Contract Source Code:
File 1 of 1 : MATH
pragma solidity ^0.5.11;
/*
* Creator: Andrew Yang Token
/*
* Abstract Token Smart Contract
*
*/
/*
* Safe Math Smart Contract.
* https://github.com/OpenZeppelin/zeppelin-solidity/blob/master/contracts/math/SafeMath.sol
*/
contract SafeMath {
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;
}
function safeDiv(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 c;
}
function safeSub(uint256 a, uint256 b) internal pure returns (uint256) {
assert(b <= a);
return a - b;
}
function safeAdd(uint256 a, uint256 b) internal pure returns (uint256) {
uint256 c = a + b;
assert(c >= a);
return c;
}
}
/**
* ERC-20 standard token interface, as defined
* <a href="http://github.com/ethereum/EIPs/issues/20">here</a>.
*/
contract Token {
function totalSupply() public view returns (uint256 supply);
function balanceOf(address _owner) public view returns (uint256 balance);
function transfer(address _to, uint256 _value) public returns (bool success);
function transferFrom(address _from, address _to, uint256 _value) public returns (bool success);
function approve(address _spender, uint256 _value) public returns (bool success);
function allowance(address _owner, address _spender) public view returns (uint256 remaining);
event Transfer(address indexed _from, address indexed _to, uint256 _value);
event Approval(address indexed _owner, address indexed _spender, uint256 _value);
}
/**
* Abstract Token Smart Contract that could be used as a base contract for
* ERC-20 token contracts.
*/
contract AbstractToken is Token, SafeMath {
/**
* Create new Abstract Token contract.
*/
constructor () public {
// Do nothing
}
/**
* Get number of tokens currently belonging to given owner.
*
* @param _owner address to get number of tokens currently belonging to the
* owner of
* @return number of tokens currently belonging to the owner of given address
*/
function balanceOf(address _owner) public view returns (uint256 balance) {
return accounts [_owner];
}
/**
* Transfer given number of tokens from message sender to given recipient.
*
* @param _to address to transfer tokens to the owner of
* @param _value number of tokens to transfer to the owner of given address
* @return true if tokens were transferred successfully, false otherwise
* accounts [_to] + _value > accounts [_to] for overflow check
* which is already in safeMath
*/
function transfer(address _to, uint256 _value) public returns (bool success) {
require(_to != address(0));
if (accounts [msg.sender] < _value) return false;
if (_value > 0 && msg.sender != _to) {
accounts [msg.sender] = safeSub (accounts [msg.sender], _value);
accounts [_to] = safeAdd (accounts [_to], _value);
}
emit Transfer (msg.sender, _to, _value);
return true;
}
/**
* Transfer given number of tokens from given owner to given recipient.
*
* @param _from address to transfer tokens from the owner of
* @param _to address to transfer tokens to the owner of
* @param _value number of tokens to transfer from given owner to given
* recipient
* @return true if tokens were transferred successfully, false otherwise
* accounts [_to] + _value > accounts [_to] for overflow check
* which is already in safeMath
*/
function transferFrom(address _from, address _to, uint256 _value) public
returns (bool success) {
require(_to != address(0));
if (allowances [_from][msg.sender] < _value) return false;
if (accounts [_from] < _value) return false;
if (_value > 0 && _from != _to) {
allowances [_from][msg.sender] = safeSub (allowances [_from][msg.sender], _value);
accounts [_from] = safeSub (accounts [_from], _value);
accounts [_to] = safeAdd (accounts [_to], _value);
}
emit Transfer(_from, _to, _value);
return true;
}
/**
* Allow given spender to transfer given number of tokens from message sender.
* @param _spender address to allow the owner of to transfer tokens from message sender
* @param _value number of tokens to allow to transfer
* @return true if token transfer was successfully approved, false otherwise
*/
function approve (address _spender, uint256 _value) public returns (bool success) {
allowances [msg.sender][_spender] = _value;
emit Approval (msg.sender, _spender, _value);
return true;
}
/**
* Tell how many tokens given spender is currently allowed to transfer from
* given owner.
*
* @param _owner address to get number of tokens allowed to be transferred
* from the owner of
* @param _spender address to get number of tokens allowed to be transferred
* by the owner of
* @return number of tokens given spender is currently allowed to transfer
* from given owner
*/
function allowance(address _owner, address _spender) public view
returns (uint256 remaining) {
return allowances [_owner][_spender];
}
/**
* Mapping from addresses of token holders to the numbers of tokens belonging
* to these token holders.
*/
mapping (address => uint256) accounts;
/**
* Mapping from addresses of token holders to the mapping of addresses of
* spenders to the allowances set by these token holders to these spenders.
*/
mapping (address => mapping (address => uint256)) private allowances;
}
/**
* Andrew Yang Token smart contract.
*/
contract MATH is AbstractToken {
/**
* Maximum allowed number of tokens in circulation.
* tokenSupply = tokensIActuallyWant * (10 ^ decimals)
*/
uint256 constant MAX_TOKEN_COUNT = 3141592653 * (10**2);
/**
* Address of the owner of this smart contract.
*/
address private owner;
/**
* Frozen account list holder
*/
mapping (address => bool) private frozenAccount;
/**
* Current number of tokens in circulation.
*/
uint256 tokenCount = 0;
/**
* True if tokens transfers are currently frozen, false otherwise.
*/
bool frozen = false;
/**
* Create new token smart contract and make msg.sender the
* owner of this smart contract.
*/
constructor () public {
owner = msg.sender;
}
/**
* Get total number of tokens in circulation.
*
* @return total number of tokens in circulation
*/
function totalSupply() public view returns (uint256 supply) {
return tokenCount;
}
string constant public name = "Andrew Yang Token";
string constant public symbol = "MATH";
uint8 constant public decimals = 2;
/**
* Transfer given number of tokens from message sender to given recipient.
* @param _to address to transfer tokens to the owner of
* @param _value number of tokens to transfer to the owner of given address
* @return true if tokens were transferred successfully, false otherwise
*/
function transfer(address _to, uint256 _value) public returns (bool success) {
require(!frozenAccount[msg.sender]);
if (frozen) return false;
else return AbstractToken.transfer (_to, _value);
}
/**
* Transfer given number of tokens from given owner to given recipient.
*
* @param _from address to transfer tokens from the owner of
* @param _to address to transfer tokens to the owner of
* @param _value number of tokens to transfer from given owner to given
* recipient
* @return true if tokens were transferred successfully, false otherwise
*/
function transferFrom(address _from, address _to, uint256 _value) public
returns (bool success) {
require(!frozenAccount[_from]);
if (frozen) return false;
else return AbstractToken.transferFrom (_from, _to, _value);
}
/**
* Change how many tokens given spender is allowed to transfer from message
* spender. In order to prevent double spending of allowance,
* To change the approve amount you first have to reduce the addresses`
* allowance to zero by calling `approve(_spender, 0)` if it is not
* already 0 to mitigate the race condition described here:
* https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
* @param _spender address to allow the owner of to transfer tokens from
* message sender
* @param _value number of tokens to allow to transfer
* @return true if token transfer was successfully approved, false otherwise
*/
function approve (address _spender, uint256 _value) public
returns (bool success) {
require(allowance (msg.sender, _spender) == 0 || _value == 0);
return AbstractToken.approve (_spender, _value);
}
/**
* Create _value new tokens and give new created tokens to msg.sender.
* May only be called by smart contract owner.
*
* @param _value number of tokens to create
* @return true if tokens were created successfully, false otherwise
*/
function createTokens(uint256 _value) public
returns (bool success) {
require (msg.sender == owner);
if (_value > 0) {
if (_value > safeSub (MAX_TOKEN_COUNT, tokenCount)) return false;
accounts [msg.sender] = safeAdd (accounts [msg.sender], _value);
tokenCount = safeAdd (tokenCount, _value);
// adding transfer event and _from address as null address
emit Transfer(address(0), msg.sender, _value);
return true;
}
return false;
}
/**
* Set new owner for the smart contract.
* May only be called by smart contract owner.
*
* @param _newOwner address of new owner of the smart contract
*/
function setOwner(address _newOwner) public {
require (msg.sender == owner);
owner = _newOwner;
}
/**
* Freeze ALL token transfers.
* May only be called by smart contract owner.
*/
function freezeTransfers () public {
require (msg.sender == owner);
if (!frozen) {
frozen = true;
emit Freeze ();
}
}
/**
* Unfreeze ALL token transfers.
* May only be called by smart contract owner.
*/
function unfreezeTransfers () public {
require (msg.sender == owner);
if (frozen) {
frozen = false;
emit Unfreeze ();
}
}
/*A user is able to unintentionally send tokens to a contract
* and if the contract is not prepared to refund them they will get stuck in the contract.
* The same issue used to happen for Ether too but new Solidity versions added the payable modifier to
* prevent unintended Ether transfers. However, there’s no such mechanism for token transfers.
* so the below function is created
*/
function refundTokens(address _token, address _refund, uint256 _value) public {
require (msg.sender == owner);
require(_token != address(this));
AbstractToken token = AbstractToken(_token);
token.transfer(_refund, _value);
emit RefundTokens(_token, _refund, _value);
}
/**
* Freeze specific account
* May only be called by smart contract owner.
*/
function freezeAccount(address _target, bool freeze) public {
require (msg.sender == owner);
require (msg.sender != _target);
frozenAccount[_target] = freeze;
emit FrozenFunds(_target, freeze);
}
/**
* Logged when token transfers were frozen.
*/
event Freeze ();
/**
* Logged when token transfers were unfrozen.
*/
event Unfreeze ();
/**
* Logged when a particular account is frozen.
*/
event FrozenFunds(address target, bool frozen);
/**
* when accidentally send other tokens are refunded
*/
event RefundTokens(address _token, address _refund, uint256 _value);
}