pragma solidity ^0.5.0; import "./ivip-180.sol"; import "./safe-math.sol"; /** * @dev Implementation of the {IVIP180} interface. */ contract VIP180 is IVIP180 { using SafeMath for uint256; mapping (address => uint256) private _balances; mapping (address => mapping (address => uint256)) private _allowances; uint256 private _totalSupply; /** * @dev See {IVIP180-totalSupply}. */ function totalSupply() public view returns (uint256) { return _totalSupply; } /** * @dev See {IVIP180-balanceOf}. */ function balanceOf(address account) public view returns (uint256) { return _balances[account]; } /** * @dev See {IVIP180-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 returns (bool) { _transfer(msg.sender, recipient, amount); return true; } /** * @dev See {IVIP180-allowance}. */ function allowance(address owner, address spender) public view returns (uint256) { return _allowances[owner][spender]; } /** * @dev See {IVIP180-approve}. * * Requirements: * * - `spender` cannot be the zero address. */ function approve(address spender, uint256 amount) public returns (bool) { _approve(msg.sender, spender, amount); return true; } /** * @dev See {IVIP180-transferFrom}. * * Emits an {Approval} event indicating the updated allowance. This is not * required by the EIP. See the note at the beginning of {VIP180}; * * 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 returns (bool) { _transfer(sender, recipient, amount); _approve(sender, msg.sender, _allowances[sender][msg.sender].sub(amount, "VIP180: transfer amount exceeds allowance")); 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 {IVIP180-approve}. * * Emits an {Approval} event indicating the updated allowance. * * Requirements: * * - `spender` cannot be the zero address. */ function increaseAllowance(address spender, uint256 addedValue) public returns (bool) { _approve(msg.sender, spender, _allowances[msg.sender][spender].add(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 {IVIP180-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 returns (bool) { _approve(msg.sender, spender, _allowances[msg.sender][spender].sub(subtractedValue, "VIP180: decreased allowance below zero")); 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 { require(sender != address(0), "VIP180: transfer from the zero address"); require(recipient != address(0), "VIP180: transfer to the zero address"); _balances[sender] = _balances[sender].sub(amount, "VIP180: transfer amount exceeds balance"); _balances[recipient] = _balances[recipient].add(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 { require(account != address(0), "ERC20: mint to the zero address"); _totalSupply = _totalSupply.add(amount); _balances[account] = _balances[account].add(amount); emit Transfer(address(0), account, amount); } /** * @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 * 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 { require(owner != address(0), "VIP180: approve from the zero address"); require(spender != address(0), "VIP180: approve to the zero address"); _allowances[owner][spender] = amount; emit Approval(owner, spender, amount); } }