--- /dev/null
+pragma solidity ^0.8.4;
+
+pragma solidity ^0.8.0;
+
+/**
+ * @dev Interface of the ERC20 standard as defined in the EIP.
+ */
+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);
+}
+
+contract Token is IERC20 {
+ mapping (address => uint256) private _balances;
+
+ mapping (address => mapping (address => uint256)) private _allowances;
+
+ uint256 private _totalSupply;
+
+ string private _name;
+ string private _symbol;
+
+ /**
+ * @dev Sets the values for {name} and {symbol}.
+ *
+ * The defaut value of {decimals} is 18. To select a different value for
+ * {decimals} you should overload it.
+ *
+ * All two of these values are immutable: they can only be set once during
+ * construction.
+ */
+ constructor (string memory name_, string memory symbol_) {
+ _name = name_;
+ _symbol = symbol_;
+ }
+
+ /**
+ * @dev Returns the name of the token.
+ */
+ function name() public view virtual override returns (string memory) {
+ return _name;
+ }
+
+ /**
+ * @dev Returns the symbol of the token, usually a shorter version of the
+ * name.
+ */
+ function symbol() public view virtual override returns (string memory) {
+ return _symbol;
+ }
+
+ /**
+ * @dev Returns the number of decimals used to get its user representation.
+ * For example, if `decimals` equals `2`, a balance of `505` tokens should
+ * be displayed to a user as `5,05` (`505 / 10 ** 2`).
+ *
+ * Tokens usually opt for a value of 18, imitating the relationship between
+ * Ether and Wei. This is the value {ERC20} uses, unless this function is
+ * overridden;
+ *
+ * NOTE: This information is only used for _display_ purposes: it in
+ * no way affects any of the arithmetic of the contract, including
+ * {IERC20-balanceOf} and {IERC20-transfer}.
+ */
+ function decimals() public view virtual override returns (uint8) {
+ return 18;
+ }
+
+ /**
+ * @dev See {IERC20-totalSupply}.
+ */
+ function totalSupply() public view virtual override returns (uint256) {
+ return _totalSupply;
+ }
+
+ /**
+ * @dev See {IERC20-balanceOf}.
+ */
+ function balanceOf(address account) public view virtual override returns (uint256) {
+ return _balances[account];
+ }
+
+ /**
+ * @dev See {IERC20-transfer}.
+ *
+ * Requirements:
+ *
+ * - `recipient` cannot be the zero address.
+ * - the caller must have a balance of at least `amount`.
+ */
+ function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
+ _transfer(_msgSender(), recipient, amount);
+ return true;
+ }
+
+ /**
+ * @dev See {IERC20-allowance}.
+ */
+ function allowance(address owner, address spender) public view virtual override returns (uint256) {
+ return _allowances[owner][spender];
+ }
+
+ /**
+ * @dev See {IERC20-approve}.
+ *
+ * Requirements:
+ *
+ * - `spender` cannot be the zero address.
+ */
+ function approve(address spender, uint256 amount) public virtual override returns (bool) {
+ _approve(_msgSender(), spender, amount);
+ return true;
+ }
+
+ /**
+ * @dev See {IERC20-transferFrom}.
+ *
+ * Emits an {Approval} event indicating the updated allowance. This is not
+ * required by the EIP. See the note at the beginning of {ERC20}.
+ *
+ * Requirements:
+ *
+ * - `sender` and `recipient` cannot be the zero address.
+ * - `sender` must have a balance of at least `amount`.
+ * - the caller must have allowance for ``sender``'s tokens of at least
+ * `amount`.
+ */
+ function transferFrom(address sender, address recipient, uint256 amount) public virtual override returns (bool) {
+ _transfer(sender, recipient, amount);
+
+ uint256 currentAllowance = _allowances[sender][_msgSender()];
+ require(currentAllowance >= amount, "ERC20: transfer amount exceeds allowance");
+ _approve(sender, _msgSender(), currentAllowance - amount);
+
+ return true;
+ }
+
+ /**
+ * @dev Atomically increases the allowance granted to `spender` by the caller.
+ *
+ * This is an alternative to {approve} that can be used as a mitigation for
+ * problems described in {IERC20-approve}.
+ *
+ * Emits an {Approval} event indicating the updated allowance.
+ *
+ * Requirements:
+ *
+ * - `spender` cannot be the zero address.
+ */
+ function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
+ _approve(_msgSender(), spender, _allowances[_msgSender()][spender] + addedValue);
+ return true;
+ }
+
+ /**
+ * @dev Atomically decreases the allowance granted to `spender` by the caller.
+ *
+ * This is an alternative to {approve} that can be used as a mitigation for
+ * problems described in {IERC20-approve}.
+ *
+ * Emits an {Approval} event indicating the updated allowance.
+ *
+ * Requirements:
+ *
+ * - `spender` cannot be the zero address.
+ * - `spender` must have allowance for the caller of at least
+ * `subtractedValue`.
+ */
+ function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
+ uint256 currentAllowance = _allowances[_msgSender()][spender];
+ require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
+ _approve(_msgSender(), spender, currentAllowance - subtractedValue);
+
+ return true;
+ }
+
+ /**
+ * @dev Moves tokens `amount` from `sender` to `recipient`.
+ *
+ * This is internal function is equivalent to {transfer}, and can be used to
+ * e.g. implement automatic token fees, slashing mechanisms, etc.
+ *
+ * Emits a {Transfer} event.
+ *
+ * Requirements:
+ *
+ * - `sender` cannot be the zero address.
+ * - `recipient` cannot be the zero address.
+ * - `sender` must have a balance of at least `amount`.
+ */
+ function _transfer(address sender, address recipient, uint256 amount) internal virtual {
+ require(sender != address(0), "ERC20: transfer from the zero address");
+ require(recipient != address(0), "ERC20: transfer to the zero address");
+
+ _beforeTokenTransfer(sender, recipient, amount);
+
+ uint256 senderBalance = _balances[sender];
+ require(senderBalance >= amount, "ERC20: transfer amount exceeds balance");
+ _balances[sender] = senderBalance - amount;
+ _balances[recipient] += amount;
+
+ emit Transfer(sender, recipient, amount);
+ }
+
+ /** @dev Creates `amount` tokens and assigns them to `account`, increasing
+ * the total supply.
+ *
+ * Emits a {Transfer} event with `from` set to the zero address.
+ *
+ * Requirements:
+ *
+ * - `to` cannot be the zero address.
+ */
+ function _mint(address account, uint256 amount) internal virtual {
+ require(account != address(0), "ERC20: mint to the zero address");
+
+ _beforeTokenTransfer(address(0), account, amount);
+
+ _totalSupply += amount;
+ _balances[account] += amount;
+ emit Transfer(address(0), account, amount);
+ }
+
+ /**
+ * @dev Destroys `amount` tokens from `account`, reducing the
+ * total supply.
+ *
+ * Emits a {Transfer} event with `to` set to the zero address.
+ *
+ * Requirements:
+ *
+ * - `account` cannot be the zero address.
+ * - `account` must have at least `amount` tokens.
+ */
+ function _burn(address account, uint256 amount) internal virtual {
+ require(account != address(0), "ERC20: burn from the zero address");
+
+ _beforeTokenTransfer(account, address(0), amount);
+
+ uint256 accountBalance = _balances[account];
+ require(accountBalance >= amount, "ERC20: burn amount exceeds balance");
+ _balances[account] = accountBalance - amount;
+ _totalSupply -= amount;
+
+ emit Transfer(account, address(0), amount);
+ }
+
+ /**
+ * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
+ *
+ * This internal function is equivalent to `approve`, and can be used to
+ * e.g. set automatic allowances for certain subsystems, etc.
+ *
+ * Emits an {Approval} event.
+ *
+ * Requirements:
+ *
+ * - `owner` cannot be the zero address.
+ * - `spender` cannot be the zero address.
+ */
+ function _approve(address owner, address spender, uint256 amount) internal virtual {
+ 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);
+ }
+
+ /**
+ * @dev Hook that is called before any transfer of tokens. This includes
+ * minting and burning.
+ *
+ * Calling conditions:
+ *
+ * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
+ * will be to transferred to `to`.
+ * - when `from` is zero, `amount` tokens will be minted for `to`.
+ * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
+ * - `from` and `to` are never both zero.
+ *
+ * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
+ */
+ function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual { }
+}
projects / sandbox / blobdiff