contract ERC721BasicToken is ERC721Basic {
    using SafeMath for uint256;
    using AddressUtils for address;

    // Equals to `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`
    // which can be also obtained as `ERC721Receiver(0).onERC721Received.selector`
    bytes4 public constant ERC721_RECEIVED = 0x150b7a02;

    // Mapping from token ID to owner
    mapping (uint256 => address) internal tokenOwner;

    // Mapping from token ID to approved address
    mapping (uint256 => address) internal tokenApprovals;

    // Mapping from owner to number of owned token
    mapping (address => uint256) internal ownedTokensCount;

    // Mapping from owner to operator approvals
    mapping (address => mapping (address => bool)) internal operatorApprovals;

    /**
    * @dev Guarantees msg.sender is owner of the given token
    * @param _tokenId uint256 ID of the token to validate its ownership belongs to msg.sender
    */
    modifier onlyOwnerOf(uint256 _tokenId) {
        require (ownerOf(_tokenId) == msg.sender);
        _;
    }

    /**
    * @dev Checks msg.sender can transfer a token, by being owner, approved, or operator
    * @param _tokenId uint256 ID of the token to validate
    */
    modifier canTransfer(uint256 _tokenId) {
        require (isApprovedOrOwner(msg.sender, _tokenId));
        _;
    }

    /**
    * @dev Gets the balance of the specified address
    * @param _owner address to query the balance of
    * @return uint256 representing the amount owned by the passed address
    */
    function balanceOf(address _owner) public view returns (uint256) {
        require (_owner != address(0));
        return ownedTokensCount[_owner];
    }

    /**
    * @dev Gets the owner of the specified token ID
    * @param _tokenId uint256 ID of the token to query the owner of
    * @return owner address currently marked as the owner of the given token ID
    */
    function ownerOf(uint256 _tokenId) public view returns (address) {
        address owner = tokenOwner[_tokenId];
        require (owner != address(0));
        return owner;
    }

    /**
    * @dev Returns whether the specified token exists
    * @param _tokenId uint256 ID of the token to query the existence of
    * @return whether the token exists
    */
    function exists(uint256 _tokenId) public view returns (bool) {
        address owner = tokenOwner[_tokenId];
        return owner != address(0);
    }

    /**
    * @dev Approves another address to transfer the given token ID
    * @dev The zero address indicates there is no approved address.
    * @dev There can only be one approved address per token at a given time.
    * @dev Can only be called by the token owner or an approved operator.
    * @param _to address to be approved for the given token ID
    * @param _tokenId uint256 ID of the token to be approved
    */
    function approve(address _to, uint256 _tokenId) public {
        address owner = ownerOf(_tokenId);
        require (_to != owner);
        require (msg.sender == owner || isApprovedForAll(owner, msg.sender));

        tokenApprovals[_tokenId] = _to;
        emit Approval(owner, _to, _tokenId);
    }

    /**
    * @dev Gets the approved address for a token ID, or zero if no address set
    * @param _tokenId uint256 ID of the token to query the approval of
    * @return address currently approved for the given token ID
    */
    function getApproved(uint256 _tokenId) public view returns (address) {
        return tokenApprovals[_tokenId];
    }

    /**
    * @dev Sets or unsets the approval of a given operator
    * @dev An operator is allowed to transfer all tokens of the sender on their behalf
    * @param _to operator address to set the approval
    * @param _approved representing the status of the approval to be set
    */
    function setApprovalForAll(address _to, bool _approved) public {
        require (_to != msg.sender);
        operatorApprovals[msg.sender][_to] = _approved;
        emit ApprovalForAll(msg.sender, _to, _approved);
    }

    /**
    * @dev Tells whether an operator is approved by a given owner
    * @param _owner owner address which you want to query the approval of
    * @param _operator operator address which you want to query the approval of
    * @return bool whether the given operator is approved by the given owner
    */
    function isApprovedForAll(
        address _owner,
        address _operator
    )
        public
        view
        returns (bool)
    {
        return operatorApprovals[_owner][_operator];
    }

    /**
    * @dev Transfers the ownership of a given token ID to another address
    * @dev Usage of this method is discouraged, use `safeTransferFrom` whenever possible
    * @dev Requires the msg sender to be the owner, approved, or operator
    * @param _from current owner of the token
    * @param _to address to receive the ownership of the given token ID
    * @param _tokenId uint256 ID of the token to be transferred
    */
    function transferFrom(
        address _from,
        address _to,
        uint256 _tokenId
    )
        public
        canTransfer(_tokenId)
    {
        require (_from != address(0));
        require (_to != address(0));

        clearApproval(_from, _tokenId);
        removeTokenFrom(_from, _tokenId);
        addTokenTo(_to, _tokenId);

        emit Transfer(_from, _to, _tokenId);
    }

    /**
    * @dev Safely transfers the ownership of a given token ID to another address
    * @dev If the target address is a contract, it must implement `onERC721Received`,
    *  which is called upon a safe transfer, and return the magic value
    *  `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`; otherwise,
    *  the transfer is reverted.
    * @dev Requires the msg sender to be the owner, approved, or operator
    * @param _from current owner of the token
    * @param _to address to receive the ownership of the given token ID
    * @param _tokenId uint256 ID of the token to be transferred
    */
    function safeTransferFrom(
        address _from,
        address _to,
        uint256 _tokenId
    )
        public
        canTransfer(_tokenId)
    {
        // solium-disable-next-line arg-overflow
        safeTransferFrom(_from, _to, _tokenId, "");
    }

    /**
    * @dev Safely transfers the ownership of a given token ID to another address
    * @dev If the target address is a contract, it must implement `onERC721Received`,
    *  which is called upon a safe transfer, and return the magic value
    *  `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`; otherwise,
    *  the transfer is reverted.
    * @dev Requires the msg sender to be the owner, approved, or operator
    * @param _from current owner of the token
    * @param _to address to receive the ownership of the given token ID
    * @param _tokenId uint256 ID of the token to be transferred
    * @param _data bytes data to send along with a safe transfer check
    */
    function safeTransferFrom(
        address _from,
        address _to,
        uint256 _tokenId,
        bytes _data
    )
        public
        canTransfer(_tokenId)
    {
        transferFrom(_from, _to, _tokenId);
        // solium-disable-next-line arg-overflow
        require (checkAndCallSafeTransfer(_from, _to, _tokenId, _data));
    }

    /**
    * @dev Returns whether the given spender can transfer a given token ID
    * @param _spender address of the spender to query
    * @param _tokenId uint256 ID of the token to be transferred
    * @return bool whether the msg.sender is approved for the given token ID,
    *  is an operator of the owner, or is the owner of the token
    */
    function isApprovedOrOwner(
        address _spender,
        uint256 _tokenId
    )
        internal
        view
        returns (bool)
    {
        address owner = ownerOf(_tokenId);
        // Disable solium check because of
        // https://github.com/duaraghav8/Solium/issues/175
        // solium-disable-next-line operator-whitespace
        return (
        _spender == owner ||
        getApproved(_tokenId) == _spender ||
        isApprovedForAll(owner, _spender)
        );
    }

    /**
    * @dev Internal function to mint a new token
    * @dev Reverts if the given token ID already exists
    * @param _to The address that will own the minted token
    * @param _tokenId uint256 ID of the token to be minted by the msg.sender
    */
    function _mint(address _to, uint256 _tokenId) internal {
        require (_to != address(0));
        addTokenTo(_to, _tokenId);
        emit Transfer(address(0), _to, _tokenId);
    }

    /**
    * @dev Internal function to burn a specific token
    * @dev Reverts if the token does not exist
    * @param _tokenId uint256 ID of the token being burned by the msg.sender
    */
    function _burn(address _owner, uint256 _tokenId) internal {
        clearApproval(_owner, _tokenId);
        removeTokenFrom(_owner, _tokenId);
        emit Transfer(_owner, address(0), _tokenId);
    }

    /**
    * @dev Internal function to clear current approval of a given token ID
    * @dev Reverts if the given address is not indeed the owner of the token
    * @param _owner owner of the token
    * @param _tokenId uint256 ID of the token to be transferred
    */
    function clearApproval(address _owner, uint256 _tokenId) internal {
        require (ownerOf(_tokenId) == _owner);
        if (tokenApprovals[_tokenId] != address(0)) {
            tokenApprovals[_tokenId] = address(0);
        }
    }

    /**
    * @dev Internal function to add a token ID to the list of a given address
    * @param _to address representing the new owner of the given token ID
    * @param _tokenId uint256 ID of the token to be added to the tokens list of the given address
    */
    function addTokenTo(address _to, uint256 _tokenId) internal {
        require (tokenOwner[_tokenId] == address(0));
        tokenOwner[_tokenId] = _to;
        ownedTokensCount[_to] = ownedTokensCount[_to].add(1);
    }

    /**
    * @dev Internal function to remove a token ID from the list of a given address
    * @param _from address representing the previous owner of the given token ID
    * @param _tokenId uint256 ID of the token to be removed from the tokens list of the given address
    */
    function removeTokenFrom(address _from, uint256 _tokenId) internal {
        require (ownerOf(_tokenId) == _from);
        ownedTokensCount[_from] = ownedTokensCount[_from].sub(1);
        tokenOwner[_tokenId] = address(0);
    }

    /**
    * @dev Internal function to invoke `onERC721Received` on a target address
    * @dev The call is not executed if the target address is not a contract
    * @param _from address representing the previous owner of the given token ID
    * @param _to target address that will receive the tokens
    * @param _tokenId uint256 ID of the token to be transferred
    * @param _data bytes optional data to send along with the call
    * @return whether the call correctly returned the expected magic value
    */
    function checkAndCallSafeTransfer(
        address _from,
        address _to,
        uint256 _tokenId,
        bytes _data
    )
        internal
        returns (bool)
    {
        if (!_to.isContract()) {
            return true;
        }
        bytes4 retval = ERC721Receiver(_to).onERC721Received(
            msg.sender, _from, _tokenId, _data);
        return (retval == ERC721_RECEIVED);
    }
}
/**
 * @title ERC721 Non-Fungible Token Standard basic implementation
 * @dev see https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
 */
function approve(address _to, uint256 _tokenId) public {
    address owner = ownerOf(_tokenId);
    require (_to != owner);
    require (msg.sender == owner || isApprovedForAll(owner, msg.sender));

    tokenApprovals[_tokenId] = _to;
    emit Approval(owner, _to, _tokenId);
}

/**
 * @dev Approves another address to transfer the given token ID
 * @dev The zero address indicates there is no approved address.
 * @dev There can only be one approved address per token at a given time.
 * @dev Can only be called by the token owner or an approved operator.
 * @param _to address to be approved for the given token ID
 * @param _tokenId uint256 ID of the token to be approved
 */