129 lines
3.1 KiB
Solidity
129 lines
3.1 KiB
Solidity
pragma solidity ^0.4.24;
|
|
|
|
import "./ERC20Token.sol";
|
|
|
|
contract StandardToken is ERC20Token {
|
|
|
|
uint256 private supply;
|
|
mapping (address => uint256) balances;
|
|
mapping (address => mapping (address => uint256)) allowed;
|
|
|
|
constructor() internal { }
|
|
|
|
function transfer(
|
|
address _to,
|
|
uint256 _value
|
|
)
|
|
external
|
|
returns (bool success)
|
|
{
|
|
return transfer(msg.sender, _to, _value);
|
|
}
|
|
|
|
function approve(
|
|
address _to,
|
|
uint256 _value
|
|
)
|
|
external
|
|
returns (bool success)
|
|
{
|
|
return approve(msg.sender, _to, _value);
|
|
}
|
|
|
|
function transferFrom(
|
|
address _from,
|
|
address _to,
|
|
uint256 _value
|
|
)
|
|
external
|
|
returns (bool success)
|
|
{
|
|
if (balances[_from] >= _value &&
|
|
allowed[_from][msg.sender] >= _value &&
|
|
_value > 0) {
|
|
allowed[_from][msg.sender] -= _value;
|
|
return transfer(_from, _to, _value);
|
|
} else {
|
|
return false;
|
|
}
|
|
}
|
|
|
|
function allowance(address _owner, address _spender)
|
|
external
|
|
view
|
|
returns (uint256 remaining)
|
|
{
|
|
return allowed[_owner][_spender];
|
|
}
|
|
|
|
function balanceOf(address _owner)
|
|
external
|
|
view
|
|
returns (uint256 balance)
|
|
{
|
|
return balances[_owner];
|
|
}
|
|
|
|
function totalSupply()
|
|
external
|
|
view
|
|
returns(uint256 currentTotalSupply)
|
|
{
|
|
return supply;
|
|
}
|
|
|
|
/**
|
|
* @dev Aprove the passed address to spend the specified amount of tokens on behalf of msg.sender.
|
|
* @param _from The address that is approving the spend
|
|
* @param _spender The address which will spend the funds.
|
|
* @param _value The amount of tokens to be spent.
|
|
*/
|
|
function approve(address _from, address _spender, uint256 _value) internal returns (bool) {
|
|
|
|
// 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
|
|
require((_value == 0) || (allowed[_from][_spender] == 0), "Bad usage");
|
|
|
|
allowed[_from][_spender] = _value;
|
|
emit Approval(_from, _spender, _value);
|
|
return true;
|
|
}
|
|
|
|
function mint(
|
|
address _to,
|
|
uint256 _amount
|
|
)
|
|
internal
|
|
{
|
|
balances[_to] += _amount;
|
|
supply += _amount;
|
|
emit Transfer(0x0, _to, _amount);
|
|
}
|
|
|
|
function transfer(
|
|
address _from,
|
|
address _to,
|
|
uint256 _value
|
|
)
|
|
internal
|
|
returns (bool success)
|
|
{
|
|
if (balances[_from] >= _value && _value > 0) {
|
|
balances[_from] -= _value;
|
|
if(_to == address(0)) {
|
|
supply -= _value;
|
|
} else {
|
|
balances[_to] += _value;
|
|
}
|
|
emit Transfer(_from, _to, _value);
|
|
return true;
|
|
} else {
|
|
return false;
|
|
}
|
|
}
|
|
|
|
|
|
}
|