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"content": "// SPDX-License-Identifier: MIT\n// ERC721A Contracts v4.2.0\n// Creator: Chiru Labs\n\npragma solidity ^0.8.4;\n\nimport './IERC721A.sol';\n\n/**\n * @dev Interface of ERC721 token receiver.\n */\ninterface ERC721A__IERC721Receiver {\n function onERC721Received(\n address operator,\n address from,\n uint256 tokenId,\n bytes calldata data\n ) external returns (bytes4);\n}\n\n/**\n * @title ERC721A\n *\n * @dev Implementation of the [ERC721](https://eips.ethereum.org/EIPS/eip-721)\n * Non-Fungible Token Standard, including the Metadata extension.\n * Optimized for lower gas during batch mints.\n *\n * Token IDs are minted in sequential order (e.g. 0, 1, 2, 3, ...)\n * starting from `_startTokenId()`.\n *\n * Assumptions:\n *\n * - An owner cannot have more than 2**64 - 1 (max value of uint64) of supply.\n * - The maximum token ID cannot exceed 2**256 - 1 (max value of uint256).\n */\ncontract ERC721A is IERC721A {\n // Reference type for token approval.\n struct TokenApprovalRef {\n address value;\n }\n\n // =============================================================\n // CONSTANTS\n // =============================================================\n\n // Mask of an entry in packed address data.\n uint256 private constant _BITMASK_ADDRESS_DATA_ENTRY = (1 << 64) - 1;\n\n // The bit position of `numberMinted` in packed address data.\n uint256 private constant _BITPOS_NUMBER_MINTED = 64;\n\n // The bit position of `numberBurned` in packed address data.\n uint256 private constant _BITPOS_NUMBER_BURNED = 128;\n\n // The bit position of `aux` in packed address data.\n uint256 private constant _BITPOS_AUX = 192;\n\n // Mask of all 256 bits in packed address data except the 64 bits for `aux`.\n uint256 private constant _BITMASK_AUX_COMPLEMENT = (1 << 192) - 1;\n\n // The bit position of `startTimestamp` in packed ownership.\n uint256 private constant _BITPOS_START_TIMESTAMP = 160;\n\n // The bit mask of the `burned` bit in packed ownership.\n uint256 private constant _BITMASK_BURNED = 1 << 224;\n\n // The bit position of the `nextInitialized` bit in packed ownership.\n uint256 private constant _BITPOS_NEXT_INITIALIZED = 225;\n\n // The bit mask of the `nextInitialized` bit in packed ownership.\n uint256 private constant _BITMASK_NEXT_INITIALIZED = 1 << 225;\n\n // The bit position of `extraData` in packed ownership.\n uint256 private constant _BITPOS_EXTRA_DATA = 232;\n\n // Mask of all 256 bits in a packed ownership except the 24 bits for `extraData`.\n uint256 private constant _BITMASK_EXTRA_DATA_COMPLEMENT = (1 << 232) - 1;\n\n // The mask of the lower 160 bits for addresses.\n uint256 private constant _BITMASK_ADDRESS = (1 << 160) - 1;\n\n // The maximum `quantity` that can be minted with {_mintERC2309}.\n // This limit is to prevent overflows on the address data entries.\n // For a limit of 5000, a total of 3.689e15 calls to {_mintERC2309}\n // is required to cause an overflow, which is unrealistic.\n uint256 private constant _MAX_MINT_ERC2309_QUANTITY_LIMIT = 5000;\n\n // The `Transfer` event signature is given by:\n // `keccak256(bytes(\"Transfer(address,address,uint256)\"))`.\n bytes32 private constant _TRANSFER_EVENT_SIGNATURE =\n 0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef;\n\n // =============================================================\n // STORAGE\n // =============================================================\n\n // The next token ID to be minted.\n uint256 private _currentIndex;\n\n // The number of tokens burned.\n uint256 private _burnCounter;\n\n // Token name\n string private _name;\n\n // Token symbol\n string private _symbol;\n\n // Mapping from token ID to ownership details\n // An empty struct value does not necessarily mean the token is unowned.\n // See {_packedOwnershipOf} implementation for details.\n //\n // Bits Layout:\n // - [0..159] `addr`\n // - [160..223] `startTimestamp`\n // - [224] `burned`\n // - [225] `nextInitialized`\n // - [232..255] `extraData`\n mapping(uint256 => uint256) private _packedOwnerships;\n\n // Mapping owner address to address data.\n //\n // Bits Layout:\n // - [0..63] `balance`\n // - [64..127] `numberMinted`\n // - [128..191] `numberBurned`\n // - [192..255] `aux`\n mapping(address => uint256) private _packedAddressData;\n\n // Mapping from token ID to approved address.\n mapping(uint256 => TokenApprovalRef) private _tokenApprovals;\n\n // Mapping from owner to operator approvals\n mapping(address => mapping(address => bool)) private _operatorApprovals;\n\n // =============================================================\n // CONSTRUCTOR\n // =============================================================\n\n constructor(string memory name_, string memory symbol_) {\n _name = name_;\n _symbol = symbol_;\n _currentIndex = _startTokenId();\n }\n\n // =============================================================\n // TOKEN COUNTING OPERATIONS\n // =============================================================\n\n /**\n * @dev Returns the starting token ID.\n * To change the starting token ID, please override this function.\n */\n function _startTokenId() internal view virtual returns (uint256) {\n return 0;\n }\n\n /**\n * @dev Returns the next token ID to be minted.\n */\n function _nextTokenId() internal view virtual returns (uint256) {\n return _currentIndex;\n }\n\n /**\n * @dev Returns the total number of tokens in existence.\n * Burned tokens will reduce the count.\n * To get the total number of tokens minted, please see {_totalMinted}.\n */\n function totalSupply() public view virtual override returns (uint256) {\n // Counter underflow is impossible as _burnCounter cannot be incremented\n // more than `_currentIndex - _startTokenId()` times.\n unchecked {\n return _currentIndex - _burnCounter - _startTokenId();\n }\n }\n\n /**\n * @dev Returns the total amount of tokens minted in the contract.\n */\n function _totalMinted() internal view virtual returns (uint256) {\n // Counter underflow is impossible as `_currentIndex` does not decrement,\n // and it is initialized to `_startTokenId()`.\n unchecked {\n return _currentIndex - _startTokenId();\n }\n }\n\n /**\n * @dev Returns the total number of tokens burned.\n */\n function _totalBurned() internal view virtual returns (uint256) {\n return _burnCounter;\n }\n\n // =============================================================\n // ADDRESS DATA OPERATIONS\n // =============================================================\n\n /**\n * @dev Returns the number of tokens in `owner`'s account.\n */\n function balanceOf(address owner) public view virtual override returns (uint256) {\n if (owner == address(0)) revert BalanceQueryForZeroAddress();\n return _packedAddressData[owner] & _BITMASK_ADDRESS_DATA_ENTRY;\n }\n\n /**\n * Returns the number of tokens minted by `owner`.\n */\n function _numberMinted(address owner) internal view returns (uint256) {\n return (_packedAddressData[owner] >> _BITPOS_NUMBER_MINTED) & _BITMASK_ADDRESS_DATA_ENTRY;\n }\n\n /**\n * Returns the number of tokens burned by or on behalf of `owner`.\n */\n function _numberBurned(address owner) internal view returns (uint256) {\n return (_packedAddressData[owner] >> _BITPOS_NUMBER_BURNED) & _BITMASK_ADDRESS_DATA_ENTRY;\n }\n\n /**\n * Returns the auxiliary data for `owner`. (e.g. number of whitelist mint slots used).\n */\n function _getAux(address owner) internal view returns (uint64) {\n return uint64(_packedAddressData[owner] >> _BITPOS_AUX);\n }\n\n /**\n * Sets the auxiliary data for `owner`. (e.g. number of whitelist mint slots used).\n * If there are multiple variables, please pack them into a uint64.\n */\n function _setAux(address owner, uint64 aux) internal virtual {\n uint256 packed = _packedAddressData[owner];\n uint256 auxCasted;\n // Cast `aux` with assembly to avoid redundant masking.\n assembly {\n auxCasted := aux\n }\n packed = (packed & _BITMASK_AUX_COMPLEMENT) | (auxCasted << _BITPOS_AUX);\n _packedAddressData[owner] = packed;\n }\n\n // =============================================================\n // IERC165\n // =============================================================\n\n /**\n * @dev Returns true if this contract implements the interface defined by\n * `interfaceId`. See the corresponding\n * [EIP section](https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified)\n * to learn more about how these ids are created.\n *\n * This function call must use less than 30000 gas.\n */\n function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {\n // The interface IDs are constants representing the first 4 bytes\n // of the XOR of all function selectors in the interface.\n // See: [ERC165](https://eips.ethereum.org/EIPS/eip-165)\n // (e.g. `bytes4(i.functionA.selector ^ i.functionB.selector ^ ...)`)\n return\n interfaceId == 0x01ffc9a7 || // ERC165 interface ID for ERC165.\n interfaceId == 0x80ac58cd || // ERC165 interface ID for ERC721.\n interfaceId == 0x5b5e139f; // ERC165 interface ID for ERC721Metadata.\n }\n\n // =============================================================\n // IERC721Metadata\n // =============================================================\n\n /**\n * @dev Returns the token collection name.\n */\n function name() public view virtual override returns (string memory) {\n return _name;\n }\n\n /**\n * @dev Returns the token collection symbol.\n */\n function symbol() public view virtual override returns (string memory) {\n return _symbol;\n }\n\n /**\n * @dev Returns the Uniform Resource Identifier (URI) for `tokenId` token.\n */\n function tokenURI(uint256 tokenId) public view virtual override returns (string memory) {\n if (!_exists(tokenId)) revert URIQueryForNonexistentToken();\n\n string memory baseURI = _baseURI();\n return bytes(baseURI).length != 0 ? string(abi.encodePacked(baseURI, _toString(tokenId))) : '';\n }\n\n /**\n * @dev Base URI for computing {tokenURI}. If set, the resulting URI for each\n * token will be the concatenation of the `baseURI` and the `tokenId`. Empty\n * by default, it can be overridden in child contracts.\n */\n function _baseURI() internal view virtual returns (string memory) {\n return '';\n }\n\n // =============================================================\n // OWNERSHIPS OPERATIONS\n // =============================================================\n\n /**\n * @dev Returns the owner of the `tokenId` token.\n *\n * Requirements:\n *\n * - `tokenId` must exist.\n */\n function ownerOf(uint256 tokenId) public view virtual override returns (address) {\n return address(uint160(_packedOwnershipOf(tokenId)));\n }\n\n /**\n * @dev Gas spent here starts off proportional to the maximum mint batch size.\n * It gradually moves to O(1) as tokens get transferred around over time.\n */\n function _ownershipOf(uint256 tokenId) internal view virtual returns (TokenOwnership memory) {\n return _unpackedOwnership(_packedOwnershipOf(tokenId));\n }\n\n /**\n * @dev Returns the unpacked `TokenOwnership` struct at `index`.\n */\n function _ownershipAt(uint256 index) internal view virtual returns (TokenOwnership memory) {\n return _unpackedOwnership(_packedOwnerships[index]);\n }\n\n /**\n * @dev Initializes the ownership slot minted at `index` for efficiency purposes.\n */\n function _initializeOwnershipAt(uint256 index) internal virtual {\n if (_packedOwnerships[index] == 0) {\n _packedOwnerships[index] = _packedOwnershipOf(index);\n }\n }\n\n /**\n * Returns the packed ownership data of `tokenId`.\n */\n function _packedOwnershipOf(uint256 tokenId) private view returns (uint256) {\n uint256 curr = tokenId;\n\n unchecked {\n if (_startTokenId() <= curr)\n if (curr < _currentIndex) {\n uint256 packed = _packedOwnerships[curr];\n // If not burned.\n if (packed & _BITMASK_BURNED == 0) {\n // Invariant:\n // There will always be an initialized ownership slot\n // (i.e. `ownership.addr != address(0) && ownership.burned == false`)\n // before an unintialized ownership slot\n // (i.e. `ownership.addr == address(0) && ownership.burned == false`)\n // Hence, `curr` will not underflow.\n //\n // We can directly compare the packed value.\n // If the address is zero, packed will be zero.\n while (packed == 0) {\n packed = _packedOwnerships[--curr];\n }\n return packed;\n }\n }\n }\n revert OwnerQueryForNonexistentToken();\n }\n\n /**\n * @dev Returns the unpacked `TokenOwnership` struct from `packed`.\n */\n function _unpackedOwnership(uint256 packed) private pure returns (TokenOwnership memory ownership) {\n ownership.addr = address(uint160(packed));\n ownership.startTimestamp = uint64(packed >> _BITPOS_START_TIMESTAMP);\n ownership.burned = packed & _BITMASK_BURNED != 0;\n ownership.extraData = uint24(packed >> _BITPOS_EXTRA_DATA);\n }\n\n /**\n * @dev Packs ownership data into a single uint256.\n */\n function _packOwnershipData(address owner, uint256 flags) private view returns (uint256 result) {\n assembly {\n // Mask `owner` to the lower 160 bits, in case the upper bits somehow aren't clean.\n owner := and(owner, _BITMASK_ADDRESS)\n // `owner | (block.timestamp << _BITPOS_START_TIMESTAMP) | flags`.\n result := or(owner, or(shl(_BITPOS_START_TIMESTAMP, timestamp()), flags))\n }\n }\n\n /**\n * @dev Returns the `nextInitialized` flag set if `quantity` equals 1.\n */\n function _nextInitializedFlag(uint256 quantity) private pure returns (uint256 result) {\n // For branchless setting of the `nextInitialized` flag.\n assembly {\n // `(quantity == 1) << _BITPOS_NEXT_INITIALIZED`.\n result := shl(_BITPOS_NEXT_INITIALIZED, eq(quantity, 1))\n }\n }\n\n // =============================================================\n // APPROVAL OPERATIONS\n // =============================================================\n\n /**\n * @dev Gives permission to `to` to transfer `tokenId` token to another account.\n * The approval is cleared when the token is transferred.\n *\n * Only a single account can be approved at a time, so approving the\n * zero address clears previous approvals.\n *\n * Requirements:\n *\n * - The caller must own the token or be an approved operator.\n * - `tokenId` must exist.\n *\n * Emits an {Approval} event.\n */\n function approve(address to, uint256 tokenId) public virtual override {\n address owner = ownerOf(tokenId);\n\n if (_msgSenderERC721A() != owner)\n if (!isApprovedForAll(owner, _msgSenderERC721A())) {\n revert ApprovalCallerNotOwnerNorApproved();\n }\n\n _tokenApprovals[tokenId].value = to;\n emit Approval(owner, to, tokenId);\n }\n\n /**\n * @dev Returns the account approved for `tokenId` token.\n *\n * Requirements:\n *\n * - `tokenId` must exist.\n */\n function getApproved(uint256 tokenId) public view virtual override returns (address) {\n if (!_exists(tokenId)) revert ApprovalQueryForNonexistentToken();\n\n return _tokenApprovals[tokenId].value;\n }\n\n /**\n * @dev Approve or remove `operator` as an operator for the caller.\n * Operators can call {transferFrom} or {safeTransferFrom}\n * for any token owned by the caller.\n *\n * Requirements:\n *\n * - The `operator` cannot be the caller.\n *\n * Emits an {ApprovalForAll} event.\n */\n function setApprovalForAll(address operator, bool approved) public virtual override {\n if (operator == _msgSenderERC721A()) revert ApproveToCaller();\n\n _operatorApprovals[_msgSenderERC721A()][operator] = approved;\n emit ApprovalForAll(_msgSenderERC721A(), operator, approved);\n }\n\n /**\n * @dev Returns if the `operator` is allowed to manage all of the assets of `owner`.\n *\n * See {setApprovalForAll}.\n */\n function isApprovedForAll(address owner, address operator) public view virtual override returns (bool) {\n return _operatorApprovals[owner][operator];\n }\n\n /**\n * @dev Returns whether `tokenId` exists.\n *\n * Tokens can be managed by their owner or approved accounts via {approve} or {setApprovalForAll}.\n *\n * Tokens start existing when they are minted. See {_mint}.\n */\n function _exists(uint256 tokenId) internal view virtual returns (bool) {\n return\n _startTokenId() <= tokenId &&\n tokenId < _currentIndex && // If within bounds,\n _packedOwnerships[tokenId] & _BITMASK_BURNED == 0; // and not burned.\n }\n\n /**\n * @dev Returns whether `msgSender` is equal to `approvedAddress` or `owner`.\n */\n function _isSenderApprovedOrOwner(\n address approvedAddress,\n address owner,\n address msgSender\n ) private pure returns (bool result) {\n assembly {\n // Mask `owner` to the lower 160 bits, in case the upper bits somehow aren't clean.\n owner := and(owner, _BITMASK_ADDRESS)\n // Mask `msgSender` to the lower 160 bits, in case the upper bits somehow aren't clean.\n msgSender := and(msgSender, _BITMASK_ADDRESS)\n // `msgSender == owner || msgSender == approvedAddress`.\n result := or(eq(msgSender, owner), eq(msgSender, approvedAddress))\n }\n }\n\n /**\n * @dev Returns the storage slot and value for the approved address of `tokenId`.\n */\n function _getApprovedSlotAndAddress(uint256 tokenId)\n private\n view\n returns (uint256 approvedAddressSlot, address approvedAddress)\n {\n TokenApprovalRef storage tokenApproval = _tokenApprovals[tokenId];\n // The following is equivalent to `approvedAddress = _tokenApprovals[tokenId]`.\n assembly {\n approvedAddressSlot := tokenApproval.slot\n approvedAddress := sload(approvedAddressSlot)\n }\n }\n\n // =============================================================\n // TRANSFER OPERATIONS\n // =============================================================\n\n /**\n * @dev Transfers `tokenId` from `from` to `to`.\n *\n * Requirements:\n *\n * - `from` cannot be the zero address.\n * - `to` cannot be the zero address.\n * - `tokenId` token must be owned by `from`.\n * - If the caller is not `from`, it must be approved to move this token\n * by either {approve} or {setApprovalForAll}.\n *\n * Emits a {Transfer} event.\n */\n function transferFrom(\n address from,\n address to,\n uint256 tokenId\n ) public virtual override {\n uint256 prevOwnershipPacked = _packedOwnershipOf(tokenId);\n\n if (address(uint160(prevOwnershipPacked)) != from) revert TransferFromIncorrectOwner();\n\n (uint256 approvedAddressSlot, address approvedAddress) = _getApprovedSlotAndAddress(tokenId);\n\n // The nested ifs save around 20+ gas over a compound boolean condition.\n if (!_isSenderApprovedOrOwner(approvedAddress, from, _msgSenderERC721A()))\n if (!isApprovedForAll(from, _msgSenderERC721A())) revert TransferCallerNotOwnerNorApproved();\n\n if (to == address(0)) revert TransferToZeroAddress();\n\n _beforeTokenTransfers(from, to, tokenId, 1);\n\n // Clear approvals from the previous owner.\n assembly {\n if approvedAddress {\n // This is equivalent to `delete _tokenApprovals[tokenId]`.\n sstore(approvedAddressSlot, 0)\n }\n }\n\n // Underflow of the sender's balance is impossible because we check for\n // ownership above and the recipient's balance can't realistically overflow.\n // Counter overflow is incredibly unrealistic as `tokenId` would have to be 2**256.\n unchecked {\n // We can directly increment and decrement the balances.\n --_packedAddressData[from]; // Updates: `balance -= 1`.\n ++_packedAddressData[to]; // Updates: `balance += 1`.\n\n // Updates:\n // - `address` to the next owner.\n // - `startTimestamp` to the timestamp of transfering.\n // - `burned` to `false`.\n // - `nextInitialized` to `true`.\n _packedOwnerships[tokenId] = _packOwnershipData(\n to,\n _BITMASK_NEXT_INITIALIZED | _nextExtraData(from, to, prevOwnershipPacked)\n );\n\n // If the next slot may not have been initialized (i.e. `nextInitialized == false`) .\n if (prevOwnershipPacked & _BITMASK_NEXT_INITIALIZED == 0) {\n uint256 nextTokenId = tokenId + 1;\n // If the next slot's address is zero and not burned (i.e. packed value is zero).\n if (_packedOwnerships[nextTokenId] == 0) {\n // If the next slot is within bounds.\n if (nextTokenId != _currentIndex) {\n // Initialize the next slot to maintain correctness for `ownerOf(tokenId + 1)`.\n _packedOwnerships[nextTokenId] = prevOwnershipPacked;\n }\n }\n }\n }\n\n emit Transfer(from, to, tokenId);\n _afterTokenTransfers(from, to, tokenId, 1);\n }\n\n /**\n * @dev Equivalent to `safeTransferFrom(from, to, tokenId, '')`.\n */\n function safeTransferFrom(\n address from,\n address to,\n uint256 tokenId\n ) public virtual override {\n safeTransferFrom(from, to, tokenId, '');\n }\n\n /**\n * @dev Safely transfers `tokenId` token from `from` to `to`.\n *\n * Requirements:\n *\n * - `from` cannot be the zero address.\n * - `to` cannot be the zero address.\n * - `tokenId` token must exist and be owned by `from`.\n * - If the caller is not `from`, it must be approved to move this token\n * by either {approve} or {setApprovalForAll}.\n * - If `to` refers to a smart contract, it must implement\n * {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.\n *\n * Emits a {Transfer} event.\n */\n function safeTransferFrom(\n address from,\n address to,\n uint256 tokenId,\n bytes memory _data\n ) public virtual override {\n transferFrom(from, to, tokenId);\n if (to.code.length != 0)\n if (!_checkContractOnERC721Received(from, to, tokenId, _data)) {\n revert TransferToNonERC721ReceiverImplementer();\n }\n }\n\n /**\n * @dev Hook that is called before a set of serially-ordered token IDs\n * are about to be transferred. This includes minting.\n * And also called before burning one token.\n *\n * `startTokenId` - the first token ID to be transferred.\n * `quantity` - the amount to be transferred.\n *\n * Calling conditions:\n *\n * - When `from` and `to` are both non-zero, `from`'s `tokenId` will be\n * transferred to `to`.\n * - When `from` is zero, `tokenId` will be minted for `to`.\n * - When `to` is zero, `tokenId` will be burned by `from`.\n * - `from` and `to` are never both zero.\n */\n function _beforeTokenTransfers(\n address from,\n address to,\n uint256 startTokenId,\n uint256 quantity\n ) internal virtual {}\n\n /**\n * @dev Hook that is called after a set of serially-ordered token IDs\n * have been transferred. This includes minting.\n * And also called after one token has been burned.\n *\n * `startTokenId` - the first token ID to be transferred.\n * `quantity` - the amount to be transferred.\n *\n * Calling conditions:\n *\n * - When `from` and `to` are both non-zero, `from`'s `tokenId` has been\n * transferred to `to`.\n * - When `from` is zero, `tokenId` has been minted for `to`.\n * - When `to` is zero, `tokenId` has been burned by `from`.\n * - `from` and `to` are never both zero.\n */\n function _afterTokenTransfers(\n address from,\n address to,\n uint256 startTokenId,\n uint256 quantity\n ) internal virtual {}\n\n /**\n * @dev Private function to invoke {IERC721Receiver-onERC721Received} on a target contract.\n *\n * `from` - Previous owner of the given token ID.\n * `to` - Target address that will receive the token.\n * `tokenId` - Token ID to be transferred.\n * `_data` - Optional data to send along with the call.\n *\n * Returns whether the call correctly returned the expected magic value.\n */\n function _checkContractOnERC721Received(\n address from,\n address to,\n uint256 tokenId,\n bytes memory _data\n ) private returns (bool) {\n try ERC721A__IERC721Receiver(to).onERC721Received(_msgSenderERC721A(), from, tokenId, _data) returns (\n bytes4 retval\n ) {\n return retval == ERC721A__IERC721Receiver(to).onERC721Received.selector;\n } catch (bytes memory reason) {\n if (reason.length == 0) {\n revert TransferToNonERC721ReceiverImplementer();\n } else {\n assembly {\n revert(add(32, reason), mload(reason))\n }\n }\n }\n }\n\n // =============================================================\n // MINT OPERATIONS\n // =============================================================\n\n /**\n * @dev Mints `quantity` tokens and transfers them to `to`.\n *\n * Requirements:\n *\n * - `to` cannot be the zero address.\n * - `quantity` must be greater than 0.\n *\n * Emits a {Transfer} event for each mint.\n */\n function _mint(address to, uint256 quantity) internal virtual {\n uint256 startTokenId = _currentIndex;\n if (quantity == 0) revert MintZeroQuantity();\n\n _beforeTokenTransfers(address(0), to, startTokenId, quantity);\n\n // Overflows are incredibly unrealistic.\n // `balance` and `numberMinted` have a maximum limit of 2**64.\n // `tokenId` has a maximum limit of 2**256.\n unchecked {\n // Updates:\n // - `balance += quantity`.\n // - `numberMinted += quantity`.\n //\n // We can directly add to the `balance` and `numberMinted`.\n _packedAddressData[to] += quantity * ((1 << _BITPOS_NUMBER_MINTED) | 1);\n\n // Updates:\n // - `address` to the owner.\n // - `startTimestamp` to the timestamp of minting.\n // - `burned` to `false`.\n // - `nextInitialized` to `quantity == 1`.\n _packedOwnerships[startTokenId] = _packOwnershipData(\n to,\n _nextInitializedFlag(quantity) | _nextExtraData(address(0), to, 0)\n );\n\n uint256 toMasked;\n uint256 end = startTokenId + quantity;\n\n // Use assembly to loop and emit the `Transfer` event for gas savings.\n assembly {\n // Mask `to` to the lower 160 bits, in case the upper bits somehow aren't clean.\n toMasked := and(to, _BITMASK_ADDRESS)\n // Emit the `Transfer` event.\n log4(\n 0, // Start of data (0, since no data).\n 0, // End of data (0, since no data).\n _TRANSFER_EVENT_SIGNATURE, // Signature.\n 0, // `address(0)`.\n toMasked, // `to`.\n startTokenId // `tokenId`.\n )\n\n for {\n let tokenId := add(startTokenId, 1)\n } iszero(eq(tokenId, end)) {\n tokenId := add(tokenId, 1)\n } {\n // Emit the `Transfer` event. Similar to above.\n log4(0, 0, _TRANSFER_EVENT_SIGNATURE, 0, toMasked, tokenId)\n }\n }\n if (toMasked == 0) revert MintToZeroAddress();\n\n _currentIndex = end;\n }\n _afterTokenTransfers(address(0), to, startTokenId, quantity);\n }\n\n /**\n * @dev Mints `quantity` tokens and transfers them to `to`.\n *\n * This function is intended for efficient minting only during contract creation.\n *\n * It emits only one {ConsecutiveTransfer} as defined in\n * [ERC2309](https://eips.ethereum.org/EIPS/eip-2309),\n * instead of a sequence of {Transfer} event(s).\n *\n * Calling this function outside of contract creation WILL make your contract\n * non-compliant with the ERC721 standard.\n * For full ERC721 compliance, substituting ERC721 {Transfer} event(s) with the ERC2309\n * {ConsecutiveTransfer} event is only permissible during contract creation.\n *\n * Requirements:\n *\n * - `to` cannot be the zero address.\n * - `quantity` must be greater than 0.\n *\n * Emits a {ConsecutiveTransfer} event.\n */\n function _mintERC2309(address to, uint256 quantity) internal virtual {\n uint256 startTokenId = _currentIndex;\n if (to == address(0)) revert MintToZeroAddress();\n if (quantity == 0) revert MintZeroQuantity();\n if (quantity > _MAX_MINT_ERC2309_QUANTITY_LIMIT) revert MintERC2309QuantityExceedsLimit();\n\n _beforeTokenTransfers(address(0), to, startTokenId, quantity);\n\n // Overflows are unrealistic due to the above check for `quantity` to be below the limit.\n unchecked {\n // Updates:\n // - `balance += quantity`.\n // - `numberMinted += quantity`.\n //\n // We can directly add to the `balance` and `numberMinted`.\n _packedAddressData[to] += quantity * ((1 << _BITPOS_NUMBER_MINTED) | 1);\n\n // Updates:\n // - `address` to the owner.\n // - `startTimestamp` to the timestamp of minting.\n // - `burned` to `false`.\n // - `nextInitialized` to `quantity == 1`.\n _packedOwnerships[startTokenId] = _packOwnershipData(\n to,\n _nextInitializedFlag(quantity) | _nextExtraData(address(0), to, 0)\n );\n\n emit ConsecutiveTransfer(startTokenId, startTokenId + quantity - 1, address(0), to);\n\n _currentIndex = startTokenId + quantity;\n }\n _afterTokenTransfers(address(0), to, startTokenId, quantity);\n }\n\n /**\n * @dev Safely mints `quantity` tokens and transfers them to `to`.\n *\n * Requirements:\n *\n * - If `to` refers to a smart contract, it must implement\n * {IERC721Receiver-onERC721Received}, which is called for each safe transfer.\n * - `quantity` must be greater than 0.\n *\n * See {_mint}.\n *\n * Emits a {Transfer} event for each mint.\n */\n function _safeMint(\n address to,\n uint256 quantity,\n bytes memory _data\n ) internal virtual {\n _mint(to, quantity);\n\n unchecked {\n if (to.code.length != 0) {\n uint256 end = _currentIndex;\n uint256 index = end - quantity;\n do {\n if (!_checkContractOnERC721Received(address(0), to, index++, _data)) {\n revert TransferToNonERC721ReceiverImplementer();\n }\n } while (index < end);\n // Reentrancy protection.\n if (_currentIndex != end) revert();\n }\n }\n }\n\n /**\n * @dev Equivalent to `_safeMint(to, quantity, '')`.\n */\n function _safeMint(address to, uint256 quantity) internal virtual {\n _safeMint(to, quantity, '');\n }\n\n // =============================================================\n // BURN OPERATIONS\n // =============================================================\n\n /**\n * @dev Equivalent to `_burn(tokenId, false)`.\n */\n function _burn(uint256 tokenId) internal virtual {\n _burn(tokenId, false);\n }\n\n /**\n * @dev Destroys `tokenId`.\n * The approval is cleared when the token is burned.\n *\n * Requirements:\n *\n * - `tokenId` must exist.\n *\n * Emits a {Transfer} event.\n */\n function _burn(uint256 tokenId, bool approvalCheck) internal virtual {\n uint256 prevOwnershipPacked = _packedOwnershipOf(tokenId);\n\n address from = address(uint160(prevOwnershipPacked));\n\n (uint256 approvedAddressSlot, address approvedAddress) = _getApprovedSlotAndAddress(tokenId);\n\n if (approvalCheck) {\n // The nested ifs save around 20+ gas over a compound boolean condition.\n if (!_isSenderApprovedOrOwner(approvedAddress, from, _msgSenderERC721A()))\n if (!isApprovedForAll(from, _msgSenderERC721A())) revert TransferCallerNotOwnerNorApproved();\n }\n\n _beforeTokenTransfers(from, address(0), tokenId, 1);\n\n // Clear approvals from the previous owner.\n assembly {\n if approvedAddress {\n // This is equivalent to `delete _tokenApprovals[tokenId]`.\n sstore(approvedAddressSlot, 0)\n }\n }\n\n // Underflow of the sender's balance is impossible because we check for\n // ownership above and the recipient's balance can't realistically overflow.\n // Counter overflow is incredibly unrealistic as `tokenId` would have to be 2**256.\n unchecked {\n // Updates:\n // - `balance -= 1`.\n // - `numberBurned += 1`.\n //\n // We can directly decrement the balance, and increment the number burned.\n // This is equivalent to `packed -= 1; packed += 1 << _BITPOS_NUMBER_BURNED;`.\n _packedAddressData[from] += (1 << _BITPOS_NUMBER_BURNED) - 1;\n\n // Updates:\n // - `address` to the last owner.\n // - `startTimestamp` to the timestamp of burning.\n // - `burned` to `true`.\n // - `nextInitialized` to `true`.\n _packedOwnerships[tokenId] = _packOwnershipData(\n from,\n (_BITMASK_BURNED | _BITMASK_NEXT_INITIALIZED) | _nextExtraData(from, address(0), prevOwnershipPacked)\n );\n\n // If the next slot may not have been initialized (i.e. `nextInitialized == false`) .\n if (prevOwnershipPacked & _BITMASK_NEXT_INITIALIZED == 0) {\n uint256 nextTokenId = tokenId + 1;\n // If the next slot's address is zero and not burned (i.e. packed value is zero).\n if (_packedOwnerships[nextTokenId] == 0) {\n // If the next slot is within bounds.\n if (nextTokenId != _currentIndex) {\n // Initialize the next slot to maintain correctness for `ownerOf(tokenId + 1)`.\n _packedOwnerships[nextTokenId] = prevOwnershipPacked;\n }\n }\n }\n }\n\n emit Transfer(from, address(0), tokenId);\n _afterTokenTransfers(from, address(0), tokenId, 1);\n\n // Overflow not possible, as _burnCounter cannot be exceed _currentIndex times.\n unchecked {\n _burnCounter++;\n }\n }\n\n // =============================================================\n // EXTRA DATA OPERATIONS\n // =============================================================\n\n /**\n * @dev Directly sets the extra data for the ownership data `index`.\n */\n function _setExtraDataAt(uint256 index, uint24 extraData) internal virtual {\n uint256 packed = _packedOwnerships[index];\n if (packed == 0) revert OwnershipNotInitializedForExtraData();\n uint256 extraDataCasted;\n // Cast `extraData` with assembly to avoid redundant masking.\n assembly {\n extraDataCasted := extraData\n }\n packed = (packed & _BITMASK_EXTRA_DATA_COMPLEMENT) | (extraDataCasted << _BITPOS_EXTRA_DATA);\n _packedOwnerships[index] = packed;\n }\n\n /**\n * @dev Called during each token transfer to set the 24bit `extraData` field.\n * Intended to be overridden by the cosumer contract.\n *\n * `previousExtraData` - the value of `extraData` before transfer.\n *\n * Calling conditions:\n *\n * - When `from` and `to` are both non-zero, `from`'s `tokenId` will be\n * transferred to `to`.\n * - When `from` is zero, `tokenId` will be minted for `to`.\n * - When `to` is zero, `tokenId` will be burned by `from`.\n * - `from` and `to` are never both zero.\n */\n function _extraData(\n address from,\n address to,\n uint24 previousExtraData\n ) internal view virtual returns (uint24) {}\n\n /**\n * @dev Returns the next extra data for the packed ownership data.\n * The returned result is shifted into position.\n */\n function _nextExtraData(\n address from,\n address to,\n uint256 prevOwnershipPacked\n ) private view returns (uint256) {\n uint24 extraData = uint24(prevOwnershipPacked >> _BITPOS_EXTRA_DATA);\n return uint256(_extraData(from, to, extraData)) << _BITPOS_EXTRA_DATA;\n }\n\n // =============================================================\n // OTHER OPERATIONS\n // =============================================================\n\n /**\n * @dev Returns the message sender (defaults to `msg.sender`).\n *\n * If you are writing GSN compatible contracts, you need to override this function.\n */\n function _msgSenderERC721A() internal view virtual returns (address) {\n return msg.sender;\n }\n\n /**\n * @dev Converts a uint256 to its ASCII string decimal representation.\n */\n function _toString(uint256 value) internal pure virtual returns (string memory ptr) {\n assembly {\n // The maximum value of a uint256 contains 78 digits (1 byte per digit),\n // but we allocate 128 bytes to keep the free memory pointer 32-byte word aliged.\n // We will need 1 32-byte word to store the length,\n // and 3 32-byte words to store a maximum of 78 digits. Total: 32 + 3 * 32 = 128.\n ptr := add(mload(0x40), 128)\n // Update the free memory pointer to allocate.\n mstore(0x40, ptr)\n\n // Cache the end of the memory to calculate the length later.\n let end := ptr\n\n // We write the string from the rightmost digit to the leftmost digit.\n // The following is essentially a do-while loop that also handles the zero case.\n // Costs a bit more than early returning for the zero case,\n // but cheaper in terms of deployment and overall runtime costs.\n for {\n // Initialize and perform the first pass without check.\n let temp := value\n // Move the pointer 1 byte leftwards to point to an empty character slot.\n ptr := sub(ptr, 1)\n // Write the character to the pointer.\n // The ASCII index of the '0' character is 48.\n mstore8(ptr, add(48, mod(temp, 10)))\n temp := div(temp, 10)\n } temp {\n // Keep dividing `temp` until zero.\n temp := div(temp, 10)\n } {\n // Body of the for loop.\n ptr := sub(ptr, 1)\n mstore8(ptr, add(48, mod(temp, 10)))\n }\n\n let length := sub(end, ptr)\n // Move the pointer 32 bytes leftwards to make room for the length.\n ptr := sub(ptr, 32)\n // Store the length.\n mstore(ptr, length)\n }\n }\n}\n"
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