【成长随笔】开源中心化区块链预言机区块链开发预言机-Oracle

前言
2020～2021是一个Defi的时代，很多公链都开始支持EVM，开始搞web3.0。包括，Algorand，BCH，BSC，NEO和Conflux等等等等。很多公链生态应用都是出现爆发式出现，例如Gamefi，多种Defi协议。然而，Defi各种生态里，预言机服务是非常非常重要的一个服务。很多Defi协议都需要一个预言机合约进行报价，为了解决新生公链生态没有预言机的问题，我开源了我在TriangleDAO写的一个中心化区块链预言机。核心团队 or 核心社区人员可以部署到对应的链上，做一个临时的中心化区块链预言机方案。这同样也适合联盟链，联盟链应该是很少或者几乎没有预言机服务的吧。
开源地址：
【【成长随笔】开源中心化区块链预言机】https://github.com/shanxuanch...
技术架构 ( v1.0)
核心其实是2个合约：一个是TriangleOracle.sol，另外一个PriceFeed.sol。
TriangleOracle.sol继承了IERC2362标准，主要是2个函数：一个是putPirce和ValueFor。有一个定时的进程每5分钟会从Binance和Okex读取价格，然后触发putPrice，把价格写到链上。

pragma solidity 0.6.11; import "./Ownable.sol"; import "./Interfaces/IERC2362.sol"; contract TriangleOracle is Ownable, IERC2362 {// 32 + 16 + 16 = 64 bytes // default 1e+18 struct PriceOracle { int256 price; // 16 bytes uint256 timestamp; uint256 status; // 16 bytes } PriceOracle latestPrice; event PutLatestTokenPrice(int256 price, uint256 timestamp, uint256 status); function putPrice(bytes32 _id, int256 price, uint256 timestamp) public onlyOwner {uint256 _status = 200; latestPrice = PriceOracle ({ price: price, timestamp: timestamp, status: _status }); emit PutLatestTokenPrice(price,timestamp, _status); }function valueFor(bytes32 _id) external view override returns(int256,uint256,uint256) { return (latestPrice.price, latestPrice.timestamp, latestPrice.status); }}

PriceFeed合约的职责是读TriangleOracle.sol的价格，然后把价格保存到lastGoodPrice这个变量中，以便其他合约读取这个价格。这里有其他逻辑，例如scale。比较重要的是，这里涉及到可更新和合约交互的逻辑，让我对智能合约的理解提升了一个数量级。

// SPDX-License-Identifier: MIT pragma solidity 0.6.11; import "./Dependencies/SafeMath.sol"; import "./Interfaces/IERC2362.sol"; import "./Interfaces/IPriceFeed.sol"; import "./Dependencies/Initializable.sol"; import "./Dependencies/CheckContract.sol"; contract PriceFeed is CheckContract, IPriceFeed, Initializable { using SafeMath for uint256; uint constant public TARGET_DIGITS = 18; // CFX/USDT assertID bytes32 constant public assetID = bytes32(0x65784185a07d3add5e7a99a6ddd4477e3c8caad717bac3ba3c3361d99a978c29); struct WitnetResponse { int256 value; uint256 _timestamp; uint256 status; }IERC2362 public witnet; uint public lastGoodPrice; event LastGoodPriceUpdated(uint _lastGoodPrice); // --- Dependency setters ---function initialize(address _IWitnetCFXUSDTAddress) public initializer { checkContract(_IWitnetCFXUSDTAddress); witnet = IERC2362(_IWitnetCFXUSDTAddress); WitnetResponse memory witnetResponse = _getCurrentWitnetResponse(assetID); _storePrice(witnetResponse); }function getPrice() external view returns (uint) { return lastGoodPrice; }function fetchPrice() external override returns (uint) { WitnetResponse memory witnetResponse = _getCurrentWitnetResponse(assetID); _storePrice(witnetResponse); return lastGoodPrice; }function _getCurrentWitnetResponse(bytes32 _assetID) internal view returns(WitnetResponse memory response) { try witnet.valueFor(_assetID) returns ( int256 value, uint256 _timestamp, uint256 status ) { response.value = https://www.it610.com/article/value; response._timestamp = _timestamp; response.status = status; } catch { // If call to Chainlink aggregator reverts, return a zero response with success = false return response; } }function _storePrice(WitnetResponse memory witnetResponse) internal { require(witnetResponse.status == 200,"witnet Response is not 200. response error."); uint goodPrice = _scaleWitnetPriceByDigits(uint(witnetResponse.value), 6); if (goodPrice != lastGoodPrice) { lastGoodPrice = goodPrice; emit LastGoodPriceUpdated(lastGoodPrice); } }function _scaleWitnetPriceByDigits(uint _price, uint _answerDigits) internal pure returns (uint) { /* * Convert the price returned by the Chainlink oracle to an 18-digit decimal for use by Liquity. * At date of Liquity launch, Chainlink uses an 8-digit price, but we also handle the possibility of * future changes. * */ uint price; if (_answerDigits >= TARGET_DIGITS) { // Scale the returned price value down to Liquity's target precision price = _price.div(10 ** (_answerDigits - TARGET_DIGITS)); } else if (_answerDigits < TARGET_DIGITS) { // Scale the returned price value up to Liquity's target precision price = _price.mul(10 ** (TARGET_DIGITS - _answerDigits)); } return price; }}

总结
地址：https://github.com/shanxuanch...
总体而言没有什么技术难度，就是一个定时脚步读写任务而已。中心化的预言机服务是比较简单的，但是去中心化就非常有难度了。现在为止有接近$300W的TVL了，虽然token的价格波动很大，但是我内心非常有信心。原因？可能是我提前知道各种利好吧。如果Token解锁了，我想所有帮助我一路上爬过来的人都分发一部分token，想了想，可能这是我去北京之前唯一能拿得出手的礼物了。