Contract Source Code:
File 1 of 1 : ChangeCoin
pragma solidity ^0.4.16;
/**
* @title Ownable
* @dev The Ownable contract has an owner address, and provides basic authorization control
* functions, this simplifies the implementation of "user permissions".
*/
contract Ownable {
address public owner;
/**
* @dev The Ownable constructor sets the original `owner` of the contract to the sender
* account.
*/
function Ownable() {
owner = msg.sender;
}
/**
* @dev Throws if called by any account other than the owner.
*/
modifier onlyOwner() {
require(msg.sender == owner);
_;
}
/**
* @dev Allows the current owner to transfer control of the contract to a newOwner.
* @param newOwner The address to transfer ownership to.
*/
function transferOwnership(address newOwner) onlyOwner {
if (newOwner != address(0)) {
owner = newOwner;
}
}
}
/**
* @title SafeMath
* @dev Math operations with safety checks that throw on error
*/
library SafeMath {
function mul(uint256 a, uint256 b) internal constant returns (uint256) {
uint256 c = a * b;
assert(a == 0 || c / a == b);
return c;
}
function div(uint256 a, uint256 b) internal constant returns (uint256) {
// assert(b > 0); // Solidity automatically throws when dividing by 0
uint256 c = a / b;
// assert(a == b * c + a % b); // There is no case in which this doesn't hold
return c;
}
function sub(uint256 a, uint256 b) internal constant returns (uint256) {
assert(b <= a);
return a - b;
}
function add(uint256 a, uint256 b) internal constant returns (uint256) {
uint256 c = a + b;
assert(c >= a);
return c;
}
}
/**
* @title ERC20Basic
* @dev Simpler version of ERC20 interface
* @dev see https://github.com/ethereum/EIPs/issues/179
*/
contract ERC20Basic {
uint256 public totalSupply;
function balanceOf(address who) constant returns (uint256);
function transfer(address to, uint256 value) returns (bool);
event Transfer(address indexed from, address indexed to, uint256 value);
}
/**
* @title Basic token
* @dev Basic version of StandardToken, with no allowances.
*/
contract BasicToken is ERC20Basic {
using SafeMath for uint256;
mapping(address => uint256) balances;
/**
* @dev transfer token for a specified address
* @param _to The address to transfer to.
* @param _value The amount to be transferred.
*/
function transfer(address _to, uint256 _value) returns (bool) {
balances[msg.sender] = balances[msg.sender].sub(_value);
balances[_to] = balances[_to].add(_value);
Transfer(msg.sender, _to, _value);
return true;
}
/**
* @dev Gets the balance of the specified address.
* @param _owner The address to query the the balance of.
* @return An uint256 representing the amount owned by the passed address.
*/
function balanceOf(address _owner) constant returns (uint256 balance) {
return balances[_owner];
}
}
/**
* @title ERC20 interface
* @dev see https://github.com/ethereum/EIPs/issues/20
*/
contract ERC20 is ERC20Basic {
function allowance(address owner, address spender) constant returns (uint256);
function transferFrom(address from, address to, uint256 value) returns (bool);
function approve(address spender, uint256 value) returns (bool);
event Approval(address indexed owner, address indexed spender, uint256 value);
}
contract StandardToken is ERC20, BasicToken {
mapping (address => mapping (address => uint256)) 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 amout of tokens to be transfered
*/
function transferFrom(address _from, address _to, uint256 _value) returns (bool) {
var _allowance = allowed[_from][msg.sender];
// Check is not needed because sub(_allowance, _value) will already throw if this condition is not met
// require (_value <= _allowance);
balances[_to] = balances[_to].add(_value);
balances[_from] = balances[_from].sub(_value);
allowed[_from][msg.sender] = _allowance.sub(_value);
Transfer(_from, _to, _value);
return true;
}
/**
* @dev Aprove the passed address to spend the specified amount of tokens on behalf of msg.sender.
* @param _spender The address which will spend the funds.
* @param _value The amount of tokens to be spent.
*/
function approve(address _spender, uint256 _value) 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[msg.sender][_spender] == 0));
allowed[msg.sender][_spender] = _value;
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 specifing the amount of tokens still avaible for the spender.
*/
function allowance(address _owner, address _spender) constant returns (uint256 remaining) {
return allowed[_owner][_spender];
}
}
contract MintableToken is StandardToken, Ownable {
event MintFinished();
bool public mintingFinished = false;
modifier canMint() {
require(!mintingFinished);
_;
}
/**
* @dev Function to mint tokens
* @param _to The address that will recieve the minted tokens.
* @param _amount The amount of tokens to mint.
* @return A boolean that indicates if the operation was successful.
*/
function mint(address _to, uint256 _amount) onlyOwner canMint returns (bool) {
totalSupply = totalSupply.add(_amount);
balances[_to] = balances[_to].add(_amount);
Transfer(0X0, _to, _amount);
return true;
}
/**
* @dev Function to stop minting new tokens.
* @return True if the operation was successful.
*/
function finishMinting() onlyOwner returns (bool) {
mintingFinished = true;
MintFinished();
return true;
}
}
contract ChangeCoin is MintableToken {
string public name = "Change COIN";
string public symbol = "CAG";
uint256 public decimals = 18;
bool public tradingStarted = false;
/**
* @dev modifier that throws if trading has not started yet
*/
modifier hasStartedTrading() {
require(tradingStarted);
_;
}
/**
* @dev Allows the owner to enable the trading. This can not be undone
*/
function startTrading() onlyOwner {
tradingStarted = true;
}
/**
* @dev Allows anyone to transfer the Change tokens once trading has started
* @param _to the recipient address of the tokens.
* @param _value number of tokens to be transfered.
*/
function transfer(address _to, uint _value) hasStartedTrading returns (bool){
return super.transfer(_to, _value);
}
/**
* @dev Allows anyone to transfer the Change tokens once trading has started
* @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 uint the amout of tokens to be transfered
*/
function transferFrom(address _from, address _to, uint _value) hasStartedTrading returns (bool){
return super.transferFrom(_from, _to, _value);
}
}
contract ChangeCoinPresale is Ownable {
using SafeMath for uint256;
// The token being sold
ChangeCoin public token;
// start and end block where investments are allowed (both inclusive)
uint256 public startTimestamp;
uint256 public endTimestamp;
// address where funds are collected
address public hardwareWallet;
// how many token units a buyer gets per wei
uint256 public rate;
// amount of raised money in wei
uint256 public weiRaised;
// minimum contributio to participate in tokensale
uint256 public minContribution;
// maximum amount of ether being raised
uint256 public hardcap;
// number of participants in presale
uint256 public numberOfPurchasers = 0;
event TokenPurchase(address indexed purchaser, address indexed beneficiary, uint256 value, uint256 amount);
event PreSaleClosed();
function ChangeCoinPresale() {
startTimestamp = 1504945800;
endTimestamp = 1505397600;
rate = 500;
hardwareWallet = 0x71B1Ee0848c4F68df05429490fc4237089692e1e;
token = new ChangeCoin();
minContribution = 9.9 ether;
hardcap = 50000 ether;
require(startTimestamp >= now);
require(endTimestamp >= startTimestamp);
}
/**
* @dev Calculates the amount of bonus coins the buyer gets
* @param tokens uint the amount of tokens you get according to current rate
* @return uint the amount of bonus tokens the buyer gets
*/
function bonusAmmount(uint256 tokens) internal returns(uint256) {
// first 500 get extra 30%
if (numberOfPurchasers < 501) {
return tokens * 3 / 10;
} else {
return tokens /4;
}
}
// check if valid purchase
modifier validPurchase {
require(now >= startTimestamp);
require(now <= endTimestamp);
require(msg.value >= minContribution);
require(weiRaised.add(msg.value) <= hardcap);
_;
}
// @return true if crowdsale event has ended
function hasEnded() public constant returns (bool) {
bool timeLimitReached = now > endTimestamp;
bool capReached = weiRaised >= hardcap;
return timeLimitReached || capReached;
}
// low level token purchase function
function buyTokens(address beneficiary) payable validPurchase {
require(beneficiary != 0x0);
uint256 weiAmount = msg.value;
// calculate token amount to be created
uint256 tokens = weiAmount.mul(rate);
tokens = tokens + bonusAmmount(tokens);
// update state
weiRaised = weiRaised.add(weiAmount);
numberOfPurchasers = numberOfPurchasers + 1;
token.mint(beneficiary, tokens);
TokenPurchase(msg.sender, beneficiary, weiAmount, tokens);
hardwareWallet.transfer(msg.value);
}
// transfer ownership of the token to the owner of the presale contract
function finishPresale() public onlyOwner {
require(hasEnded());
token.transferOwnership(owner);
PreSaleClosed();
}
// fallback function can be used to buy tokens
function () payable {
buyTokens(msg.sender);
}
}