ERC20Diff
创建于 差异永不过期
pragma solidity ^0.5.0;
pragma solidity ^0.5.0;
import "../../GSN/Context.sol";
import "openzeppelin-solidity/contracts/GSN/Context.sol";
import "./IERC20.sol";
import "openzeppelin-solidity/contracts/token/ERC20/IERC20.sol";
import "../../math/SafeMath.sol";
import "openzeppelin-solidity/contracts/math/SafeMath.sol";
/**
/**
* @dev Implementation of the {IERC20} interface.
* @dev Implementation of the {IERC20} interface.
*
*
* This implementation is agnostic to the way tokens are created. This means
* This implementation is agnostic to the way tokens are created. This means
* that a supply mechanism has to be added in a derived contract using {_mint}.
* that a supply mechanism has to be added in a derived contract using {_mint}.
* For a generic mechanism see {ERC20Mintable}.
* For a generic mechanism see {ERC20Mintable}.
*
*
* TIP: For a detailed writeup see our guide
* TIP: For a detailed writeup see our guide
* https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
* https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
* to implement supply mechanisms].
* to implement supply mechanisms].
*
*
* We have followed general OpenZeppelin guidelines: functions revert instead
* We have followed general OpenZeppelin guidelines: functions revert instead
* of returning `false` on failure. This behavior is nonetheless conventional
* of returning `false` on failure. This behavior is nonetheless conventional
* and does not conflict with the expectations of ERC20 applications.
* and does not conflict with the expectations of ERC20 applications.
*
*
* Additionally, an {Approval} event is emitted on calls to {transferFrom}.
* Additionally, an {Approval} event is emitted on calls to {transferFrom}.
* This allows applications to reconstruct the allowance for all accounts just
* This allows applications to reconstruct the allowance for all accounts just
* by listening to said events. Other implementations of the EIP may not emit
* by listening to said events. Other implementations of the EIP may not emit
* these events, as it isn't required by the specification.
* these events, as it isn't required by the specification.
*
*
* Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
* Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
* functions have been added to mitigate the well-known issues around setting
* functions have been added to mitigate the well-known issues around setting
* allowances. See {IERC20-approve}.
* allowances. See {IERC20-approve}.
*/
*/
contract ERC20 is Context, IERC20 {
contract ERC20 is Context, IERC20 {
using SafeMath for uint256;
using SafeMath for uint256;
mapping (address => uint256) private _balances;
mapping (address => uint256) internal _balances;
mapping (address => mapping (address => uint256)) private _allowances;
mapping (address => mapping (address => uint256)) private _allowances;
uint256 private _totalSupply;
uint256 private _totalSupply;
/**
/**
* @dev See {IERC20-totalSupply}.
* @dev See {IERC20-totalSupply}.
*/
*/
function totalSupply() public view returns (uint256) {
function totalSupply() public view returns (uint256) {
return _totalSupply;
return _totalSupply;
}
}
/**
/**
* @dev See {IERC20-balanceOf}.
* @dev See {IERC20-balanceOf}.
*/
*/
function balanceOf(address account) public view returns (uint256) {
function balanceOf(address account) public view returns (uint256) {
return _balances[account];
return _balances[account];
}
}
/**
/**
* @dev See {IERC20-transfer}.
* @dev See {IERC20-transfer}.
*
*
* Requirements:
* Requirements:
*
*
* - `recipient` cannot be the zero address.
* - `recipient` cannot be the zero address.
* - the caller must have a balance of at least `amount`.
* - the caller must have a balance of at least `amount`.
*/
*/
function transfer(address recipient, uint256 amount) public returns (bool) {
function transfer(address recipient, uint256 amount) public returns (bool) {
_transfer(_msgSender(), recipient, amount);
_transfer(_msgSender(), recipient, amount);
return true;
return true;
}
}
/**
/**
* @dev See {IERC20-allowance}.
* @dev See {IERC20-allowance}.
*/
*/
function allowance(address owner, address spender) public view returns (uint256) {
function allowance(address owner, address spender) public view returns (uint256) {
return _allowances[owner][spender];
return _allowances[owner][spender];
}
}
/**
/**
* @dev See {IERC20-approve}.
* @dev See {IERC20-approve}.
*
*
* Requirements:
* Requirements:
*
*
* - `spender` cannot be the zero address.
* - `spender` cannot be the zero address.
*/
*/
function approve(address spender, uint256 amount) public returns (bool) {
function approve(address spender, uint256 amount) public returns (bool) {
_approve(_msgSender(), spender, amount);
_approve(_msgSender(), spender, amount);
return true;
return true;
}
}
/**
/**
* @dev See {IERC20-transferFrom}.
* @dev See {IERC20-transferFrom}.
*
*
* Emits an {Approval} event indicating the updated allowance. This is not
* Emits an {Approval} event indicating the updated allowance. This is not
* required by the EIP. See the note at the beginning of {ERC20};
* required by the EIP. See the note at the beginning of {ERC20};
*
*
* Requirements:
* Requirements:
* - `sender` and `recipient` cannot be the zero address.
* - `sender` and `recipient` cannot be the zero address.
* - `sender` must have a balance of at least `amount`.
* - `sender` must have a balance of at least `amount`.
* - the caller must have allowance for `sender`'s tokens of at least
* - the caller must have allowance for `sender`'s tokens of at least
* `amount`.
* `amount`.
*/
*/
function transferFrom(address sender, address recipient, uint256 amount) public returns (bool) {
function transferFrom(address sender, address recipient, uint256 amount) public returns (bool) {
_transfer(sender, recipient, amount);
_transfer(sender, recipient, amount);
_approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, "ERC20: transfer amount exceeds allowance"));
_approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, "ERC20: transfer amount exceeds allowance"));
return true;
return true;
}
}
/**
/**
* @dev Atomically increases the allowance granted to `spender` by the caller.
* @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
* This is an alternative to {approve} that can be used as a mitigation for
* problems described in {IERC20-approve}.
* problems described in {IERC20-approve}.
*
*
* Emits an {Approval} event indicating the updated allowance.
* Emits an {Approval} event indicating the updated allowance.
*
*
* Requirements:
* Requirements:
*
*
* - `spender` cannot be the zero address.
* - `spender` cannot be the zero address.
*/
*/
function increaseAllowance(address spender, uint256 addedValue) public returns (bool) {
function increaseAllowance(address spender, uint256 addedValue) public returns (bool) {
_approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(addedValue));
_approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(addedValue));
return true;
return true;
}
}
/**
/**
* @dev Atomically decreases the allowance granted to `spender` by the caller.
* @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
* This is an alternative to {approve} that can be used as a mitigation for
* problems described in {IERC20-approve}.
* problems described in {IERC20-approve}.
*
*
* Emits an {Approval} event indicating the updated allowance.
* Emits an {Approval} event indicating the updated allowance.
*
*
* Requirements:
* Requirements:
*
*
* - `spender` cannot be the zero address.
* - `spender` cannot be the zero address.
* - `spender` must have allowance for the caller of at least
* - `spender` must have allowance for the caller of at least
* `subtractedValue`.
* `subtractedValue`.
*/
*/
function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) {
function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) {
_approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
_approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
return true;
return true;
}
}
/**
/**
* @dev Moves tokens `amount` from `sender` to `recipient`.
* @dev Moves tokens `amount` from `sender` to `recipient`.
*
*
* This is internal function is equivalent to {transfer}, and can be used to
* This is internal function is equivalent to {transfer}, and can be used to
* e.g. implement automatic token fees, slashing mechanisms, etc.
* e.g. implement automatic token fees, slashing mechanisms, etc.
*
*
* Emits a {Transfer} event.
* Emits a {Transfer} event.
*
*
* Requirements:
* Requirements:
*
*
* - `sender` cannot be the zero address.
* - `sender` cannot be the zero address.
* - `recipient` cannot be the zero address.
* - `recipient` cannot be the zero address.
* - `sender` must have a balance of at least `amount`.
* - `sender` must have a balance of at least `amount`.
*/
*/
function _transfer(address sender, address recipient, uint256 amount) internal {
function _transfer(address sender, address recipient, uint256 amount) internal {
require(sender != address(0), "ERC20: transfer from the zero address");
require(sender != address(0), "ERC20: transfer from the zero address");
require(recipient != address(0), "ERC20: transfer to the zero address");
require(recipient != address(0), "ERC20: transfer to the zero address");
_balances[sender] = _balances[sender].sub(amount, "ERC20: transfer amount exceeds balance");
_balances[sender] = _balances[sender].sub(amount, "ERC20: transfer amount exceeds balance");
_balances[recipient] = _balances[recipient].add(amount);
_balances[recipient] = _balances[recipient].add(amount);
emit Transfer(sender, recipient, amount);
emit Transfer(sender, recipient, amount);
}
}
/** @dev Creates `amount` tokens and assigns them to `account`, increasing
/** @dev Creates `amount` tokens and assigns them to `account`, increasing
* the total supply.
* the total supply.
*
*
* Emits a {Transfer} event with `from` set to the zero address.
* Emits a {Transfer} event with `from` set to the zero address.
*
*
* Requirements
* Requirements
*
*
* - `to` cannot be the zero address.
* - `to` cannot be the zero address.
*/
*/
function _mint(address account, uint256 amount) internal {
function _mint(address account, uint256 amount) internal {
require(account != address(0), "ERC20: mint to the zero address");
require(account != address(0), "ERC20: mint to the zero address");
_totalSupply = _totalSupply.add(amount);
_totalSupply = _totalSupply.add(amount);
_balances[account] = _balances[account].add(amount);
_balances[account] = _balances[account].add(amount);
emit Transfer(address(0), account, amount);
emit Transfer(address(0), account, amount);
}
}
/**
/**
* @dev Destroys `amount` tokens from `account`, reducing the
* @dev Destroys `amount` tokens from `account`, reducing the
* total supply.
* total supply.
*
*
* Emits a {Transfer} event with `to` set to the zero address.
* Emits a {Transfer} event with `to` set to the zero address.
*
*
* Requirements
* Requirements
*
*
* - `account` cannot be the zero address.
* - `account` cannot be the zero address.
* - `account` must have at least `amount` tokens.
* - `account` must have at least `amount` tokens.
*/
*/
function _burn(address account, uint256 amount) internal {
function _burn(address account, uint256 amount) internal {
require(account != address(0), "ERC20: burn from the zero address");
require(account != address(0), "ERC20: burn from the zero address");
_balances[account] = _balances[account].sub(amount, "ERC20: burn amount exceeds balance");
_balances[account] = _balances[account].sub(amount, "ERC20: burn amount exceeds balance");
_totalSupply = _totalSupply.sub(amount);
_totalSupply = _totalSupply.sub(amount);
emit Transfer(account, address(0), amount);
emit Transfer(account, address(0), amount);
}
}
/**
/**
* @dev Sets `amount` as the allowance of `spender` over the `owner`s tokens.
* @dev Sets `amount` as the allowance of `spender` over the `owner`s tokens.
*
*
* This is internal function is equivalent to `approve`, and can be used to
* This is internal function is equivalent to `approve`, and can be used to
* e.g. set automatic allowances for certain subsystems, etc.
* e.g. set automatic allowances for certain subsystems, etc.
*
*
* Emits an {Approval} event.
* Emits an {Approval} event.
*
*
* Requirements:
* Requirements:
*
*
* - `owner` cannot be the zero address.
* - `owner` cannot be the zero address.
* - `spender` cannot be the zero address.
* - `spender` cannot be the zero address.
*/
*/
function _approve(address owner, address spender, uint256 amount) internal {
function _approve(address owner, address spender, uint256 amount) internal {
require(owner != address(0), "ERC20: approve from the zero address");
require(owner != address(0), "ERC20: approve from the zero address");
require(spender != address(0), "ERC20: approve to the zero address");
require(spender != address(0), "ERC20: approve to the zero address");
_allowances[owner][spender] = amount;
_allowances[owner][spender] = amount;
emit Approval(owner, spender, amount);
emit Approval(owner, spender, amount);
}
}
/**
/**
* @dev Destroys `amount` tokens from `account`.`amount` is then deducted
* @dev Destroys `amount` tokens from `account`.`amount` is then deducted
* from the caller's allowance.
* from the caller's allowance.
*
*
* See {_burn} and {_approve}.
* See {_burn} and {_approve}.
*/
*/
function _burnFrom(address account, uint256 amount) internal {
function _burnFrom(address account, uint256 amount) internal {
_burn(account, amount);
_burn(account, amount);
_approve(account, _msgSender(), _allowances[account][_msgSender()].sub(amount, "ERC20: burn amount exceeds allowance"));
_approve(account, _msgSender(), _allowances[account][_msgSender()].sub(amount, "ERC20: burn amount exceeds allowance"));
}
}
}
}