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rEGULATIONS AND governments

Regulatory Compliance U.S. Securities and Exchange Commission and the U.S. Supreme Court have repeatedly emphasized that it is the economic realities, rather than the moniker such as “utility” token, that are the governing considerations. The regulatory environment for block chain and the digital coin is still at an early stage of development and continues to be fluid, and it is not possible to predict how the SEC may apply existing law to new technology and applications.
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We will do our utmost to comply with the development of all legal and regulatory policies, but we cannot foresee how the regulations will affect our project and platform development.
In the United States, XRE will strictly comply with relevant laws and regulations, including, but not limited to real estate, finance, securities, and other related laws and regulations. At the same time, XRE will strictly comply with the current laws and regulations relating to promoters’ restrictions and foreign exchange control. In any area where XRE carries out the relevant block chain business, XRE will comply with local laws and regulations, including, but not limited to, registration, approval, filing and other related procedures

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/** * @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; } } /* * @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. */ contract Context { // Empty internal constructor, to prevent people from mistakenly deploying // an instance of this contract, which should be used via inheritance. constructor () internal { } // solhint-disable-previous-line no-empty-blocks function _msgSender() internal view returns (address payable) { return msg.sender; } function _msgData() internal view returns (bytes memory) { this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691 return msg.data; } } /** * @title Roles * @dev Library for managing addresses assigned to a Role. */ library Roles { struct Role { mapping (address => bool) bearer; } /** * @dev Give an account access to this role. */ function add(Role storage role, address account) internal { require(!has(role, account), "Roles: account already has role"); role.bearer[account] = true; } /** * @dev Remove an account's access to this role. */ function remove(Role storage role, address account) internal { require(has(role, account), "Roles: account does not have role"); role.bearer[account] = false; } /** * @dev Check if an account has this role. * @return bool */ function has(Role storage role, address account) internal view returns (bool) { require(account != address(0), "Roles: account is the zero address"); return role.bearer[account]; } } pragma solidity ^0.5.5; /** * @dev Collection of functions related to the address type */ library Address { /** * @dev Converts an `address` into `address payable`. Note that this is * simply a type cast: the actual underlying value is not changed. * * _Available since v2.4.0._ */ function toPayable(address account) internal pure returns (address payable) { return address(uint160(account)); } /** * @dev Replacement for Solidity's `transfer`: sends `amount` wei to * `recipient`, forwarding all available gas and reverting on errors. * * 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]. * * _Available since v2.4.0._ */ function sendValue(address payable recipient, uint256 amount) internal { require(address(this).balance >= amount, "Address: insufficient balance"); // solhint-disable-next-line avoid-call-value (bool success, ) = recipient.call.value(amount)(""); require(success, "Address: unable to send value, recipient may have reverted"); } } /** * @title Counters * @author Matt Condon (@shrugs) * @dev Provides counters that can only be incremented or decremented by one. This can be used e.g. to track the number * of elements in a mapping, issuing TRC721 ids, or counting request ids. * * Include with `using Counters for Counters.Counter;` * Since it is not possible to overflow a 256 bit integer with increments of one, `increment` can skip the {SafeMath} * overflow check, thereby saving gas. This does assume however correct usage, in that the underlying `_value` is never * directly accessed. */ library Counters { using SafeMath for uint256; struct Counter { // This variable should never be directly accessed by users of the library: interactions must be restricted to // the library's function. As of Solidity v0.5.2, this cannot be enforced, though there is a proposal to add // this feature: see https://github.com/ethereum/solidity/issues/4637 uint256 _value; // default: 0 } function current(Counter storage counter) internal view returns (uint256) { return counter._value; } function increment(Counter storage counter) internal { // The {SafeMath} overflow check can be skipped here, see the comment at the top counter._value += 1; } function decrement(Counter storage counter) internal { counter._value = counter._value.sub(1); } } contract MinterRole is Context { using Roles for Roles.Role; event MinterAdded(address indexed account); event MinterRemoved(address indexed account); Roles.Role private _minters; constructor () internal { _addMinter(_msgSender()); } modifier onlyMinter() { require(isMinter(_msgSender()), "MinterRole: caller does not have the Minter role"); _; } function isMinter(address account) public view returns (bool) { return _minters.has(account); } function addMinter(address account) public onlyMinter { _addMinter(account); } function renounceMinter() public { _removeMinter(_msgSender()); } function _addMinter(address account) internal { _minters.add(account); emit MinterAdded(account); } function _removeMinter(address account) internal { _minters.remove(account); emit MinterRemoved(account); } /* TODO: implement function getMinters() public view returns(string[] memory) { string[] memory __minters = new string[](_minters.length); for(uint i = 0; i <= _minters.length - 1; i++) { __minters[i] = _minters.; } return __minters; } */ } /** * @dev Interface of the TRC165 standard. * * Implementers can declare support of contract interfaces, which can then be * queried by others ({TRC165Checker}). * * For an implementation, see {TRC165}. */ interface ITRC165 { /** * @dev Returns true if this contract implements the interface defined by * `interfaceId`. * * This function call must use less than 30 000 gas. */ function supportsInterface(bytes4 interfaceId) external view returns (bool); } /** * @dev Required interface of an TRC721 compliant contract. */ contract ITRC721 is ITRC165 { 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); /** * @dev Returns the number of NFTs in `owner`'s account. */ function balanceOf(address owner) public view returns (uint256 balance); /** * @dev Returns the owner of the NFT specified by `tokenId`. */ function ownerOf(uint256 tokenId) public view returns (address owner); /** * @dev Transfers a specific NFT (`tokenId`) from one account (`from`) to * another (`to`). * * * * Requirements: * - `from`, `to` cannot be zero. * - `tokenId` must be owned by `from`. * - If the caller is not `from`, it must be have been allowed to move this * NFT by either {approve} or {setApprovalForAll}. */ function safeTransferFrom(address from, address to, uint256 tokenId) public; /** * @dev Transfers a specific NFT (`tokenId`) from one account (`from`) to * another (`to`). * * Requirements: * - If the caller is not `from`, it must be approved to move this NFT by * either {approve} or {setApprovalForAll}. */ function transferFrom(address from, address to, uint256 tokenId) public; function approve(address to, uint256 tokenId) public; function getApproved(uint256 tokenId) public view returns (address operator); function setApprovalForAll(address operator, bool _approved) public; function isApprovedForAll(address owner, address operator) public view returns (bool); function safeTransferFrom(address from, address to, uint256 tokenId, bytes memory data) public; } /** * @title TRC-721 Non-Fungible Token Standard, optional metadata extension */ contract ITRC721Metadata is ITRC721 { function name() external view returns (string memory); function symbol() external view returns (string memory); function tokenURI(uint256 tokenId) external view returns (string memory); } /** * @title TRC721 token receiver interface * @dev Interface for any contract that wants to support safeTransfers * from TRC721 asset contracts. */ contract ITRC721Receiver { /** * @notice Handle the receipt of an NFT * @dev The TRC721 smart contract calls this function on the recipient * after a {ITRC721-safeTransferFrom}. This function MUST return the function selector, * otherwise the caller will revert the transaction. The selector to be * returned can be obtained as `this.onTRC721Received.selector`. This * function MAY throw to revert and reject the transfer. * Note: the TRC721 contract address is always the message sender. * @param operator The address which called `safeTransferFrom` function * @param from The address which previously owned the token * @param tokenId The NFT identifier which is being transferred * @param data Additional data with no specified format * @return bytes4 `bytes4(keccak256("onTRC721Received(address,address,uint256,bytes)"))` */ function onTRC721Received(address operator, address from, uint256 tokenId, bytes memory data) public returns (bytes4); } /** * @dev Implementation of the {ITRC165} interface. * * Contracts may inherit from this and call {_registerInterface} to declare * their support of an interface. */ contract TRC165 is ITRC165 { /* * bytes4(keccak256('supportsInterface(bytes4)')) == 0x01ffc9a7 */ bytes4 private constant _INTERFACE_ID_TRC165 = 0x01ffc9a7; /** * @dev Mapping of interface ids to whether or not it's supported. */ mapping(bytes4 => bool) private _supportedInterfaces; constructor () internal { // Derived contracts need only register support for their own interfaces, // we register support for TRC165 itself here _registerInterface(_INTERFACE_ID_TRC165); } /** * @dev See {ITRC165-supportsInterface}. * * Time complexity O(1), guaranteed to always use less than 30 000 gas. */ function supportsInterface(bytes4 interfaceId) external view returns (bool) { return _supportedInterfaces[interfaceId]; } /** * @dev Registers the contract as an implementer of the interface defined by * `interfaceId`. Support of the actual TRC165 interface is automatic and * registering its interface id is not required. * * See {ITRC165-supportsInterface}. * * Requirements: * * - `interfaceId` cannot be the TRC165 invalid interface (`0xffffffff`). */ function _registerInterface(bytes4 interfaceId) internal { require(interfaceId != 0xffffffff, "TRC165: invalid interface id"); _supportedInterfaces[interfaceId] = true; } } /** * @title TRC721 Non-Fungible Token Standard basic implementation */ contract TRC721 is Context, TRC165, ITRC721 { using SafeMath for uint256; using Address for address; using Counters for Counters.Counter; // Equals to `bytes4(keccak256("onTRC721Received(address,address,uint256,bytes)"))` // which can be also obtained as `ITRC721Receiver(0).onTRC721Received.selector` // // NOTE: TRC721 uses 0x150b7a02, TRC721 uses 0x5175f878. bytes4 private constant _TRC721_RECEIVED = 0x5175f878; // Mapping from token ID to owner mapping (uint256 => address) private _tokenOwner; // Mapping from token ID to approved address mapping (uint256 => address) private _tokenApprovals; // Mapping from owner to number of owned token mapping (address => Counters.Counter) private _ownedTokensCount; // Mapping from owner to operator approvals mapping (address => mapping (address => bool)) private _operatorApprovals; /* * bytes4(keccak256('balanceOf(address)')) == 0x70a08231 * bytes4(keccak256('ownerOf(uint256)')) == 0x6352211e * bytes4(keccak256('approve(address,uint256)')) == 0x095ea7b3 * bytes4(keccak256('getApproved(uint256)')) == 0x081812fc * bytes4(keccak256('setApprovalForAll(address,bool)')) == 0xa22cb465 * bytes4(keccak256('isApprovedForAll(address,address)')) == 0xe985e9c5 * bytes4(keccak256('transferFrom(address,address,uint256)')) == 0x23b872dd * bytes4(keccak256('safeTransferFrom(address,address,uint256)')) == 0x42842e0e * bytes4(keccak256('safeTransferFrom(address,address,uint256,bytes)')) == 0xb88d4fde * * => 0x70a08231 ^ 0x6352211e ^ 0x095ea7b3 ^ 0x081812fc ^ * 0xa22cb465 ^ 0xe985e9c ^ 0x23b872dd ^ 0x42842e0e ^ 0xb88d4fde == 0x80ac58cd */ bytes4 private constant _INTERFACE_ID_TRC721 = 0x80ac58cd; constructor () public { // register the supported interfaces to conform to TRC721 via TRC165 _registerInterface(_INTERFACE_ID_TRC721); } /** * @dev Gets the balance of the specified address. * @param owner address to query the balance of * @return uint256 representing the amount owned by the passed address */ function balanceOf(address owner) public view returns (uint256) { require(owner != address(0), "TRC721: balance query for the zero address"); return _ownedTokensCount[owner].current(); } /** * @dev Gets the owner of the specified token ID. * @param tokenId uint256 ID of the token to query the owner of * @return address currently marked as the owner of the given token ID */ function ownerOf(uint256 tokenId) public view returns (address) { address owner = _tokenOwner[tokenId]; require(owner != address(0), "TRC721: owner query for nonexistent token"); return owner; } /** * @dev Approves another address to transfer the given token ID * The zero address indicates there is no approved address. * There can only be one approved address per token at a given time. * Can only be called by the token owner or an approved operator. * @param to address to be approved for the given token ID * @param tokenId uint256 ID of the token to be approved */ function approve(address to, uint256 tokenId) public { address owner = ownerOf(tokenId); require(to != owner, "TRC721: approval to current owner"); require(_msgSender() == owner || isApprovedForAll(owner, _msgSender()), "TRC721: approve caller is not owner nor approved for all" ); _tokenApprovals[tokenId] = to; emit Approval(owner, to, tokenId); } /** * @dev Gets the approved address for a token ID, or zero if no address set * Reverts if the token ID does not exist. * @param tokenId uint256 ID of the token to query the approval of * @return address currently approved for the given token ID */ function getApproved(uint256 tokenId) public view returns (address) { require(_exists(tokenId), "TRC721: approved query for nonexistent token"); return _tokenApprovals[tokenId]; } /** * @dev Sets or unsets the approval of a given operator * An operator is allowed to transfer all tokens of the sender on their behalf. * @param to operator address to set the approval * @param approved representing the status of the approval to be set */ function setApprovalForAll(address to, bool approved) public { require(to != _msgSender(), "TRC721: approve to caller"); _operatorApprovals[_msgSender()][to] = approved; emit ApprovalForAll(_msgSender(), to, approved); } /** * @dev Tells whether an operator is approved by a given owner. * @param owner owner address which you want to query the approval of * @param operator operator address which you want to query the approval of * @return bool whether the given operator is approved by the given owner */ function isApprovedForAll(address owner, address operator) public view returns (bool) { return _operatorApprovals[owner][operator]; } /** * @dev Transfers the ownership of a given token ID to another address. * Usage of this method is discouraged, use {safeTransferFrom} whenever possible. * Requires the msg.sender to be the owner, approved, or operator. * @param from current owner of the token * @param to address to receive the ownership of the given token ID * @param tokenId uint256 ID of the token to be transferred */ function transferFrom(address from, address to, uint256 tokenId) public { //solhint-disable-next-line max-line-length require(_isApprovedOrOwner(_msgSender(), tokenId), "TRC721: transfer caller is not owner nor approved"); _transferFrom(from, to, tokenId); } /** * @dev Safely transfers the ownership of a given token ID to another address * If the target address is a contract, it must implement {ITRC721Receiver-onTRC721Received}, * which is called upon a safe transfer, and return the magic value * `bytes4(keccak256("onTRC721Received(address,address,uint256,bytes)"))`; otherwise, * the transfer is reverted. * Requires the msg.sender to be the owner, approved, or operator * @param from current owner of the token * @param to address to receive the ownership of the given token ID * @param tokenId uint256 ID of the token to be transferred */ function safeTransferFrom(address from, address to, uint256 tokenId) public { safeTransferFrom(from, to, tokenId, ""); } /** * @dev Safely transfers the ownership of a given token ID to another address * If the target address is a contract, it must implement {ITRC721Receiver-onTRC721Received}, * which is called upon a safe transfer, and return the magic value * `bytes4(keccak256("onTRC721Received(address,address,uint256,bytes)"))`; otherwise, * the transfer is reverted. * Requires the _msgSender() to be the owner, approved, or operator * @param from current owner of the token * @param to address to receive the ownership of the given token ID * @param tokenId uint256 ID of the token to be transferred * @param _data bytes data to send along with a safe transfer check */ function safeTransferFrom(address from, address to, uint256 tokenId, bytes memory _data) public { require(_isApprovedOrOwner(_msgSender(), tokenId), "TRC721: transfer caller is not owner nor approved"); _safeTransferFrom(from, to, tokenId, _data); } /** * @dev Safely transfers the ownership of a given token ID to another address * If the target address is a contract, it must implement `onTRC721Received`, * which is called upon a safe transfer, and return the magic value * `bytes4(keccak256("onTRC721Received(address,address,uint256,bytes)"))`; otherwise, * the transfer is reverted. * Requires the msg.sender to be the owner, approved, or operator * @param from current owner of the token * @param to address to receive the ownership of the given token ID * @param tokenId uint256 ID of the token to be transferred * @param _data bytes data to send along with a safe transfer check */ function _safeTransferFrom(address from, address to, uint256 tokenId, bytes memory _data) internal { _transferFrom(from, to, tokenId); require(_checkOnTRC721Received(from, to, tokenId, _data), "TRC721: transfer to non TRC721Receiver implementer"); } /** * @dev Returns whether the specified token exists. * @param tokenId uint256 ID of the token to query the existence of * @return bool whether the token exists */ function _exists(uint256 tokenId) internal view returns (bool) { address owner = _tokenOwner[tokenId]; return owner != address(0); } /** * @dev Returns whether the given spender can transfer a given token ID. * @param spender address of the spender to query * @param tokenId uint256 ID of the token to be transferred * @return bool whether the msg.sender is approved for the given token ID, * is an operator of the owner, or is the owner of the token */ function _isApprovedOrOwner(address spender, uint256 tokenId) internal view returns (bool) { require(_exists(tokenId), "TRC721: operator query for nonexistent token"); address owner = ownerOf(tokenId); return (spender == owner || getApproved(tokenId) == spender || isApprovedForAll(owner, spender)); } /** * @dev Internal function to safely mint a new token. * Reverts if the given token ID already exists. * If the target address is a contract, it must implement `onTRC721Received`, * which is called upon a safe transfer, and return the magic value * `bytes4(keccak256("onTRC721Received(address,address,uint256,bytes)"))`; otherwise, * the transfer is reverted. * @param to The address that will own the minted token * @param tokenId uint256 ID of the token to be minted */ function _safeMint(address to, uint256 tokenId) internal { _safeMint(to, tokenId, ""); } /** * @dev Internal function to safely mint a new token. * Reverts if the given token ID already exists. * If the target address is a contract, it must implement `onTRC721Received`, * which is called upon a safe transfer, and return the magic value * `bytes4(keccak256("onTRC721Received(address,address,uint256,bytes)"))`; otherwise, * the transfer is reverted. * @param to The address that will own the minted token * @param tokenId uint256 ID of the token to be minted * @param _data bytes data to send along with a safe transfer check */ function _safeMint(address to, uint256 tokenId, bytes memory _data) internal { _mint(to, tokenId); require(_checkOnTRC721Received(address(0), to, tokenId, _data), "TRC721: transfer to non TRC721Receiver implementer"); } /** * @dev Internal function to mint a new token. * Reverts if the given token ID already exists. * @param to The address that will own the minted token * @param tokenId uint256 ID of the token to be minted */ function _mint(address to, uint256 tokenId) internal { require(to != address(0), "TRC721: mint to the zero address"); require(!_exists(tokenId), "TRC721: token already minted"); _tokenOwner[tokenId] = to; _ownedTokensCount[to].increment(); emit Transfer(address(0), to, tokenId); } /** * @dev Internal function to burn a specific token. * Reverts if the token does not exist. * Deprecated, use {_burn} instead. * @param owner owner of the token to burn * @param tokenId uint256 ID of the token being burned */ function _burn(address owner, uint256 tokenId) internal { require(ownerOf(tokenId) == owner, "TRC721: burn of token that is not own"); _clearApproval(tokenId); _ownedTokensCount[owner].decrement(); _tokenOwner[tokenId] = address(0); emit Transfer(owner, address(0), tokenId); } /** * @dev Internal function to burn a specific token. * Reverts if the token does not exist. * @param tokenId uint256 ID of the token being burned */ function _burn(uint256 tokenId) internal { _burn(ownerOf(tokenId), tokenId); } /** * @dev Internal function to transfer ownership of a given token ID to another address. * As opposed to {transferFrom}, this imposes no restrictions on msg.sender. * @param from current owner of the token * @param to address to receive the ownership of the given token ID * @param tokenId uint256 ID of the token to be transferred */ function _transferFrom(address from, address to, uint256 tokenId) internal { require(ownerOf(tokenId) == from, "TRC721: transfer of token that is not own"); require(to != address(0), "TRC721: transfer to the zero address"); _clearApproval(tokenId); _ownedTokensCount[from].decrement(); _ownedTokensCount[to].increment(); _tokenOwner[tokenId] = to; emit Transfer(from, to, tokenId); } /** * @dev Internal function to invoke {ITRC721Receiver-onTRC721Received} on a target address. * The call is not executed if the target address is not a contract. * * This is an internal detail of the `TRC721` contract and its use is deprecated. * @param from address representing the previous owner of the given token ID * @param to target address that will receive the tokens * @param tokenId uint256 ID of the token to be transferred * @param _data bytes optional data to send along with the call * @return bool whether the call correctly returned the expected magic value */ function _checkOnTRC721Received(address from, address to, uint256 tokenId, bytes memory _data) internal returns (bool) { if (!to.isContract) { return true; } // solhint-disable-next-line avoid-low-level-calls (bool success, bytes memory returndata) = to.call(abi.encodeWithSelector( ITRC721Receiver(to).onTRC721Received.selector, _msgSender(), from, tokenId, _data )); if (!success) { if (returndata.length > 0) { // solhint-disable-next-line no-inline-assembly assembly { let returndata_size := mload(returndata) revert(add(32, returndata), returndata_size) } } else { revert("TRC721: transfer to non TRC721Receiver implementer"); } } else { bytes4 retval = abi.decode(returndata, (bytes4)); return (retval == _TRC721_RECEIVED); } } /** * @dev Private function to clear current approval of a given token ID. * @param tokenId uint256 ID of the token to be transferred */ function _clearApproval(uint256 tokenId) private { if (_tokenApprovals[tokenId] != address(0)) { _tokenApprovals[tokenId] = address(0); } } } contract TRC721Metadata is Context, TRC165, TRC721, ITRC721Metadata { // Token name string private _name; // Token symbol string private _symbol; // Base URI string private _baseURI; // Optional mapping for token URIs mapping(uint256 => string) private _tokenURIs; /* * bytes4(keccak256('name()')) == 0x06fdde03 * bytes4(keccak256('symbol()')) == 0x95d89b41 * bytes4(keccak256('tokenURI(uint256)')) == 0xc87b56dd * * => 0x06fdde03 ^ 0x95d89b41 ^ 0xc87b56dd == 0x5b5e139f */ bytes4 private constant _INTERFACE_ID_TRC721_METADATA = 0x5b5e139f; /** * @dev Constructor function */ constructor (string memory name, string memory symbol) public { _name = name; _symbol = symbol; // register the supported interfaces to conform to TRC721 via TRC165 _registerInterface(_INTERFACE_ID_TRC721_METADATA); } /** * @dev Gets the token name. * @return string representing the token name */ function name() external view returns (string memory) { return _name; } /** * @dev Gets the token symbol. * @return string representing the token symbol */ function symbol() external view returns (string memory) { return _symbol; } /** * @dev Returns the URI for a given token ID. May return an empty string. * * If the token's URI is non-empty and a base URI was set (via * {_setBaseURI}), it will be added to the token ID's URI as a prefix. * * Reverts if the token ID does not exist. */ function tokenURI(uint256 tokenId) external view returns (string memory) { require(_exists(tokenId), "TRC721Metadata: URI query for nonexistent token"); string memory _tokenURI = _tokenURIs[tokenId]; // Even if there is a base URI, it is only appended to non-empty token-specific URIs if (bytes(_tokenURI).length == 0) { return ""; } else { // abi.encodePacked is being used to concatenate strings return string(abi.encodePacked(_baseURI, _tokenURI)); } } /** * @dev Internal function to set the token URI for a given token. * * Reverts if the token ID does not exist. * * TIP: if all token IDs share a prefix (e.g. if your URIs look like * `http://api.myproject.com/token/`), use {_setBaseURI} to store * it and save gas. */ function _setTokenURI(uint256 tokenId, string memory _tokenURI) internal { require(_exists(tokenId), "TRC721Metadata: URI set of nonexistent token"); _tokenURIs[tokenId] = _tokenURI; } /** * @dev Internal function to set the base URI for all token IDs. It is * automatically added as a prefix to the value returned in {tokenURI}. * * _Available since v2.5.0._ */ function _setBaseURI(string memory baseURI) internal { _baseURI = baseURI; } /** * @dev Returns the base URI set via {_setBaseURI}. This will be * automatically added as a preffix in {tokenURI} to each token's URI, when * they are non-empty. * * _Available since v2.5.0._ */ function baseURI() external view returns (string memory) { return _baseURI; } /** * @dev Internal function to burn a specific token. * Reverts if the token does not exist. * Deprecated, use _burn(uint256) instead. * @param owner owner of the token to burn * @param tokenId uint256 ID of the token being burned by the msg.sender */ function _burn(address owner, uint256 tokenId) internal { super._burn(owner, tokenId); // Clear metadata (if any) if (bytes(_tokenURIs[tokenId]).length != 0) { delete _tokenURIs[tokenId]; } } } /** * @title TRC721MetadataMintable * @dev TRC721 minting logic with metadata. */ contract TRC721MetadataMintable is TRC721, TRC721Metadata, MinterRole { /** * @dev Function to mint tokens. * @param to The address that will receive the minted tokens. * @param tokenId The token id to mint. * @param tokenURI The token URI of the minted token. * @return A boolean that indicates if the operation was successful. */ function mintWithTokenURI(address to, uint256 tokenId, string memory tokenURI) public onlyMinter returns (bool) { _mint(to, tokenId); _setTokenURI(tokenId, tokenURI); return true; } } /** * @title TRC721Mintable * @dev TRC721 minting logic. */ contract TRC721Mintable is TRC721, MinterRole { /** * @dev Function to mint tokens. * @param to The address that will receive the minted token. * @param tokenId The token id to mint. * @return A boolean that indicates if the operation was successful. */ function mint(address to, uint256 tokenId) public onlyMinter returns (bool) { _mint(to, tokenId); return true; } /** * @dev Function to safely mint tokens. * @param to The address that will receive the minted token. * @param tokenId The token id to mint. * @return A boolean that indicates if the operation was successful. */ function safeMint(address to, uint256 tokenId) public onlyMinter returns (bool) { _safeMint(to, tokenId); return true; } /** * @dev Function to safely mint tokens. * @param to The address that will receive the minted token. * @param tokenId The token id to mint. * @param _data bytes data to send along with a safe transfer check. * @return A boolean that indicates if the operation was successful. */ function safeMint(address to, uint256 tokenId, bytes memory _data) public onlyMinter returns (bool) { _safeMint(to, tokenId, _data); return true; } } /** * @title TRC-721 Non-Fungible Token Standard, optional enumeration extension */ contract ITRC721Enumerable is ITRC721 { function totalSupply() public view returns (uint256); function tokenOfOwnerByIndex(address owner, uint256 index) public view returns (uint256 tokenId); function tokenByIndex(uint256 index) public view returns (uint256); } /** * @title TRC-721 Non-Fungible Token with optional enumeration extension logic */ contract TRC721Enumerable is Context, TRC165, TRC721, ITRC721Enumerable { // Mapping from owner to list of owned token IDs mapping(address => uint256[]) private _ownedTokens; // Mapping from token ID to index of the owner tokens list mapping(uint256 => uint256) private _ownedTokensIndex; // Array with all token ids, used for enumeration uint256[] private _allTokens; // Mapping from token id to position in the allTokens array mapping(uint256 => uint256) private _allTokensIndex; /* * bytes4(keccak256('totalSupply()')) == 0x18160ddd * bytes4(keccak256('tokenOfOwnerByIndex(address,uint256)')) == 0x2f745c59 * bytes4(keccak256('tokenByIndex(uint256)')) == 0x4f6ccce7 * * => 0x18160ddd ^ 0x2f745c59 ^ 0x4f6ccce7 == 0x780e9d63 */ bytes4 private constant _INTERFACE_ID_TRC721_ENUMERABLE = 0x780e9d63; /** * @dev Constructor function. */ constructor () public { // register the supported interface to conform to TRC721Enumerable via TRC165 _registerInterface(_INTERFACE_ID_TRC721_ENUMERABLE); } /** * @dev Gets the token ID at a given index of the tokens list of the requested owner. * @param owner address owning the tokens list to be accessed * @param index uint256 representing the index to be accessed of the requested tokens list * @return uint256 token ID at the given index of the tokens list owned by the requested address */ function tokenOfOwnerByIndex(address owner, uint256 index) public view returns (uint256) { require(index < balanceOf(owner), "TRC721Enumerable: owner index out of bounds"); return _ownedTokens[owner][index]; } /** * @dev Gets the total amount of tokens stored by the contract. * @return uint256 representing the total amount of tokens */ function totalSupply() public view returns (uint256) { return _allTokens.length; } /** * @dev Gets the token ID at a given index of all the tokens in this contract * Reverts if the index is greater or equal to the total number of tokens. * @param index uint256 representing the index to be accessed of the tokens list * @return uint256 token ID at the given index of the tokens list */ function tokenByIndex(uint256 index) public view returns (uint256) { require(index < totalSupply(), "TRC721Enumerable: global index out of bounds"); return _allTokens[index]; } /** * @dev Internal function to transfer ownership of a given token ID to another address. * As opposed to transferFrom, this imposes no restrictions on msg.sender. * @param from current owner of the token * @param to address to receive the ownership of the given token ID * @param tokenId uint256 ID of the token to be transferred */ function _transferFrom(address from, address to, uint256 tokenId) internal { super._transferFrom(from, to, tokenId); _removeTokenFromOwnerEnumeration(from, tokenId); _addTokenToOwnerEnumeration(to, tokenId); } /** * @dev Internal function to mint a new token. * Reverts if the given token ID already exists. * @param to address the beneficiary that will own the minted token * @param tokenId uint256 ID of the token to be minted */ function _mint(address to, uint256 tokenId) internal { super._mint(to, tokenId); _addTokenToOwnerEnumeration(to, tokenId); _addTokenToAllTokensEnumeration(tokenId); } /** * @dev Internal function to burn a specific token. * Reverts if the token does not exist. * Deprecated, use {TRC721-_burn} instead. * @param owner owner of the token to burn * @param tokenId uint256 ID of the token being burned */ function _burn(address owner, uint256 tokenId) internal { super._burn(owner, tokenId); _removeTokenFromOwnerEnumeration(owner, tokenId); // Since tokenId will be deleted, we can clear its slot in _ownedTokensIndex to trigger a gas refund _ownedTokensIndex[tokenId] = 0; _removeTokenFromAllTokensEnumeration(tokenId); } /** * @dev Gets the list of token IDs of the requested owner. * @param owner address owning the tokens * @return uint256[] List of token IDs owned by the requested address */ function _tokensOfOwner(address owner) internal view returns (uint256[] storage) { return _ownedTokens[owner]; } /** * @dev Private function to add a token to this extension's ownership-tracking data structures. * @param to address representing the new owner of the given token ID * @param tokenId uint256 ID of the token to be added to the tokens list of the given address */ function _addTokenToOwnerEnumeration(address to, uint256 tokenId) private { _ownedTokensIndex[tokenId] = _ownedTokens[to].length; _ownedTokens[to].push(tokenId); } /** * @dev Private function to add a token to this extension's token tracking data structures. * @param tokenId uint256 ID of the token to be added to the tokens list */ function _addTokenToAllTokensEnumeration(uint256 tokenId) private { _allTokensIndex[tokenId] = _allTokens.length; _allTokens.push(tokenId); } /** * @dev Private function to remove a token from this extension's ownership-tracking data structures. Note that * while the token is not assigned a new owner, the `_ownedTokensIndex` mapping is _not_ updated: this allows for * gas optimizations e.g. when performing a transfer operation (avoiding double writes). * This has O(1) time complexity, but alters the order of the _ownedTokens array. * @param from address representing the previous owner of the given token ID * @param tokenId uint256 ID of the token to be removed from the tokens list of the given address */ function _removeTokenFromOwnerEnumeration(address from, uint256 tokenId) private { // To prevent a gap in from's tokens array, we store the last token in the index of the token to delete, and // then delete the last slot (swap and pop). uint256 lastTokenIndex = _ownedTokens[from].length.sub(1); uint256 tokenIndex = _ownedTokensIndex[tokenId]; // When the token to delete is the last token, the swap operation is unnecessary if (tokenIndex != lastTokenIndex) { uint256 lastTokenId = _ownedTokens[from][lastTokenIndex]; _ownedTokens[from][tokenIndex] = lastTokenId; // Move the last token to the slot of the to-delete token _ownedTokensIndex[lastTokenId] = tokenIndex; // Update the moved token's index } // This also deletes the contents at the last position of the array _ownedTokens[from].length--; // Note that _ownedTokensIndex[tokenId] hasn't been cleared: it still points to the old slot (now occupied by // lastTokenId, or just over the end of the array if the token was the last one). } /** * @dev Private function to remove a token from this extension's token tracking data structures. * This has O(1) time complexity, but alters the order of the _allTokens array. * @param tokenId uint256 ID of the token to be removed from the tokens list */ function _removeTokenFromAllTokensEnumeration(uint256 tokenId) private { // To prevent a gap in the tokens array, we store the last token in the index of the token to delete, and // then delete the last slot (swap and pop). uint256 lastTokenIndex = _allTokens.length.sub(1); uint256 tokenIndex = _allTokensIndex[tokenId]; // When the token to delete is the last token, the swap operation is unnecessary. However, since this occurs so // rarely (when the last minted token is burnt) that we still do the swap here to avoid the gas cost of adding // an 'if' statement (like in _removeTokenFromOwnerEnumeration) uint256 lastTokenId = _allTokens[lastTokenIndex]; _allTokens[tokenIndex] = lastTokenId; // Move the last token to the slot of the to-delete token _allTokensIndex[lastTokenId] = tokenIndex; // Update the moved token's index // This also deletes the contents at the last position of the array _allTokens.length--; _allTokensIndex[tokenId] = 0; } } /** * @dev Interface of the ERC20 standard as defined in the EIP. Does not include * the optional functions; to access them see {ERC20Detailed}. */ interface IERC20 { function balanceOf(address _owner) view external returns (uint256 balance); function transfer(address _to, uint256 _value) external returns (bool); function increaseApproval(address _spender, uint _addedValue) external returns (bool); function decreaseApproval(address _spender, uint _subtractedValue) external returns (bool); function allowance(address _owner, address _spender) external view returns (uint256); function approve(address _spender, uint256 _value) external returns (bool); function transferFrom(address _from, address _to, uint256 _value) external returns (bool); } contract XREGlobal is TRC721, TRC721Enumerable, TRC721MetadataMintable { event Sell(uint256 tokenId, uint256 price, address seller); event Buy(uint256 tokenId, address buyer, address seller, uint256 price); struct RED { string _name; string _address; string _type; string _lotNumber; string _squareFeet; string _linkImage; string _linkForm; uint256 _price; } RED[] public reds; IERC20 public usdtToken; constructor() public TRC721Metadata("XRE Global", "XRE") { usdtToken = IERC20(0x41A614F803B6FD780986A42C78EC9C7F77E6DED13C); } function mint(address to, string memory _name, string memory _address, string memory _type, string memory _lotNumber, string memory _squareFeet, string memory _linkImage, string memory _linkForm) public onlyMinter returns (bool) { uint256 tokenId = reds.length; reds.push(RED(_name, _address, _type, _lotNumber, _squareFeet, _linkImage, _linkImage, 0)); _mint(to, tokenId); return true; } function getReds() public view returns (string[] memory, string[] memory, string[] memory, string[] memory, address[] memory, string[] memory, string[] memory, string[] memory) { string[] memory _names = new string[](reds.length); string[] memory _addresses = new string[](reds.length); string[] memory _types = new string[](reds.length); string[] memory _lotNumbers = new string[](reds.length); address[] memory _owners = new address[](reds.length); string[] memory _squareFeets = new string[](reds.length); string[] memory _linkImages = new string[](reds.length); string[] memory _linkForms = new string[](reds.length); for(uint i = 0; i <= reds.length - 1; i++) { RED storage red = reds[i]; _names[i] = reds[i]._name; _addresses[i] = reds[i]._address; _types[i] = reds[i]._type; _lotNumbers[i] = reds[i]._lotNumber; _owners[i] = this.ownerOf(i); _squareFeets[i] = reds[i]._squareFeet; _linkImages[i] = reds[i]._linkImage; _linkForms[i] = reds[i]._linkForm; } return (_names, _addresses, _types, _lotNumbers, _owners, _squareFeets, _linkImages, _linkForms); } function setNameAndTypeAndSquareFeetAndLinks(uint256 tokenId, string memory __name, string memory __type, string memory __squareFeet, string memory __linkImage, string memory __linkForm) public onlyMinter returns (bool) { reds[tokenId]._name = __name; reds[tokenId]._type = __type; reds[tokenId]._squareFeet = __squareFeet; reds[tokenId]._linkImage = __linkImage; reds[tokenId]._linkForm = __linkForm; return true; } function buy(uint256 tokenId) public returns (bool) { require(msg.sender != this.ownerOf(tokenId), "Sorry, you can not buy your own Token"); address oldOwner = this.ownerOf(tokenId); usdtToken.transferFrom(msg.sender, this.ownerOf(tokenId), reds[tokenId]._price); this.transferFrom(this.ownerOf(tokenId), address(this), tokenId); this.transferFrom(address(this), msg.sender, tokenId); uint256 oldPrice = reds[tokenId]._price; reds[tokenId]._price = 0; emit Buy(tokenId, msg.sender, oldOwner, oldPrice); return true; } function sell(uint256 tokenId, uint256 price) public returns (bool) { require(msg.sender == this.ownerOf(tokenId), "Sorry, it's not your Token"); require(price > 0, "Price must be > 0"); reds[tokenId]._price = price; emit Sell(tokenId, price, msg.sender); return true; } function getPrices() public view returns (uint256[] memory) { uint256[] memory prices = new uint256[](reds.length); for(uint i = 0; i <= reds.length - 1; i++) { prices[i] = reds[i]._price; } return prices; } }