PNC-721
// SPDX-License-Identifier: MIT // // ERC-721 Non-Fungible Token implementation based on the OpenZeppelin Lib //
pragma solidity ^0.6.2;
Abstract contract Context
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
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 '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;
}
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 doesn't 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
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
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 value's 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 'swap and pop').
// 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 'if' 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
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 key's 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 key's 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 'swap and pop').
// 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 'if' 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
library Strings
{
function toString(uint256 value) internal pure returns (string memory) {
// Inspired by OraclizeAPI's 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 IERC165
Interface IERC165
{
function supportsInterface(bytes4 interfaceId) external view returns (bool);
}
Interface IERC721 is IERC165
{
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;
}
interface IERC721Metadata is IERC721 { function name() external view returns (string memory);
function symbol() external view returns (string memory);
function tokenURI(uint256 tokenId) external view returns (string memory);
}
interface IERC721Enumerable is IERC721
{
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 IERC721Receiver { function onERC721Received(address operator, address from, uint256 tokenId, bytes calldata data) external returns (bytes4);
}Contract ERC165
Contract ERC165 is IERC165
{
bytes4 private constant _INTERFACE_ID_ERC165 = 0x01ffc9a7;
mapping(bytes4 => bool) private _supportedInterfaces;
constructor () internal {
_registerInterface(_INTERFACE_ID_ERC165);
}
function supportsInterface(bytes4 interfaceId) public view override returns (bool) {
return _supportedInterfaces[interfaceId];
}
function _registerInterface(bytes4 interfaceId) internal virtual {
require(interfaceId != 0xffffffff, "ERC165: invalid interface id");
_supportedInterfaces[interfaceId] = true;
}
}Panda Network Token contract ERC721
// ERC stands for "Pando Network Token", ERC-721 is the non-fungible token // standard on the Pando network, similar to the ERC-721 standard on Pando Network Token contract ERC721 is Context, ERC165, IERC721, IERC721Metadata, IERC721Enumerable
{
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 _ERC721_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_ERC721 = 0x80ac58cd;
bytes4 private constant _INTERFACE_ID_ERC721_METADATA = 0x5b5e139f;
bytes4 private constant _INTERFACE_ID_ERC721_ENUMERABLE = 0x780e9d63;
constructor (string memory name, string memory symbol) public
{
_name = name;
_symbol = symbol;
_registerInterface(_INTERFACE_ID_ERC721);
_registerInterface(_INTERFACE_ID_ERC721_METADATA);
_registerInterface(_INTERFACE_ID_ERC721_ENUMERABLE);
}
function balanceOf(address owner) public view override returns (uint256) {
require(owner != address(0), "ERC721: balance query for the zero address");
return _holderTokens[owner].length();
}
function ownerOf(uint256 tokenId) public view override returns (address) {
return _tokenOwners.get(tokenId, "ERC721: 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), "ERC721Metadata: 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, "ERC721: approval to current owner");
require(_msgSender() == owner || isApprovedForAll(owner, _msgSender()),
"ERC721: approve caller is not owner nor approved for all");
_approve(to, tokenId);
}
function getApproved(uint256 tokenId) public view override returns (address) {
require(_exists(tokenId), "ERC721: approved query for nonexistent token");
return _tokenApprovals[tokenId];
}
function setApprovalForAll(address operator, bool approved) public virtual override
{
require(operator != _msgSender(), "ERC721: 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), "ERC721: 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), "ERC721: 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(_checkOnERC721Received(from, to, tokenId, _data), "ERC721: transfer to non ERC721Receiver 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), "ERC721: operator query for nonexistent token");
address owner = ownerOf(tokenId);
return (spender == owner || getApproved(tokenId) == spender || isApprovedForAll(owner, spender));
}
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(_checkOnERC721Received(address(0), to, tokenId, _data), "ERC721: transfer to non ERC721Receiver implementer");
}
function _mint(address to, uint256 tokenId) internal virtual {
require(to != address(0), "ERC721: mint to the zero address");
require(!_exists(tokenId), "ERC721: 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, "ERC721: transfer of token that is not own");
require(to != address(0), "ERC721: 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), "ERC721Metadata: URI set of nonexistent token");
_tokenURIs[tokenId] = _tokenURI;
}
function _setBaseURI(string memory baseURI_) internal virtual {
_baseURI = baseURI_;
}
function _checkOnERC721Received(address from, address to, uint256 tokenId, bytes memory _data)
private returns (bool)
{
if (!to.isContract()) {
return true;
}
bytes memory returndata = to.functionCall(abi.encodeWithSelector(
IERC721Receiver(to).onERC721Received.selector,
_msgSender(),
from,
tokenId,
_data
), "ERC721: transfer to non ERC721Receiver implementer");
bytes4 retval = abi.decode(returndata, (bytes4));
return (retval == _ERC721_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 ERC721 { constructor (string memory name, string memory symbol, string memory uri) public ERC721(name, symbol) { uint mintIndex = totalSupply(); _safeMint(msg.sender, mintIndex); _setTokenURI(mintIndex, uri); } }
Last updated