Contract Source Code:
File 1 of 1 : CryptoArte
pragma solidity ^0.4.23;
/**
* @title ERC721 Non-Fungible Token Standard basic interface
* @dev see https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
*/
contract ERC721Basic {
event Transfer(
address indexed _from,
address indexed _to,
uint256 _tokenId
);
event Approval(
address indexed _owner,
address indexed _approved,
uint256 _tokenId
);
event ApprovalForAll(
address indexed _owner,
address indexed _operator,
bool _approved
);
function balanceOf(address _owner) public view returns (uint256 _balance);
function ownerOf(uint256 _tokenId) public view returns (address _owner);
function exists(uint256 _tokenId) public view returns (bool _exists);
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 transferFrom(address _from, address _to, uint256 _tokenId) public;
function safeTransferFrom(address _from, address _to, uint256 _tokenId)
public;
function safeTransferFrom(
address _from,
address _to,
uint256 _tokenId,
bytes _data
)
public;
}
/**
* @title ERC-721 Non-Fungible Token Standard, optional enumeration extension
* @dev See https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
*/
contract ERC721Enumerable is ERC721Basic {
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 ERC-721 Non-Fungible Token Standard, optional metadata extension
* @dev See https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
*/
contract ERC721Metadata is ERC721Basic {
function name() public view returns (string _name);
function symbol() public view returns (string _symbol);
function tokenURI(uint256 _tokenId) public view returns (string);
}
/**
* @title ERC-721 Non-Fungible Token Standard, full implementation interface
* @dev See https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
*/
contract ERC721 is ERC721Basic, ERC721Enumerable, ERC721Metadata {
}
/**
* @title ERC721 token receiver interface
* @dev Interface for any contract that wants to support safeTransfers
* from ERC721 asset contracts.
*/
contract ERC721Receiver {
/**
* @dev Magic value to be returned upon successful reception of an NFT
* Equals to `bytes4(keccak256("onERC721Received(address,uint256,bytes)"))`,
* which can be also obtained as `ERC721Receiver(0).onERC721Received.selector`
*/
bytes4 constant ERC721_RECEIVED = 0xf0b9e5ba;
/**
* @notice Handle the receipt of an NFT
* @dev The ERC721 smart contract calls this function on the recipient
* after a `safetransfer`. This function MAY throw to revert and reject the
* transfer. This function MUST use 50,000 gas or less. Return of other
* than the magic value MUST result in the transaction being reverted.
* Note: the contract address is always the message sender.
* @param _from The sending address
* @param _tokenId The NFT identifier which is being transfered
* @param _data Additional data with no specified format
* @return `bytes4(keccak256("onERC721Received(address,uint256,bytes)"))`
*/
function onERC721Received(
address _from,
uint256 _tokenId,
bytes _data
)
public
returns(bytes4);
}
/**
* @title SafeMath
* @dev Math operations with safety checks that throw on error
*/
library SafeMath {
/**
* @dev Multiplies two numbers, throws on overflow.
*/
function mul(uint256 a, uint256 b) internal pure returns (uint256 c) {
// Gas optimization: this is cheaper than asserting 'a' not being zero, but the
// benefit is lost if 'b' is also tested.
// See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
if (a == 0) {
return 0;
}
c = a * b;
assert(c / a == b);
return c;
}
/**
* @dev Integer division of two numbers, truncating the quotient.
*/
function div(uint256 a, uint256 b) internal pure returns (uint256) {
// assert(b > 0); // Solidity automatically throws when dividing by 0
// uint256 c = a / b;
// assert(a == b * c + a % b); // There is no case in which this doesn't hold
return a / b;
}
/**
* @dev Subtracts two numbers, throws on overflow (i.e. if subtrahend is greater than minuend).
*/
function sub(uint256 a, uint256 b) internal pure returns (uint256) {
assert(b <= a);
return a - b;
}
/**
* @dev Adds two numbers, throws on overflow.
*/
function add(uint256 a, uint256 b) internal pure returns (uint256 c) {
c = a + b;
assert(c >= a);
return c;
}
}
/**
* Utility library of inline functions on addresses
*/
library AddressUtils {
/**
* Returns whether the target address is a contract
* @dev This function will return false if invoked during the constructor of a contract,
* as the code is not actually created until after the constructor finishes.
* @param addr address to check
* @return whether the target address is a contract
*/
function isContract(address addr) internal view returns (bool) {
uint256 size;
// XXX Currently there is no better way to check if there is a contract in an address
// than to check the size of the code at that address.
// See https://ethereum.stackexchange.com/a/14016/36603
// for more details about how this works.
// TODO Check this again before the Serenity release, because all addresses will be
// contracts then.
// solium-disable-next-line security/no-inline-assembly
assembly { size := extcodesize(addr) }
return size > 0;
}
}
/**
* @title ERC721 Non-Fungible Token Standard basic implementation
* @dev see https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
*/
contract ERC721BasicToken is ERC721Basic {
using SafeMath for uint256;
using AddressUtils for address;
// Equals to `bytes4(keccak256("onERC721Received(address,uint256,bytes)"))`
// which can be also obtained as `ERC721Receiver(0).onERC721Received.selector`
bytes4 constant ERC721_RECEIVED = 0xf0b9e5ba;
// 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;
/**
* @dev Guarantees msg.sender is owner of the given token
* @param _tokenId uint256 ID of the token to validate its ownership belongs to msg.sender
*/
modifier onlyOwnerOf(uint256 _tokenId) {
require(ownerOf(_tokenId) == msg.sender);
_;
}
/**
* @dev Checks msg.sender can transfer a token, by being owner, approved, or operator
* @param _tokenId uint256 ID of the token to validate
*/
modifier canTransfer(uint256 _tokenId) {
require(isApprovedOrOwner(msg.sender, _tokenId));
_;
}
/**
* @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 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) public view returns (bool) {
address owner = tokenOwner[_tokenId];
return owner != address(0);
}
/**
* @dev Approves another address to transfer the given token ID
* @dev The zero address indicates there is no approved address.
* @dev There can only be one approved address per token at a given time.
* @dev 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));
if (getApproved(_tokenId) != address(0) || _to != address(0)) {
tokenApprovals[_tokenId] = _to;
emit Approval(owner, _to, _tokenId);
}
}
/**
* @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
*/
function getApproved(uint256 _tokenId) public view returns (address) {
return tokenApprovals[_tokenId];
}
/**
* @dev Sets or unsets the approval of a given operator
* @dev 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
* @dev Usage of this method is discouraged, use `safeTransferFrom` whenever possible
* @dev 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
canTransfer(_tokenId)
{
require(_from != address(0));
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
* @dev 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,uint256,bytes)"))`; otherwise,
* the transfer is reverted.
* @dev 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
canTransfer(_tokenId)
{
// solium-disable-next-line arg-overflow
safeTransferFrom(_from, _to, _tokenId, "");
}
/**
* @dev Safely transfers the ownership of a given token ID to another address
* @dev 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,uint256,bytes)"))`; otherwise,
* the transfer is reverted.
* @dev 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
canTransfer(_tokenId)
{
transferFrom(_from, _to, _tokenId);
// solium-disable-next-line arg-overflow
require(checkAndCallSafeTransfer(_from, _to, _tokenId, _data));
}
/**
* @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
* @dev 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
* @dev 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 clear current approval of a given token ID
* @dev 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) internal {
require(ownerOf(_tokenId) == _owner);
if (tokenApprovals[_tokenId] != address(0)) {
tokenApprovals[_tokenId] = address(0);
emit Approval(_owner, address(0), _tokenId);
}
}
/**
* @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
*/
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
* @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
* @dev 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(
_from, _tokenId, _data);
return (retval == ERC721_RECEIVED);
}
}
/**
* @title Full ERC721 Token
* This implementation includes all the required and some optional functionality of the ERC721 standard
* Moreover, it includes approve all functionality using operator terminology
* @dev see https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
*/
contract ERC721Token is ERC721, ERC721BasicToken {
// Token name
string internal name_;
// Token symbol
string internal symbol_;
// Mapping from owner to list of owned token IDs
mapping(address => uint256[]) internal ownedTokens;
// Mapping from token ID to index of the owner tokens list
mapping(uint256 => uint256) internal ownedTokensIndex;
// Array with all token ids, used for enumeration
uint256[] internal allTokens;
// Mapping from token id to position in the allTokens array
mapping(uint256 => uint256) internal allTokensIndex;
// Optional mapping for token URIs
mapping(uint256 => string) internal tokenURIs;
/**
* @dev Constructor function
*/
constructor(string _name, string _symbol) public {
name_ = _name;
symbol_ = _symbol;
}
/**
* @dev Gets the token name
* @return string representing the token name
*/
function name() public view returns (string) {
return name_;
}
/**
* @dev Gets the token symbol
* @return string representing the token symbol
*/
function symbol() public view returns (string) {
return symbol_;
}
/**
* @dev Returns an URI for a given token ID
* @dev Throws if the token ID does not exist. May return an empty string.
* @param _tokenId uint256 ID of the token to query
*/
function tokenURI(uint256 _tokenId) public view returns (string) {
require(exists(_tokenId));
return tokenURIs[_tokenId];
}
/**
* @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));
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
* @dev 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());
return allTokens[_index];
}
/**
* @dev Internal function to set the token URI for a given token
* @dev Reverts if the token ID does not exist
* @param _tokenId uint256 ID of the token to set its URI
* @param _uri string URI to assign
*/
function _setTokenURI(uint256 _tokenId, string _uri) internal {
require(exists(_tokenId));
tokenURIs[_tokenId] = _uri;
}
/**
* @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
*/
function addTokenTo(address _to, uint256 _tokenId) internal {
super.addTokenTo(_to, _tokenId);
uint256 length = ownedTokens[_to].length;
ownedTokens[_to].push(_tokenId);
ownedTokensIndex[_tokenId] = length;
}
/**
* @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
*/
function removeTokenFrom(address _from, uint256 _tokenId) internal {
super.removeTokenFrom(_from, _tokenId);
uint256 tokenIndex = ownedTokensIndex[_tokenId];
uint256 lastTokenIndex = ownedTokens[_from].length.sub(1);
uint256 lastToken = ownedTokens[_from][lastTokenIndex];
ownedTokens[_from][tokenIndex] = lastToken;
ownedTokens[_from][lastTokenIndex] = 0;
// Note that this will handle single-element arrays. In that case, both tokenIndex and lastTokenIndex are going to
// be zero. Then we can make sure that we will remove _tokenId from the ownedTokens list since we are first swapping
// the lastToken to the first position, and then dropping the element placed in the last position of the list
ownedTokens[_from].length--;
ownedTokensIndex[_tokenId] = 0;
ownedTokensIndex[lastToken] = tokenIndex;
}
/**
* @dev Internal function to mint a new token
* @dev 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 by the msg.sender
*/
function _mint(address _to, uint256 _tokenId) internal {
super._mint(_to, _tokenId);
allTokensIndex[_tokenId] = allTokens.length;
allTokens.push(_tokenId);
}
/**
* @dev Internal function to burn a specific token
* @dev Reverts if the token does not exist
* @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];
}
// Reorg all tokens array
uint256 tokenIndex = allTokensIndex[_tokenId];
uint256 lastTokenIndex = allTokens.length.sub(1);
uint256 lastToken = allTokens[lastTokenIndex];
allTokens[tokenIndex] = lastToken;
allTokens[lastTokenIndex] = 0;
allTokens.length--;
allTokensIndex[_tokenId] = 0;
allTokensIndex[lastToken] = tokenIndex;
}
}
/**
* @title Ownable
* @dev The Ownable contract has an owner address, and provides basic authorization control
* functions, this simplifies the implementation of "user permissions".
*/
contract Ownable {
address public owner;
event OwnershipRenounced(address indexed previousOwner);
event OwnershipTransferred(
address indexed previousOwner,
address indexed newOwner
);
/**
* @dev The Ownable constructor sets the original `owner` of the contract to the sender
* account.
*/
constructor() public {
owner = msg.sender;
}
/**
* @dev Throws if called by any account other than the owner.
*/
modifier onlyOwner() {
require(msg.sender == owner);
_;
}
/**
* @dev Allows the current owner to relinquish control of the contract.
*/
function renounceOwnership() public onlyOwner {
emit OwnershipRenounced(owner);
owner = address(0);
}
/**
* @dev Allows the current owner to transfer control of the contract to a newOwner.
* @param _newOwner The address to transfer ownership to.
*/
function transferOwnership(address _newOwner) public onlyOwner {
_transferOwnership(_newOwner);
}
/**
* @dev Transfers control of the contract to a newOwner.
* @param _newOwner The address to transfer ownership to.
*/
function _transferOwnership(address _newOwner) internal {
require(_newOwner != address(0));
emit OwnershipTransferred(owner, _newOwner);
owner = _newOwner;
}
}
/**
* @title CryptoArte
* CryptoArte - a non-fungible token smart contract for
* paintings from the www.cryptoarte.io collection
*/
contract CryptoArte is ERC721Token, Ownable {
// Token id to painting image file hash mapping
mapping (uint256 => uint256) public tokenIdToHash;
constructor() ERC721Token("CryptoArte", "CARTE") public { }
/**
* @dev Mints a token to an address with a tokenURI and tokenHash.
* @param _to address of the future owner of the token
* @param _tokenId uint256 token ID (painting number)
* @param _tokenURI string token metadata URI
* @param _tokenHash uint256 token image Hash
*/
function mintTo(address _to, string _tokenURI, uint256 _tokenId, uint256 _tokenHash) public onlyOwner {
_mint(_to, _tokenId);
_setTokenURI(_tokenId, _tokenURI);
tokenIdToHash[_tokenId] = _tokenHash;
}
/**
* @dev Mints many tokens to an address with their tokenURIs and tokenHashes.
* @param _to address of the future owner of the tokens
* @param _tokenIds uint256 array of token IDs (painting numbers)
* @param _tokenURIPrefix string prefix for token metadata URI
* @param _tokenHashes uint256 array of token image Hashes
*/
function mintManyTo(address _to, string _tokenURIPrefix, uint256[] _tokenIds, uint256[] _tokenHashes) public onlyOwner {
require(_tokenIds.length >= 1);
require(_tokenIds.length == _tokenHashes.length);
for (uint i = 0; i < _tokenIds.length; i++) {
_mint(_to, _tokenIds[i]);
_setTokenURI(_tokenIds[i], strConcat(_tokenURIPrefix, uint256Tostr(_tokenIds[i])));
tokenIdToHash[_tokenIds[i]] = _tokenHashes[i];
}
}
/**
* @dev Updates tokenURI for tokenId - to be used to correct errors
* @dev Throws if the tokenId does not exist
* @param _tokenId uint256 token ID (painting number)
* @param _tokenURI string token metadata URI
*/
function setTokenURI(string _tokenURI, uint256 _tokenId) public onlyOwner {
_setTokenURI(_tokenId, _tokenURI);
}
/**
* @dev Updates tokenHash for tokenId - to be used only to correct errors
* @dev Throws if the tokenId does not exist
* @param _tokenId uint256 token ID (painting number)
* @param _tokenHash uint256 token image Hash
*/
function setTokenHash(uint256 _tokenHash, uint256 _tokenId) public onlyOwner {
require(exists(_tokenId));
tokenIdToHash[_tokenId] = _tokenHash;
}
/**
* @dev Contatenates two strings
* @param _a string first (left)
* @param _b string second (right)
*/
function strConcat(string _a, string _b) internal pure returns (string) {
bytes memory _ba = bytes(_a);
bytes memory _bb = bytes(_b);
string memory ab = new string(_ba.length + _bb.length);
bytes memory bab = bytes(ab);
uint k = 0;
for (uint i = 0; i < _ba.length; i++) bab[k++] = _ba[i];
for (i = 0; i < _bb.length; i++) bab[k++] = _bb[i];
return string(bab);
}
/**
* @dev Converts a uint256 to string
* @param _i uint256 the uint to convert
*/
function uint256Tostr(uint256 _i) internal pure returns (string) {
if (_i == 0) return "0";
uint256 j = _i;
uint256 len;
while (j != 0) {
len++;
j /= 10;
}
bytes memory bstr = new bytes(len);
uint256 k = len - 1;
while (_i != 0){
bstr[k--] = byte(48 + _i % 10);
_i /= 10;
}
return string(bstr);
}
}