Skip to content

Instantly share code, notes, and snippets.

@hrkrshnn
Created August 19, 2021 15:53
Show Gist options
  • Save hrkrshnn/2be89c60e18c208311a68269ba61f8bd to your computer and use it in GitHub Desktop.
Save hrkrshnn/2be89c60e18c208311a68269ba61f8bd to your computer and use it in GitHub Desktop.
ERC20 using user defined type name
pragma solidity ^0.8.7;
// User defined type name. Indicating a type with 18 decimals.
type UFixed18 is uint256;
library FixedMath
{
function add(UFixed18 a, UFixed18 b) internal pure returns (UFixed18 c) {
return UFixed18(uint(a) + uint(b));
}
function sub(UFixed18 a, UFixed18 b) internal pure returns (UFixed18 c) {
return UFixed18(uint(a) - uint(b));
}
}
contract ERC20 {
using FixedMath for UFixed18;
event Transfer(address indexed from, address indexed to, UFixed18 value);
event Approval(address indexed owner, address indexed spender, UFixed18 value);
mapping (address => UFixed18) private _balances;
mapping (address => mapping (address => UFixed18)) private _allowances;
UFixed18 private _totalSupply;
constructor() {
_mint(msg.sender, UFixed18(uint(20)));
}
function totalSupply() public view returns (UFixed18) {
return _totalSupply;
}
function balanceOf(address owner) public view returns (UFixed18) {
return _balances[owner];
}
function allowance(address owner, address spender) public view returns (UFixed18) {
return _allowances[owner][spender];
}
function transfer(address to, UFixed18 value) public returns (bool) {
_transfer(msg.sender, to, value);
return true;
}
function approve(address spender, UFixed18 value) public returns (bool) {
_approve(msg.sender, spender, value);
return true;
}
function transferFrom(address from, address to, UFixed18 value) public returns (bool) {
_transfer(from, to, value);
// The subtraction here will revert on overflow.
_approve(from, msg.sender, _allowances[from][msg.sender].sub(value));
return true;
}
function increaseAllowance(address spender, UFixed18 addedValue) public returns (bool) {
// The addition here will revert on overflow.
_approve(msg.sender, spender, _allowances[msg.sender][spender].add(addedValue));
return true;
}
function decreaseAllowance(address spender, UFixed18 subtractedValue) public returns (bool) {
// The subtraction here will revert on overflow.
_approve(msg.sender, spender, _allowances[msg.sender][spender].sub(subtractedValue));
return true;
}
function _transfer(address from, address to, UFixed18 value) internal {
require(to != address(0), "ERC20: transfer to the zero address");
// The subtraction and addition here will revert on overflow.
_balances[from] = _balances[from].sub(value);
_balances[to] = _balances[to].add(value);
emit Transfer(from, to, value);
}
function _mint(address account, UFixed18 value) internal {
require(account != address(0), "ERC20: mint to the zero address");
// The additions here will revert on overflow.
_totalSupply = _totalSupply.add(value);
_balances[account] = _balances[account].add(value);
emit Transfer(address(0), account, value);
}
function _burn(address account, UFixed18 value) internal {
require(account != address(0), "ERC20: burn from the zero address");
// The subtractions here will revert on overflow.
_totalSupply = _totalSupply.sub(value);
_balances[account] = _balances[account].sub(value);
emit Transfer(account, address(0), value);
}
function _approve(address owner, address spender, UFixed18 value) internal {
require(owner != address(0), "ERC20: approve from the zero address");
require(spender != address(0), "ERC20: approve to the zero address");
_allowances[owner][spender] = value;
emit Approval(owner, spender, value);
}
function _burnFrom(address account, UFixed18 value) internal {
_burn(account, value);
_approve(account, msg.sender, _allowances[account][msg.sender].sub(value));
}
}
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment