EthereumTokenContract.sol

pragma solidity ^0.4.16;

contract owned {
  address public owner;

  function owned() public {
    owner = msg.sender;
  }

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

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

interface tokenRecipient { function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData) public; }

contract TokenERC20 {
  // Public variables of the token
  string public name;
  string public symbol;
  uint8 public decimals = 18;
  // 18 decimals is the strongly suggested default, avoid changing it
  uint256 public totalSupply;

  // This creates an array with all balances
  mapping (address => uint256) public balanceOf;
  mapping (address => mapping (address => uint256)) public allowance;

  // This generates a public event on the blockchain that will notify clients
  event Transfer(address indexed from, address indexed to, uint256 value);

  // This notifies clients about the amount burnt
  event Burn(address indexed from, uint256 value);

  /**
  * Constrctor function
  *
    * Initializes contract with initial supply tokens to the creator of the contract
  */
  function TokenERC20(
    uint256 initialSupply,
    string tokenName,
    string tokenSymbol
  ) public {
    totalSupply = initialSupply * 10 ** uint256(decimals);  // Update total supply with the decimal amount
    balanceOf[msg.sender] = totalSupply;                // Give the creator all initial tokens
    name = tokenName;                                   // Set the name for display purposes
    symbol = tokenSymbol;                               // Set the symbol for display purposes
  }

  /**
  * Internal transfer, only can be called by this contract
  */
  function _transfer(address _from, address _to, uint _value) internal {
    // Prevent transfer to 0x0 address. Use burn() instead
    require(_to != 0x0);
    // Check if the sender has enough
    require(balanceOf[_from] >= _value);
    // Check for overflows
    require(balanceOf[_to] + _value > balanceOf[_to]);
    // Save this for an assertion in the future
    uint previousBalances = balanceOf[_from] + balanceOf[_to];
    // Subtract from the sender
    balanceOf[_from] -= _value;
    // Add the same to the recipient
    balanceOf[_to] += _value;
    Transfer(_from, _to, _value);
    // Asserts are used to use static analysis to find bugs in your code. They should never fail
    assert(balanceOf[_from] + balanceOf[_to] == previousBalances);
  }

  /**
  * Transfer tokens
  *
    * Send `_value` tokens to `_to` from your account
  *
    * @param _to The address of the recipient
  * @param _value the amount to send
  */
  function transfer(address _to, uint256 _value) public {
    _transfer(msg.sender, _to, _value);
  }

  /**
  * Transfer tokens from other address
  *
    * Send `_value` tokens to `_to` in behalf of `_from`
  *
    * @param _from The address of the sender
  * @param _to The address of the recipient
  * @param _value the amount to send
  */
  function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
    require(_value <= allowance[_from][msg.sender]);     // Check allowance
    allowance[_from][msg.sender] -= _value;
    _transfer(_from, _to, _value);
    return true;
  }

  /**
  * Set allowance for other address
  *
    * Allows `_spender` to spend no more than `_value` tokens in your behalf
    *
      * @param _spender The address authorized to spend
    * @param _value the max amount they can spend
    */
  function approve(address _spender, uint256 _value) public
  returns (bool success) {
    allowance[msg.sender][_spender] = _value;
    return true;
  }

  /**
  * Set allowance for other address and notify
  *
    * Allows `_spender` to spend no more than `_value` tokens in your behalf, and then ping the contract about it
    *
      * @param _spender The address authorized to spend
    * @param _value the max amount they can spend
    * @param _extraData some extra information to send to the approved contract
    */
  function approveAndCall(address _spender, uint256 _value, bytes _extraData)
  public
  returns (bool success) {
    tokenRecipient spender = tokenRecipient(_spender);
    if (approve(_spender, _value)) {
      spender.receiveApproval(msg.sender, _value, this, _extraData);
      return true;
    }
  }

  /**
  * Destroy tokens
  *
    * Remove `_value` tokens from the system irreversibly
  *
    * @param _value the amount of money to burn
  */
  function burn(uint256 _value) public returns (bool success) {
    require(balanceOf[msg.sender] >= _value);   // Check if the sender has enough
    balanceOf[msg.sender] -= _value;            // Subtract from the sender
    totalSupply -= _value;                      // Updates totalSupply
    Burn(msg.sender, _value);
    return true;
  }

  /**
  * Destroy tokens from other account
  *
    * Remove `_value` tokens from the system irreversibly on behalf of `_from`.
    *
    * @param _from the address of the sender
  * @param _value the amount of money to burn
  */
  function burnFrom(address _from, uint256 _value) public returns (bool success) {
    require(balanceOf[_from] >= _value);                // Check if the targeted balance is enough
    require(_value <= allowance[_from][msg.sender]);    // Check allowance
    balanceOf[_from] -= _value;                         // Subtract from the targeted balance
    allowance[_from][msg.sender] -= _value;             // Subtract from the sender's allowance
    totalSupply -= _value;                              // Update totalSupply
    Burn(_from, _value);
    return true;
  }
}

/******************************************/
/*       ADVANCED TOKEN STARTS HERE       */
/******************************************/

contract MacToken is owned, TokenERC20 {

  uint256 public sellPrice;
  uint256 public buyPrice;

  mapping (address => bool) public frozenAccount;

  /* This generates a public event on the blockchain that will notify clients */
  event FrozenFunds(address target, bool frozen);

  /* Initializes contract with initial supply tokens to the creator of the contract */
  function MacToken(
    uint256 initialSupply,
    string tokenName,
    string tokenSymbol
  ) TokenERC20(initialSupply, tokenName, tokenSymbol) public {}

  /* Internal transfer, only can be called by this contract */
  function _transfer(address _from, address _to, uint _value) internal {
    require (_to != 0x0);                               // Prevent transfer to 0x0 address. Use burn() instead
    require (balanceOf[_from] >= _value);               // Check if the sender has enough
    require (balanceOf[_to] + _value > balanceOf[_to]); // Check for overflows
    require(!frozenAccount[_from]);                     // Check if sender is frozen
    require(!frozenAccount[_to]);                       // Check if recipient is frozen
    balanceOf[_from] -= _value;                         // Subtract from the sender
    balanceOf[_to] += _value;                           // Add the same to the recipient
    Transfer(_from, _to, _value);
  }

  /// @notice Create `mintedAmount` tokens and send it to `target`
  /// @param target Address to receive the tokens
  /// @param mintedAmount the amount of tokens it will receive
  function mintToken(address target, uint256 mintedAmount) onlyOwner public {
    balanceOf[target] += mintedAmount;
    totalSupply += mintedAmount;
    Transfer(0, this, mintedAmount);
    Transfer(this, target, mintedAmount);
  }

  /// @notice `freeze? Prevent | Allow` `target` from sending & receiving tokens
  /// @param target Address to be frozen
  /// @param freeze either to freeze it or not
  function freezeAccount(address target, bool freeze) onlyOwner public {
    frozenAccount[target] = freeze;
    FrozenFunds(target, freeze);
  }

  /// @notice Allow users to buy tokens for `newBuyPrice` eth and sell tokens for `newSellPrice` eth
  /// @param newSellPrice Price the users can sell to the contract
  /// @param newBuyPrice Price users can buy from the contract
  function setPrices(uint256 newSellPrice, uint256 newBuyPrice) onlyOwner public {
    sellPrice = newSellPrice;
    buyPrice = newBuyPrice;
  }

  /// @notice Buy tokens from contract by sending ether
  function buy() payable public {
    uint amount = msg.value / buyPrice;               // calculates the amount
    _transfer(this, msg.sender, amount);              // makes the transfers
  }

  /// @notice Sell `amount` tokens to contract
  /// @param amount amount of tokens to be sold
  function sell(uint256 amount) public {
    require(this.balance >= amount * sellPrice);      // checks if the contract has enough ether to buy
    _transfer(msg.sender, this, amount);              // makes the transfers
    msg.sender.transfer(amount * sellPrice);          // sends ether to the seller. It's important to do this last to avoid recursion attacks
  }
}