You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
124 lines
4.0 KiB
124 lines
4.0 KiB
pragma solidity ^0.4.24;
|
|
|
|
import "./BasicToken.sol";
|
|
import "./ERC20.sol";
|
|
|
|
|
|
/**
|
|
* @title Standard ERC20 token
|
|
*
|
|
* @dev Implementation of the basic standard token.
|
|
* https://github.com/ethereum/EIPs/issues/20
|
|
* Based on code by FirstBlood: https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
|
|
*/
|
|
contract StandardToken is ERC20, BasicToken {
|
|
|
|
mapping (address => mapping (address => uint256)) internal allowed;
|
|
|
|
|
|
/**
|
|
* @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(_value <= balances[_from]);
|
|
require(_value <= allowed[_from][msg.sender]);
|
|
require(_to != address(0));
|
|
|
|
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;
|
|
}
|
|
|
|
/**
|
|
* @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) {
|
|
allowed[msg.sender][_spender] = _value;
|
|
emit Approval(msg.sender, _spender, _value);
|
|
return true;
|
|
}
|
|
|
|
/**
|
|
* @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];
|
|
}
|
|
|
|
/**
|
|
* @dev Increase the amount of tokens that an owner allowed to a spender.
|
|
* approve should be called when allowed[_spender] == 0. To increment
|
|
* allowed value is better to use this function to avoid 2 calls (and wait until
|
|
* the first transaction is mined)
|
|
* From MonolithDAO Token.sol
|
|
* @param _spender The address which will spend the funds.
|
|
* @param _addedValue The amount of tokens to increase the allowance by.
|
|
*/
|
|
function increaseApproval(
|
|
address _spender,
|
|
uint256 _addedValue
|
|
)
|
|
public
|
|
returns (bool)
|
|
{
|
|
allowed[msg.sender][_spender] = (
|
|
allowed[msg.sender][_spender].add(_addedValue));
|
|
emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
|
|
return true;
|
|
}
|
|
|
|
/**
|
|
* @dev Decrease the amount of tokens that an owner allowed to a spender.
|
|
* approve should be called when allowed[_spender] == 0. To decrement
|
|
* allowed value is better to use this function to avoid 2 calls (and wait until
|
|
* the first transaction is mined)
|
|
* From MonolithDAO Token.sol
|
|
* @param _spender The address which will spend the funds.
|
|
* @param _subtractedValue The amount of tokens to decrease the allowance by.
|
|
*/
|
|
function decreaseApproval(
|
|
address _spender,
|
|
uint256 _subtractedValue
|
|
)
|
|
public
|
|
returns (bool)
|
|
{
|
|
uint256 oldValue = allowed[msg.sender][_spender];
|
|
if (_subtractedValue >= oldValue) {
|
|
allowed[msg.sender][_spender] = 0;
|
|
} else {
|
|
allowed[msg.sender][_spender] = oldValue.sub(_subtractedValue);
|
|
}
|
|
emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
|
|
return true;
|
|
}
|
|
|
|
}
|
|
|