fdf687c Apr 24, 2018
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@maurelian @simondlr @skmgoldin
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Implements EIP20 token standard:
pragma solidity ^0.4.21;
import "./EIP20Interface.sol";
contract EIP20 is EIP20Interface {
uint256 constant private MAX_UINT256 = 2**256 - 1;
mapping (address => uint256) public balances;
mapping (address => mapping (address => uint256)) public allowed;
The following variables are OPTIONAL vanities. One does not have to include them.
They allow one to customise the token contract & in no way influences the core functionality.
Some wallets/interfaces might not even bother to look at this information.
string public name; //fancy name: eg Simon Bucks
uint8 public decimals; //How many decimals to show.
string public symbol; //An identifier: eg SBX
function EIP20(
uint256 _initialAmount,
string _tokenName,
uint8 _decimalUnits,
string _tokenSymbol
) public {
balances[msg.sender] = _initialAmount; // Give the creator all initial tokens
totalSupply = _initialAmount; // Update total supply
name = _tokenName; // Set the name for display purposes
decimals = _decimalUnits; // Amount of decimals for display purposes
symbol = _tokenSymbol; // Set the symbol for display purposes
function transfer(address _to, uint256 _value) public returns (bool success) {
require(balances[msg.sender] >= _value);
balances[msg.sender] -= _value;
balances[_to] += _value;
emit Transfer(msg.sender, _to, _value); //solhint-disable-line indent, no-unused-vars
return true;
function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
uint256 allowance = allowed[_from][msg.sender];
require(balances[_from] >= _value && allowance >= _value);
balances[_to] += _value;
balances[_from] -= _value;
if (allowance < MAX_UINT256) {
allowed[_from][msg.sender] -= _value;
emit Transfer(_from, _to, _value); //solhint-disable-line indent, no-unused-vars
return true;
function balanceOf(address _owner) public view returns (uint256 balance) {
return balances[_owner];
function approve(address _spender, uint256 _value) public returns (bool success) {
allowed[msg.sender][_spender] = _value;
emit Approval(msg.sender, _spender, _value); //solhint-disable-line indent, no-unused-vars
return true;
function allowance(address _owner, address _spender) public view returns (uint256 remaining) {
return allowed[_owner][_spender];