(int256 a, int256 b)
    - 2.3 sub(int256 a, int256 b)
    - 2.4 add(int256 a, int256 b)

0. 版本

[openzeppelin]：v4.8.3，[forge-std]：v1.5.6

0.1 SignedSafeMath.sol

Github: https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v4.8.3/contracts/utils/math/SignedSafeMath.sol

SignedSafeMath库就是直接对solidity内置的int256类型的加减乘除运算的函数封装。

注：从solidity 0.8版本开始，SignedSafeMath已经不再被广泛使用。因为从0.8版本开始，solidity编译器已经内置了运算符的溢出检查。

1. 目标合约

封装SignedSafeMath library成为一个可调用合约：

Github: https://github.com/RevelationOfTuring/foundry-openzeppelin-contracts/blob/master/src/utils/math/MockSignedSafeMath.sol

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.0;

import "openzeppelin-contracts/contracts/utils/math/SignedSafeMath.sol";

contract MockSignedSafeMath {
    using SignedSafeMath for int;

    function mul(int a, int b) external pure returns (int) {
        return a.mul(b);
    }

    function div(int a, int b) external pure returns (int){
        return a.div(b);
    }

    function sub(int a, int b) external pure returns (int){
        return a.sub(b);
    }

    function add(int a, int b) external pure returns (int) {
        return a.add(b);
    }
}

全部foundry测试合约：

Github: https://github.com/RevelationOfTuring/foundry-openzeppelin-contracts/blob/master/test/utils/math/SignedSafeMath.t.sol

2. 代码精读

2.1 mul(int256 a, int256 b)

返回两个int256的乘积，如果产生溢出会revert。

    function mul(int256 a, int256 b) internal pure returns (int256) {
        // 是直接对a*b的函数封装，返回a与b的乘积
        return a * b;
    }

foundry代码验证

contract SignedSafeMathTest is Test {
    MockSignedSafeMath mssm = new MockSignedSafeMath();

    function test_Mul() external {
        assertEq(mssm.mul(3, 2), 6);
        assertEq(mssm.mul(3, - 2), - 6);
        assertEq(mssm.mul(- 3, 2), - 6);
        assertEq(mssm.mul(- 3, - 2), 6);
        // overflow
        vm.expectRevert();
        mssm.mul(type(int).max, 2);
        vm.expectRevert();
        mssm.mul(type(int).min, 2);
    }
}

2.2 div(int256 a, int256 b)

返回两个int256的商，如果除数为0会revert。

注：计算结果向0取整。

    function div(int256 a, int256 b) internal pure returns (int256) {
        // 是直接对a/b的函数封装，返回a与b的商
        return a / b;
    }

foundry代码验证

contract SignedSafeMathTest is Test {
    MockSignedSafeMath mssm = new MockSignedSafeMath();

    function test_Div() external {
        assertEq(mssm.div(3, 2), 1);
        assertEq(mssm.div(3, - 2), - 1);
        assertEq(mssm.div(- 3, 2), - 1);
        assertEq(mssm.div(- 3, - 2), 1);
        // overflow
        vm.expectRevert();
        mssm.div(1, 0);
    }
}

2.3 sub(int256 a, int256 b)

返回两个int256的差，如果产生溢出会revert

    function sub(int256 a, int256 b) internal pure returns (int256) {
        // 是直接对a-b的函数封装，返回a与b的差
        return a - b;
    }

foundry代码验证

contract SignedSafeMathTest is Test {
    MockSignedSafeMath mssm = new MockSignedSafeMath();

    function test_Sub() external {
        assertEq(mssm.sub(3, 2), 1);
        assertEq(mssm.sub(3, - 2), 5);
        assertEq(mssm.sub(- 3, 2), - 5);
        assertEq(mssm.sub(- 3, - 2), - 1);
        // overflow
        vm.expectRevert();
        mssm.sub(type(int).min, 1);
    }
}

2.4 add(int256 a, int256 b)

返回两个int256的和，如果产生溢出会revert。

    function add(int256 a, int256 b) internal pure returns (int256) {
        // 是直接对a+b的函数封装，返回a与b的和
        return a + b;
    }

foundry代码验证

contract SignedSafeMathTest is Test {
    MockSignedSafeMath mssm = new MockSignedSafeMath();

    function test_Add() external {
        assertEq(mssm.add(1, 2), 3);
        assertEq(mssm.add(- 1, 2), 1);
        assertEq(mssm.add(- 1, - 2), - 3);
        // overflow
        vm.expectRevert();
        mssm.add(type(int).max, 1);
    }
}