Contract Source Code:
File 1 of 1 : GOLDFARM
// goldfarm.io
// GoldFarm is a cross-chain DeFi FaaS protocol that allows users to deploy crypto and NFT farms on BSC and ETH with no code required!
// 1,000,000 $GOLD tokens will be minted and split between BSC and ETH blockchains.
// 1,000,000 $GOLD will be the max supply and the initial circulating supply will be 900,000 $GOLD.
// GoldFarm is a cross-chain DeFi protocol designed to bring utility to any token by turning it into an NFT farm with no code required on
// both BSC and ETH blockchains. With an innovative suite of visual tools, any project can deploy the world's most exciting new farm
// with custom rules that incentivize the behaviors they value most. It's easy to reward liquidity providers, incentivize longer stakes
// or even provide special access to your project's services through NFTs with utility.
// GoldFarm provides a bridge between current crypto ecosystems and the explosive gaming industry.
// NFTs from GoldFarm and Official Partner Farms will gain utility within real AAA video games,
// in this ecosystem, NFTs are no longer just pixels on a screen, but hold the power to unlock unique digital experiences.
// Twitter: https://twitter.com/goldfarmio
// Telegram: https://t.me/GoldFarmChat
// Website: https://goldfarm.io
// Telegram ANN: https://t.me/goldfarmio
// SPDX-License-Identifier: UNLICENSED
pragma solidity 0.6.12;
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;
}
}
abstract 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 virtual 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;
}
}
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);
}
contract ERC20 is Context, IERC20 {
using SafeMath for uint256;
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 virtual returns (string memory) {
return _name;
}
/**
* @dev Returns the symbol of the token, usually a shorter version of the
* name.
*/
function symbol() public view virtual 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 virtual returns (uint8) {
return _decimals;
}
/**
* @dev See {IERC20-totalSupply}.
*/
function totalSupply() public view virtual override returns (uint256) {
return _totalSupply;
}
/**
* @dev See {IERC20-balanceOf}.
*/
function balanceOf(address account) public view virtual 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 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 virtual {
_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 { }
}
abstract contract ERC20Capped is ERC20 {
using SafeMath for uint256;
uint256 private _cap;
/**
* @dev Sets the value of the `cap`. This value is immutable, it can only be
* set once during construction.
*/
constructor (uint256 cap_) internal {
require(cap_ > 0, "ERC20Capped: cap is 0");
_cap = cap_;
}
/**
* @dev Returns the cap on the token's total supply.
*/
function cap() public view virtual returns (uint256) {
return _cap;
}
/**
* @dev See {ERC20-_beforeTokenTransfer}.
*
* Requirements:
*
* - minted tokens must not cause the total supply to go over the cap.
*/
function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual override {
super._beforeTokenTransfer(from, to, amount);
if (from == address(0)) { // When minting tokens
require(totalSupply().add(amount) <= cap(), "ERC20Capped: cap exceeded");
}
}
}
contract GOLDFARM is ERC20Capped, Ownable {
/// A version number for this Token contract's interface.
uint256 public version = 1;
/**
Construct a new Token by providing it a name, ticker, and supply cap.
@param _name The name of the new Token.
@param _ticker The ticker symbol of the new Token.
@param _cap The supply cap of the new Token.
*/
constructor (string memory _name, string memory _ticker, uint256 _cap) public ERC20(_name, _ticker) ERC20Capped(_cap) { }
/**
* @dev Destroys `amount` tokens from the caller.
*
* See {ERC20-_burn}.
*/
function burn(uint256 amount) public virtual {
_burn(_msgSender(), amount);
}
/**
* @dev Destroys `amount` tokens from `account`, deducting from the caller's
* allowance.
*
* See {ERC20-_burn} and {ERC20-allowance}.
*
* Requirements:
*
* - the caller must have allowance for ``accounts``'s tokens of at least
* `amount`.
*/
function burnFrom(address account, uint256 amount) public virtual {
uint256 decreasedAllowance = allowance(account, _msgSender()).sub(amount, "ERC20: burn amount exceeds allowance");
_approve(account, _msgSender(), decreasedAllowance);
_burn(account, amount);
}
/**
Allows Token creator to mint `_amount` of this Token to the address `_to`.
New tokens of this Token cannot be minted if it would exceed the supply cap.
Users are delegated votes when they are minted Token.
@param _to the address to mint Tokens to.
@param _amount the amount of new Token to mint.
*/
function mint(address _to, uint256 _amount) external onlyOwner {
_mint(_to, _amount);
_moveDelegates(address(0), _delegates[_to], _amount);
}
/**
Allows users to transfer tokens to a recipient, moving delegated votes with
the transfer.
@param recipient The address to transfer tokens to.
@param amount The amount of tokens to send to `recipient`.
*/
function transfer(address recipient, uint256 amount) public override returns (bool) {
_transfer(_msgSender(), recipient, amount);
_moveDelegates(_delegates[msg.sender], _delegates[recipient], amount);
return true;
}
/// @dev A mapping to record delegates for each address.
mapping (address => address) internal _delegates;
/// A checkpoint structure to mark some number of votes from a given block.
struct Checkpoint {
uint32 fromBlock;
uint256 votes;
}
/// A mapping to record indexed Checkpoint votes for each address.
mapping (address => mapping (uint32 => Checkpoint)) public checkpoints;
/// A mapping to record the number of Checkpoints for each address.
mapping (address => uint32) public numCheckpoints;
/// The EIP-712 typehash for the contract's domain.
bytes32 public constant DOMAIN_TYPEHASH = keccak256("EIP712Domain(string name,uint256 chainId,address verifyingContract)");
/// The EIP-712 typehash for the delegation struct used by the contract.
bytes32 public constant DELEGATION_TYPEHASH = keccak256("Delegation(address delegatee,uint256 nonce,uint256 expiry)");
/// A mapping to record per-address states for signing / validating signatures.
mapping (address => uint) public nonces;
/// An event emitted when an address changes its delegate.
event DelegateChanged(address indexed delegator, address indexed fromDelegate, address indexed toDelegate);
/// An event emitted when the vote balance of a delegated address changes.
event DelegateVotesChanged(address indexed delegate, uint previousBalance, uint newBalance);
/**
Return the address delegated to by `delegator`.
@return The address delegated to by `delegator`.
*/
function delegates(address delegator) external view returns (address) {
return _delegates[delegator];
}
/**
Delegate votes from `msg.sender` to `delegatee`.
@param delegatee The address to delegate votes to.
*/
function delegate(address delegatee) external {
return _delegate(msg.sender, delegatee);
}
/**
Delegate votes from signatory to `delegatee`.
@param delegatee The address to delegate votes to.
@param nonce The contract state required for signature matching.
@param expiry The time at which to expire the signature.
@param v The recovery byte of the signature.
@param r Half of the ECDSA signature pair.
@param s Half of the ECDSA signature pair.
*/
function delegateBySig(address delegatee, uint nonce, uint expiry, uint8 v, bytes32 r, bytes32 s) external {
bytes32 domainSeparator = keccak256(
abi.encode(
DOMAIN_TYPEHASH,
keccak256(bytes(name())),
getChainId(),
address(this)));
bytes32 structHash = keccak256(
abi.encode(
DELEGATION_TYPEHASH,
delegatee,
nonce,
expiry));
bytes32 digest = keccak256(
abi.encodePacked(
"\x19\x01",
domainSeparator,
structHash));
address signatory = ecrecover(digest, v, r, s);
require(signatory != address(0), "Invalid signature.");
require(nonce == nonces[signatory]++, "Invalid nonce.");
require(now <= expiry, "Signature expired.");
return _delegate(signatory, delegatee);
}
/**
Get the current votes balance for the address `account`.
@param account The address to get the votes balance of.
@return The number of current votes for `account`.
*/
function getCurrentVotes(address account) external view returns (uint256) {
uint32 nCheckpoints = numCheckpoints[account];
return nCheckpoints > 0 ? checkpoints[account][nCheckpoints - 1].votes : 0;
}
/**
Determine the prior number of votes for an address as of a block number.
@dev The block number must be a finalized block or else this function will revert to prevent misinformation.
@param account The address to check.
@param blockNumber The block number to get the vote balance at.
@return The number of votes the account had as of the given block.
*/
function getPriorVotes(address account, uint blockNumber) external view returns (uint256) {
require(blockNumber < block.number, "The specified block is not yet finalized.");
uint32 nCheckpoints = numCheckpoints[account];
if (nCheckpoints == 0) {
return 0;
}
// First check the most recent balance.
if (checkpoints[account][nCheckpoints - 1].fromBlock <= blockNumber) {
return checkpoints[account][nCheckpoints - 1].votes;
}
// Then check the implicit zero balance.
if (checkpoints[account][0].fromBlock > blockNumber) {
return 0;
}
uint32 lower = 0;
uint32 upper = nCheckpoints - 1;
while (upper > lower) {
uint32 center = upper - (upper - lower) / 2; // ceil, avoiding overflow
Checkpoint memory cp = checkpoints[account][center];
if (cp.fromBlock == blockNumber) {
return cp.votes;
} else if (cp.fromBlock < blockNumber) {
lower = center;
} else {
upper = center - 1;
}
}
return checkpoints[account][lower].votes;
}
/**
An internal function to actually perform the delegation of votes.
@param delegator The address delegating to `delegatee`.
@param delegatee The address receiving delegated votes.
*/
function _delegate(address delegator, address delegatee) internal {
address currentDelegate = _delegates[delegator];
uint256 delegatorBalance = balanceOf(delegator);
_delegates[delegator] = delegatee;
/* console.log('a-', currentDelegate, delegator, delegatee); */
emit DelegateChanged(delegator, currentDelegate, delegatee);
_moveDelegates(currentDelegate, delegatee, delegatorBalance);
}
/**
An internal function to move delegated vote amounts between addresses.
@param srcRep the previous representative who received delegated votes.
@param dstRep the new representative to receive these delegated votes.
@param amount the amount of delegated votes to move between representatives.
*/
function _moveDelegates(address srcRep, address dstRep, uint256 amount) internal {
if (srcRep != dstRep && amount > 0) {
// Decrease the number of votes delegated to the previous representative.
if (srcRep != address(0)) {
uint32 srcRepNum = numCheckpoints[srcRep];
uint256 srcRepOld = srcRepNum > 0 ? checkpoints[srcRep][srcRepNum - 1].votes : 0;
uint256 srcRepNew = srcRepOld.sub(amount);
_writeCheckpoint(srcRep, srcRepNum, srcRepOld, srcRepNew);
}
// Increase the number of votes delegated to the new representative.
if (dstRep != address(0)) {
uint32 dstRepNum = numCheckpoints[dstRep];
uint256 dstRepOld = dstRepNum > 0 ? checkpoints[dstRep][dstRepNum - 1].votes : 0;
uint256 dstRepNew = dstRepOld.add(amount);
_writeCheckpoint(dstRep, dstRepNum, dstRepOld, dstRepNew);
}
}
}
/**
An internal function to write a checkpoint of modified vote amounts.
This function is guaranteed to add at most one checkpoint per block.
@param delegatee The address whose vote count is changed.
@param nCheckpoints The number of checkpoints by address `delegatee`.
@param oldVotes The prior vote count of address `delegatee`.
@param newVotes The new vote count of address `delegatee`.
*/
function _writeCheckpoint(address delegatee, uint32 nCheckpoints, uint256 oldVotes, uint256 newVotes) internal {
uint32 blockNumber = safe32(block.number, "Block number exceeds 32 bits.");
if (nCheckpoints > 0 && checkpoints[delegatee][nCheckpoints - 1].fromBlock == blockNumber) {
checkpoints[delegatee][nCheckpoints - 1].votes = newVotes;
} else {
checkpoints[delegatee][nCheckpoints] = Checkpoint(blockNumber, newVotes);
numCheckpoints[delegatee] = nCheckpoints + 1;
}
emit DelegateVotesChanged(delegatee, oldVotes, newVotes);
}
/**
A function to safely limit a number to less than 2^32.
@param n the number to limit.
@param errorMessage the error message to revert with should `n` be too large.
@return The number `n` limited to 32 bits.
*/
function safe32(uint n, string memory errorMessage) internal pure returns (uint32) {
require(n < 2**32, errorMessage);
return uint32(n);
}
/**
A function to return the ID of the contract's particular network or chain.
@return The ID of the contract's network or chain.
*/
function getChainId() internal pure returns (uint) {
uint256 chainId;
assembly { chainId := chainid() }
return chainId;
}
}
library SafeMath {
/**
* @dev Returns the addition of two unsigned integers, with an overflow flag.
*
* _Available since v3.4._
*/
function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
uint256 c = a + b;
if (c < a) return (false, 0);
return (true, c);
}
/**
* @dev Returns the substraction of two unsigned integers, with an overflow flag.
*
* _Available since v3.4._
*/
function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
if (b > a) return (false, 0);
return (true, a - b);
}
/**
* @dev Returns the multiplication of two unsigned integers, with an overflow flag.
*
* _Available since v3.4._
*/
function tryMul(uint256 a, uint256 b) internal pure returns (bool, 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 (true, 0);
uint256 c = a * b;
if (c / a != b) return (false, 0);
return (true, c);
}
/**
* @dev Returns the division of two unsigned integers, with a division by zero flag.
*
* _Available since v3.4._
*/
function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
if (b == 0) return (false, 0);
return (true, a / b);
}
/**
* @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
*
* _Available since v3.4._
*/
function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
if (b == 0) return (false, 0);
return (true, a % b);
}
/**
* @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) {
require(b <= a, "SafeMath: subtraction overflow");
return a - b;
}
/**
* @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) {
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, reverting 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) {
require(b > 0, "SafeMath: division by zero");
return a / b;
}
/**
* @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
* reverting 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) {
require(b > 0, "SafeMath: modulo by zero");
return a % b;
}
/**
* @dev Returns the subtraction of two unsigned integers, reverting with custom message on
* overflow (when the result is negative).
*
* CAUTION: This function is deprecated because it requires allocating memory for the error
* message unnecessarily. For custom revert reasons use {trySub}.
*
* 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);
return a - b;
}
/**
* @dev Returns the integer division of two unsigned integers, reverting with custom message on
* division by zero. The result is rounded towards zero.
*
* CAUTION: This function is deprecated because it requires allocating memory for the error
* message unnecessarily. For custom revert reasons use {tryDiv}.
*
* 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);
return a / b;
}
/**
* @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
* reverting with custom message when dividing by zero.
*
* CAUTION: This function is deprecated because it requires allocating memory for the error
* message unnecessarily. For custom revert reasons use {tryMod}.
*
* 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;
}
}