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pragma solidity ^0.4.11;
import '../token/MintableToken.sol';
import '../math/SafeMath.sol';
/**
* @title Crowdsale
* @dev Crowdsale is a base contract for managing a token crowdsale.
* Crowdsales have a start and end block, where investors can make
* token purchases and the crowdsale will assign them tokens based
* on a token per ETH rate. Funds collected are forwarded to a wallet
* as they arrive.
*/
contract Crowdsale {
using SafeMath for uint256;
// The token being sold
MintableToken public token;
// start and end block where investments are allowed (both inclusive)
uint256 public startBlock;
uint256 public endBlock;
// address where funds are collected
address public wallet;
// how many token units a buyer gets per wei
uint256 public rate;
// amount of raised money in wei
uint256 public weiRaised;
/**
* event for token purchase logging
* @param purchaser who paid for the tokens
* @param beneficiary who got the tokens
* @param value weis paid for purchase
* @param amount amount of tokens purchased
*/
event TokenPurchase(address indexed purchaser, address indexed beneficiary, uint256 value, uint256 amount);
constructor(uint256 _startBlock, uint256 _endBlock, uint256 _rate, address _wallet) {
require(_startBlock >= block.number);
require(_endBlock >= _startBlock);
require(_rate > 0);
require(_wallet != address(0x0));
token = createTokenContract();
startBlock = _startBlock;
endBlock = _endBlock;
rate = _rate;
wallet = _wallet;
}
// creates the token to be sold.
// override this method to have crowdsale of a specific mintable token.
function createTokenContract() internal returns (MintableToken) {
return new MintableToken();
}
// fallback function can be used to buy tokens
function () external payable {
buyTokens(msg.sender);
}
// low level token purchase function
function buyTokens(address beneficiary) payable {
require(beneficiary != address(0x0));
require(validPurchase());
uint256 weiAmount = msg.value;
uint256 updatedWeiRaised = weiRaised.add(weiAmount);
// calculate token amount to be created
uint256 tokens = weiAmount.mul(rate);
// update state
weiRaised = updatedWeiRaised;
token.mint(beneficiary, tokens);
emit TokenPurchase(msg.sender, beneficiary, weiAmount, tokens);
forwardFunds();
}
// send ether to the fund collection wallet
// override to create custom fund forwarding mechanisms
function forwardFunds() internal {
wallet.transfer(msg.value);
}
// @return true if the transaction can buy tokens
function validPurchase() internal view returns (bool) {
uint256 current = block.number;
bool withinPeriod = current >= startBlock && current <= endBlock;
bool nonZeroPurchase = msg.value != 0;
return withinPeriod && nonZeroPurchase;
}
// @return true if crowdsale event has ended
function hasEnded() public view returns (bool) {
return block.number > endBlock;
}
}
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