Theta Smart Contracts | ThetaScan.io

Node:

Token Contract Details

Contract:

0xa525a5df451441e389ea265f063c54afd825f26a

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Published Contract:

// SPDX-License-Identifier: MIT
// 
// TNT-721 Non-Fungible Token implementation based on the OpenZeppelin Lib
//

pragma solidity ^0.6.2;

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;
 }
}

library SafeMath {
 function add(uint256 a, uint256 b) internal pure returns (uint256) {
 uint256 c = a + b;
 require(c >= a, "SafeMath: addition overflow");

 return c;
 }

 function sub(uint256 a, uint256 b) internal pure returns (uint256) {
 return sub(a, b, "SafeMath: subtraction overflow");
 }

 function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
 require(b <= a, errorMessage);
 uint256 c = a - b;

 return c;
 }

 function mul(uint256 a, uint256 b) internal pure returns (uint256) {
 // Gas optimization: this is cheaper than requiring 9a9 not being zero, but the
 // benefit is lost if 9b9 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;
 }

 function div(uint256 a, uint256 b) internal pure returns (uint256) {
 return div(a, b, "SafeMath: division by 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 doesn9t hold

 return c;
 }

 function mod(uint256 a, uint256 b) internal pure returns (uint256) {
 return mod(a, b, "SafeMath: modulo by zero");
 }

 function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
 require(b != 0, errorMessage);
 return a % b;
 }
}

library Address {

 function isContract(address account) internal view returns (bool) {
 // This method relies on extcodesize, which returns 0 for contracts in
 // construction, since the code is only stored at the end of the
 // constructor execution.

 uint256 size;
 // solhint-disable-next-line no-inline-assembly
 assembly { size := extcodesize(account) }
 return size > 0;
 }

 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");
 }

 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");

 // 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);
 }
 }
 }
}

library EnumerableSet {

 struct Set {
 // Storage of set values
 bytes32[] _values;

 // Position of the value in the `values` array, plus 1 because index 0
 // means a value is not in the set.
 mapping (bytes32 => uint256) _indexes;
 }

 function _add(Set storage set, bytes32 value) private returns (bool) {
 if (!_contains(set, value)) {
 set._values.push(value);
 // The value is stored at length-1, but we add 1 to all indexes
 // and use 0 as a sentinel value
 set._indexes[value] = set._values.length;
 return true;
 } else {
 return false;
 }
 }

 function _remove(Set storage set, bytes32 value) private returns (bool) {
 // We read and store the value9s index to prevent multiple reads from the same storage slot
 uint256 valueIndex = set._indexes[value];

 if (valueIndex != 0) { // Equivalent to contains(set, value)
 // To delete an element from the _values array in O(1), we swap the element to delete with the last one in
 // the array, and then remove the last element (sometimes called as 9swap and pop9).
 // This modifies the order of the array, as noted in {at}.

 uint256 toDeleteIndex = valueIndex - 1;
 uint256 lastIndex = set._values.length - 1;

 // When the value to delete is the last one, the swap operation is unnecessary. However, since this occurs
 // so rarely, we still do the swap anyway to avoid the gas cost of adding an 9if9 statement.

 bytes32 lastvalue = set._values[lastIndex];

 // Move the last value to the index where the value to delete is
 set._values[toDeleteIndex] = lastvalue;
 // Update the index for the moved value
 set._indexes[lastvalue] = toDeleteIndex + 1; // All indexes are 1-based

 // Delete the slot where the moved value was stored
 set._values.pop();

 // Delete the index for the deleted slot
 delete set._indexes[value];

 return true;
 } else {
 return false;
 }
 }

 function _contains(Set storage set, bytes32 value) private view returns (bool) {
 return set._indexes[value] != 0;
 }

 function _length(Set storage set) private view returns (uint256) {
 return set._values.length;
 }

 function _at(Set storage set, uint256 index) private view returns (bytes32) {
 require(set._values.length > index, "EnumerableSet: index out of bounds");
 return set._values[index];
 }

 struct AddressSet {
 Set _inner;
 }

 function add(AddressSet storage set, address value) internal returns (bool) {
 return _add(set._inner, bytes32(uint256(value)));
 }

 function remove(AddressSet storage set, address value) internal returns (bool) {
 return _remove(set._inner, bytes32(uint256(value)));
 }

 function contains(AddressSet storage set, address value) internal view returns (bool) {
 return _contains(set._inner, bytes32(uint256(value)));
 }

 function length(AddressSet storage set) internal view returns (uint256) {
 return _length(set._inner);
 }

 function at(AddressSet storage set, uint256 index) internal view returns (address) {
 return address(uint256(_at(set._inner, index)));
 }

 struct UintSet {
 Set _inner;
 }

 function add(UintSet storage set, uint256 value) internal returns (bool) {
 return _add(set._inner, bytes32(value));
 }

 function remove(UintSet storage set, uint256 value) internal returns (bool) {
 return _remove(set._inner, bytes32(value));
 }

 function contains(UintSet storage set, uint256 value) internal view returns (bool) {
 return _contains(set._inner, bytes32(value));
 }

 function length(UintSet storage set) internal view returns (uint256) {
 return _length(set._inner);
 }

 function at(UintSet storage set, uint256 index) internal view returns (uint256) {
 return uint256(_at(set._inner, index));
 }
}

library EnumerableMap {

 struct MapEntry {
 bytes32 _key;
 bytes32 _value;
 }

 struct Map {
 // Storage of map keys and values
 MapEntry[] _entries;

 // Position of the entry defined by a key in the `entries` array, plus 1
 // because index 0 means a key is not in the map.
 mapping (bytes32 => uint256) _indexes;
 }

 function _set(Map storage map, bytes32 key, bytes32 value) private returns (bool) {
 // We read and store the key9s index to prevent multiple reads from the same storage slot
 uint256 keyIndex = map._indexes[key];

 if (keyIndex == 0) { // Equivalent to !contains(map, key)
 map._entries.push(MapEntry({ _key: key, _value: value }));
 // The entry is stored at length-1, but we add 1 to all indexes
 // and use 0 as a sentinel value
 map._indexes[key] = map._entries.length;
 return true;
 } else {
 map._entries[keyIndex - 1]._value = value;
 return false;
 }
 }

 function _remove(Map storage map, bytes32 key) private returns (bool) {
 // We read and store the key9s index to prevent multiple reads from the same storage slot
 uint256 keyIndex = map._indexes[key];

 if (keyIndex != 0) { // Equivalent to contains(map, key)
 // To delete a key-value pair from the _entries array in O(1), we swap the entry to delete with the last one
 // in the array, and then remove the last entry (sometimes called as 9swap and pop9).
 // This modifies the order of the array, as noted in {at}.

 uint256 toDeleteIndex = keyIndex - 1;
 uint256 lastIndex = map._entries.length - 1;

 // When the entry to delete is the last one, the swap operation is unnecessary. However, since this occurs
 // so rarely, we still do the swap anyway to avoid the gas cost of adding an 9if9 statement.

 MapEntry storage lastEntry = map._entries[lastIndex];

 // Move the last entry to the index where the entry to delete is
 map._entries[toDeleteIndex] = lastEntry;
 // Update the index for the moved entry
 map._indexes[lastEntry._key] = toDeleteIndex + 1; // All indexes are 1-based

 // Delete the slot where the moved entry was stored
 map._entries.pop();

 // Delete the index for the deleted slot
 delete map._indexes[key];

 return true;
 } else {
 return false;
 }
 }

 function _contains(Map storage map, bytes32 key) private view returns (bool) {
 return map._indexes[key] != 0;
 }

 function _length(Map storage map) private view returns (uint256) {
 return map._entries.length;
 }

 function _at(Map storage map, uint256 index) private view returns (bytes32, bytes32) {
 require(map._entries.length > index, "EnumerableMap: index out of bounds");

 MapEntry storage entry = map._entries[index];
 return (entry._key, entry._value);
 }

 function _get(Map storage map, bytes32 key) private view returns (bytes32) {
 return _get(map, key, "EnumerableMap: nonexistent key");
 }

 function _get(Map storage map, bytes32 key, string memory errorMessage) private view returns (bytes32) {
 uint256 keyIndex = map._indexes[key];
 require(keyIndex != 0, errorMessage); // Equivalent to contains(map, key)
 return map._entries[keyIndex - 1]._value; // All indexes are 1-based
 }

 struct UintToAddressMap {
 Map _inner;
 }

 function set(UintToAddressMap storage map, uint256 key, address value) internal returns (bool) {
 return _set(map._inner, bytes32(key), bytes32(uint256(value)));
 }

 function remove(UintToAddressMap storage map, uint256 key) internal returns (bool) {
 return _remove(map._inner, bytes32(key));
 }

 function contains(UintToAddressMap storage map, uint256 key) internal view returns (bool) {
 return _contains(map._inner, bytes32(key));
 }

 function length(UintToAddressMap storage map) internal view returns (uint256) {
 return _length(map._inner);
 }

 function at(UintToAddressMap storage map, uint256 index) internal view returns (uint256, address) {
 (bytes32 key, bytes32 value) = _at(map._inner, index);
 return (uint256(key), address(uint256(value)));
 }

 function get(UintToAddressMap storage map, uint256 key) internal view returns (address) {
 return address(uint256(_get(map._inner, bytes32(key))));
 }

 function get(UintToAddressMap storage map, uint256 key, string memory errorMessage) internal view returns (address) {
 return address(uint256(_get(map._inner, bytes32(key), errorMessage)));
 }
}

library Strings {

 function toString(uint256 value) internal pure returns (string memory) {
 // Inspired by OraclizeAPI9s implementation - MIT licence
 // https://github.com/oraclize/ethereum-api/blob/b42146b063c7d6ee1358846c198246239e9360e8/oraclizeAPI_0.4.25.sol

 if (value == 0) {
 return "0";
 }
 uint256 temp = value;
 uint256 digits;
 while (temp != 0) {
 digits++;
 temp /= 10;
 }
 bytes memory buffer = new bytes(digits);
 uint256 index = digits - 1;
 temp = value;
 while (temp != 0) {
 buffer[index--] = byte(uint8(48 + temp % 10));
 temp /= 10;
 }
 return string(buffer);
 }
}

interface ITNT165 {
 function supportsInterface(bytes4 interfaceId) external view returns (bool);
}

interface ITNT721 is ITNT165 {
 event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);
 event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);
 event ApprovalForAll(address indexed owner, address indexed operator, bool approved);
 function balanceOf(address owner) external view returns (uint256 balance);
 function ownerOf(uint256 tokenId) external view returns (address owner);
 function safeTransferFrom(address from, address to, uint256 tokenId) external;
 function transferFrom(address from, address to, uint256 tokenId) external;
 function approve(address to, uint256 tokenId) external;
 function getApproved(uint256 tokenId) external view returns (address operator);
 function setApprovalForAll(address operator, bool _approved) external;
 function isApprovedForAll(address owner, address operator) external view returns (bool);
 function safeTransferFrom(address from, address to, uint256 tokenId, bytes calldata data) external;
 function mint(address to, string calldata uri) external;
}

interface ITNT721Metadata is ITNT721 {
 function name() external view returns (string memory);
 function symbol() external view returns (string memory);
 function tokenURI(uint256 tokenId) external view returns (string memory);
}

interface ITNT721Enumerable is ITNT721 {
 function totalSupply() external view returns (uint256);
 function tokenOfOwnerByIndex(address owner, uint256 index) external view returns (uint256 tokenId);
 function tokenByIndex(uint256 index) external view returns (uint256);
}

interface ITNT721Receiver {
 function onTNT721Received(address operator, address from, uint256 tokenId, bytes calldata data)
 external returns (bytes4);
}

contract TNT165 is ITNT165 {

 bytes4 private constant _INTERFACE_ID_TNT165 = 0x01ffc9a7;

 mapping(bytes4 => bool) private _supportedInterfaces;

 constructor () internal {
 _registerInterface(_INTERFACE_ID_TNT165);
 }

 function supportsInterface(bytes4 interfaceId) public view override returns (bool) {
 return _supportedInterfaces[interfaceId];
 }

 function _registerInterface(bytes4 interfaceId) internal virtual {
 require(interfaceId != 0xffffffff, "TNT165: invalid interface id");
 _supportedInterfaces[interfaceId] = true;
 }
}

// TNT stands for "Theta Network Token", TNT-721 is the non-fungible token
// standard on the Theta network, similar to the ERC-721 standard on Ethereum
contract TNT721 is Context, TNT165, ITNT721, ITNT721Metadata, ITNT721Enumerable {
 using SafeMath for uint256;
 using Address for address;
 using EnumerableSet for EnumerableSet.UintSet;
 using EnumerableMap for EnumerableMap.UintToAddressMap;
 using Strings for uint256;
 bytes4 private constant _TNT721_RECEIVED = 0x150b7a02;
 mapping (address => EnumerableSet.UintSet) private _holderTokens;
 EnumerableMap.UintToAddressMap private _tokenOwners;
 mapping (uint256 => address) private _tokenApprovals;
 mapping (address => mapping (address => bool)) private _operatorApprovals;
 string private _name;
 string private _symbol;
 mapping (uint256 => string) private _tokenURIs;
 string private _baseURI;
 bytes4 private constant _INTERFACE_ID_TNT721 = 0x80ac58cd;
 bytes4 private constant _INTERFACE_ID_TNT721_METADATA = 0x5b5e139f;
 bytes4 private constant _INTERFACE_ID_TNT721_ENUMERABLE = 0x780e9d63;

 constructor (string memory name, string memory symbol) public {
 _name = name;
 _symbol = symbol;
 _registerInterface(_INTERFACE_ID_TNT721);
 _registerInterface(_INTERFACE_ID_TNT721_METADATA);
 _registerInterface(_INTERFACE_ID_TNT721_ENUMERABLE);
 }

 function balanceOf(address owner) public view override returns (uint256) {
 require(owner != address(0), "TNT721: balance query for the zero address");

 return _holderTokens[owner].length();
 }

 function ownerOf(uint256 tokenId) public view override returns (address) {
 return _tokenOwners.get(tokenId, "TNT721: owner query for nonexistent token");
 }

 function name() public view override returns (string memory) {
 return _name;
 }

 function symbol() public view override returns (string memory) {
 return _symbol;
 }

 function tokenURI(uint256 tokenId) public view override returns (string memory) {
 require(_exists(tokenId), "TNT721Metadata: URI query for nonexistent token");

 string memory _tokenURI = _tokenURIs[tokenId];

 // If there is no base URI, return the token URI.
 if (bytes(_baseURI).length == 0) {
 return _tokenURI;
 }
 // If both are set, concatenate the baseURI and tokenURI (via abi.encodePacked).
 if (bytes(_tokenURI).length > 0) {
 return string(abi.encodePacked(_baseURI, _tokenURI));
 }
 // If there is a baseURI but no tokenURI, concatenate the tokenID to the baseURI.
 return string(abi.encodePacked(_baseURI, tokenId.toString()));
 }

 function baseURI() public view returns (string memory) {
 return _baseURI;
 }

 function tokenOfOwnerByIndex(address owner, uint256 index) public view override returns (uint256) {
 return _holderTokens[owner].at(index);
 }

 function totalSupply() public view override returns (uint256) {
 // _tokenOwners are indexed by tokenIds, so .length() returns the number of tokenIds
 return _tokenOwners.length();
 }

 function tokenByIndex(uint256 index) public view override returns (uint256) {
 (uint256 tokenId, ) = _tokenOwners.at(index);
 return tokenId;
 }

 function approve(address to, uint256 tokenId) public virtual override {
 address owner = ownerOf(tokenId);
 require(to != owner, "TNT721: approval to current owner");

 require(_msgSender() == owner || isApprovedForAll(owner, _msgSender()),
 "TNT721: approve caller is not owner nor approved for all"
 );

 _approve(to, tokenId);
 }

 function getApproved(uint256 tokenId) public view override returns (address) {
 require(_exists(tokenId), "TNT721: approved query for nonexistent token");

 return _tokenApprovals[tokenId];
 }

 function setApprovalForAll(address operator, bool approved) public virtual override {
 require(operator != _msgSender(), "TNT721: approve to caller");

 _operatorApprovals[_msgSender()][operator] = approved;
 emit ApprovalForAll(_msgSender(), operator, approved);
 }

 function isApprovedForAll(address owner, address operator) public view override returns (bool) {
 return _operatorApprovals[owner][operator];
 }

 function transferFrom(address from, address to, uint256 tokenId) public virtual override {
 //solhint-disable-next-line max-line-length
 require(_isApprovedOrOwner(_msgSender(), tokenId), "TNT721: transfer caller is not owner nor approved");

 _transfer(from, to, tokenId);
 }

 function safeTransferFrom(address from, address to, uint256 tokenId) public virtual override {
 safeTransferFrom(from, to, tokenId, "");
 }

 function safeTransferFrom(address from, address to, uint256 tokenId, bytes memory _data) public virtual override {
 require(_isApprovedOrOwner(_msgSender(), tokenId), "TNT721: transfer caller is not owner nor approved");
 _safeTransfer(from, to, tokenId, _data);
 }

 function _safeTransfer(address from, address to, uint256 tokenId, bytes memory _data) internal virtual {
 _transfer(from, to, tokenId);
 require(_checkOnTNT721Received(from, to, tokenId, _data), "TNT721: transfer to non TNT721Receiver implementer");
 }

 function _exists(uint256 tokenId) internal view returns (bool) {
 return _tokenOwners.contains(tokenId);
 }

 function _isApprovedOrOwner(address spender, uint256 tokenId) internal view returns (bool) {
 require(_exists(tokenId), "TNT721: operator query for nonexistent token");
 address owner = ownerOf(tokenId);
 return (spender == owner || getApproved(tokenId) == spender || isApprovedForAll(owner, spender));
 }

 function mint(address to, string memory uri) public virtual override {
 uint mintIndex = totalSupply();
 _safeMint(to, mintIndex);
 _setTokenURI(mintIndex, uri);
 }

 function _safeMint(address to, uint256 tokenId) internal virtual {
 _safeMint(to, tokenId, "");
 }

 function _safeMint(address to, uint256 tokenId, bytes memory _data) internal virtual {
 _mint(to, tokenId);
 require(_checkOnTNT721Received(address(0), to, tokenId, _data), "TNT721: transfer to non TNT721Receiver implementer");
 }

 function _mint(address to, uint256 tokenId) internal virtual {
 require(to != address(0), "TNT721: mint to the zero address");
 require(!_exists(tokenId), "TNT721: token already minted");

 _beforeTokenTransfer(address(0), to, tokenId);

 _holderTokens[to].add(tokenId);

 _tokenOwners.set(tokenId, to);

 emit Transfer(address(0), to, tokenId);
 }

 function _burn(uint256 tokenId) internal virtual {
 address owner = ownerOf(tokenId);

 _beforeTokenTransfer(owner, address(0), tokenId);

 // Clear approvals
 _approve(address(0), tokenId);

 // Clear metadata (if any)
 if (bytes(_tokenURIs[tokenId]).length != 0) {
 delete _tokenURIs[tokenId];
 }

 _holderTokens[owner].remove(tokenId);

 _tokenOwners.remove(tokenId);

 emit Transfer(owner, address(0), tokenId);
 }

 function _transfer(address from, address to, uint256 tokenId) internal virtual {
 require(ownerOf(tokenId) == from, "TNT721: transfer of token that is not own");
 require(to != address(0), "TNT721: transfer to the zero address");

 _beforeTokenTransfer(from, to, tokenId);

 // Clear approvals from the previous owner
 _approve(address(0), tokenId);

 _holderTokens[from].remove(tokenId);
 _holderTokens[to].add(tokenId);

 _tokenOwners.set(tokenId, to);

 emit Transfer(from, to, tokenId);
 }

 function _setTokenURI(uint256 tokenId, string memory _tokenURI) internal virtual {
 require(_exists(tokenId), "TNT721Metadata: URI set of nonexistent token");
 _tokenURIs[tokenId] = _tokenURI;
 }

 function _setBaseURI(string memory baseURI_) internal virtual {
 _baseURI = baseURI_;
 }

 function _checkOnTNT721Received(address from, address to, uint256 tokenId, bytes memory _data)
 private returns (bool)
 {
 if (!to.isContract()) {
 return true;
 }
 bytes memory returndata = to.functionCall(abi.encodeWithSelector(
 ITNT721Receiver(to).onTNT721Received.selector,
 _msgSender(),
 from,
 tokenId,
 _data
 ), "TNT721: transfer to non TNT721Receiver implementer");
 bytes4 retval = abi.decode(returndata, (bytes4));
 return (retval == _TNT721_RECEIVED);
 }

 function _approve(address to, uint256 tokenId) private {
 _tokenApprovals[tokenId] = to;
 emit Approval(ownerOf(tokenId), to, tokenId);
 }

 function _beforeTokenTransfer(address from, address to, uint256 tokenId) internal virtual { }
}

contract CoolNFT is TNT721 {
 constructor (string memory name, string memory symbol, string memory uri) public TNT721(name, symbol) { 
 uint mintIndex = totalSupply();
 _safeMint(msg.sender, mintIndex);
 _setTokenURI(mintIndex, uri);
 }
}

Contract ABI:

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