项目实战

实战4：从零实现BTC区块链

我们今天来开发我们的BTC区块链系统。

简单来说，从数据结构的角度上来说，区块链，就是区块组成的链。

以下就是BTC区块链典型的结构：

那最小单元就是区块：block。

这个block包含两部分：区块头，区块体。

我们先忽略Merkle树，先简化所有数据结构，只保留最基本的数据结构。

那区块头，就包含：时间截；前一个区块地址

区块体，就包含交易数据，我们用一个vector来存储。

代码如下 ：

///交易结构体
#[derive(Clone, Hash, Serialize, Deserialize, Debug)]
pub struct Transaction {
    sender: String,    //发送者
    recipient: String, //接收者
    amount: i64,       //交易数量
}
/// 区块结构体
#[derive(Clone, Hash, Serialize, Deserialize, Debug)]
pub struct Block {
    pub index: u64,                     //区块高度
    timestamp: DateTime<Utc>,           //时间截
    pub transactions: Vec<Transaction>, //交易
    pub proof: u64,                     //证明
    pub previous_hash: String,          //上一个区块哈希地址
}
//区块链结构体
#[derive(Default)]
pub struct Blockchain {
    pub chain: Vec<Block>,                  //区块链帐本
    current_transactions: Vec<Transaction>, //交易集合
    pub nodes: HashSet<String>,             //节点集合
}

现在我们创建了一个基本的区块数据结构，现在我们来让矿工来创建区块吧。

怎么让不同的矿工，积极地创建区块呢？

我们引入一个机制叫：POW共识机制。

什么叫POW？简单来说，就是大家根据给定的一个数值proof，进行hash计算，谁最先算出来的结果值符合某个条件，就拥有创建新的区块，并把这个区块连接到原来的区块链上的权力。

比如，困难程度为5，那有个矿工用proof数据进行SHA哈希计算，出如下结果：

0x0000010000000000000000000000000000000000000000000000000000000000

这个结果，前面的0（除了0x外）是5个，则这就是结果值。

如果，没有计算出上面的结果值，矿工将proof自增1，再进行SHA哈希计算，直到计算出这个符合条件的结果值为止。

而那个给定的数据值proof，也要放在区块头，这个值在每次创建新区块的时候由矿工产生并写入区块头。

当然，如果 两个节点都算出结果并加入了新区块，这时，会产生链的分叉，这时如何决定冲突呢？

我们用最长链原则，即给定周期内，哪个节点拥有的链最长，就用哪个。

所以我们的共识机制是：POW+最长链原则

这个共识机制核心 代码如下：

impl Blockchain {
    //创建创世区块
    pub fn new() -> Blockchain {
        let mut blockchain = Blockchain {
            chain: vec![],
            current_transactions: vec![],
            nodes: HashSet::new(),
        };
        blockchain.new_block(100, Some("1"));
        blockchain
    }
    /// Create a new Block in the Blockchain
    ///
    /// :param proof: The proof given by the Proof of Work algorithm
    /// :param previous_hash: (Optional) hash of previous Block
    /// :return: New Bloc
    /// 创建新区块
    pub fn new_block(&mut self, proof: u64, previous_hash: Option<&str>) -> Block {
        let block = Block {
            index: (self.chain.len() + 1) as u64,
            timestamp: Utc::now(),
            transactions: self.current_transactions.drain(0..).collect(),
            proof,
            previous_hash: previous_hash.unwrap_or("0").to_string(),
        };

        self.chain.push(block.clone());
        block
    }
    /// Creates a new transaction to go into the next mined Block
    ///
    /// :param sender: Address of the ??ender
    /// :param recipient: Address of the recipient
    /// :param amount: Amount
    /// :return: The index of the Block that will hold this transaction
    /// 发起一个新交易，将写入下一个区块
    pub fn new_transaction(&mut self, sender: &str, recipient: &str, amount: i64) -> u64 {
        self.current_transactions.push(Transaction {
            sender: sender.to_string(),
            recipient: recipient.to_string(),
            amount,
        });
        self.last_block().unwrap().index + 1
    }
    /// Simple Proof of Work Algorithm:
    /// - Find a number p' such that hash(pp') contains 4 leading zeroes,
    ///   where p is the previous proof, and p' is the new proof
    /// POW工作量证明共识机制算法
    pub fn proof_of_work(last_block: &Block) -> u64 {
        let mut proof = 0;
        let last_proof = last_block.proof;
        let last_hash = &last_block.previous_hash;
        while !Self::valid_proof(last_proof, proof, last_hash) {
            proof += 1;
        }
        proof
    }
    /// Validates the Proof: Does hash(last_proof, proof, last_hash) containt 4 leading zeroes
    //验证工作证明数字
    fn valid_proof(last_proof: u64, proof: u64, last_hash: &String) -> bool {
        let guess = format!("{}{}{}", last_proof, proof, last_hash);
        let guess_hash = hex_digest(Algorithm::SHA256, guess.as_bytes());
        guess_hash.ends_with("00000") //困难度为5
    }

    /// Creates a SHA-256 hash of a Block
    ///
    /// :param block: Block
    /// :return hash for the block
    /// 创建一个区块 的哈希值，基SHA-256算法
    pub fn hash(block: &Block) -> String {
        let serialized = serde_json::to_string(&block).unwrap();
        hex_digest(Algorithm::SHA256, serialized.as_bytes())
    }
    /// Returns the last Block in the chain
    /// 返回最后一个区块
    pub fn last_block(&self) -> Option<&Block> {
        self.chain.last()
    }

    /// Add a new node to the list of nodes
    ///
    /// :param address: Address of the node. Eg. 'http://192.168.0.5:5000'
    ///
    /// 节点注册，即新节点加入区块链网络,注册地址参数为节点服务器地址，如：'http://192.168.0.5:5000‘
    pub fn register_node(&mut self, address: &str) {
        let parsed_url = urlparse(address);
        self.nodes.insert(parsed_url.netloc);
    }

    /// Determine if a given blockchain is valid
    /// 链的验证
    fn valid_chain(&self, chain: &[Block]) -> bool {
        let mut last_block = &chain[0];
        let mut current_index: usize = 1;
        while current_index < chain.len() {
            let block = &chain[current_index];
            println!("{:?}", last_block);
            println!("{:?}", block);
            println!("-----------");
            if block.previous_hash != Blockchain::hash(last_block) {
                return false;
            }
            if !Blockchain::valid_proof(last_block.proof, block.proof, &last_block.previous_hash) {
                return false;
            }

            last_block = block;
            current_index += 1;
        }
        true
    }

    /// This is our Consensus Algorithm, it resolves conflicts
    /// by replacing our chain with the longest one in the network.
    ///
    /// :return True if our chain was replaced and false otherwise
    /// 解决冲突的机制，即共识机制,最长链原则处理逻辑，即共识机制为（POw+最长链原则）
    pub fn resolve_conflicts(&mut self) -> bool {
        let mut max_length = self.chain.len();
        let mut new_chain: Option<Vec<Block>> = None;

        // Grab and verify the chains from all the nodes in our network
        for node in &self.nodes {
            let mut response = reqwest::get(&format!("http://{}/chain", node)).unwrap();
            if response.status().is_success() {
                let node_chain: Chain = response.json().unwrap();
                if node_chain.length > max_length && self.valid_chain(&node_chain.chain) {
                    max_length = node_chain.length;
                    new_chain = Some(node_chain.chain);
                }
            }
        }
        // Replace our chain if we discovered a new, valid chain longer than ours
        match new_chain {
            Some(x) => {
                self.chain = x;
                true
            }
            None => false,
        }
    }
}

以上代码，我们放在当前工程目录下的src/blockchain.rs，完整代码如下 ：

use crate::api::Chain;
use chrono::{DateTime, Utc};
use crypto_hash::{hex_digest, Algorithm};
use reqwest;
use serde::{Deserialize, Serialize};
use std::collections::HashSet;
use urlparse::urlparse;
///交易结构体
#[derive(Clone, Hash, Serialize, Deserialize, Debug)]
pub struct Transaction {
    sender: String,    //发送者
    recipient: String, //接收者
    amount: i64,       //交易数量
}
/// 区块结构体
#[derive(Clone, Hash, Serialize, Deserialize, Debug)]
pub struct Block {
    pub index: u64,                     //区块高度
    timestamp: DateTime<Utc>,           //时间截
    pub transactions: Vec<Transaction>, //交易
    pub proof: u64,                     //证明
    pub previous_hash: String,          //上一个区块哈希地址
}
//区块链结构体
#[derive(Default)]
pub struct Blockchain {
    pub chain: Vec<Block>,                  //区块链帐本
    current_transactions: Vec<Transaction>, //交易集合
    pub nodes: HashSet<String>,             //节点集合
}

impl Blockchain {
    //创建创世区块
    pub fn new() -> Blockchain {
        let mut blockchain = Blockchain {
            chain: vec![],
            current_transactions: vec![],
            nodes: HashSet::new(),
        };
        blockchain.new_block(100, Some("1"));
        blockchain
    }
    /// Create a new Block in the Blockchain
    ///
    /// :param proof: The proof given by the Proof of Work algorithm
    /// :param previous_hash: (Optional) hash of previous Block
    /// :return: New Bloc
    /// 创建新区块
    pub fn new_block(&mut self, proof: u64, previous_hash: Option<&str>) -> Block {
        let block = Block {
            index: (self.chain.len() + 1) as u64,
            timestamp: Utc::now(),
            transactions: self.current_transactions.drain(0..).collect(),
            proof,
            previous_hash: previous_hash.unwrap_or("0").to_string(),
        };

        self.chain.push(block.clone());
        block
    }
    /// Creates a new transaction to go into the next mined Block
    ///
    /// :param sender: Address of the ??ender
    /// :param recipient: Address of the recipient
    /// :param amount: Amount
    /// :return: The index of the Block that will hold this transaction
    /// 发起一个新交易，将写入下一个区块
    pub fn new_transaction(&mut self, sender: &str, recipient: &str, amount: i64) -> u64 {
        self.current_transactions.push(Transaction {
            sender: sender.to_string(),
            recipient: recipient.to_string(),
            amount,
        });
        self.last_block().unwrap().index + 1
    }
    /// Simple Proof of Work Algorithm:
    /// - Find a number p' such that hash(pp') contains 4 leading zeroes,
    ///   where p is the previous proof, and p' is the new proof
    /// POW工作量证明共识机制算法
    pub fn proof_of_work(last_block: &Block) -> u64 {
        let mut proof = 0;
        let last_proof = last_block.proof;
        let last_hash = &last_block.previous_hash;
        while !Self::valid_proof(last_proof, proof, last_hash) {
            proof += 1;
        }
        proof
    }
    /// Validates the Proof: Does hash(last_proof, proof, last_hash) containt 4 leading zeroes
    //验证工作证明数字
    fn valid_proof(last_proof: u64, proof: u64, last_hash: &String) -> bool {
        let guess = format!("{}{}{}", last_proof, proof, last_hash);
        let guess_hash = hex_digest(Algorithm::SHA256, guess.as_bytes());
        guess_hash.ends_with("00000") //困难度为5
    }

    /// Creates a SHA-256 hash of a Block
    ///
    /// :param block: Block
    /// :return hash for the block
    /// 创建一个区块 的哈希值，基SHA-256算法
    pub fn hash(block: &Block) -> String {
        let serialized = serde_json::to_string(&block).unwrap();
        hex_digest(Algorithm::SHA256, serialized.as_bytes())
    }
    /// Returns the last Block in the chain
    /// 返回最后一个区块
    pub fn last_block(&self) -> Option<&Block> {
        self.chain.last()
    }

    /// Add a new node to the list of nodes
    ///
    /// :param address: Address of the node. Eg. 'http://192.168.0.5:5000'
    ///
    /// 节点注册，即新节点加入区块链网络,注册地址参数为节点服务器地址，如：'http://192.168.0.5:5000‘
    pub fn register_node(&mut self, address: &str) {
        let parsed_url = urlparse(address);
        self.nodes.insert(parsed_url.netloc);
    }

    /// Determine if a given blockchain is valid
    /// 链的验证
    fn valid_chain(&self, chain: &[Block]) -> bool {
        let mut last_block = &chain[0];
        let mut current_index: usize = 1;
        while current_index < chain.len() {
            let block = &chain[current_index];
            println!("{:?}", last_block);
            println!("{:?}", block);
            println!("-----------");
            if block.previous_hash != Blockchain::hash(last_block) {
                return false;
            }
            if !Blockchain::valid_proof(last_block.proof, block.proof, &last_block.previous_hash) {
                return false;
            }

            last_block = block;
            current_index += 1;
        }
        true
    }

    /// This is our Consensus Algorithm, it resolves conflicts
    /// by replacing our chain with the longest one in the network.
    ///
    /// :return True if our chain was replaced and false otherwise
    /// 最长链原则处理逻辑，即共识机制为（POw+最长链原则）
    pub fn resolve_conflicts(&mut self) -> bool {
        let mut max_length = self.chain.len();
        let mut new_chain: Option<Vec<Block>> = None;

        // Grab and verify the chains from all the nodes in our network
        for node in &self.nodes {
            let mut response = reqwest::get(&format!("http://{}/chain", node)).unwrap();
            if response.status().is_success() {
                let node_chain: Chain = response.json().unwrap();
                if node_chain.length > max_length && self.valid_chain(&node_chain.chain) {
                    max_length = node_chain.length;
                    new_chain = Some(node_chain.chain);
                }
            }
        }
        // Replace our chain if we discovered a new, valid chain longer than ours
        match new_chain {
            Some(x) => {
                self.chain = x;
                true
            }
            None => false,
        }
    }
}

现在 我们向外界提供一些可用的API。

我们新建一个文件：src/api.rs，代码如下 ：

use crate::blockchain::{Block, Blockchain, Transaction};

use actix_web::{web, HttpRequest, HttpResponse};
use serde::{Deserialize, Serialize};
use std::sync::Mutex;
///返回消息体
#[derive(Serialize, Deserialize)]
pub struct MessageResponse {
    message: String,
}
//交易请求信息
#[derive(Serialize, Deserialize)]
pub struct TransactionRequest {
    sender: String,
    recipient: String,
    amount: i64,
}
///挖矿响应消息
#[derive(Serialize)]
pub struct MiningRespose {
    message: String,
    index: u64,
    transactions: Vec<Transaction>,
    proof: u64,
    previous_hash: String,
}
///链结构体，代表现在网络上的最长链
#[derive(Serialize, Deserialize)]
pub struct Chain {
    pub chain: Vec<Block>,
    pub length: usize,
}
///节点注册请求信息
#[derive(Deserialize)]
pub struct RegisterRequest {
    nodes: Vec<String>,
}
///节点注册响应信息
#[derive(Serialize)]
pub struct RegisterResponse {
    message: String,
    total_nodes: Vec<String>,
}
//解决冲突响应信息
#[derive(Serialize)]
pub struct ResolveResponse {
    message: String,
    chain: Vec<Block>,
}
///发起新交易
pub fn new_transaction(
    state: web::Data<Mutex<Blockchain>>,
    req: web::Json<TransactionRequest>,
) -> HttpResponse {
    let sender = req.sender.to_owned();
    let recipient = req.recipient.to_owned();
    let index = state
        .lock()
        .unwrap()
        .new_transaction(&sender, &recipient, req.amount);
    HttpResponse::Created().json(MessageResponse {
        message: format! {"Transaction will be added to Block {}", index},
    })
}
///矿工挖矿
pub fn mine(
    node_identifier: web::Data<String>,
    state: web::Data<Mutex<Blockchain>>,
    _req: HttpRequest,
) -> HttpResponse {
    let (proof, previous_hash) = {
        let blockchain = state.lock().unwrap();
        let last_block = blockchain.last_block().unwrap();
        let proof = Blockchain::proof_of_work(&last_block);
        let previous_hash = Blockchain::hash(last_block);
        (proof, previous_hash)
    };
    let mut blockchain = state.lock().unwrap();
    blockchain.new_transaction("0", &*node_identifier, 1);
    let block = blockchain.new_block(proof, Some(&previous_hash));
    HttpResponse::Ok().json(MiningRespose {
        message: "New Block Forged".to_string(),
        index: block.index,
        transactions: block.transactions,
        proof,
        previous_hash,
    })
}
///当前最新链的信息
pub fn chain(state: web::Data<Mutex<Blockchain>>, _req: HttpRequest) -> HttpResponse {
    let length = state.lock().unwrap().chain.len();
    HttpResponse::Ok().json(Chain {
        chain: state.lock().unwrap().chain.clone(),
        length,
    })
}
///节点注册
pub fn register_node(
    state: web::Data<Mutex<Blockchain>>,
    req: web::Json<RegisterRequest>,
) -> HttpResponse {
    if req.nodes.is_empty() {
        return HttpResponse::BadRequest().json(MessageResponse {
            message: "Error: Please supply a valid list of nodes".to_string(),
        });
    }
    let mut blockchain = state.lock().unwrap();
    for node in req.nodes.iter() {
        blockchain.register_node(node)
    }
    HttpResponse::Created().json(RegisterResponse {
        message: "New nodes have been added".to_string(),
        total_nodes: blockchain.nodes.iter().cloned().collect(),
    })
}
///跟网络上其他节点达成共识，即解决冲突
pub fn resolve_nodes(state: web::Data<Mutex<Blockchain>>, _req: HttpRequest) -> HttpResponse {
    let mut blockchain = state.lock().unwrap();
    let replaced = blockchain.resolve_conflicts();
    let message = if replaced {
        "Our chain was replaced"
    } else {
        "Our chain is authorative"
    };
    HttpResponse::Ok().json(ResolveResponse {
        message: message.to_string(),
        chain: blockchain.chain.clone(),
    })
}

当然，我们要用到一些好用的库，在我们的Cargo.toml文件，我们加入依赖，完整代码如下：

[dependencies]
chrono = { version = "0.4.6", features = ["serde"] }
crypto-hash = "0.3.3"
serde = { version = "1.0.90", features = ["derive"] }
serde_json = "1.0"
actix-web = "1.0"
uuid = { version = "0.7", features = ["v4"] }
urlparse = "0.7.3"
reqwest = "=0.9.17"

最后我们的主程序 src/main.rs如下：

pub mod api;
pub mod blockchain;

use actix_web::{web, App, HttpServer};
use std::env;
use std::sync::Mutex;
use uuid::Uuid;

fn main() {
    let args: Vec<String> = env::args().collect();
    let port = match args.as_slice() {
        [_, key, value] => {
            if key == "--p" {
                value
            } else {
                panic!("Illegal arguments passed to the program.");
            }
        }
        _ => "5000",
    };
    // TODO: make chain shared across threads
    let sharedchain = web::Data::new(Mutex::new(blockchain::Blockchain::new()));
    let node_identifier = web::Data::new(Uuid::new_v4().to_simple().to_string());

    HttpServer::new(move || {
        App::new()
            .register_data(sharedchain.clone())
            .register_data(node_identifier.clone())
            .data(web::JsonConfig::default().limit(4096))
            .service(web::resource("/mine").route(web::get().to(api::mine)))
            .service(web::resource("/transactions/new").route(web::post().to(api::new_transaction)))
            .service(web::resource("/chain").route(web::get().to(api::chain)))
            .service(web::resource("/nodes/register").route(web::post().to(api::register_node)))
            .service(web::resource("/nodes/resolve").route(web::get().to(api::resolve_nodes)))
    })
    .bind(format!("127.0.0.1:{}", port))
    .unwrap()
    .run();
}

然后我们可以用以下命令来调用 ：

挖矿:

curl http://localhost:5000/mine

创建新交易:

curl -H "Content-Type: application/json" --request POST --data '{"sender":"e79fcabd1d70433191701d17c4d13112", "recipient":"some-other-address", "amount":5}' http://localhost:5000/transactions/new

查看整条链信息:

curl http://localhost:5000/chain

注册节点:

curl -H "Content-Type: application/json" --request POST --data '{"nodes":["http://localhost:5001"]}' http://localhost:5000/nodes/register

与其他节点达成共识(共识机制):

curl http://localhost:5000/nodes/resolve

以上，希望对你有用。

如果遇到什么问题，欢迎加入：rust新手群，在这里我可以提供一些简单的帮助，加微信：360369487，注明：博客园+rust

https://asymmetric.github.io/2018/02/11/blockchain-rust/

https://jeiwan.net/posts/building-blockchain-in-go-part-1/

https://freestartupkits.com/articles/technology/cryptocurrency-news-and-tips/ultimate-rust-blockchain-tutorial/

https://hackernoon.com/learn-blockchains-by-building-one-117428612f46

https://medium.com/@vanflymen/learn-blockchains-by-building-one-117428612f46?

https://github.com/Koura/blockchain-example

原文地址：https://www.cnblogs.com/gyc567/p/12079503.html