# ETH源码学习（3）getBlock

By [point](https://paragraph.com/@point) · 2022-05-12

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通过上篇getBalance和这个getBlock，理论上eth也能变成一个中心化的服务，因为用户和交易最终也都是保存到了数据库，那就和我们平时开发的项目没什么区别。这还蛮有意思的，eth实际上是区块链+传统项目的结合体。

源码
--

### 入口

    //命令
    eth.getBlock(1,true)
    //跳过了前面几层
    func (bc *BlockChain) GetBlockByNumber(number uint64) *types.Block {
            //用block number换block的hash
        hash := rawdb.ReadCanonicalHash(bc.db, number)
        if hash == (common.Hash{}) {
            return nil
        }
            //根据hash和number获取block
        return bc.GetBlock(hash, number)
    }
    

    //获取hash
    func ReadCanonicalHash(db ethdb.Reader, number uint64) common.Hash {
      //这个还没弄明白
       data, _ := db.Ancient(freezerHashTable, number)
       if len(data) == 0 {
      //从db中读
          data, _ = db.Get(headerHashKey(number))
          if len(data) == 0 {
             data, _ = db.Ancient(freezerHashTable, number)
          }
       }
       if len(data) == 0 {
          return common.Hash{}
       }
       return common.BytesToHash(data)
    }
    

    //获取区块
    func (bc *BlockChain) GetBlock(hash common.Hash, number uint64) *types.Block {
       //从缓存中读，这里用到了lur
       if block, ok := bc.blockCache.Get(hash); ok {
          return block.(*types.Block)
       }
    //从db中读，内容和getbalance一样，里面是先获取header，再获取body，然后创建区块，将header和body copy到block返回
       block := rawdb.ReadBlock(bc.db, hash, number)
       if block == nil {
          return nil
       }
    //缓存区块
       bc.blockCache.Add(block.Hash(), block)
       return block
    }
    

两篇get方法都是大同小异，进一步了解到eth是可以很简单的实现的，那些很牛逼的东西，都是为了满足区块链、性能这些需求。

另外这篇内容的主要代码都在blockchain内，又一次出现了这个，说明很重要，而statedb却没有出现，目前可以猜测statedb和账户有关，和block无关，需要后续验证。

也能知道leveldb里大致存的内容

1.  用户数据
    
2.  header
    
3.  number→hash
    
4.  body,body里存了tx，uncle
    
5.  可以想象还有receipt
    

    //block的例子
    {
      difficulty: 1461115576915,
      extraData: "0x476574682f76312e302e312f6c696e75782f676f312e342e32",
      gasLimit: 22150,
      gasUsed: 21000,
      hash: "0xeecb25ce31fb7a212500443a31d463b663a2c5f65e7838c5364bb8110a0750f1",
      logsBloom: "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
      miner: "0x47ff6576639c2e94762ea5443978d7681c0e78dc",
      mixHash: "0xaaad7bf5c87f1b2fc08ed73a1519dae6832b458a112891cd7c5a0a86125a8321",
      nonce: "0x4e164418632effd2",
      number: 46251,
      parentHash: "0x3c93a7ff6fb6f39e63456e9ea6fb069c7783f3c00b1012e36f0a8a02bdae604a",
      receiptsRoot: "0x5add83c7805c02ab079871e3a2379b6a764d34e557d758ddce00b6a1bf5cc79f",
      sha3Uncles: "0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347",
      size: 652,
      stateRoot: "0x7692ecfeac33453620701bad9eae23f89c01e845274f0e5adec78a5ea96f5083",
      timestamp: 1438919990,
      totalDifficulty: 42835839136947252,
      transactions: [{
          blockHash: "0xeecb25ce31fb7a212500443a31d463b663a2c5f65e7838c5364bb8110a0750f1",
          blockNumber: 46251,
          from: "0xfd2605a2bf58fdbb90db1da55df61628b47f9e8c",
          gas: 21000,
          gasPrice: 88893746891,
          hash: "0x304346de678ddca5b1311970e7e8d3f26a42d2924aaa2f2d73b8781a9a9a2c73",
          input: "0x",
          nonce: 1,
          r: "0x26f3e5c541f526b549d9f003c8e7de442d3cf4bbf9c66934027672693a88275f",
          s: "0x7bd40d54be85b58444d6f0a28f22591474a84380fc8a6a7515bda42b5ebb0e2b",
          to: "0x073f70b5bfade6409e4951ef72bc8f4157677729",
          transactionIndex: 0,
          v: "0x1c",
          value: 10000000000000000
      }],
      transactionsRoot: "0xf642520ac0ce7008292d2c835b8d2e6eb90822f8a68b8ae368b0774229371b5d",
      uncles: []
    }

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*Originally published on [point](https://paragraph.com/@point/eth-3-getblock)*