Contract Source Code:
File 1 of 1 : Mooniswap
/*
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*/
// File: @openzeppelin/contracts/GSN/Context.sol
// SPDX-License-Identifier: MIT
pragma solidity ^0.6.0;
/*
* @dev Provides information about the current execution context, including the
* sender of the transaction and its data. While these are generally available
* via msg.sender and msg.data, they should not be accessed in such a direct
* manner, since when dealing with GSN meta-transactions the account sending and
* paying for execution may not be the actual sender (as far as an application
* is concerned).
*
* This contract is only required for intermediate, library-like contracts.
*/
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;
}
}
// File: @openzeppelin/contracts/access/Ownable.sol
pragma solidity ^0.6.0;
/**
* @dev Contract module which provides a basic access control mechanism, where
* there is an account (an owner) that can be granted exclusive access to
* specific functions.
*
* By default, the owner account will be the one that deploys the contract. This
* can later be changed with {transferOwnership}.
*
* This module is used through inheritance. It will make available the modifier
* `onlyOwner`, which can be applied to your functions to restrict their use to
* the owner.
*/
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;
}
}
// File: @openzeppelin/contracts/utils/ReentrancyGuard.sol
pragma solidity ^0.6.0;
/**
* @dev Contract module that helps prevent reentrant calls to a function.
*
* Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
* available, which can be applied to functions to make sure there are no nested
* (reentrant) calls to them.
*
* Note that because there is a single `nonReentrant` guard, functions marked as
* `nonReentrant` may not call one another. This can be worked around by making
* those functions `private`, and then adding `external` `nonReentrant` entry
* points to them.
*
* TIP: If you would like to learn more about reentrancy and alternative ways
* to protect against it, check out our blog post
* https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
*/
contract ReentrancyGuard {
// Booleans are more expensive than uint256 or any type that takes up a full
// word because each write operation emits an extra SLOAD to first read the
// slot's contents, replace the bits taken up by the boolean, and then write
// back. This is the compiler's defense against contract upgrades and
// pointer aliasing, and it cannot be disabled.
// The values being non-zero value makes deployment a bit more expensive,
// but in exchange the refund on every call to nonReentrant will be lower in
// amount. Since refunds are capped to a percentage of the total
// transaction's gas, it is best to keep them low in cases like this one, to
// increase the likelihood of the full refund coming into effect.
uint256 private constant _NOT_ENTERED = 1;
uint256 private constant _ENTERED = 2;
uint256 private _status;
constructor () internal {
_status = _NOT_ENTERED;
}
/**
* @dev Prevents a contract from calling itself, directly or indirectly.
* Calling a `nonReentrant` function from another `nonReentrant`
* function is not supported. It is possible to prevent this from happening
* by making the `nonReentrant` function external, and make it call a
* `private` function that does the actual work.
*/
modifier nonReentrant() {
// On the first call to nonReentrant, _notEntered will be true
require(_status != _ENTERED, "ReentrancyGuard: reentrant call");
// Any calls to nonReentrant after this point will fail
_status = _ENTERED;
_;
// By storing the original value once again, a refund is triggered (see
// https://eips.ethereum.org/EIPS/eip-2200)
_status = _NOT_ENTERED;
}
}
// File: @openzeppelin/contracts/math/Math.sol
pragma solidity ^0.6.0;
/**
* @dev Standard math utilities missing in the Solidity language.
*/
library Math {
/**
* @dev Returns the largest of two numbers.
*/
function max(uint256 a, uint256 b) internal pure returns (uint256) {
return a >= b ? a : b;
}
/**
* @dev Returns the smallest of two numbers.
*/
function min(uint256 a, uint256 b) internal pure returns (uint256) {
return a < b ? a : b;
}
/**
* @dev Returns the average of two numbers. The result is rounded towards
* zero.
*/
function average(uint256 a, uint256 b) internal pure returns (uint256) {
// (a + b) / 2 can overflow, so we distribute
return (a / 2) + (b / 2) + ((a % 2 + b % 2) / 2);
}
}
// File: @openzeppelin/contracts/math/SafeMath.sol
pragma solidity ^0.6.0;
/**
* @dev Wrappers over Solidity's arithmetic operations with added overflow
* checks.
*
* Arithmetic operations in Solidity wrap on overflow. This can easily result
* in bugs, because programmers usually assume that an overflow raises an
* error, which is the standard behavior in high level programming languages.
* `SafeMath` restores this intuition by reverting the transaction when an
* operation overflows.
*
* Using this library instead of the unchecked operations eliminates an entire
* class of bugs, so it's recommended to use it always.
*/
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;
}
}
// File: @openzeppelin/contracts/token/ERC20/IERC20.sol
pragma solidity ^0.6.0;
/**
* @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);
}
// File: @openzeppelin/contracts/utils/Address.sol
pragma solidity ^0.6.2;
/**
* @dev Collection of functions related to the address type
*/
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);
}
}
}
}
// File: @openzeppelin/contracts/token/ERC20/ERC20.sol
pragma solidity ^0.6.0;
/**
* @dev Implementation of the {IERC20} interface.
*
* 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}.
* For a generic mechanism see {ERC20PresetMinterPauser}.
*
* TIP: For a detailed writeup see our guide
* https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
* to implement supply mechanisms].
*
* We have followed general OpenZeppelin guidelines: functions revert instead
* of returning `false` on failure. This behavior is nonetheless conventional
* and does not conflict with the expectations of ERC20 applications.
*
* Additionally, an {Approval} event is emitted on calls to {transferFrom}.
* This allows applications to reconstruct the allowance for all accounts just
* by listening to said events. Other implementations of the EIP may not emit
* these events, as it isn't required by the specification.
*
* Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
* functions have been added to mitigate the well-known issues around setting
* allowances. See {IERC20-approve}.
*/
contract ERC20 is Context, IERC20 {
using SafeMath for uint256;
using Address for address;
mapping (address => uint256) private _balances;
mapping (address => mapping (address => uint256)) private _allowances;
uint256 private _totalSupply;
string private _name;
string private _symbol;
uint8 private _decimals;
/**
* @dev Sets the values for {name} and {symbol}, initializes {decimals} with
* a default value of 18.
*
* To select a different value for {decimals}, use {_setupDecimals}.
*
* All three of these values are immutable: they can only be set once during
* construction.
*/
constructor (string memory name, string memory symbol) public {
_name = name;
_symbol = symbol;
_decimals = 18;
}
/**
* @dev Returns the name of the token.
*/
function name() public view returns (string memory) {
return _name;
}
/**
* @dev Returns the symbol of the token, usually a shorter version of the
* name.
*/
function symbol() public view 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 {_setupDecimals} is
* called.
*
* 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 returns (uint8) {
return _decimals;
}
/**
* @dev See {IERC20-totalSupply}.
*/
function totalSupply() public view override returns (uint256) {
return _totalSupply;
}
/**
* @dev See {IERC20-balanceOf}.
*/
function balanceOf(address account) public view 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);
_approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, "ERC20: 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 {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].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 {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) {
_approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, "ERC20: 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 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);
_balances[sender] = _balances[sender].sub(amount, "ERC20: 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 virtual {
require(account != address(0), "ERC20: mint to the zero address");
_beforeTokenTransfer(address(0), account, amount);
_totalSupply = _totalSupply.add(amount);
_balances[account] = _balances[account].add(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);
_balances[account] = _balances[account].sub(amount, "ERC20: burn amount exceeds balance");
_totalSupply = _totalSupply.sub(amount);
emit Transfer(account, address(0), 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 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 Sets {decimals} to a value other than the default one of 18.
*
* WARNING: This function should only be called from the constructor. Most
* applications that interact with token contracts will not expect
* {decimals} to ever change, and may work incorrectly if it does.
*/
function _setupDecimals(uint8 decimals_) internal {
_decimals = decimals_;
}
/**
* @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 { }
}
// File: @openzeppelin/contracts/token/ERC20/SafeERC20.sol
pragma solidity ^0.6.0;
/**
* @title SafeERC20
* @dev Wrappers around ERC20 operations that throw on failure (when the token
* contract returns false). Tokens that return no value (and instead revert or
* throw on failure) are also supported, non-reverting calls are assumed to be
* successful.
* To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
* which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
*/
library SafeERC20 {
using SafeMath for uint256;
using Address for address;
function safeTransfer(IERC20 token, address to, uint256 value) internal {
_callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
}
function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
_callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
}
/**
* @dev Deprecated. This function has issues similar to the ones found in
* {IERC20-approve}, and its usage is discouraged.
*
* Whenever possible, use {safeIncreaseAllowance} and
* {safeDecreaseAllowance} instead.
*/
function safeApprove(IERC20 token, address spender, uint256 value) internal {
// safeApprove should only be called when setting an initial allowance,
// or when resetting it to zero. To increase and decrease it, use
// 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
// solhint-disable-next-line max-line-length
require((value == 0) || (token.allowance(address(this), spender) == 0),
"SafeERC20: approve from non-zero to non-zero allowance"
);
_callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
}
function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
uint256 newAllowance = token.allowance(address(this), spender).add(value);
_callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
}
function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
_callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
}
/**
* @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
* on the return value: the return value is optional (but if data is returned, it must not be false).
* @param token The token targeted by the call.
* @param data The call data (encoded using abi.encode or one of its variants).
*/
function _callOptionalReturn(IERC20 token, bytes memory data) private {
// We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
// we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
// the target address contains contract code and also asserts for success in the low-level call.
bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
if (returndata.length > 0) { // Return data is optional
// solhint-disable-next-line max-line-length
require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
}
}
}
// File: contracts/libraries/UniERC20.sol
pragma solidity ^0.6.0;
library UniERC20 {
using SafeMath for uint256;
using SafeERC20 for IERC20;
function isETH(IERC20 token) internal pure returns(bool) {
return (address(token) == address(0));
}
function uniBalanceOf(IERC20 token, address account) internal view returns (uint256) {
if (isETH(token)) {
return account.balance;
} else {
return token.balanceOf(account);
}
}
function uniTransfer(IERC20 token, address payable to, uint256 amount) internal {
if (amount > 0) {
if (isETH(token)) {
to.transfer(amount);
} else {
token.safeTransfer(to, amount);
}
}
}
function uniTransferFromSenderToThis(IERC20 token, uint256 amount) internal {
if (amount > 0) {
if (isETH(token)) {
require(msg.value >= amount, "UniERC20: not enough value");
if (msg.value > amount) {
// Return remainder if exist
msg.sender.transfer(msg.value.sub(amount));
}
} else {
token.safeTransferFrom(msg.sender, address(this), amount);
}
}
}
function uniSymbol(IERC20 token) internal view returns(string memory) {
if (isETH(token)) {
return "ETH";
}
(bool success, bytes memory data) = address(token).staticcall{ gas: 20000 }(
abi.encodeWithSignature("symbol()")
);
if (!success) {
(success, data) = address(token).staticcall{ gas: 20000 }(
abi.encodeWithSignature("SYMBOL()")
);
}
if (success && data.length >= 96) {
(uint256 offset, uint256 len) = abi.decode(data, (uint256, uint256));
if (offset == 0x20 && len > 0 && len <= 256) {
return string(abi.decode(data, (bytes)));
}
}
if (success && data.length == 32) {
uint len = 0;
while (len < data.length && data[len] >= 0x20 && data[len] <= 0x7E) {
len++;
}
if (len > 0) {
bytes memory result = new bytes(len);
for (uint i = 0; i < len; i++) {
result[i] = data[i];
}
return string(result);
}
}
return _toHex(address(token));
}
function _toHex(address account) private pure returns(string memory) {
return _toHex(abi.encodePacked(account));
}
function _toHex(bytes memory data) private pure returns(string memory) {
bytes memory str = new bytes(2 + data.length * 2);
str[0] = "0";
str[1] = "x";
uint j = 2;
for (uint i = 0; i < data.length; i++) {
uint a = uint8(data[i]) >> 4;
uint b = uint8(data[i]) & 0x0f;
str[j++] = byte(uint8(a + 48 + (a/10)*39));
str[j++] = byte(uint8(b + 48 + (b/10)*39));
}
return string(str);
}
}
// File: contracts/libraries/Sqrt.sol
pragma solidity ^0.6.0;
library Sqrt {
// babylonian method (https://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Babylonian_method)
function sqrt(uint256 y) internal pure returns (uint256) {
if (y > 3) {
uint256 z = y;
uint256 x = y / 2 + 1;
while (x < z) {
z = x;
x = (y / x + x) / 2;
}
return z;
} else if (y != 0) {
return 1;
} else {
return 0;
}
}
}
// File: contracts/Mooniswap.sol
pragma solidity ^0.6.0;
interface IFactory {
function fee() external view returns(uint256);
}
library VirtualBalance {
using SafeMath for uint256;
struct Data {
uint216 balance;
uint40 time;
}
uint256 public constant DECAY_PERIOD = 5 minutes;
function set(VirtualBalance.Data storage self, uint256 balance) internal {
self.balance = uint216(balance);
self.time = uint40(block.timestamp);
}
function update(VirtualBalance.Data storage self, uint256 realBalance) internal {
set(self, current(self, realBalance));
}
function scale(VirtualBalance.Data storage self, uint256 realBalance, uint256 num, uint256 denom) internal {
set(self, current(self, realBalance).mul(num).add(denom.sub(1)).div(denom));
}
function current(VirtualBalance.Data memory self, uint256 realBalance) internal view returns(uint256) {
uint256 timePassed = Math.min(DECAY_PERIOD, block.timestamp.sub(self.time));
uint256 timeRemain = DECAY_PERIOD.sub(timePassed);
return uint256(self.balance).mul(timeRemain).add(
realBalance.mul(timePassed)
).div(DECAY_PERIOD);
}
}
contract Mooniswap is ERC20, ReentrancyGuard, Ownable {
using Sqrt for uint256;
using SafeMath for uint256;
using UniERC20 for IERC20;
using VirtualBalance for VirtualBalance.Data;
struct Balances {
uint256 src;
uint256 dst;
}
struct SwapVolumes {
uint128 confirmed;
uint128 result;
}
event Deposited(
address indexed account,
uint256 amount
);
event Withdrawn(
address indexed account,
uint256 amount
);
event Swapped(
address indexed account,
address indexed src,
address indexed dst,
uint256 amount,
uint256 result,
uint256 srcBalance,
uint256 dstBalance,
uint256 totalSupply,
address referral
);
uint256 public constant REFERRAL_SHARE = 20; // 1/share = 5% of LPs revenue
uint256 public constant BASE_SUPPLY = 1000; // Total supply on first deposit
uint256 public constant FEE_DENOMINATOR = 1e18;
IFactory public factory;
IERC20[] public tokens;
mapping(IERC20 => bool) public isToken;
mapping(IERC20 => SwapVolumes) public volumes;
mapping(IERC20 => VirtualBalance.Data) public virtualBalancesForAddition;
mapping(IERC20 => VirtualBalance.Data) public virtualBalancesForRemoval;
constructor(IERC20[] memory assets, string memory name, string memory symbol) public ERC20(name, symbol) {
require(bytes(name).length > 0, "Mooniswap: name is empty");
require(bytes(symbol).length > 0, "Mooniswap: symbol is empty");
require(assets.length == 2, "Mooniswap: only 2 tokens allowed");
factory = IFactory(msg.sender);
tokens = assets;
for (uint i = 0; i < assets.length; i++) {
require(!isToken[assets[i]], "Mooniswap: duplicate tokens");
isToken[assets[i]] = true;
}
}
function fee() public view returns(uint256) {
return factory.fee();
}
function getTokens() external view returns(IERC20[] memory) {
return tokens;
}
function decayPeriod() external pure returns(uint256) {
return VirtualBalance.DECAY_PERIOD;
}
function getBalanceForAddition(IERC20 token) public view returns(uint256) {
uint256 balance = token.uniBalanceOf(address(this));
return Math.max(virtualBalancesForAddition[token].current(balance), balance);
}
function getBalanceForRemoval(IERC20 token) public view returns(uint256) {
uint256 balance = token.uniBalanceOf(address(this));
return Math.min(virtualBalancesForRemoval[token].current(balance), balance);
}
function getReturn(IERC20 src, IERC20 dst, uint256 amount) external view returns(uint256) {
return _getReturn(src, dst, amount, getBalanceForAddition(src), getBalanceForRemoval(dst));
}
function deposit(uint256[] calldata amounts, uint256[] calldata minAmounts) external payable nonReentrant returns(uint256 fairSupply) {
IERC20[] memory _tokens = tokens;
require(amounts.length == _tokens.length, "Mooniswap: wrong amounts length");
require(msg.value == (_tokens[0].isETH() ? amounts[0] : (_tokens[1].isETH() ? amounts[1] : 0)), "Mooniswap: wrong value usage");
uint256[] memory realBalances = new uint256[](amounts.length);
for (uint i = 0; i < realBalances.length; i++) {
realBalances[i] = _tokens[i].uniBalanceOf(address(this)).sub(_tokens[i].isETH() ? msg.value : 0);
}
uint256 totalSupply = totalSupply();
if (totalSupply == 0) {
fairSupply = BASE_SUPPLY.mul(99);
_mint(address(this), BASE_SUPPLY); // Donate up to 1%
// Use the greatest token amount but not less than 99k for the initial supply
for (uint i = 0; i < amounts.length; i++) {
fairSupply = Math.max(fairSupply, amounts[i]);
}
}
else {
// Pre-compute fair supply
fairSupply = type(uint256).max;
for (uint i = 0; i < amounts.length; i++) {
fairSupply = Math.min(fairSupply, totalSupply.mul(amounts[i]).div(realBalances[i]));
}
}
uint256 fairSupplyCached = fairSupply;
for (uint i = 0; i < amounts.length; i++) {
require(amounts[i] > 0, "Mooniswap: amount is zero");
uint256 amount = (totalSupply == 0) ? amounts[i] :
realBalances[i].mul(fairSupplyCached).add(totalSupply - 1).div(totalSupply);
require(amount >= minAmounts[i], "Mooniswap: minAmount not reached");
_tokens[i].uniTransferFromSenderToThis(amount);
if (totalSupply > 0) {
uint256 confirmed = _tokens[i].uniBalanceOf(address(this)).sub(realBalances[i]);
fairSupply = Math.min(fairSupply, totalSupply.mul(confirmed).div(realBalances[i]));
}
}
if (totalSupply > 0) {
for (uint i = 0; i < amounts.length; i++) {
virtualBalancesForRemoval[_tokens[i]].scale(realBalances[i], totalSupply.add(fairSupply), totalSupply);
virtualBalancesForAddition[_tokens[i]].scale(realBalances[i], totalSupply.add(fairSupply), totalSupply);
}
}
require(fairSupply > 0, "Mooniswap: result is not enough");
_mint(msg.sender, fairSupply);
emit Deposited(msg.sender, fairSupply);
}
function withdraw(uint256 amount, uint256[] memory minReturns) external nonReentrant {
uint256 totalSupply = totalSupply();
_burn(msg.sender, amount);
for (uint i = 0; i < tokens.length; i++) {
IERC20 token = tokens[i];
uint256 preBalance = token.uniBalanceOf(address(this));
uint256 value = preBalance.mul(amount).div(totalSupply);
token.uniTransfer(msg.sender, value);
require(i >= minReturns.length || value >= minReturns[i], "Mooniswap: result is not enough");
virtualBalancesForAddition[token].scale(preBalance, totalSupply.sub(amount), totalSupply);
virtualBalancesForRemoval[token].scale(preBalance, totalSupply.sub(amount), totalSupply);
}
emit Withdrawn(msg.sender, amount);
}
function swap(IERC20 src, IERC20 dst, uint256 amount, uint256 minReturn, address referral) external payable nonReentrant returns(uint256 result) {
require(msg.value == (src.isETH() ? amount : 0), "Mooniswap: wrong value usage");
Balances memory balances = Balances({
src: src.uniBalanceOf(address(this)).sub(src.isETH() ? msg.value : 0),
dst: dst.uniBalanceOf(address(this))
});
// catch possible airdrops and external balance changes for deflationary tokens
uint256 srcAdditionBalance = Math.max(virtualBalancesForAddition[src].current(balances.src), balances.src);
uint256 dstRemovalBalance = Math.min(virtualBalancesForRemoval[dst].current(balances.dst), balances.dst);
src.uniTransferFromSenderToThis(amount);
uint256 confirmed = src.uniBalanceOf(address(this)).sub(balances.src);
result = _getReturn(src, dst, confirmed, srcAdditionBalance, dstRemovalBalance);
require(result > 0 && result >= minReturn, "Mooniswap: return is not enough");
dst.uniTransfer(msg.sender, result);
// Update virtual balances to the same direction only at imbalanced state
if (srcAdditionBalance != balances.src) {
virtualBalancesForAddition[src].set(srcAdditionBalance.add(confirmed));
}
if (dstRemovalBalance != balances.dst) {
virtualBalancesForRemoval[dst].set(dstRemovalBalance.sub(result));
}
// Update virtual balances to the opposite direction
virtualBalancesForRemoval[src].update(balances.src);
virtualBalancesForAddition[dst].update(balances.dst);
if (referral != address(0)) {
uint256 invariantRatio = uint256(1e36);
invariantRatio = invariantRatio.mul(balances.src.add(confirmed)).div(balances.src);
invariantRatio = invariantRatio.mul(balances.dst.sub(result)).div(balances.dst);
if (invariantRatio > 1e36) {
// calculate share only if invariant increased
uint256 referralShare = invariantRatio.sqrt().sub(1e18).mul(totalSupply()).div(1e18).div(REFERRAL_SHARE);
if (referralShare > 0) {
_mint(referral, referralShare);
}
}
}
emit Swapped(msg.sender, address(src), address(dst), confirmed, result, balances.src, balances.dst, totalSupply(), referral);
// Overflow of uint128 is desired
volumes[src].confirmed += uint128(confirmed);
volumes[src].result += uint128(result);
}
function rescueFunds(IERC20 token, uint256 amount) external nonReentrant onlyOwner {
uint256[] memory balances = new uint256[](tokens.length);
for (uint i = 0; i < balances.length; i++) {
balances[i] = tokens[i].uniBalanceOf(address(this));
}
token.uniTransfer(msg.sender, amount);
for (uint i = 0; i < balances.length; i++) {
require(tokens[i].uniBalanceOf(address(this)) >= balances[i], "Mooniswap: access denied");
}
require(balanceOf(address(this)) >= BASE_SUPPLY, "Mooniswap: access denied");
}
function _getReturn(IERC20 src, IERC20 dst, uint256 amount, uint256 srcBalance, uint256 dstBalance) internal view returns(uint256) {
if (isToken[src] && isToken[dst] && src != dst && amount > 0) {
uint256 taxedAmount = amount.sub(amount.mul(fee()).div(FEE_DENOMINATOR));
return taxedAmount.mul(dstBalance).div(srcBalance.add(taxedAmount));
}
}
}