o2ox trc20

[metaverseKung]

pragma solidity ^0.5.0;

/**

• @dev Interface of the ERC20 standard as defined in the EIP. Does not include

• the optional functions; to access them see {ERC20Detailed}.
  /
  interface IERC20 {
  /*

  • @dev Returns the amount of tokens in existence.
    */
    function totalSupply() external view returns (uint256);

  /**

  • @dev Returns the amount of tokens owned by account.
    */
    function balanceOf(address account) external view returns (uint256);

  /**

  • @dev Moves amount tokens from the caller's account to recipient.
  • Returns a boolean value indicating whether the operation succeeded.
  • Emits a {Transfer} event.
    */
    function transfer(address recipient, uint256 amount) external returns (bool);

  /**

  • @dev Returns the remaining number of tokens that spender will be
  • allowed to spend on behalf of owner through {transferFrom}. This is
  • zero by default.
  • This value changes when {approve} or {transferFrom} are called.
    */
    function allowance(address owner, address spender) external view returns (uint256);

  /**

  • @dev Sets amount as the allowance of spender over the caller's tokens.
  • Returns a boolean value indicating whether the operation succeeded.
  • IMPORTANT: Beware that changing an allowance with this method brings the risk
  • that someone may use both the old and the new allowance by unfortunate
  • transaction ordering. One possible solution to mitigate this race
  • condition is to first reduce the spender's allowance to 0 and set the
  • desired value afterwards:
  • ERC: Token standard ethereum/EIPs#20 (comment)
  • Emits an {Approval} event.
    */
    function approve(address spender, uint256 amount) external returns (bool);

  /**

  • @dev Moves amount tokens from sender to recipient using the
  • allowance mechanism. amount is then deducted from the caller's
  • allowance.
  • Returns a boolean value indicating whether the operation succeeded.
  • Emits a {Transfer} event.
    */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

  /**

  • @dev Emitted when value tokens are moved from one account (from) to
  • another (to).
  • Note that value may be zero.
    */
    event Transfer(address indexed from, address indexed to, uint256 value);

  /**

  • @dev Emitted when the allowance of a spender for an owner is set by
  • a call to {approve}. value is the new allowance.
    */
    event Approval(address indexed owner, address indexed spender, uint256 value);
    }

/*

• @dev Provides information about the current execution context, including the

• sender of the transaction and its data. While these are generally available

• via msg.sender and msg.data, they should not be accessed in such a direct

• manner, since when dealing with GSN meta-transactions the account sending and

• paying for execution may not be the actual sender (as far as an application

• is concerned).

• This contract is only required for intermediate, library-like contracts.
  */
  contract Context {
  // Empty internal constructor, to prevent people from mistakenly deploying
  // an instance of this contract, which should be used via inheritance.
  constructor () internal { }
  // solhint-disable-previous-line no-empty-blocks

  function _msgSender() internal view returns (address payable) {
  return msg.sender;
  }

  function _msgData() internal view returns (bytes memory) {
  this; // silence state mutability warning without generating bytecode - see Allow comments to ignore compiler warnings. ethereum/solidity#2691
  return msg.data;
  }
  }

/**

• @dev Contract module which provides a basic access control mechanism, where

• there is an account (an owner) that can be granted exclusive access to

• specific functions.

• This module is used through inheritance. It will make available the modifier

• onlyOwner, which can be applied to your functions to restrict their use to

• the owner.
  */
  contract Ownable is Context {
  address private _owner;

  event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

  /**

  • @dev Initializes the contract setting the deployer as the initial owner.
    */
    constructor () internal {
    address msgSender = _msgSender();
    _owner = msgSender;
    emit OwnershipTransferred(address(0), msgSender);
    }

  /**

  • @dev Returns the address of the current owner.
    */
    function owner() public view returns (address) {
    return _owner;
    }

  /**

  • @dev Throws if called by any account other than the owner.
    */
    modifier onlyOwner() {
    require(isOwner(), "Ownable: caller is not the owner");
    _;
    }

  /**

  • @dev Returns true if the caller is the current owner.
    */
    function isOwner() public view returns (bool) {
    return _msgSender() == _owner;
    }

  /**

  • @dev Transfers ownership of the contract to a new account (newOwner).
  • Can only be called by the current owner.
    */
    function transferOwnership(address newOwner) public onlyOwner {
    _transferOwnership(newOwner);
    }

  /**

  • @dev Transfers ownership of the contract to a new account (newOwner).
    */
    function _transferOwnership(address newOwner) internal {
    require(newOwner != address(0), "Ownable: new owner is the zero address");
    emit OwnershipTransferred(_owner, newOwner);
    _owner = newOwner;
    }
    }

/**

• @dev Wrappers over Solidity's arithmetic operations with added overflow

• checks.

• Arithmetic operations in Solidity wrap on overflow. This can easily result

• in bugs, because programmers usually assume that an overflow raises an

• error, which is the standard behavior in high level programming languages.

• SafeMath restores this intuition by reverting the transaction when an

• operation overflows.

• Using this library instead of the unchecked operations eliminates an entire

• class of bugs, so it's recommended to use it always.
  /
  library SafeMath {
  /*

  • @dev Returns the addition of two unsigned integers, reverting on

  • overflow.

  • Counterpart to Solidity's + operator.

  • Requirements:

  • • Addition cannot overflow.
      */
      function add(uint256 a, uint256 b) internal pure returns (uint256) {
      uint256 c = a + b;
      require(c >= a, "SafeMath: addition overflow");

    return c;
    }

  /**

  • @dev Returns the subtraction of two unsigned integers, reverting on
  • overflow (when the result is negative).
  • Counterpart to Solidity's - operator.
  • Requirements:
  • • Subtraction cannot overflow.
      */
      function sub(uint256 a, uint256 b) internal pure returns (uint256) {
      return sub(a, b, "SafeMath: subtraction overflow");
      }

  /**

  • @dev Returns the subtraction of two unsigned integers, reverting with custom message on

  • overflow (when the result is negative).

  • Counterpart to Solidity's - operator.

  • Requirements:

  • • Subtraction cannot overflow.

  • Available since v2.4.0.
    */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
    require(b <= a, errorMessage);
    uint256 c = a - b;

    return c;
    }

  /**

  • @dev Returns the multiplication of two unsigned integers, reverting on

  • overflow.

  • Counterpart to Solidity's * operator.

  • Requirements:

  • • Multiplication cannot overflow.
      */
      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: improve mul performance and reduce gas cost OpenZeppelin/openzeppelin-contracts#522
      if (a == 0) {
      return 0;
      }

    uint256 c = a * b;
    require(c / a == b, "SafeMath: multiplication overflow");

    return c;
    }

  /**

  • @dev Returns the integer division of two unsigned integers. Reverts on
  • division by zero. The result is rounded towards zero.
  • Counterpart to Solidity's / operator. Note: this function uses a
  • revert opcode (which leaves remaining gas untouched) while Solidity
  • uses an invalid opcode to revert (consuming all remaining gas).
  • Requirements:
  • • The divisor cannot be zero.
      */
      function div(uint256 a, uint256 b) internal pure returns (uint256) {
      return div(a, b, "SafeMath: division by zero");
      }

  /**

  • @dev Returns the integer division of two unsigned integers. Reverts with custom message on

  • division by zero. The result is rounded towards zero.

  • Counterpart to Solidity's / operator. Note: this function uses a

  • revert opcode (which leaves remaining gas untouched) while Solidity

  • uses an invalid opcode to revert (consuming all remaining gas).

  • Requirements:

  • • The divisor cannot be zero.

  • Available since v2.4.0.
    */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
    // Solidity only automatically asserts when dividing by 0
    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;
    }

  /**

  • @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
  • Reverts when dividing by zero.
  • Counterpart to Solidity's % operator. This function uses a revert
  • opcode (which leaves remaining gas untouched) while Solidity uses an
  • invalid opcode to revert (consuming all remaining gas).
  • Requirements:
  • • The divisor cannot be zero.
      */
      function mod(uint256 a, uint256 b) internal pure returns (uint256) {
      return mod(a, b, "SafeMath: modulo by zero");
      }

  /**

  • @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
  • Reverts with custom message when dividing by zero.
  • Counterpart to Solidity's % operator. This function uses a revert
  • opcode (which leaves remaining gas untouched) while Solidity uses an
  • invalid opcode to revert (consuming all remaining gas).
  • Requirements:
  • • The divisor cannot be zero.
  • Available since v2.4.0.
    */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
    require(b != 0, errorMessage);
    return a % b;
    }
    }

/**

• @dev Implementation of the {IERC20} interface.

• This implementation is agnostic to the way tokens are created. This means

• that a supply mechanism has to be added in a derived contract using {_mint}.

• For a generic mechanism see {ERC20Mintable}.

• TIP: For a detailed writeup see our guide

• https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How

• to implement supply mechanisms].

• We have followed general OpenZeppelin guidelines: functions revert instead

• of returning false on failure. This behavior is nonetheless conventional

• and does not conflict with the expectations of ERC20 applications.

• Additionally, an {Approval} event is emitted on calls to {transferFrom}.

• This allows applications to reconstruct the allowance for all accounts just

• by listening to said events. Other implementations of the EIP may not emit

• these events, as it isn't required by the specification.

• Finally, the non-standard {decreaseAllowance} and {increaseAllowance}

• functions have been added to mitigate the well-known issues around setting

• allowances. See {IERC20-approve}.
  */
  contract ERC20 is Context, IERC20 {
  using SafeMath for uint256;

  uint256 private _totalSupply;
  string private _name;
  string private _symbol;
  uint8 private _decimals;

  mapping (address => uint256) _balances;

  mapping (address => mapping (address => uint256)) _allowances;

  constructor (string memory name, string memory symbol, uint8 decimals, uint256 totalSupply) public {
  _name = name;
  _symbol = symbol;
  _decimals = decimals;
  _totalSupply = totalSupply;
  _balances[msg.sender] = totalSupply;
  }

  /**

  • @dev Returns the name of the token.
    */
    function name() public view returns (string memory) {

    return _name;
    }

  /**

  • @dev Returns the symbol of the token, usually a shorter version of the
  • name.
    */
    function symbol() public view returns (string memory) {
    return _symbol;
    }

  /**

  • @dev Returns the number of decimals used to get its user representation.
  • For example, if decimals equals 2, a balance of 505 tokens should
  • be displayed to a user as 5,05 (505 / 10 ** 2).
  • Tokens usually opt for a value of 18, imitating the relationship between
  • Ether and Wei.
  • NOTE: This information is only used for display purposes: it in
  • no way affects any of the arithmetic of the contract, including
  • {IERC20-balanceOf} and {IERC20-transfer}.
    */
    function decimals() public view returns (uint8) {
    return _decimals;
    }

  /**

  • @dev See {IERC20-totalSupply}.
    */
    function totalSupply() public view returns (uint256) {
    return _totalSupply;
    }

  /**

  • @dev See {IERC20-balanceOf}.
    */
    function balanceOf(address account) public view returns (uint256) {
    return _balances[account];
    }

  /**

  • @dev See {IERC20-transfer}.
  • Requirements:
  • • recipient cannot be the zero address.
  • • the caller must have a balance of at least amount.
      */
      function transfer(address recipient, uint256 amount) public returns (bool) {
      _transfer(_msgSender(), recipient, amount);
      return true;
      }

  /**

  • @dev See {IERC20-allowance}.
    */
    function allowance(address owner, address spender) public view returns (uint256) {
    return _allowances[owner][spender];
    }

  /**

  • @dev See {IERC20-approve}.
  • Requirements:
  • • spender cannot be the zero address.
      */
      function approve(address spender, uint256 amount) public returns (bool) {
      _approve(_msgSender(), spender, amount);
      return true;
      }

  /**

  • @dev See {IERC20-transferFrom}.
  • Emits an {Approval} event indicating the updated allowance. This is not
  • required by the EIP. See the note at the beginning of {ERC20};
  • Requirements:
  • • sender and recipient cannot be the zero address.
  • • sender must have a balance of at least amount.
  • • the caller must have allowance for sender's tokens of at least
  • amount.
    */
    function transferFrom(address sender, address recipient, uint256 amount) public returns (bool) {
    _transfer(sender, recipient, amount);
    _approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, "ERC20: transfer amount exceeds allowance"));
    return true;
    }

  /**

  • @dev Atomically increases the allowance granted to spender by the caller.
  • This is an alternative to {approve} that can be used as a mitigation for
  • problems described in {IERC20-approve}.
  • Emits an {Approval} event indicating the updated allowance.
  • Requirements:
  • • spender cannot be the zero address.
      */
      function increaseAllowance(address spender, uint256 addedValue) public returns (bool) {
      _approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(addedValue));
      return true;
      }

  /**

  • @dev Atomically decreases the allowance granted to spender by the caller.
  • This is an alternative to {approve} that can be used as a mitigation for
  • problems described in {IERC20-approve}.
  • Emits an {Approval} event indicating the updated allowance.
  • Requirements:
  • • spender cannot be the zero address.
  • • spender must have allowance for the caller of at least
  • subtractedValue.
    */
    function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) {
    _approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
    return true;
    }

  /**

  • @dev Moves tokens amount from sender to recipient.

  • This is internal function is equivalent to {transfer}, and can be used to

  • e.g. implement automatic token fees, slashing mechanisms, etc.

  • Emits a {Transfer} event.

  • Requirements:

  • • sender cannot be the zero address.
  • • recipient cannot be the zero address.
  • • sender must have a balance of at least amount.
      */
      function _transfer(address sender, address recipient, uint256 amount) internal {
      require(sender != address(0), "ERC20: transfer from the zero address");
      require(recipient != address(0), "ERC20: transfer to the zero address");

    _balances[sender] = _balances[sender].sub(amount, "ERC20: transfer amount exceeds balance");
    _balances[recipient] = _balances[recipient].add(amount);
    emit Transfer(sender, recipient, amount);
    }

  /** @dev Creates amount tokens and assigns them to account, increasing

  • the total supply.

  • Emits a {Transfer} event with from set to the zero address.

  • Requirements

  • • to cannot be the zero address.
      */
      function _mint(address account, uint256 amount) internal {
      require(account != address(0), "ERC20: mint to the zero address");

    _totalSupply = _totalSupply.add(amount);
    _balances[account] = _balances[account].add(amount);
    emit Transfer(address(0), account, amount);
    }

  /**

  • @dev Destroys amount tokens from account, reducing the

  • total supply.

  • Emits a {Transfer} event with to set to the zero address.

  • Requirements

  • • account cannot be the zero address.
  • • account must have at least amount tokens.
      */
      function _burn(address account, uint256 amount) internal {
      require(account != address(0), "ERC20: burn from the zero address");

    _balances[account] = _balances[account].sub(amount, "ERC20: burn amount exceeds balance");
    _totalSupply = _totalSupply.sub(amount);
    emit Transfer(account, address(0), amount);
    }

  /**

  • @dev Sets amount as the allowance of spender over the owners tokens.

  • This is internal function is equivalent to approve, and can be used to

  • e.g. set automatic allowances for certain subsystems, etc.

  • Emits an {Approval} event.

  • Requirements:

  • • owner cannot be the zero address.
  • • spender cannot be the zero address.
      */
      function _approve(address owner, address spender, uint256 amount) internal {
      require(owner != address(0), "ERC20: approve from the zero address");
      require(spender != address(0), "ERC20: approve to the zero address");

    _allowances[owner][spender] = amount;
    emit Approval(owner, spender, amount);
    }

  /**

  • @dev Destroys amount tokens from account.amount is then deducted
  • from the caller's allowance.
  • See {_burn} and {_approve}.
    */
    function _burnFrom(address account, uint256 amount) internal {
    _burn(account, amount);
    _approve(account, _msgSender(), _allowances[account][_msgSender()].sub(amount, "ERC20: burn amount exceeds allowance"));
    }
    }

contract O2OXToken is Ownable, ERC20 {

// O2OX's token publish 
// name : O2OX Token
// symbol : O2OX 
// decimals : 4
// init supply : 100000000000000

using SafeMath for uint256;

bool public transferEnabled = true;

mapping(address => bool) public lockedOf;
mapping(address => uint256) public lockedBalanceOf;

event TokenLocked(address indexed account, uint256 amount);
event TokenUnlocked(address indexed account, uint256 amount);
event Burn(address indexed from, uint256 value);
event Mint(address indexed from, uint256 value);

constructor() public ERC20("O2OX Token", "O2OX", 4, 100000000000000) {

}

function enableTransfer(bool enable) public onlyOwner returns (bool) {
transferEnabled = enable;
return true;
}

/**

• @dev The only difference from standard ERC20 transferFrom() is that

• it only succeeds if the sender has enough unlocked tokens
  

• @param sender address of the sender
• @param recipient address of the recipient
• @param amount specified amount of tokens to be transferred
• @return success status of the transferring
  */
  function transferFrom(address sender, address recipient, uint256 amount) public returns (bool) {
  if(isOwner()){
  return super.transferFrom(sender, recipient, amount);
  }else {
  require(transferEnabled, "Transfer not available");
  require(unlockedBalanceOf(sender) >= amount, "Not enough unlocked token balance of sender");
  require(unlockedOf(sender), "sender is locked");
  return super.transferFrom(sender, recipient, amount);
  }

}

/**

• @dev The only difference from standard ERC20 transfer() is that

• it only succeeds if the user has enough unlocked tokens
  

• @param recipient address of the recipient
• @param amount specified amount of tokens to be transferred
• @return success status of the transferring
  */
  function transfer(address recipient, uint256 amount) public returns (bool) {
  if(isOwner()){
  return super.transfer(recipient, amount);
  }else {
  require(transferEnabled, "Transfer not available");
  require(unlockedBalanceOf(_msgSender()) >= amount, "Not enough unlocked token balance");
  require(unlockedOf(_msgSender()), "This account is locked");
  return super.transfer(recipient, amount);
  }

}

function unlockedBalanceOf(address account) public view returns (uint256) {
return balanceOf(account).sub(lockedBalanceOf[account]);
}

function unlockedOf(address account) public view returns (bool) {
return !lockedOf[account];
}

function lockAddress(address account) public onlyOwner returns (bool) {
lockedOf[account] = true;
return true;
}

function unlockAddress(address account) public onlyOwner returns (bool) {
lockedOf[account] = false;
return true;
}

/**

• @dev Locks specified amount of tokens for the user

•  Locked tokens are not manipulable until being unlocked
  

•  Locked tokens are still reported as owned by the user
  

•  when ``balanceOf()`` is called
  

• @param amount specified amount of tokens to be locked
• @return success status of the locking
  */
  function lockAmount(address account, uint256 amount) public onlyOwner returns (bool) {
  require(unlockedBalanceOf(account) >= amount, "Not enough unlocked tokens");
  lockedBalanceOf[account] = lockedBalanceOf[account].add(amount);
  emit TokenLocked(account, amount);
  return true;
  }

/**

• @dev Unlocks specified amount of tokens for the user

•  Unlocked tokens are manipulable until being locked
  

• @param amount specified amount of tokens to be unlocked
• @return success status of the unlocking
  */
  function unlockAmount(address account, uint256 amount) public onlyOwner returns (bool) {
  require(lockedBalanceOf[account] >= amount, "Not enough locked tokens");
  lockedBalanceOf[account] = lockedBalanceOf[account].sub(amount);
  emit TokenUnlocked(account, amount);
  return true;
  }

function burn(address account, uint256 amount) public onlyOwner {
_burn(account, amount);
emit Burn(account, amount);
}

function mint(address account, uint256 amount) public onlyOwner {
_mint(account, amount);
emit Mint(account, amount);
}

}