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ERC721BasicToken.sol
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ERC721BasicToken.sol
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pragma solidity ^0.4.24;
import "./ERC721Basic.sol";
import "./ERC721Receiver.sol";
import "./SafeMath.sol";
import "./AddressUtils.sol";
import "./SupportsInterfaceWithLookup.sol";
/**
* @title ERC721 Non-Fungible Token Standard basic implementation
*/
contract ERC721BasicToken is SupportsInterfaceWithLookup, ERC721Basic {
using SafeMath for uint256;
using AddressUtils for address;
// Equals to `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`
// which can be also obtained as `ERC721Receiver(0).onERC721Received.selector`
bytes4 private constant ERC721_RECEIVED = 0x150b7a02;
// Mapping from token ID to owner
mapping (uint256 => address) internal tokenOwner;
// Mapping from token ID to approved address
mapping (uint256 => address) internal tokenApprovals;
// Mapping from owner to number of owned token
mapping (address => uint256) internal ownedTokensCount;
// Mapping from owner to operator approvals
mapping (address => mapping (address => bool)) internal operatorApprovals;
constructor()
public
{
// register the supported interfaces to conform to ERC721 via ERC165
_registerInterface(InterfaceId_ERC721);
_registerInterface(InterfaceId_ERC721Exists);
}
/**
* @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
*/
// number 1
function balanceOf(address _owner) public view returns (uint256) {
// YOUR CODE HERE
}
/**
* @dev Gets the owner of the specified token ID
* @param _tokenId uint256 ID of the token to query the owner of
* @return owner address currently marked as the owner of the given token ID
*/
// number 2
//hint: the owner should be exist to return its address
function ownerOf(uint256 _tokenId) public view returns (address) {
// YOUR CODE HERE
}
/**
* @dev Returns whether the specified token exists
* @param _tokenId uint256 ID of the token to query the existence of
* @return whether the token exists
*/
// number 3
function exists(uint256 _tokenId) public view returns (bool) {
// YOUR CODE HERE
}
/**
* @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
*/
// number 4
function isApprovedForAll(
address _owner,
address _operator
)
public
view
returns (bool)
{
// YOUR CODE HERE
}
/**
* @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
*/
// number 5
// hint: the approver should be the owner or should be approved for all tokens that owned by the owner
function approve(address _to, uint256 _tokenId) public {
// YOUR CODE HERE
}
/**
* @dev Gets the approved address for a token ID, or zero if no address set
* @param _tokenId uint256 ID of the token to query the approval of
* @return address currently approved for the given token ID
*/
// number 6
function getApproved(uint256 _tokenId) public view returns (address) {
// YOUR CODE HERE
}
/**
* @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
*/
// number 7
function setApprovalForAll(address _to, bool _approved) public {
// YOUR CODE HERE
}
/**
* @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
*/
// number 8
function isApprovedOrOwner(
address _spender,
uint256 _tokenId
)
internal
view
returns (bool)
{
// YOUR CODE HERE
}
/**
* @dev Internal function to clear current approval of a given token ID
* Reverts if the given address is not indeed the owner of the token
* @param _owner owner of the token
* @param _tokenId uint256 ID of the token to be transferred
*/
// number 9
function clearApproval(address _owner, uint256 _tokenId) internal {
// YOUR CODE HERE
}
/**
* @dev Internal function to remove a token ID from the list of a given address
* @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
*/
// number 10
function removeTokenFrom(address _from, uint256 _tokenId) internal {
// YOUR CODE HERE
}
/**
* @dev Internal function to add a token ID to the list of a given address
* @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
*/
// number 11
function addTokenTo(address _to, uint256 _tokenId) internal {
// YOUR CODE HERE
}
/**
* @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
*/
// number 12
function transferFrom(
address _from,
address _to,
uint256 _tokenId
)
public
{
// YOUR CODE HERE
}
/**
* @dev Safely transfers the ownership of a given token ID to another address
* If the target address is a contract, it must implement `onERC721Received`,
* which is called upon a safe transfer, and return the magic value
* `bytes4(keccak256("onERC721Received(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 `onERC721Received`,
* which is called upon a safe transfer, and return the magic value
* `bytes4(keccak256("onERC721Received(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 _data
)
public
{
transferFrom(_from, _to, _tokenId);
require(checkAndCallSafeTransfer(_from, _to, _tokenId, _data));
}
/**
* @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 by the msg.sender
*/
// number 13
function _mint(address _to, uint256 _tokenId) internal {
require(_to != address(0));
addTokenTo(_to, _tokenId);
emit Transfer(address(0), _to, _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 by the msg.sender
*/
// number 14
function _burn(address _owner, uint256 _tokenId) internal {
clearApproval(_owner, _tokenId);
removeTokenFrom(_owner, _tokenId);
emit Transfer(_owner, address(0), _tokenId);
}
/**
* @dev Internal function to invoke `onERC721Received` on a target address
* The call is not executed if the target address is not a contract
* @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 whether the call correctly returned the expected magic value
*/
function checkAndCallSafeTransfer(
address _from,
address _to,
uint256 _tokenId,
bytes _data
)
internal
returns (bool)
{
if (!_to.isContract()) {
return true;
}
bytes4 retval = ERC721Receiver(_to).onERC721Received(
msg.sender, _from, _tokenId, _data);
return (retval == ERC721_RECEIVED);
}
}