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pragma solidity ^0.4.24;
library SafeMath {
function mul(uint256 a, uint256 b) internal pure returns (uint256) {
if (a == 0) {
return 0;
}
uint256 c = a * b;
require(c / a == b);
return c;
}
function div(uint256 a, uint256 b) internal pure returns (uint256) {
require(b > 0); // Solidity only automatically asserts when dividing by 0
uint256 c = a / b;
return c;
}
/**
* @dev Subtracts two numbers, reverts on overflow (i.e. if subtrahend is greater than minuend).
*/
function sub(uint256 a, uint256 b) internal pure returns (uint256) {
require(b <= a);
uint256 c = a - b;
return c;
}
function add(uint256 a, uint256 b) internal pure returns (uint256) {
uint256 c = a + b;
require(c >= a);
return c;
}
function mod(uint256 a, uint256 b) internal pure returns (uint256) {
require(b != 0);
return a % b;
}
}
contract StandardERC20{
using SafeMath for uint256;
string public _name;
string public _symbol;
uint8 public _decimals;
constructor(string name, string symbol, uint8 decimals, uint256 totalSupply) public {
_name = name;
_symbol = symbol;
_decimals = decimals;
_totalSupply = totalSupply;
}
mapping (address => uint256) private _balances;
mapping (address => mapping (address => uint256)) private _allowed;
uint256 public _totalSupply;
event Transfer(
address indexed from,
address indexed to,
uint256 value
);
event Approval(
address indexed owner,
address indexed spender,
uint256 value
);
function totalSupply() public view returns (uint256) {
return _totalSupply;
}
function balanceOf(address owner) public view returns (uint256) {
return _balances[owner];
}
function allowance(
address owner,
address spender
)
public
view
returns (uint256)
{
return _allowed[owner][spender];
}
function transfer(address to, uint256 value) public returns (bool) {
_transfer(msg.sender, to, value);
return true;
}
function approve(address spender, uint256 value) public returns (bool) {
require(spender != address(0));
_allowed[msg.sender][spender] = value;
emit Approval(msg.sender, spender, value);
return true;
}
function transferFrom(
address from,
address to,
uint256 value
)
public
returns (bool)
{
require(value <= _allowed[from][msg.sender]);
_allowed[from][msg.sender] = _allowed[from][msg.sender].sub(value);
_transfer(from, to, value);
return true;
}
function increaseAllowance(
address spender,
uint256 addedValue
)
public
returns (bool)
{
require(spender != address(0));
_allowed[msg.sender][spender] = (
_allowed[msg.sender][spender].add(addedValue));
emit Approval(msg.sender, spender, _allowed[msg.sender][spender]);
return true;
}
function decreaseAllowance(
address spender,
uint256 subtractedValue
)
public
returns (bool)
{
require(spender != address(0));
_allowed[msg.sender][spender] = (
_allowed[msg.sender][spender].sub(subtractedValue));
emit Approval(msg.sender, spender, _allowed[msg.sender][spender]);
return true;
}
function _transfer(address from, address to, uint256 value) internal {
require(value <= _balances[from]);
require(to != address(0));
_balances[from] = _balances[from].sub(value);
_balances[to] = _balances[to].add(value);
emit Transfer(from, to, value);
}
function _mint(address account, uint256 value) internal {
require(account != 0);
_totalSupply = _totalSupply.add(value);
_balances[account] = _balances[account].add(value);
emit Transfer(address(0), account, value);
}
function _burn(address account, uint256 value) internal {
require(account != 0);
require(value <= _balances[account]);
_totalSupply = _totalSupply.sub(value);
_balances[account] = _balances[account].sub(value);
emit Transfer(account, address(0), value);
}
function _burnFrom(address account, uint256 value) internal {
require(value <= _allowed[account][msg.sender]);
_allowed[account][msg.sender] = _allowed[account][msg.sender].sub(
value);
_burn(account, value);
}
}
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