Contract Source Code:
// SPDX-License-Identifier: MIT
pragma solidity 0.6.11;
/**
* Based on the OpenZeppelin IER20 interface:
* https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/IERC20.sol
*
* @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);
function increaseAllowance(address spender, uint256 addedValue) external returns (bool);
function decreaseAllowance(address spender, uint256 subtractedValue) external returns (bool);
/**
* @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);
function name() external view returns (string memory);
function symbol() external view returns (string memory);
function decimals() external view returns (uint8);
/**
* @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);
}
// SPDX-License-Identifier: MIT
pragma solidity 0.6.11;
/**
* @dev Interface of the ERC2612 standard as defined in the EIP.
*
* Adds the {permit} method, which can be used to change one's
* {IERC20-allowance} without having to send a transaction, by signing a
* message. This allows users to spend tokens without having to hold Ether.
*
* See https://eips.ethereum.org/EIPS/eip-2612.
*
* Code adapted from https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2237/
*/
interface IERC2612 {
/**
* @dev Sets `amount` as the allowance of `spender` over `owner`'s tokens,
* given `owner`'s signed approval.
*
* IMPORTANT: The same issues {IERC20-approve} has related to transaction
* ordering also apply here.
*
* Emits an {Approval} event.
*
* Requirements:
*
* - `owner` cannot be the zero address.
* - `spender` cannot be the zero address.
* - `deadline` must be a timestamp in the future.
* - `v`, `r` and `s` must be a valid `secp256k1` signature from `owner`
* over the EIP712-formatted function arguments.
* - the signature must use ``owner``'s current nonce (see {nonces}).
*
* For more information on the signature format, see the
* https://eips.ethereum.org/EIPS/eip-2612#specification[relevant EIP
* section].
*/
function permit(address owner, address spender, uint256 amount,
uint256 deadline, uint8 v, bytes32 r, bytes32 s) external;
/**
* @dev Returns the current ERC2612 nonce for `owner`. This value must be
* included whenever a signature is generated for {permit}.
*
* Every successful call to {permit} increases `owner`'s nonce by one. This
* prevents a signature from being used multiple times.
*
* `owner` can limit the time a Permit is valid for by setting `deadline` to
* a value in the near future. The deadline argument can be set to uint(-1) to
* create Permits that effectively never expire.
*/
function nonces(address owner) external view returns (uint256);
function version() external view returns (string memory);
function permitTypeHash() external view returns (bytes32);
function domainSeparator() external view returns (bytes32);
}
// SPDX-License-Identifier: MIT
pragma solidity 0.6.11;
import "./IERC20.sol";
import "./IERC2612.sol";
interface IYETIToken is IERC20, IERC2612 {
function sendToSYETI(address _sender, uint256 _amount) external;
function getDeploymentStartTime() external view returns (uint256);
}
// SPDX-License-Identifier: MIT
pragma solidity 0.6.11;
/**
* Based on OpenZeppelin's SafeMath:
* https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/math/SafeMath.sol
*
* @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.
*
* _Available since v2.4.0._
*/
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.
*
* _Available since v2.4.0._
*/
function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
// Solidity only automatically asserts when dividing by 0
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.
*
* _Available since v2.4.0._
*/
function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
require(b != 0, errorMessage);
return a % b;
}
}
// SPDX-License-Identifier: MIT
pragma solidity 0.6.11;
import "./SafeMath.sol";
import "./IYETIToken.sol";
/*
* Brought to you by @YetiFinance
*
* Based upon OpenZeppelin's ERC20 contract:
* https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/ERC20.sol
*
* and their EIP2612 (ERC20Permit / ERC712) functionality:
* https://github.com/OpenZeppelin/openzeppelin-contracts/blob/53516bc555a454862470e7860a9b5254db4d00f5/contracts/token/ERC20/ERC20Permit.sol
*
*
* --- Functionality added specific to the YETIToken ---
*
* 1) Transfer protection: Prevent accidentally sending YETI to directly to this address
*
* 2) sendToSYETI(): Only callable by the SYETI contract to transfer YETI for staking.
*
* 3) Supply hard-capped at 500 million
*
* 4) Yeti Finance Treasury and Yeti Finance Team addresses set at deployment
*
* 5) 365 million tokens are minted at deployment to the Yeti Finance Treasury
*
* 6) 135 million tokens are minted at deployment to the Yeti Finance Team
*
*/
contract YETIToken is IYETIToken {
using SafeMath for uint256;
// --- ERC20 Data ---
string constant internal _NAME = "Yeti Finance";
string constant internal _SYMBOL = "YETI";
string constant internal _VERSION = "1";
uint8 constant internal _DECIMALS = 18;
mapping (address => uint256) private _balances;
mapping (address => mapping (address => uint256)) private _allowances;
uint private _totalSupply;
// --- EIP 2612 Data ---
bytes32 private constant _PERMIT_TYPEHASH = keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
bytes32 private constant _TYPE_HASH = keccak256("EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)");
// Cache the domain separator as an immutable value, but also store the chain id that it corresponds to, in order to
// invalidate the cached domain separator if the chain id changes.
bytes32 private immutable _CACHED_DOMAIN_SEPARATOR;
uint256 private immutable _CACHED_CHAIN_ID;
bytes32 private immutable _HASHED_NAME;
bytes32 private immutable _HASHED_VERSION;
mapping (address => uint256) private _nonces;
// --- YETIToken specific data ---
// uint for use with SafeMath
uint internal _1_MILLION = 1e24; // 1e6 * 1e18 = 1e24
uint internal immutable deploymentStartTime;
address public immutable sYETIAddress;
// --- Functions ---
constructor
(
address _sYETIAddress,
address _treasuryAddress,
address _teamAddress
)
public
{
deploymentStartTime = block.timestamp;
sYETIAddress = _sYETIAddress;
bytes32 hashedName = keccak256(bytes(_NAME));
bytes32 hashedVersion = keccak256(bytes(_VERSION));
_HASHED_NAME = hashedName;
_HASHED_VERSION = hashedVersion;
_CACHED_CHAIN_ID = _chainID();
_CACHED_DOMAIN_SEPARATOR = _buildDomainSeparator(_TYPE_HASH, hashedName, hashedVersion);
// --- Initial YETI allocations ---
// Allocate 365 million for Yeti Finance Treasury
uint treasuryEntitlement = _1_MILLION.mul(365);
_totalSupply = _totalSupply.add(treasuryEntitlement);
_balances[_treasuryAddress] = _balances[_treasuryAddress].add(treasuryEntitlement);
// Allocate 135 million for Yeti Finance Team
uint teamEntitlement = _1_MILLION.mul(135);
_totalSupply = _totalSupply.add(teamEntitlement);
_balances[_teamAddress] = _balances[_teamAddress].add(teamEntitlement);
}
// --- External functions ---
function transfer(address recipient, uint256 amount) external override returns (bool) {
_requireValidRecipient(recipient);
// Otherwise, standard transfer functionality
_transfer(msg.sender, recipient, amount);
return true;
}
function approve(address spender, uint256 amount) external override returns (bool) {
_approve(msg.sender, spender, amount);
return true;
}
function transferFrom(address sender, address recipient, uint256 amount) external override returns (bool) {
_requireValidRecipient(recipient);
_transfer(sender, recipient, amount);
_approve(sender, msg.sender, _allowances[sender][msg.sender].sub(amount, "YETI: transfer amount exceeds allowance"));
return true;
}
function increaseAllowance(address spender, uint256 addedValue) external override returns (bool) {
_approve(msg.sender, spender, _allowances[msg.sender][spender].add(addedValue));
return true;
}
function decreaseAllowance(address spender, uint256 subtractedValue) external override returns (bool) {
_approve(msg.sender, spender, _allowances[msg.sender][spender].sub(subtractedValue, "YETI: decreased allowance below zero"));
return true;
}
function sendToSYETI(address _sender, uint256 _amount) external override {
_requireCallerIsSYETI();
_transfer(_sender, sYETIAddress, _amount);
}
// --- EIP 2612 functionality ---
function domainSeparator() public view override returns (bytes32) {
if (_chainID() == _CACHED_CHAIN_ID) {
return _CACHED_DOMAIN_SEPARATOR;
} else {
return _buildDomainSeparator(_TYPE_HASH, _HASHED_NAME, _HASHED_VERSION);
}
}
function permit
(
address owner,
address spender,
uint amount,
uint deadline,
uint8 v,
bytes32 r,
bytes32 s
)
external
override
{
require(deadline >= now, 'YETI: expired deadline');
bytes32 digest = keccak256(abi.encodePacked('\x19\x01',
domainSeparator(), keccak256(abi.encode(
_PERMIT_TYPEHASH, owner, spender, amount,
_nonces[owner]++, deadline))));
address recoveredAddress = ecrecover(digest, v, r, s);
require(recoveredAddress == owner, 'YETI: invalid signature');
_approve(owner, spender, amount);
}
function nonces(address owner) external view override returns (uint256) { // FOR EIP 2612
return _nonces[owner];
}
// --- Internal functions ---
function _chainID() private pure returns (uint256 chainID) {
assembly {
chainID := chainid()
}
}
function _buildDomainSeparator(bytes32 typeHash, bytes32 name, bytes32 version) private view returns (bytes32) {
return keccak256(abi.encode(typeHash, name, version, _chainID(), address(this)));
}
function _transfer(address sender, address recipient, uint256 amount) internal {
require(sender != address(0), "YETI: transfer from the zero address");
_balances[sender] = _balances[sender].sub(amount, "YETI: transfer amount exceeds balance");
_balances[recipient] = _balances[recipient].add(amount);
emit Transfer(sender, recipient, amount);
}
function _approve(address owner, address spender, uint256 amount) internal {
_allowances[owner][spender] = amount;
emit Approval(owner, spender, amount);
}
// --- 'require' functions ---
function _requireValidRecipient(address _recipient) internal view {
require(
_recipient != address(this),
"YETI: Cannot transfer tokens directly to the YETI token contract"
);
}
function _requireCallerIsSYETI() internal view {
require(msg.sender == sYETIAddress, "YETI: caller must be the SYETI contract");
}
// --- External View functions ---
function balanceOf(address account) external view override returns (uint256) {
return _balances[account];
}
function allowance(address owner, address spender) external view override returns (uint256) {
return _allowances[owner][spender];
}
function totalSupply() external view override returns (uint256) {
return _totalSupply;
}
function getDeploymentStartTime() external view override returns (uint256) {
return deploymentStartTime;
}
function name() external view override returns (string memory) {
return _NAME;
}
function symbol() external view override returns (string memory) {
return _SYMBOL;
}
function decimals() external view override returns (uint8) {
return _DECIMALS;
}
function version() external view override returns (string memory) {
return _VERSION;
}
function permitTypeHash() external view override returns (bytes32) {
return _PERMIT_TYPEHASH;
}
}