艺术品区块链溯源防伪平台(连载二)数字资产的投资与数字资产的份额化

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艺术品区块链溯源防伪平台(连载二)数字资产的投资与数字资产的份额化

netkiller 2018-11-22 12:37:34 浏览1895
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作者正在找工作,联系方式 13113668890
Mr. Neo Chan, 陈景峯(BG7NYT)
中国广东省深圳市望海路半岛城邦三期 518067 +86 13113668890 <netkiller@msn.com>
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2.10.5. 资产投资与份额持有

传统艺术品投资门槛非常高,一是用户不知道从哪些渠道可以投资,二是艺术品价值过高,三是艺术品简单难。这导致了投资艺术品门槛过高。 Token 能实现份额化,实现人人参与,人人持有,P2P交易。

例如某机构上链一件艺术品,用户可以投资该艺术品的一定份额,可以转让他持有的权益。且交易去中心化,不受任何机构,管理者的制约。

下面的合约可以展示如何分割艺术品份额,最终达到链上资产的份额分割和持有与交易。

		
pragma solidity ^0.4.25;

/**
 * @title SafeMath
 * @dev Math operations with safety checks that revert on error
 */
library SafeMath {

  /**
  * @dev Multiplies two numbers, reverts on 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: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
    if (a == 0) {
      return 0;
    }

    uint256 c = a * b;
    require(c / a == b);

    return c;
  }

  /**
  * @dev Integer division of two numbers truncating the quotient, reverts on division by zero.
  */
  function div(uint256 a, uint256 b) internal pure returns (uint256) {
    require(b > 0); // Solidity only automatically asserts 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 c;
  }

  /**
  * @dev Subtracts two numbers, reverts on overflow (i.e. if subtrahend is greater than minuend).
  */
  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
    require(b <= a);
    uint256 c = a - b;

    return c;
  }

  /**
  * @dev Adds two numbers, reverts on overflow.
  */
  function add(uint256 a, uint256 b) internal pure returns (uint256) {
    uint256 c = a + b;
    require(c >= a);

    return c;
  }

  /**
  * @dev Divides two numbers and returns the remainder (unsigned integer modulo),
  * reverts when dividing by zero.
  */
  function mod(uint256 a, uint256 b) internal pure returns (uint256) {
    require(b != 0);
    return a % b;
  }
}        

contract Ownable {
    
    address public owner;
    
    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
    
    constructor() public {
        owner = msg.sender;
    }
    
    modifier onlyOwner() {
        require(msg.sender == owner);
        _;
    }
    
    function transferOwnership(address newOwner) public onlyOwner {
        require(newOwner != address(0));
        emit OwnershipTransferred(owner, newOwner);
        owner = newOwner;
    }

}

contract NetkillerAssetsToken is Ownable {
    using SafeMath for uint256;
    
    string public name;
    string public symbol;
    uint public decimals;
    uint256 public totalSupply;
    
    mapping(address => mapping(string => uint256)) internal balances;
    mapping(string => address) internal tokens;
    
    event Transfer(address indexed _from, address indexed _to, string indexed _tokenId);
    event Burn(address indexed from, string _tokenId);
    
    constructor(
        string tokenName,
        string tokenSymbol,
        uint decimalUnits
    ) public {
        owner = msg.sender;
        name = tokenName;
        symbol = tokenSymbol; 
        decimals = decimalUnits;
        totalSupply = 0; 
    }
    
    function add(address _owner, string _tokenId) onlyOwner returns(bool status){
        balances[_owner][_tokenId] = 100 * 10 ** uint256(decimals);
        tokens[_tokenId] = _owner;
        totalSupply = totalSupply.add(1);
        return true;
    }
    
    function balanceOf(address _owner, string _tokenId) constant returns(uint balance){ 
        return balances[_owner][_tokenId];
    }

    function ownerOf(string _tokenId) constant returns (address owner) {
        return tokens[_tokenId];
    }
    
    function transfer(address _to, string _tokenId){
        
        address _from = msg.sender;
        uint256 amount = balances[_from][_tokenId];
        transfer(_to, amount, _tokenId);
    }
    function transfer(address _to, uint256 _value, string _tokenId){
        require(msg.sender == ownerOf(_tokenId));
        require(msg.sender != _to);
        require(_to != address(0));
        
        address _from = msg.sender;
        uint256 amount = balances[_from][_tokenId];
        require(amount >= _value);
        
        balances[_from][_tokenId] = balances[_from][_tokenId].sub(_value);
        balances[_to][_tokenId] = balances[_to][_tokenId].add(_value);
        tokens[_tokenId] = _to;

        emit Transfer(_from, _to, _tokenId);
    }
    
    function burn(address _owner, string _tokenId) onlyOwner public returns (bool success) {
        require(balances[_owner][_tokenId] > 0 && balances[_owner][_tokenId] == 100 * 10 ** uint256(decimals));

        balances[_owner][_tokenId] = 0;
        tokens[_tokenId] = address(0);

        totalSupply = totalSupply.sub(1);
        emit Burn(msg.sender, _tokenId);
        return true;
    }
    
}		
		
		

由于 ERC721 不太符合我的需求,所以我结合 ERC20 和 ERC721 写出了我的合约。合约尽量保持了ERC20的使用习惯,函数定义尽量兼容 ERC20。

我们来看下面的构造方法,每个种类的物品一个合约,例如字画,陶瓷,青铜器。

		
    constructor(
        string tokenName,
        string tokenSymbol,
        uint decimalUnits
    ) public {
        owner = msg.sender;
        name = tokenName;
        symbol = tokenSymbol; 
        decimals = decimalUnits;
        totalSupply = 0; 
    }
		
		

通过下面函数,添加资产到 Token,使链上资产与Token绑定。

		
    function add(address _owner, string _tokenId) onlyOwner returns(bool status){
        balances[_owner][_tokenId] = 100 * 10 ** uint256(decimals);
        tokens[_tokenId] = _owner;
        totalSupply = totalSupply.add(1);
        return true;
    }		
		
		

balances[_owner][_tokenId] = 100 * 10 ** uint256(decimals); 初始化份额是 100 表示 100%

totalSupply = totalSupply.add(1); 物品件数加一。可以用于统计链上资产的数量。

下面函数是查询资产的持有人

		
function ownerOf(string _tokenId) constant returns (address owner) {
        return tokens[_tokenId];
    }		
		
		

下面函数是,权益转让和权益份额转让。

		
    function transfer(address _to, string _tokenId){
        
        address _from = msg.sender;
        uint256 amount = balances[_from][_tokenId];
        transfer(_to, amount, _tokenId);
    }
    function transfer(address _to, uint256 _value, string _tokenId){
        require(msg.sender == ownerOf(_tokenId));
        require(msg.sender != _to);
        require(_to != address(0));
        
        address _from = msg.sender;
        uint256 amount = balances[_from][_tokenId];
        require(amount >= _value);
        
        balances[_from][_tokenId] = balances[_from][_tokenId].sub(_value);
        balances[_to][_tokenId] = balances[_to][_tokenId].add(_value);
        tokens[_tokenId] = _to;

        emit Transfer(_from, _to, _tokenId);
    }		
		
		

接下来,我们就是可以开发 Dapp 钱包了,在钱包中实现资产的转移交易。

这个合约可以一直到 EOS 上,Hyperledger Fabric 不可以,因为 Fabric 没有锁的机制,会导致计算出错。




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