smart_contract_dataset/block number dependency/220.sol

pragma solidity ^0.4.24;

library SafeMath {

   
  function mul(uint256 a, uint256 b) internal pure returns (uint256 c) {
     
     
     
    if (a == 0) {
      return 0;
    }

    c = a * b;
    assert(c / a == b);
    return c;
  }

   
  function div(uint256 a, uint256 b) internal pure returns (uint256) {
     
     
     
    return a / b;
  }

   
  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
    assert(b <= a);
    return a - b;
  }

   
  function add(uint256 a, uint256 b) internal pure returns (uint256 c) {
    c = a + b;
    assert(c >= a);
    return c;
  }
}

contract Ownable {
  address public owner;


  event OwnershipRenounced(address indexed previousOwner);
  event OwnershipTransferred(
    address indexed previousOwner,
    address indexed newOwner
  );


   
  constructor() public {
    owner = msg.sender;
  }

   
  modifier onlyOwner() {
    require(msg.sender == owner);
    _;
  }

   
  function renounceOwnership() public onlyOwner {
    emit OwnershipRenounced(owner);
    owner = address(0);
  }

   
  function transferOwnership(address _newOwner) public onlyOwner {
    _transferOwnership(_newOwner);
  }

   
  function _transferOwnership(address _newOwner) internal {
    require(_newOwner != address(0));
    emit OwnershipTransferred(owner, _newOwner);
    owner = _newOwner;
  }
}

contract Claimable is Ownable {
  address public pendingOwner;

   
  modifier onlyPendingOwner() {
    require(msg.sender == pendingOwner);
    _;
  }

   
  function transferOwnership(address newOwner) onlyOwner public {
    pendingOwner = newOwner;
  }

   
  function claimOwnership() onlyPendingOwner public {
    emit OwnershipTransferred(owner, pendingOwner);
    owner = pendingOwner;
    pendingOwner = address(0);
  }
}

contract SimpleFlyDropToken is Claimable {
    using SafeMath for uint256;

    ERC20 internal erc20tk;

    function setToken(address _token) onlyOwner public {
        require(_token != address(0));
        erc20tk = ERC20(_token);
    }

     
    function multiSend(address[] _destAddrs, uint256[] _values) onlyOwner public returns (uint256) {
        require(_destAddrs.length == _values.length);

        uint256 i = 0;
        for (; i < _destAddrs.length; i = i.add(1)) {
            if (!erc20tk.transfer(_destAddrs[i], _values[i])) {
                break;
            }
        }

        return (i);
    }
}

contract DelayedClaimable is Claimable {

  uint256 public end;
  uint256 public start;

   
  function setLimits(uint256 _start, uint256 _end) onlyOwner public {
    require(_start <= _end);
    end = _end;
    start = _start;
  }

   
  function claimOwnership() onlyPendingOwner public {
    require((block.number <= end) && (block.number >= start));
    emit OwnershipTransferred(owner, pendingOwner);
    owner = pendingOwner;
    pendingOwner = address(0);
    end = 0;
  }

}

contract FlyDropTokenMgr is DelayedClaimable {
    using SafeMath for uint256;

    address[] dropTokenAddrs;
    SimpleFlyDropToken currentDropTokenContract;
     

     
    function prepare(uint256 _rand,
                     address _from,
                     address _token,
                     uint256 _value) onlyOwner public returns (bool) {
        require(_token != address(0));
        require(_from != address(0));
        require(_rand > 0);

        if (ERC20(_token).allowance(_from, this) < _value) {
            return false;
        }

        if (_rand > dropTokenAddrs.length) {
            SimpleFlyDropToken dropTokenContract = new SimpleFlyDropToken();
            dropTokenAddrs.push(address(dropTokenContract));
            currentDropTokenContract = dropTokenContract;
        } else {
            currentDropTokenContract = SimpleFlyDropToken(dropTokenAddrs[_rand.sub(1)]);
        }

        currentDropTokenContract.setToken(_token);
        return ERC20(_token).transferFrom(_from, currentDropTokenContract, _value);
         
         
         
    }

     
     
     

     
     

     
    function flyDrop(address[] _destAddrs, uint256[] _values) onlyOwner public returns (uint256) {
        require(address(currentDropTokenContract) != address(0));
        return currentDropTokenContract.multiSend(_destAddrs, _values);
    }

}

contract ERC20Basic {
  function totalSupply() public view returns (uint256);
  function balanceOf(address who) public view returns (uint256);
  function transfer(address to, uint256 value) public returns (bool);
  event Transfer(address indexed from, address indexed to, uint256 value);
}

contract ERC20 is ERC20Basic {
  function allowance(address owner, address spender)
    public view returns (uint256);

  function transferFrom(address from, address to, uint256 value)
    public returns (bool);

  function approve(address spender, uint256 value) public returns (bool);
  event Approval(
    address indexed owner,
    address indexed spender,
    uint256 value
  );
}