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ERC20 Basic
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pragma solidity 0.6.6; | |
interface IERC20 { | |
function totalSupply() external view returns (uint256); | |
function balanceOf(address account) external view returns (uint256); | |
function allowance(address owner, address spender) external view returns (uint256); | |
function transfer(address recipient, uint256 amount) external returns (bool); | |
function approve(address spender, uint256 amount) external returns (bool); | |
function transferFrom(address sender, address recipient, uint256 amount) external returns (bool); | |
event Transfer(address indexed from, address indexed to, uint256 value); | |
event Approval(address indexed owner, address indexed spender, uint256 value); | |
} | |
contract ERC20Basic is IERC20 { | |
string public constant name = "OPPToken"; | |
string public constant symbol = "OPP"; | |
uint8 public constant decimals = 18; | |
event Approval(address indexed tokenOwner, address indexed spender, uint tokens); | |
event Transfer(address indexed from, address indexed to, uint tokens); | |
mapping(address => uint256) balances; | |
mapping(address => mapping (address => uint256)) allowed; | |
uint256 totalSupply_; | |
using SafeMath for uint256; | |
constructor(uint256 total) public { | |
totalSupply_ = total; | |
balances[msg.sender] = totalSupply_; | |
} | |
function totalSupply() public override view returns (uint256) { | |
return totalSupply_; | |
} | |
function balanceOf(address tokenOwner) public override view returns (uint256) { | |
return balances[tokenOwner]; | |
} | |
function transfer(address receiver, uint256 numTokens) public override returns (bool) { | |
require(numTokens <= balances[msg.sender]); | |
balances[msg.sender] = balances[msg.sender].sub(numTokens); | |
balances[receiver] = balances[receiver].add(numTokens); | |
emit Transfer(msg.sender, receiver, numTokens); | |
return true; | |
} | |
function approve(address delegate, uint256 numTokens) public override returns (bool) { | |
allowed[msg.sender][delegate] = numTokens; | |
emit Approval(msg.sender, delegate, numTokens); | |
return true; | |
} | |
function allowance(address owner, address delegate) public override view returns (uint) { | |
return allowed[owner][delegate]; | |
} | |
function transferFrom(address owner, address buyer, uint256 numTokens) public override returns (bool) { | |
require(numTokens <= balances[owner]); | |
require(numTokens <= allowed[owner][msg.sender]); | |
balances[owner] = balances[owner].sub(numTokens); | |
allowed[owner][msg.sender] = allowed[owner][msg.sender].sub(numTokens); | |
balances[buyer] = balances[buyer].add(numTokens); | |
emit Transfer(owner, buyer, numTokens); | |
return true; | |
} | |
} | |
library SafeMath { | |
function sub(uint256 a, uint256 b) internal pure returns (uint256) { | |
assert(b <= a); | |
return a - b; | |
} | |
function add(uint256 a, uint256 b) internal pure returns (uint256) { | |
uint256 c = a + b; | |
assert(c >= a); | |
return c; | |
} | |
} |
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