ioedeveloper
3 years ago
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// SPDX-License-Identifier: MIT |
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pragma solidity ^0.8.0; |
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import "./IERC20.sol"; |
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import "./extensions/IERC20Metadata.sol"; |
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import "../../utils/Context.sol"; |
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|
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/** |
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* @dev Implementation of the {IERC20} interface. |
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* |
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* This implementation is agnostic to the way tokens are created. This means |
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* that a supply mechanism has to be added in a derived contract using {_mint}. |
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* For a generic mechanism see {ERC20PresetMinterPauser}. |
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* |
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* TIP: For a detailed writeup see our guide |
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* https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How |
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* to implement supply mechanisms]. |
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* |
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* We have followed general OpenZeppelin Contracts guidelines: functions revert |
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* instead returning `false` on failure. This behavior is nonetheless |
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* conventional and does not conflict with the expectations of ERC20 |
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* applications. |
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* |
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* Additionally, an {Approval} event is emitted on calls to {transferFrom}. |
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* This allows applications to reconstruct the allowance for all accounts just |
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* by listening to said events. Other implementations of the EIP may not emit |
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* these events, as it isn't required by the specification. |
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* |
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* Finally, the non-standard {decreaseAllowance} and {increaseAllowance} |
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* functions have been added to mitigate the well-known issues around setting |
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* allowances. See {IERC20-approve}. |
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*/ |
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contract ERC20 is Context, IERC20, IERC20Metadata { |
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mapping(address => uint256) private _balances; |
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mapping(address => mapping(address => uint256)) private _allowances; |
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uint256 private _totalSupply; |
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string private _name; |
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string private _symbol; |
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|
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/** |
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* @dev Sets the values for {name} and {symbol}. |
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* |
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* The default value of {decimals} is 18. To select a different value for |
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* {decimals} you should overload it. |
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* |
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* All two of these values are immutable: they can only be set once during |
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* construction. |
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*/ |
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constructor(string memory name_, string memory symbol_) { |
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_name = name_; |
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_symbol = symbol_; |
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} |
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|
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/** |
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* @dev Returns the name of the token. |
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*/ |
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function name() public view virtual override returns (string memory) { |
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return _name; |
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} |
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|
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/** |
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* @dev Returns the symbol of the token, usually a shorter version of the |
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* name. |
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*/ |
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function symbol() public view virtual override returns (string memory) { |
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return _symbol; |
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} |
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|
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/** |
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* @dev Returns the number of decimals used to get its user representation. |
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* For example, if `decimals` equals `2`, a balance of `505` tokens should |
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* be displayed to a user as `5.05` (`505 / 10 ** 2`). |
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* |
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* Tokens usually opt for a value of 18, imitating the relationship between |
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* Ether and Wei. This is the value {ERC20} uses, unless this function is |
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* overridden; |
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* |
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* NOTE: This information is only used for _display_ purposes: it in |
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* no way affects any of the arithmetic of the contract, including |
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* {IERC20-balanceOf} and {IERC20-transfer}. |
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*/ |
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function decimals() public view virtual override returns (uint8) { |
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return 18; |
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} |
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|
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/** |
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* @dev See {IERC20-totalSupply}. |
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*/ |
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function totalSupply() public view virtual override returns (uint256) { |
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return _totalSupply; |
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} |
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|
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/** |
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* @dev See {IERC20-balanceOf}. |
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*/ |
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function balanceOf(address account) public view virtual override returns (uint256) { |
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return _balances[account]; |
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} |
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|
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/** |
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* @dev See {IERC20-transfer}. |
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* |
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* Requirements: |
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* |
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* - `recipient` cannot be the zero address. |
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* - the caller must have a balance of at least `amount`. |
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*/ |
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function transfer(address recipient, uint256 amount) public virtual override returns (bool) { |
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_transfer(_msgSender(), recipient, amount); |
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return true; |
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} |
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|
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/** |
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* @dev See {IERC20-allowance}. |
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*/ |
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function allowance(address owner, address spender) public view virtual override returns (uint256) { |
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return _allowances[owner][spender]; |
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} |
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|
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/** |
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* @dev See {IERC20-approve}. |
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* |
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* Requirements: |
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* |
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* - `spender` cannot be the zero address. |
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*/ |
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function approve(address spender, uint256 amount) public virtual override returns (bool) { |
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_approve(_msgSender(), spender, amount); |
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return true; |
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} |
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|
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/** |
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* @dev See {IERC20-transferFrom}. |
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* |
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* Emits an {Approval} event indicating the updated allowance. This is not |
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* required by the EIP. See the note at the beginning of {ERC20}. |
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* |
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* Requirements: |
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* |
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* - `sender` and `recipient` cannot be the zero address. |
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* - `sender` must have a balance of at least `amount`. |
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* - the caller must have allowance for ``sender``'s tokens of at least |
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* `amount`. |
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*/ |
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function transferFrom( |
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address sender, |
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address recipient, |
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uint256 amount |
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) public virtual override returns (bool) { |
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_transfer(sender, recipient, amount); |
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|
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uint256 currentAllowance = _allowances[sender][_msgSender()]; |
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require(currentAllowance >= amount, "ERC20: transfer amount exceeds allowance"); |
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unchecked { |
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_approve(sender, _msgSender(), currentAllowance - amount); |
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} |
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return true; |
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} |
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|
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/** |
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* @dev Atomically increases the allowance granted to `spender` by the caller. |
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* |
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* This is an alternative to {approve} that can be used as a mitigation for |
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* problems described in {IERC20-approve}. |
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* |
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* Emits an {Approval} event indicating the updated allowance. |
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* |
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* Requirements: |
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* |
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* - `spender` cannot be the zero address. |
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*/ |
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function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) { |
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_approve(_msgSender(), spender, _allowances[_msgSender()][spender] + addedValue); |
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return true; |
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} |
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|
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/** |
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* @dev Atomically decreases the allowance granted to `spender` by the caller. |
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* |
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* This is an alternative to {approve} that can be used as a mitigation for |
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* problems described in {IERC20-approve}. |
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* |
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* Emits an {Approval} event indicating the updated allowance. |
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* |
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* Requirements: |
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* |
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* - `spender` cannot be the zero address. |
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* - `spender` must have allowance for the caller of at least |
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* `subtractedValue`. |
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*/ |
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function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) { |
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uint256 currentAllowance = _allowances[_msgSender()][spender]; |
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require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero"); |
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unchecked { |
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_approve(_msgSender(), spender, currentAllowance - subtractedValue); |
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} |
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return true; |
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} |
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/** |
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* @dev Moves `amount` of tokens from `sender` to `recipient`. |
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* |
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* This internal function is equivalent to {transfer}, and can be used to |
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* e.g. implement automatic token fees, slashing mechanisms, etc. |
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* |
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* Emits a {Transfer} event. |
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* |
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* Requirements: |
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* |
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* - `sender` cannot be the zero address. |
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* - `recipient` cannot be the zero address. |
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* - `sender` must have a balance of at least `amount`. |
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*/ |
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function _transfer( |
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address sender, |
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address recipient, |
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uint256 amount |
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) internal virtual { |
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require(sender != address(0), "ERC20: transfer from the zero address"); |
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require(recipient != address(0), "ERC20: transfer to the zero address"); |
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_beforeTokenTransfer(sender, recipient, amount); |
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uint256 senderBalance = _balances[sender]; |
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require(senderBalance >= amount, "ERC20: transfer amount exceeds balance"); |
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unchecked { |
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_balances[sender] = senderBalance - amount; |
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} |
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_balances[recipient] += amount; |
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emit Transfer(sender, recipient, amount); |
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_afterTokenTransfer(sender, recipient, amount); |
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} |
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/** @dev Creates `amount` tokens and assigns them to `account`, increasing |
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* the total supply. |
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* |
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* Emits a {Transfer} event with `from` set to the zero address. |
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* |
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* Requirements: |
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* |
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* - `account` cannot be the zero address. |
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*/ |
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function _mint(address account, uint256 amount) internal virtual { |
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require(account != address(0), "ERC20: mint to the zero address"); |
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_beforeTokenTransfer(address(0), account, amount); |
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_totalSupply += amount; |
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_balances[account] += amount; |
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emit Transfer(address(0), account, amount); |
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_afterTokenTransfer(address(0), account, amount); |
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} |
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/** |
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* @dev Destroys `amount` tokens from `account`, reducing the |
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* total supply. |
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* |
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* Emits a {Transfer} event with `to` set to the zero address. |
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* |
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* Requirements: |
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* |
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* - `account` cannot be the zero address. |
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* - `account` must have at least `amount` tokens. |
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*/ |
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function _burn(address account, uint256 amount) internal virtual { |
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require(account != address(0), "ERC20: burn from the zero address"); |
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_beforeTokenTransfer(account, address(0), amount); |
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uint256 accountBalance = _balances[account]; |
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require(accountBalance >= amount, "ERC20: burn amount exceeds balance"); |
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unchecked { |
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_balances[account] = accountBalance - amount; |
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} |
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_totalSupply -= amount; |
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emit Transfer(account, address(0), amount); |
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_afterTokenTransfer(account, address(0), amount); |
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} |
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/** |
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* @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens. |
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* |
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* This internal function is equivalent to `approve`, and can be used to |
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* e.g. set automatic allowances for certain subsystems, etc. |
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* |
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* Emits an {Approval} event. |
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* |
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* Requirements: |
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* |
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* - `owner` cannot be the zero address. |
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* - `spender` cannot be the zero address. |
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*/ |
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function _approve( |
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address owner, |
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address spender, |
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uint256 amount |
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) internal virtual { |
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require(owner != address(0), "ERC20: approve from the zero address"); |
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require(spender != address(0), "ERC20: approve to the zero address"); |
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_allowances[owner][spender] = amount; |
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emit Approval(owner, spender, amount); |
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} |
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/** |
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* @dev Hook that is called before any transfer of tokens. This includes |
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* minting and burning. |
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* |
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* Calling conditions: |
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* |
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* - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens |
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* will be transferred to `to`. |
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* - when `from` is zero, `amount` tokens will be minted for `to`. |
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* - when `to` is zero, `amount` of ``from``'s tokens will be burned. |
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* - `from` and `to` are never both zero. |
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* |
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* To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks]. |
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*/ |
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function _beforeTokenTransfer( |
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address from, |
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address to, |
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uint256 amount |
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) internal virtual {} |
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/** |
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* @dev Hook that is called after any transfer of tokens. This includes |
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* minting and burning. |
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* |
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* Calling conditions: |
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* |
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* - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens |
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* has been transferred to `to`. |
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* - when `from` is zero, `amount` tokens have been minted for `to`. |
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* - when `to` is zero, `amount` of ``from``'s tokens have been burned. |
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* - `from` and `to` are never both zero. |
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* |
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* To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks]. |
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*/ |
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function _afterTokenTransfer( |
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address from, |
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address to, |
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uint256 amount |
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) internal virtual {} |
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} |
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@ -1,81 +0,0 @@ |
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// SPDX-License-Identifier: MIT |
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pragma solidity ^0.8.0; |
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/** |
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* @dev Interface of the ERC20 standard as defined in the EIP. |
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*/ |
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interface IERC20 { |
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/** |
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* @dev Returns the amount of tokens in existence. |
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*/ |
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function totalSupply() external view returns (uint256); |
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|
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/** |
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* @dev Returns the amount of tokens owned by `account`. |
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*/ |
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function balanceOf(address account) external view returns (uint256); |
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/** |
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* @dev Moves `amount` tokens from the caller's account to `recipient`. |
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* |
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* Returns a boolean value indicating whether the operation succeeded. |
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* |
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* Emits a {Transfer} event. |
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*/ |
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function transfer(address recipient, uint256 amount) external returns (bool); |
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/** |
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* @dev Returns the remaining number of tokens that `spender` will be |
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* allowed to spend on behalf of `owner` through {transferFrom}. This is |
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* zero by default. |
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* |
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* This value changes when {approve} or {transferFrom} are called. |
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*/ |
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function allowance(address owner, address spender) external view returns (uint256); |
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/** |
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* @dev Sets `amount` as the allowance of `spender` over the caller's tokens. |
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* |
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* Returns a boolean value indicating whether the operation succeeded. |
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* |
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* IMPORTANT: Beware that changing an allowance with this method brings the risk |
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* that someone may use both the old and the new allowance by unfortunate |
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* transaction ordering. One possible solution to mitigate this race |
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* condition is to first reduce the spender's allowance to 0 and set the |
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* desired value afterwards: |
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* https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729 |
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* |
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* Emits an {Approval} event. |
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*/ |
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function approve(address spender, uint256 amount) external returns (bool); |
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/** |
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* @dev Moves `amount` tokens from `sender` to `recipient` using the |
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* allowance mechanism. `amount` is then deducted from the caller's |
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* allowance. |
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* |
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* Returns a boolean value indicating whether the operation succeeded. |
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* |
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* Emits a {Transfer} event. |
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*/ |
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function transferFrom( |
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address sender, |
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address recipient, |
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uint256 amount |
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) external returns (bool); |
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/** |
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* @dev Emitted when `value` tokens are moved from one account (`from`) to |
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* another (`to`). |
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* |
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* Note that `value` may be zero. |
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*/ |
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event Transfer(address indexed from, address indexed to, uint256 value); |
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/** |
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* @dev Emitted when the allowance of a `spender` for an `owner` is set by |
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* a call to {approve}. `value` is the new allowance. |
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*/ |
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event Approval(address indexed owner, address indexed spender, uint256 value); |
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} |
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@ -1,27 +0,0 @@ |
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// SPDX-License-Identifier: MIT |
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pragma solidity ^0.8.0; |
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import "../IERC20.sol"; |
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/** |
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* @dev Interface for the optional metadata functions from the ERC20 standard. |
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* |
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* _Available since v4.1._ |
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*/ |
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interface IERC20Metadata is IERC20 { |
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/** |
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* @dev Returns the name of the token. |
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*/ |
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function name() external view returns (string memory); |
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|
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/** |
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* @dev Returns the symbol of the token. |
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*/ |
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function symbol() external view returns (string memory); |
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/** |
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* @dev Returns the decimals places of the token. |
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*/ |
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function decimals() external view returns (uint8); |
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} |
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@ -1,23 +0,0 @@ |
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// SPDX-License-Identifier: MIT |
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pragma solidity ^0.8.0; |
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/** |
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* @dev Provides information about the current execution context, including the |
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* sender of the transaction and its data. While these are generally available |
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* via msg.sender and msg.data, they should not be accessed in such a direct |
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* manner, since when dealing with meta-transactions the account sending and |
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* paying for execution may not be the actual sender (as far as an application |
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* is concerned). |
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* |
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* This contract is only required for intermediate, library-like contracts. |
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*/ |
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abstract contract Context { |
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function _msgSender() internal view virtual returns (address) { |
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return msg.sender; |
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} |
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|
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function _msgData() internal view virtual returns (bytes calldata) { |
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return msg.data; |
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} |
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} |
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@ -0,0 +1 @@ |
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contract test2 { function get () returns (uint) { return 11; }} |
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