Permalink
331 lines (300 sloc) 11.4 KB
pragma solidity ^0.4.24;
import "./IERC721.sol";
import "./IERC721Receiver.sol";
import "../../math/SafeMath.sol";
import "../../utils/Address.sol";
import "../../introspection/ERC165.sol";
/**
* @title ERC721 Non-Fungible Token Standard basic implementation
* @dev see https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
*/
contract ERC721 is ERC165, IERC721 {
using SafeMath for uint256;
using Address for address;
// Equals to `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`
// which can be also obtained as `IERC721Receiver(0).onERC721Received.selector`
bytes4 private constant _ERC721_RECEIVED = 0x150b7a02;
// 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 => uint256) private _ownedTokensCount;
// Mapping from owner to operator approvals
mapping (address => mapping (address => bool)) private _operatorApprovals;
bytes4 private constant _InterfaceId_ERC721 = 0x80ac58cd;
/*
* 0x80ac58cd ===
* bytes4(keccak256('balanceOf(address)')) ^
* bytes4(keccak256('ownerOf(uint256)')) ^
* bytes4(keccak256('approve(address,uint256)')) ^
* bytes4(keccak256('getApproved(uint256)')) ^
* bytes4(keccak256('setApprovalForAll(address,bool)')) ^
* bytes4(keccak256('isApprovedForAll(address,address)')) ^
* bytes4(keccak256('transferFrom(address,address,uint256)')) ^
* bytes4(keccak256('safeTransferFrom(address,address,uint256)')) ^
* bytes4(keccak256('safeTransferFrom(address,address,uint256,bytes)'))
*/
constructor()
public
{
// register the supported interfaces to conform to ERC721 via ERC165
_registerInterface(_InterfaceId_ERC721);
}
/**
* @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));
return _ownedTokensCount[owner];
}
/**
* @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
*/
function ownerOf(uint256 tokenId) public view returns (address) {
address owner = _tokenOwner[tokenId];
require(owner != address(0));
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);
require(msg.sender == owner || isApprovedForAll(owner, msg.sender));
_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));
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 != msg.sender);
_operatorApprovals[msg.sender][to] = approved;
emit ApprovalForAll(msg.sender, 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
{
require(_isApprovedOrOwner(msg.sender, tokenId));
require(to != address(0));
_clearApproval(from, tokenId);
_removeTokenFrom(from, tokenId);
_addTokenTo(to, tokenId);
emit Transfer(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
*/
function safeTransferFrom(
address from,
address to,
uint256 tokenId
)
public
{
// solium-disable-next-line arg-overflow
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);
// solium-disable-next-line arg-overflow
require(_checkOnERC721Received(from, to, tokenId, _data));
}
/**
* @dev Returns whether the specified token exists
* @param tokenId uint256 ID of the token to query the existence of
* @return 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)
{
address owner = ownerOf(tokenId);
// Disable solium check because of
// https://github.com/duaraghav8/Solium/issues/175
// solium-disable-next-line operator-whitespace
return (
spender == owner ||
getApproved(tokenId) == spender ||
isApprovedForAll(owner, spender)
);
}
/**
* @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
*/
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
*/
function _burn(address owner, uint256 tokenId) internal {
_clearApproval(owner, tokenId);
_removeTokenFrom(owner, tokenId);
emit Transfer(owner, address(0), tokenId);
}
/**
* @dev Internal function to add a token ID to the list of a given address
* Note that this function is left internal to make ERC721Enumerable possible, but is not
* intended to be called by custom derived contracts: in particular, it emits no Transfer event.
* @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 _addTokenTo(address to, uint256 tokenId) internal {
require(_tokenOwner[tokenId] == address(0));
_tokenOwner[tokenId] = to;
_ownedTokensCount[to] = _ownedTokensCount[to].add(1);
}
/**
* @dev Internal function to remove a token ID from the list of a given address
* Note that this function is left internal to make ERC721Enumerable possible, but is not
* intended to be called by custom derived contracts: in particular, it emits no Transfer event,
* and doesn't clear approvals.
* @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 _removeTokenFrom(address from, uint256 tokenId) internal {
require(ownerOf(tokenId) == from);
_ownedTokensCount[from] = _ownedTokensCount[from].sub(1);
_tokenOwner[tokenId] = address(0);
}
/**
* @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 _checkOnERC721Received(
address from,
address to,
uint256 tokenId,
bytes _data
)
internal
returns (bool)
{
if (!to.isContract()) {
return true;
}
bytes4 retval = IERC721Receiver(to).onERC721Received(
msg.sender, from, tokenId, _data);
return (retval == _ERC721_RECEIVED);
}
/**
* @dev Private 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
*/
function _clearApproval(address owner, uint256 tokenId) private {
require(ownerOf(tokenId) == owner);
if (_tokenApprovals[tokenId] != address(0)) {
_tokenApprovals[tokenId] = address(0);
}
}
}