pragma solidity ^0.4.18;

/**
  * @title SafeMath
  * @dev Math operations with safety checks that throw on error
  */
library SafeMath {
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) {
            return 0;
        }
        uint256 c = a * b;
        assert(c / a == b);
        return c;
    }

    function div(uint256 a, uint256 b) internal pure 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 pure returns (uint256) {
        assert(b <= a);
        return a - b;
    }

    function add(uint256 a, uint256 b) internal pure 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) public view returns (uint256);
    function transfer(address to, uint256 value) public returns (bool);
    event Transfer(address indexed from, address indexed to, uint256 value);
}

/**
  * @title ERC20 interface
  * @dev see https://github.com/ethereum/EIPs/issues/20
  */
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);
}

/**
  * @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) public returns (bool) {
        require(_to != address(0));
        require(_value <= balances[msg.sender]);

        // SafeMath.sub will throw if there is not enough balance.
        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) public view returns (uint256 balance) {
        return balances[_owner];
    }
}

/**
  * @title Standard ERC20 token
  *
  * @dev Implementation of the basic standard token.
  * @dev https://github.com/ethereum/EIPs/issues/20
  * @dev Based on code by FirstBlood: https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
  */

contract StandardToken is ERC20, BasicToken {
    mapping (address => mapping (address => uint256)) internal 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 amount of tokens to be transferred
      */
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
        require(_to != address(0));
        require(_value <= balances[_from]);
        require(_value <= allowed[_from][msg.sender]);

        balances[_from] = balances[_from].sub(_value);
        balances[_to] = balances[_to].add(_value);
        allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
        Transfer(_from, _to, _value);
        return true;
    }

    /**
      * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
      *
      * Beware that changing an allowance with this method brings the risk that someone may use both the old
      * and the new allowance by unfortunate transaction ordering. One possible solution to mitigate this
      * race condition is to first reduce the spender's allowance to 0 and set the desired value afterwards:
      * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
      * @param _spender The address which will spend the funds.
      * @param _value The amount of tokens to be spent.
      */
    function approve(address _spender, uint256 _value) public returns (bool) {
        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 specifying the amount of tokens still available for the spender.
      */
    function allowance(address _owner, address _spender) public view returns (uint256) {
        return allowed[_owner][_spender];
    }

    /**
      * approve should be called when allowed[_spender] == 0. To increment
      * allowed value is better to use this function to avoid 2 calls (and wait until
      * the first transaction is mined)
      * From MonolithDAO Token.sol
      */
    function increaseApproval(address _spender, uint _addedValue) public returns (bool) {
        allowed[msg.sender][_spender] = allowed[msg.sender][_spender].add(_addedValue);
        Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
        return true;
    }

    function decreaseApproval(address _spender, uint _subtractedValue) public returns (bool) {
        uint oldValue = allowed[msg.sender][_spender];
        if (_subtractedValue > oldValue) {
            allowed[msg.sender][_spender] = 0;
        } else {
            allowed[msg.sender][_spender] = oldValue.sub(_subtractedValue);
        }
        Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
        return true;
    }
}

/**
  * @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;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
      * @dev The Ownable constructor sets the original owner of the contract to the sender
      * account.
      */
    function Ownable() internal {
        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 public {
        require(newOwner != address(0));
        OwnershipTransferred(owner, newOwner);
        owner = newOwner;
    }
}

/**
  * @title Pausable
  * @dev Base contract which allows children to implement an emergency stop mechanism.
  */
contract Pausable is Ownable {
    event Pause();
    event Unpause();

    bool public paused = false;

    /**
      * @dev Modifier to make a function callable only when the contract is not paused.
      */
    modifier whenNotPaused() {
        require(!paused);
        _;
    }

    /**
      * @dev Modifier to make a function callable only when the contract is paused.
      */
    modifier whenPaused() {
        require(paused);
        _;
    }

    /**
      * @dev called by the owner to pause, triggers stopped state
      */
    function pause() onlyOwner whenNotPaused public {
        paused = true;
        Pause();
    }

    /**
      * @dev called by the owner to unpause, returns to normal state
      */
    function unpause() onlyOwner whenPaused public {
        paused = false;
        Unpause();
    }
}

/**
  * @title Pausable token
  *
  * @dev StandardToken modified with pausable transfers.
  *
  */

contract PausableToken is StandardToken, Pausable {

    function transfer(address _to, uint256 _value) public whenNotPaused returns (bool) {
        return super.transfer(_to, _value);
    }

    function transferFrom(address _from, address _to, uint256 _value) public whenNotPaused returns (bool) {
        return super.transferFrom(_from, _to, _value);
    }

    function approve(address _spender, uint256 _value) public whenNotPaused returns (bool) {
        return super.approve(_spender, _value);
    }
}

/**
  * @title Rocktoken
  *
  * @dev Implementation of Rocktoken based on the basic standard token.
  */
contract Rocktoken is PausableToken {

    function () public {
        //if ether is sent to this address, send it back.
        revert();
    }

    /**
    * Public variables of the token
    * 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;
    uint8 public decimals;
    string public symbol;
    string public version = '1.0.0';

    /**
     * @dev Function to check the amount of tokens that an owner allowed to a spender.
     * @param _totalSupply total supply of the token.
     * @param _name token name e.g Rocktoken.
     * @param _symbol token symbol e.g Rock.
     * @param _decimals amount of decimals.
     */
    function Rocktoken(uint256 _totalSupply, string _name, string _symbol, uint8 _decimals) public {
        totalSupply = _totalSupply * 10 ** uint256(_decimals);
        balances[msg.sender] = totalSupply;    // Give the creator all initial tokens
        name = _name;
        symbol = _symbol;
        decimals = _decimals;
    }
}