انجمن توسعه قرارداد هوشمند

الگوهای طراحی قراردادهای هوشمند

در این مقاله چند نمونه از الگوهای مفید و کاربردی برای نوشتن قرارداد های هوشمند آورده شده است.

1. استفاده از require به جای if

تا جای ممکن بهتر است برای چک کردن برقرار بودن شروط از عبارت require استفاده کنید. به عنوان مثال تابع زیر، بدون ارسال هیچ exception ای با خطا مواجه می شود. این یک الگوی بد است به این خاطر که در لحظه مشخص نمی شود که تابع به درستی اجرا شده است یا خیر.

    function silentFailIfZero(uint num) public view returns (uint){
        if(num != 0){
            return num;
        }
    }

تابع زیر شرط لازم برای ادامه اجرای تابع را به کمک require چک می کند در صورتی که شرط برقرار نباشد یک exception ارسال می کند. این یک الگوی مناسب برای جلوگیری از ادامه اجرای تابع در صورت بروز خطاست.

    function throwsErrorIfZero(uint num) public view returns (uint){
        require(num != 0);
        return num;
    }

2. محدود کردن دسترسی

شما نمی توانید مانع خواندن متغیرها یا حالت های قرارداد خود توسط اشخاص یا برنامه های کامپیوتری شوید. حالت هر قرارداد هوشمند برای هرکسی بادسترسی به بلاکچین قابل دستیابی هست. با این وجود شما می توانید دسترسی سایرقراردادها به حالت برنامه را با private کردن متغیرهای حالت محدود کنید.


    contract C1 {

            uint private internalNum;
    }

همچنین شما می توانید دسترسی به توابع را به گونه ای محدود کنید که تنها یک سری آدرس های خاص اجازه اجرای توابع را داشته باشند. این الگو در مواردی که می خواهیم به تعدادی از کاربران یا سایر قراردادها دسترسی به توابع با سطح دسترسی ادمین مانند تغییر مالکیت قرارداد، پیاده سازی ارتقا و یا توقف قرارداد را بدهیم؛ مفید خواهد بود.


    contract Admin {

            mapping(address => bool) admins;

            modifier onlyAdmin {
                    require(admins[msg.sender] == true);
                    _;
            }

            function addAdmin(address _a)
                    public
                    onlyAdmin
                    returns(bool)
            {
                    admins[_a] = true;
                    return true;
            }

    }

3. منقضی شدن قرارداد به صورت خودکار

الگوی طراحی auto deprecation یک الگوی طراحی مناسب برای متوقف کردن قراردادهایی است که باید بعد از یک مدت زمان معین منقضی شوند. به عنوان مثال در مواقعی که می خواهید نسخه های آزمایشی قرارداد خود را اجرا کنید.
این نکته را به یاد داشته باشید که استفاده از timestamp ها یی مثل عبارت کلیدی now ممکن است توسط ماینرها در یک بازه 30 ثانیه ای دستکاری شود.


    pragma solidity ^0.4.25;

    contract Autodeprecate {
            uint contract_expired;
            
            modifier is_active {
                    if(!expired()) _;
            }

            modifier when_deprecated {
                    if(expired()) _;
            }

            constructor(uint duration) {
                    contract_expired = now + duration;
            }

            function expired()
                    view
                    public
                    returns(bool)
            {
                    return now > contract_expired ? true : false;
            }
    }

4. الگوی طراحی Mortal

الگوی mortal قابلیت از بین بردن قرارداد و حذف آن از بلاکچین را به ما می دهد. شما می توانید با استفاده از کلمه کلیدی selfdestruct قرارداد خود را از بین ببرید. تابعی هم که این کار را انجام می دهد معمولا Kill خوانده می شود که تنها یک پارامتر ورودی دارد و آن آدرسی است که در هنگام نابودی قرارداد، تمام مقادیری که درحال حاضر توسط قرارداد نگه داری می شود را دریافت می کند.


       pragma solidity ^0.5.0;

       import "./Ownable.sol";

       contract Mortal is Ownable {  
        
        function kill()
        {
               if(msg.sender == owner()) selfdestruct(address(uint160(owner()))); // cast owner to address payable
        }

       }

کد مربوط به قرارداد Ownable.sol

5. الگوی Withdrawal

به عنوان نمونه یک قرارداد که عمل تقسیم موجودی را انجام میدهد نگاه کنید. نکته اصلی در مورد این قرارداد این است که منطق برنامه به صورت مجزا در تابع split() نوشته شده است. تابع split() حساب ها را مدیریت می کند و msg.value که همراه با تراکنش ارسال می شود را تقسیم می کند. ولی به طور مستقیم مقادیر را برای آدرس ها ارسال نمی کند یا به عبارت دیگر هیچ تابع خارجی را فراخوانی نمی کند. تابع دیگر با نام withdraw() به آدرس های کاربری این اجازه را می دهد که مقادیر مربوط به خود که در قرارداد وجود دارد را به حساب خود بازگردانند. اصطلاحا به این الگو انتقال به شیوه push در مقابل انتقال به شیوه pull نیز می گویند که از حملات re-entrancy و DOS جلوگیری می کند.

6. Circuit Breaker

به کمک این الگو می توانیم اجرای بعضی از توابع را متوقف کنیم. در مواقعی که قرارداد بر روی بلاکچین قرار دارد و متوجه یک باگ امنیتی و یا عملکردی می شویم؛ متوقف کردن عملکرد قرارداد برای کاهش زیان قبل از برطرف شدن مشکل بسیار مفید خواهد بود.
به عنوان مثال در صورتی که شما الگوی Withdraw را پیاده سازی کرده باشید. در هنگام بروز باگ برای متوقف کردن قرارداد ابتدا باید از واریز وجه توسط افراد به قرارداد جلوگیری کنید و در عین حال به کاربرانی که موجودی دارند اجازه خارج کردن سرمایه خود را بدهید.


    contract CircuitBreaker 
    {

        bool public stopped = false;

        modifier stopInEmergency { require(!stopped); _; }
        modifier onlyInEmergency { require(stopped); _; }

        function deposit() stopInEmergency public { … }
        function withdraw() onlyInEmergency public { … } 
    }

همچنین در چنین موقعیتی شما باید اجازه دسترسی به اصلاح متغیر stopped را محدود به یک آدرس خاص به عنوان مثال مالک قرارداد یا مجموعه ای از ادمین ها کنید.

لینک های مرتبط

Link to Ownable.sol
Fund Splitter Contract
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سلام خسته نباشید من چطور میتوانم در این کانترکت فانکشن withraw بزارم ممنون میشم پاسخ بدید🙏

*Submitted for verification at Etherscan.io on 2021-04-16
*/

// SPDX-License-Identifier: Unlicensed

pragma solidity ^0.6.12;

abstract contract Context {
function _msgSender() internal view virtual returns (address payable) {
return msg.sender;
}

function _msgData() internal view virtual returns (bytes memory) {
    this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
    return msg.data;
}

}

interface IERC20 {
/**
* @dev Returns the amount of tokens in existence.
*/
function totalSupply() external view returns (uint256);

/**
 * @dev Returns the amount of tokens owned by `account`.
 */
function balanceOf(address account) external view returns (uint256);

/**
 * @dev Moves `amount` tokens from the caller's account to `recipient`.
 *
 * Returns a boolean value indicating whether the operation succeeded.
 *
 * Emits a {Transfer} event.
 */
function transfer(address recipient, uint256 amount) external returns (bool);

/**
 * @dev Returns the remaining number of tokens that `spender` will be
 * allowed to spend on behalf of `owner` through {transferFrom}. This is
 * zero by default.
 *
 * This value changes when {approve} or {transferFrom} are called.
 */
function allowance(address owner, address spender) external view returns (uint256);

/**
 * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
 *
 * Returns a boolean value indicating whether the operation succeeded.
 *
 * IMPORTANT: 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
 *
 * Emits an {Approval} event.
 */
function approve(address spender, uint256 amount) external returns (bool);

/**
 * @dev Moves `amount` tokens from `sender` to `recipient` using the
 * allowance mechanism. `amount` is then deducted from the caller's
 * allowance.
 *
 * Returns a boolean value indicating whether the operation succeeded.
 *
 * Emits a {Transfer} event.
 */
function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

/**
 * @dev Emitted when `value` tokens are moved from one account (`from`) to
 * another (`to`).
 *
 * Note that `value` may be zero.
 */
event Transfer(address indexed from, address indexed to, uint256 value);

/**
 * @dev Emitted when the allowance of a `spender` for an `owner` is set by
 * a call to {approve}. `value` is the new allowance.
 */
event Approval(address indexed owner, address indexed spender, uint256 value);

}

library SafeMath {
/**
* @dev Returns the addition of two unsigned integers, reverting on
* overflow.
*
* Counterpart to Solidity’s + operator.
*
* Requirements:
*
* - Addition cannot overflow.
*/
function add(uint256 a, uint256 b) internal pure returns (uint256) {
uint256 c = a + b;
require(c >= a, “SafeMath: addition overflow”);

    return c;
}

/**
 * @dev Returns the subtraction of two unsigned integers, reverting on
 * overflow (when the result is negative).
 *
 * Counterpart to Solidity's `-` operator.
 *
 * Requirements:
 *
 * - Subtraction cannot overflow.
 */
function sub(uint256 a, uint256 b) internal pure returns (uint256) {
    return sub(a, b, "SafeMath: subtraction overflow");
}

/**
 * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
 * overflow (when the result is negative).
 *
 * Counterpart to Solidity's `-` operator.
 *
 * Requirements:
 *
 * - Subtraction cannot overflow.
 */
function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
    require(b <= a, errorMessage);
    uint256 c = a - b;

    return c;
}

/**
 * @dev Returns the multiplication of two unsigned integers, reverting on
 * overflow.
 *
 * Counterpart to Solidity's `*` operator.
 *
 * Requirements:
 *
 * - Multiplication cannot overflow.
 */
function mul(uint256 a, uint256 b) internal pure returns (uint256) {
    // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
    // benefit is lost if 'b' is also tested.
    // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
    if (a == 0) {
        return 0;
    }

    uint256 c = a * b;
    require(c / a == b, "SafeMath: multiplication overflow");

    return c;
}

/**
 * @dev Returns the integer division of two unsigned integers. Reverts on
 * division by zero. The result is rounded towards zero.
 *
 * Counterpart to Solidity's `/` operator. Note: this function uses a
 * `revert` opcode (which leaves remaining gas untouched) while Solidity
 * uses an invalid opcode to revert (consuming all remaining gas).
 *
 * Requirements:
 *
 * - The divisor cannot be zero.
 */
function div(uint256 a, uint256 b) internal pure returns (uint256) {
    return div(a, b, "SafeMath: division by zero");
}

/**
 * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
 * division by zero. The result is rounded towards zero.
 *
 * Counterpart to Solidity's `/` operator. Note: this function uses a
 * `revert` opcode (which leaves remaining gas untouched) while Solidity
 * uses an invalid opcode to revert (consuming all remaining gas).
 *
 * Requirements:
 *
 * - The divisor cannot be zero.
 */
function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
    require(b > 0, errorMessage);
    uint256 c = a / b;
    // assert(a == b * c + a % b); // There is no case in which this doesn't hold

    return c;
}

/**
 * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
 * Reverts when dividing by zero.
 *
 * Counterpart to Solidity's `%` operator. This function uses a `revert`
 * opcode (which leaves remaining gas untouched) while Solidity uses an
 * invalid opcode to revert (consuming all remaining gas).
 *
 * Requirements:
 *
 * - The divisor cannot be zero.
 */
function mod(uint256 a, uint256 b) internal pure returns (uint256) {
    return mod(a, b, "SafeMath: modulo by zero");
}

/**
 * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
 * Reverts with custom message when dividing by zero.
 *
 * Counterpart to Solidity's `%` operator. This function uses a `revert`
 * opcode (which leaves remaining gas untouched) while Solidity uses an
 * invalid opcode to revert (consuming all remaining gas).
 *
 * Requirements:
 *
 * - The divisor cannot be zero.
 */
function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
    require(b != 0, errorMessage);
    return a % b;
}

}

library Address {
/**
* @dev Returns true if account is a contract.
*
* [IMPORTANT]
* ====
* It is unsafe to assume that an address for which this function returns
* false is an externally-owned account (EOA) and not a contract.
*
* Among others, isContract will return false for the following
* types of addresses:
*
* - an externally-owned account
* - a contract in construction
* - an address where a contract will be created
* - an address where a contract lived, but was destroyed
* ====
*/
function isContract(address account) internal view returns (bool) {
// According to EIP-1052, 0x0 is the value returned for not-yet created accounts
// and 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470 is returned
// for accounts without code, i.e. keccak256('')
bytes32 codehash;
bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
// solhint-disable-next-line no-inline-assembly
assembly { codehash := extcodehash(account) }
return (codehash != accountHash && codehash != 0x0);
}

/**
 * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
 * `recipient`, forwarding all available gas and reverting on errors.
 *
 * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
 * of certain opcodes, possibly making contracts go over the 2300 gas limit
 * imposed by `transfer`, making them unable to receive funds via
 * `transfer`. {sendValue} removes this limitation.
 *
 * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
 *
 * IMPORTANT: because control is transferred to `recipient`, care must be
 * taken to not create reentrancy vulnerabilities. Consider using
 * {ReentrancyGuard} or the
 * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
 */
function sendValue(address payable recipient, uint256 amount) internal {
    require(address(this).balance >= amount, "Address: insufficient balance");

    // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
    (bool success, ) = recipient.call{ value: amount }("");
    require(success, "Address: unable to send value, recipient may have reverted");
}

/**
 * @dev Performs a Solidity function call using a low level `call`. A
 * plain`call` is an unsafe replacement for a function call: use this
 * function instead.
 *
 * If `target` reverts with a revert reason, it is bubbled up by this
 * function (like regular Solidity function calls).
 *
 * Returns the raw returned data. To convert to the expected return value,
 * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
 *
 * Requirements:
 *
 * - `target` must be a contract.
 * - calling `target` with `data` must not revert.
 *
 * _Available since v3.1._
 */
function functionCall(address target, bytes memory data) internal returns (bytes memory) {
  return functionCall(target, data, "Address: low-level call failed");
}

/**
 * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
 * `errorMessage` as a fallback revert reason when `target` reverts.
 *
 * _Available since v3.1._
 */
function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
    return _functionCallWithValue(target, data, 0, errorMessage);
}

/**
 * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
 * but also transferring `value` wei to `target`.
 *
 * Requirements:
 *
 * - the calling contract must have an ETH balance of at least `value`.
 * - the called Solidity function must be `payable`.
 *
 * _Available since v3.1._
 */
function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
    return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
}

/**
 * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
 * with `errorMessage` as a fallback revert reason when `target` reverts.
 *
 * _Available since v3.1._
 */
function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
    require(address(this).balance >= value, "Address: insufficient balance for call");
    return _functionCallWithValue(target, data, value, errorMessage);
}

function _functionCallWithValue(address target, bytes memory data, uint256 weiValue, string memory errorMessage) private returns (bytes memory) {
    require(isContract(target), "Address: call to non-contract");

    // solhint-disable-next-line avoid-low-level-calls
    (bool success, bytes memory returndata) = target.call{ value: weiValue }(data);
    if (success) {
        return returndata;
    } else {
        // Look for revert reason and bubble it up if present
        if (returndata.length > 0) {
            // The easiest way to bubble the revert reason is using memory via assembly

            // solhint-disable-next-line no-inline-assembly
            assembly {
                let returndata_size := mload(returndata)
                revert(add(32, returndata), returndata_size)
            }
        } else {
            revert(errorMessage);
        }
    }
}

}

contract Ownable is Context {
address private _owner;

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

/**
 * @dev Initializes the contract setting the deployer as the initial owner.
 */
constructor () internal {
    address msgSender = _msgSender();
    _owner = msgSender;
    emit OwnershipTransferred(address(0), msgSender);
}

/**
 * @dev Returns the address of the current owner.
 */
function owner() public view returns (address) {
    return _owner;
}

/**
 * @dev Throws if called by any account other than the owner.
 */
modifier onlyOwner() {
    require(_owner == _msgSender(), "Ownable: caller is not the owner");
    _;
}

/**
 * @dev Leaves the contract without owner. It will not be possible to call
 * `onlyOwner` functions anymore. Can only be called by the current owner.
 *
 * NOTE: Renouncing ownership will leave the contract without an owner,
 * thereby removing any functionality that is only available to the owner.
 */
function renounceOwnership() public virtual onlyOwner {
    emit OwnershipTransferred(_owner, address(0));
    _owner = address(0);
}

/**
 * @dev Transfers ownership of the contract to a new account (`newOwner`).
 * Can only be called by the current owner.
 */
function transferOwnership(address newOwner) public virtual onlyOwner {
    require(newOwner != address(0), "Ownable: new owner is the zero address");
    emit OwnershipTransferred(_owner, newOwner);
    _owner = newOwner;
}

}

contract HokkaiduInu is Context, IERC20, Ownable {
using SafeMath for uint256;
using Address for address;

mapping (address => uint256) private _rOwned;
mapping (address => uint256) private _tOwned;
mapping (address => mapping (address => uint256)) private _allowances;

mapping (address => bool) private _isExcluded;
address[] private _excluded;

uint256 private constant MAX = ~uint256(0);
uint256 private constant _tTotal = 100000000000 * 10**6 * 10**9;
uint256 private _rTotal = (MAX - (MAX % _tTotal));
uint256 private _tFeeTotal;

string private _name = 'Hokkaidu Inu';
string private _symbol = 'HOKK';
uint8 private _decimals = 9;

constructor () public {
    _rOwned[_msgSender()] = _rTotal;
    emit Transfer(address(0), _msgSender(), _tTotal);
}

function name() public view returns (string memory) {
    return _name;
}

function symbol() public view returns (string memory) {
    return _symbol;
}

function decimals() public view returns (uint8) {
    return _decimals;
}

function totalSupply() public view override returns (uint256) {
    return _tTotal;
}

function balanceOf(address account) public view override returns (uint256) {
    if (_isExcluded[account]) return _tOwned[account];
    return tokenFromReflection(_rOwned[account]);
}

function transfer(address recipient, uint256 amount) public override returns (bool) {
    _transfer(_msgSender(), recipient, amount);
    return true;
}

function allowance(address owner, address spender) public view override returns (uint256) {
    return _allowances[owner][spender];
}

function approve(address spender, uint256 amount) public override returns (bool) {
    _approve(_msgSender(), spender, amount);
    return true;
}

function transferFrom(address sender, address recipient, uint256 amount) public override returns (bool) {
    _transfer(sender, recipient, amount);
    _approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, "ERC20: transfer amount exceeds allowance"));
    return true;
}

function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
    _approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(addedValue));
    return true;
}

function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
    _approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
    return true;
}

function isExcluded(address account) public view returns (bool) {
    return _isExcluded[account];
}

function totalFees() public view returns (uint256) {
    return _tFeeTotal;
}

function reflect(uint256 tAmount) public {
    address sender = _msgSender();
    require(!_isExcluded[sender], "Excluded addresses cannot call this function");
    (uint256 rAmount,,,,) = _getValues(tAmount);
    _rOwned[sender] = _rOwned[sender].sub(rAmount);
    _rTotal = _rTotal.sub(rAmount);
    _tFeeTotal = _tFeeTotal.add(tAmount);
}

function reflectionFromToken(uint256 tAmount, bool deductTransferFee) public view returns(uint256) {
    require(tAmount <= _tTotal, "Amount must be less than supply");
    if (!deductTransferFee) {
        (uint256 rAmount,,,,) = _getValues(tAmount);
        return rAmount;
    } else {
        (,uint256 rTransferAmount,,,) = _getValues(tAmount);
        return rTransferAmount;
    }
}

function tokenFromReflection(uint256 rAmount) public view returns(uint256) {
    require(rAmount <= _rTotal, "Amount must be less than total reflections");
    uint256 currentRate =  _getRate();
    return rAmount.div(currentRate);
}

function excludeAccount(address account) external onlyOwner() {
    require(!_isExcluded[account], "Account is already excluded");
    if(_rOwned[account] > 0) {
        _tOwned[account] = tokenFromReflection(_rOwned[account]);
    }
    _isExcluded[account] = true;
    _excluded.push(account);
}

function includeAccount(address account) external onlyOwner() {
    require(_isExcluded[account], "Account is already excluded");
    for (uint256 i = 0; i < _excluded.length; i++) {
        if (_excluded[i] == account) {
            _excluded[i] = _excluded[_excluded.length - 1];
            _tOwned[account] = 0;
            _isExcluded[account] = false;
            _excluded.pop();
            break;
        }
    }
}

function _approve(address owner, address spender, uint256 amount) private {
    require(owner != address(0), "ERC20: approve from the zero address");
    require(spender != address(0), "ERC20: approve to the zero address");

    _allowances[owner][spender] = amount;
    emit Approval(owner, spender, amount);
}

function _transfer(address sender, address recipient, uint256 amount) private {
    require(sender != address(0), "ERC20: transfer from the zero address");
    require(recipient != address(0), "ERC20: transfer to the zero address");
    require(amount > 0, "Transfer amount must be greater than zero");
    if (_isExcluded[sender] && !_isExcluded[recipient]) {
        _transferFromExcluded(sender, recipient, amount);
    } else if (!_isExcluded[sender] && _isExcluded[recipient]) {
        _transferToExcluded(sender, recipient, amount);
    } else if (!_isExcluded[sender] && !_isExcluded[recipient]) {
        _transferStandard(sender, recipient, amount);
    } else if (_isExcluded[sender] && _isExcluded[recipient]) {
        _transferBothExcluded(sender, recipient, amount);
    } else {
        _transferStandard(sender, recipient, amount);
    }
}

function _transferStandard(address sender, address recipient, uint256 tAmount) private {
    (uint256 rAmount, uint256 rTransferAmount, uint256 rFee, uint256 tTransferAmount, uint256 tFee) = _getValues(tAmount);
    _rOwned[sender] = _rOwned[sender].sub(rAmount);
    _rOwned[recipient] = _rOwned[recipient].add(rTransferAmount);      
    _reflectFee(rFee, tFee);
    emit Transfer(sender, recipient, tTransferAmount);
}

function _transferToExcluded(address sender, address recipient, uint256 tAmount) private {
    (uint256 rAmount, uint256 rTransferAmount, uint256 rFee, uint256 tTransferAmount, uint256 tFee) = _getValues(tAmount);
    _rOwned[sender] = _rOwned[sender].sub(rAmount);
    _tOwned[recipient] = _tOwned[recipient].add(tTransferAmount);
    _rOwned[recipient] = _rOwned[recipient].add(rTransferAmount);          
    _reflectFee(rFee, tFee);
    emit Transfer(sender, recipient, tTransferAmount);
}

function _transferFromExcluded(address sender, address recipient, uint256 tAmount) private {
    (uint256 rAmount, uint256 rTransferAmount, uint256 rFee, uint256 tTransferAmount, uint256 tFee) = _getValues(tAmount);
    _tOwned[sender] = _tOwned[sender].sub(tAmount);
    _rOwned[sender] = _rOwned[sender].sub(rAmount);
    _rOwned[recipient] = _rOwned[recipient].add(rTransferAmount);  
    _reflectFee(rFee, tFee);
    emit Transfer(sender, recipient, tTransferAmount);
}

function _transferBothExcluded(address sender, address recipient, uint256 tAmount) private {
    (uint256 rAmount, uint256 rTransferAmount, uint256 rFee, uint256 tTransferAmount, uint256 tFee) = _getValues(tAmount);
    _tOwned[sender] = _tOwned[sender].sub(tAmount);
    _rOwned[sender] = _rOwned[sender].sub(rAmount);
    _tOwned[recipient] = _tOwned[recipient].add(tTransferAmount);
    _rOwned[recipient] = _rOwned[recipient].add(rTransferAmount);        
    _reflectFee(rFee, tFee);
    emit Transfer(sender, recipient, tTransferAmount);
}

function _reflectFee(uint256 rFee, uint256 tFee) private {
    _rTotal = _rTotal.sub(rFee);
    _tFeeTotal = _tFeeTotal.add(tFee);
}

function _getValues(uint256 tAmount) private view returns (uint256, uint256, uint256, uint256, uint256) {
    (uint256 tTransferAmount, uint256 tFee) = _getTValues(tAmount);
    uint256 currentRate =  _getRate();
    (uint256 rAmount, uint256 rTransferAmount, uint256 rFee) = _getRValues(tAmount, tFee, currentRate);
    return (rAmount, rTransferAmount, rFee, tTransferAmount, tFee);
}

function _getTValues(uint256 tAmount) private pure returns (uint256, uint256) {
    uint256 tFee = tAmount.div(100).mul(2);
    uint256 tTransferAmount = tAmount.sub(tFee);
    return (tTransferAmount, tFee);
}

function _getRValues(uint256 tAmount, uint256 tFee, uint256 currentRate) private pure returns (uint256, uint256, uint256) {
    uint256 rAmount = tAmount.mul(currentRate);
    uint256 rFee = tFee.mul(currentRate);
    uint256 rTransferAmount = rAmount.sub(rFee);
    return (rAmount, rTransferAmount, rFee);
}

function _getRate() private view returns(uint256) {
    (uint256 rSupply, uint256 tSupply) = _getCurrentSupply();
    return rSupply.div(tSupply);
}

function _getCurrentSupply() private view returns(uint256, uint256) {
    uint256 rSupply = _rTotal;
    uint256 tSupply = _tTotal;      
    for (uint256 i = 0; i < _excluded.length; i++) {
        if (_rOwned[_excluded[i]] > rSupply || _tOwned[_excluded[i]] > tSupply) return (_rTotal, _tTotal);
        rSupply = rSupply.sub(_rOwned[_excluded[i]]);
        tSupply = tSupply.sub(_tOwned[_excluded[i]]);
    }
    if (rSupply < _rTotal.div(_tTotal)) return (_rTotal, _tTotal);
    return (rSupply, tSupply);

ممنون از مقاله خوبتون
احتمالا اپدیت هایی صورت بگیره وSELFDESTRUCTرو برای همیشه حذف کنن . به نظرم مقاله زیر در ارتباط با self destruct جالب بود که لینکشو میزارم اگر دوست داشتید مطالعه کنید

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