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/*
Copyright 2018 ZeroEx Intl.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
pragma solidity ^0.4.24;
pragma experimental ABIEncoderV2;
import "./IERC20Token.sol";
contract ERC20Token is IERC20Token {
string constant INSUFFICIENT_BALANCE = "ERC20_INSUFFICIENT_BALANCE";
string constant INSUFFICIENT_ALLOWANCE = "ERC20_INSUFFICIENT_ALLOWANCE";
string constant OVERFLOW = "Transfer would result in an overflow.";
mapping (address => uint256) balances;
mapping (address => mapping (address => uint256)) allowed;
uint256 public totalSupply;
function transfer(address _to, uint256 _value)
public
returns (bool)
{
require(
balances[msg.sender] >= _value,
INSUFFICIENT_BALANCE
);
require(
balances[_to] + _value >= balances[_to],
OVERFLOW
);
balances[msg.sender] -= _value;
balances[_to] += _value;
emit Transfer(msg.sender, _to, _value);
return true;
}
function transferFrom(address _from, address _to, uint256 _value)
public
returns (bool)
{
require(
balances[_from] >= _value,
INSUFFICIENT_BALANCE
);
require(
allowed[_from][msg.sender] >= _value,
INSUFFICIENT_ALLOWANCE
);
require(
balances[_to] + _value >= balances[_to],
OVERFLOW
);
balances[_to] += _value;
balances[_from] -= _value;
allowed[_from][msg.sender] -= _value;
emit Transfer(_from, _to, _value);
return true;
}
function approve(address _spender, uint256 _value)
public
returns (bool)
{
allowed[msg.sender][_spender] = _value;
emit Approval(msg.sender, _spender, _value);
return true;
}
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];
}
}
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