合约源码
pragma solidity ^0.4.24; /** * 使用安全计算法进行加减乘除运算 * @title SafeMath * @dev Math operations with safety checks that throw on error */ library SafeMath { /** * @dev Multiplies two numbers, throws on overflow. */ function mul(uint256 a, uint256 b) internal pure returns (uint256) { if (a == 0) { return 0; } uint256 c = a * b; assert(c / a == b); return c; } /** * @dev Integer division of two numbers, truncating the quotient. */ function div(uint256 a, uint256 b) internal pure returns (uint256) { // assert(b > 0); // Solidity automatically throws when dividing by 0 // uint256 c = a / b; // assert(a == b * c + a % b); // There is no case in which this doesn't hold return a / b; } /** * @dev Subtracts two numbers, throws on overflow (i.e. if subtrahend is greater than minuend). */ function sub(uint256 a, uint256 b) internal pure returns (uint256) { assert(b <= a); return a - b; } /** * @dev Adds two numbers, throws on overflow. */ function add(uint256 a, uint256 b) internal pure returns (uint256) { uint256 c = a + b; assert(c >= a); return c; } } contract Ownable { address public owner; /** * @dev The Ownable constructor sets the original `owner` of the contract to the sender * account. */ function Ownable() public { owner = msg.sender; } /** * @dev Throws if called by any account other than the owner. */ modifier onlyOwner() { require(msg.sender == owner); _; } /** * @dev Allows the current owner to transfer control of the contract to a newOwner. * @param newOwner The address to transfer ownership to. */ function transferOwnership(address newOwner) public onlyOwner { if (newOwner != address(0)) { owner = newOwner; } } } /** * 合约管理员可以在紧急情况下暂停合约,停止转账行为 * @title Pausable * @dev Base contract which allows children to implement an emergency stop mechanism. */ contract Pausable is Ownable { event Pause(); event Unpause(); bool public paused = false; /** * @dev Modifier to make a function callable only when the contract is not paused. */ modifier whenNotPaused() { require(!paused); _; } /** * @dev Modifier to make a function callable only when the contract is paused. */ modifier whenPaused() { require(paused); _; } /** * @dev called by the owner to pause, triggers stopped state */ function pause() onlyOwner whenNotPaused public { paused = true; emit Pause(); } /** * @dev called by the owner to unpause, returns to normal state */ function unpause() onlyOwner whenPaused public { paused = false; emit Unpause(); } } /** * @title ERC20Basic * @dev Simpler version of ERC20 interface * @dev see https://github.com/ethereum/EIPs/issues/179 */ contract ERC20Basic { function totalSupply() public view returns (uint256); function balanceOf(address who) public view returns (uint256); function transfer(address to, uint256 value) public returns (bool); event Transfer(address indexed from, address indexed to, uint256 value); } /** * @title ERC20 interface * @dev see https://github.com/ethereum/EIPs/issues/20 */ contract ERC20 is ERC20Basic { function allowance(address owner, address spender) public view returns (uint256); function transferFrom(address from, address to, uint256 value) public returns (bool); function approve(address spender, uint256 value) public returns (bool); event Approval(address indexed owner, address indexed spender, uint256 value); } /** * @title Basic token * @dev Basic version of StandardToken, with no allowances. */ contract BasicToken is ERC20Basic, Ownable { using SafeMath for uint256; mapping(address => uint256) balances; mapping(address => bool) public frozenAccount; event FrozenFunds(address target, bool frozen); uint256 totalSupply_; /** * @dev total number of tokens in existence */ function totalSupply() public view returns (uint256) { return totalSupply_; } /** * @dev transfer token for a specified address * @param _to The address to transfer to. * @param _value The amount to be transferred. */ function transfer(address _to, uint256 _value) public returns (bool) { require(!frozenAccount[msg.sender]); require(_to != address(0)); require(_value <= balances[msg.sender]); balances[msg.sender] = balances[msg.sender].sub(_value); balances[_to] = balances[_to].add(_value); emit Transfer(msg.sender, _to, _value); return true; } /** * @dev Gets the balance of the specified address. * @param _owner The address to query the the balance of. * @return An uint256 representing the amount owned by the passed address. */ function balanceOf(address _owner) public view returns (uint256 balance) { return balances[_owner]; } // freeze account function freezeAccount(address target, bool freeze) public onlyOwner { frozenAccount[target] = freeze; emit FrozenFunds(target, freeze); } } /** * @title Standard ERC20 token * * @dev Implementation of the basic standard token. * @dev https://github.com/ethereum/EIPs/issues/20 */ contract StandardToken is ERC20, BasicToken { mapping (address => mapping (address => uint256)) internal allowed; /** * 方法调用者将from账户中的代币转入to账户中 * @dev Transfer tokens from one address to another * @param _from address The address which you want to send tokens from * @param _to address The address which you want to transfer to * @param _value uint256 the amount of tokens to be transferred */ function transferFrom(address _from, address _to, uint256 _value) public returns (bool) { require(!frozenAccount[_from]); require(_to != address(0)); require(_value <= balances[_from]); require(_value <= allowed[_from][msg.sender]); balances[_from] = balances[_from].sub(_value); balances[_to] = balances[_to].add(_value); allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value); emit Transfer(_from, _to, _value); return true; } /** * 方法调用者允许spender操作自己账户中value数量的代币 * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender. * * Beware that changing an allowance with this method brings the risk that someone may use both the old * and the new allowance by unfortunate transaction ordering. One possible solution to mitigate this * race condition is to first reduce the spender's allowance to 0 and set the desired value afterwards: * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729 * @param _spender The address which will spend the funds. * @param _value The amount of tokens to be spent. */ function approve(address _spender, uint256 _value) public returns (bool) { require((_value == 0) || (allowed[msg.sender][_spender] == 0)); allowed[msg.sender][_spender] = _value; emit Approval(msg.sender, _spender, _value); return true; } /** * 查看spender还可以操作owner代币的数量是多少 * @dev Function to check the amount of tokens that an owner allowed to a spender. * @param _owner address The address which owns the funds. * @param _spender address The address which will spend the funds. * @return A uint256 specifying the amount of tokens still available for the spender. */ function allowance(address _owner, address _spender) public view returns (uint256) { return allowed[_owner][_spender]; } } // 暂停合约会影响以下方法的调用 contract PausableToken is StandardToken, Pausable { function transfer(address _to, uint256 _value) public whenNotPaused returns (bool) { return super.transfer(_to, _value); } function transferFrom(address _from, address _to, uint256 _value) public whenNotPaused returns (bool) { return super.transferFrom(_from, _to, _value); } function approve(address _spender, uint256 _value) public whenNotPaused returns (bool) { return super.approve(_spender, _value); } // 批量转账 function batchTransfer(address[] _receivers, uint256 _value) public whenNotPaused returns (bool) { require(!frozenAccount[msg.sender]); uint receiverCount = _receivers.length; require(receiverCount > 0); uint256 amount = _value.mul(uint256(receiverCount)); require(_value > 0 && balances[msg.sender] >= amount); balances[msg.sender] = balances[msg.sender].sub(amount); for (uint i = 0; i < receiverCount; i++) { balances[_receivers[i]] = balances[_receivers[i]].add(_value); emit Transfer(msg.sender, _receivers[i], _value); } return true; } } contract USDT is PausableToken { uint8 public constant decimals = 6; string public constant symbol = "USDT"; constructor() public { //发行总量 totalSupply_ = 100000 * (10 ** uint256(decimals)); balances[msg.sender] = 100000 * (10 ** uint256(decimals)); paused = false; } }