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共识/共识clique源码解析.md

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+# 以太坊共识
+# clique
+实现POA(权威证明，Proof of Authority)共识算法
+
+## 委员会成员管理
+委员会成员加入、退出
+通过投票实现。
+
+## 出块规则
+
+## 源码解析
+## 初始化部分
+```
+func New(config *params.CliqueConfig, db ethdb.Database) *Clique
+```
+
+校验header
+
+func (c *Clique) verifyHeader(chain consensus.ChainReader, header *types.Header, parents []*types.Header) error
+
+
+VerifySeal检查Head是否包含签名，接受叔块并生成快照。
+
+func (c *Clique) VerifySeal(chain consensus.ChainReader, header *types.Header)
+
+包含：
+snapshot函数恢复快照、
+snapshot解析authorization key
+检查signer
+
+检查最近一段时间出块的列表。列表内出现的signer中需要是前半段中的signer。
+```
+for seen, recent := range snap.Recents {
+		if recent == signer {
+			// Signer is among recents, only fail if the current block doesn't shift it out
+			if limit := uint64(len(snap.Signers)/2 + 1); seen > number-limit {
+				return errRecentlySigned
+			}
+		}
+	}
+```
+校验出块难度。是否轮到自己出块时的难度不同
+```
+if !c.fakeDiff {
+		inturn := snap.inturn(header.Number.Uint64(), signer)
+		if inturn && header.Difficulty.Cmp(diffInTurn) != 0 {
+			return errWrongDifficulty
+		}
+		if !inturn && header.Difficulty.Cmp(diffNoTurn) != 0 {
+			return errWrongDifficulty
+		}
+	}
+```
+
+
+func (c *Clique) Prepare(chain consensus.ChainReader, header *types.Header) error
+包括功能：
+初始化header
+epoch为一轮委员会的任期时间
+
+收集所有选票信息
+```
+// Gather all the proposals that make sense voting on
+		addresses := make([]common.Address, 0, len(c.proposals))
+		for address, authorize := range c.proposals {
+			if snap.validVote(address, authorize) {
+				addresses = append(addresses, address)
+			}
+		}
+```
+统计所有选票信息
+```
+if len(addresses) > 0 {
+			header.Coinbase = addresses[rand.Intn(len(addresses))]
+			if c.proposals[header.Coinbase] {
+				copy(header.Nonce[:], nonceAuthVote)
+			} else {
+				copy(header.Nonce[:], nonceDropVote)
+			}
+		}
+```
+
+当前块号为epoch整除的时候，输出委员会所有成员的名单
+```
+if number%c.config.Epoch == 0 {
+		for _, signer := range snap.signers() {
+			header.Extra = append(header.Extra, signer[:]...)
+		}
+	}
+```
+
+
+```
+func (c *Clique) Finalize(chain consensus.ChainReader, header *types.Header, state *state.StateDB, txs []*types.Transaction, uncles []*types.Header) {
+```
+该函数确保叔块被丢掉。挖到叔块没有奖励。
+
+
+
+
+
+```
+func (c *Clique) Authorize(signer common.Address, signFn SignerFn) 
+```
+换新的私钥出块
+
+
+```
+func (c *Clique) Seal(chain consensus.ChainReader, block *types.Block, results chan<- *types.Block, stop <-chan struct{}) error
+```
+打包生成新的块
+
+包含：
+```
+// If we're amongst the recent signers, wait for the next block
+	for seen, recent := range snap.Recents {
+		if recent == signer {
+			// Signer is among recents, only wait if the current block doesn't shift it out
+			if limit := uint64(len(snap.Signers)/2 + 1); number < limit || seen > number-limit {
+				log.Info("Signed recently, must wait for others")
+				return nil
+			}
+		}
+	}
+```
+检测是否是最近出块列表中的signer,若是则需要等待。
+若不为自己的出块轮次，则时间增加一个delay.
+```
+	// Sweet, the protocol permits us to sign the block, wait for our time
+	delay := time.Unix(int64(header.Time), 0).Sub(time.Now()) // nolint: gosimple
+	if header.Difficulty.Cmp(diffNoTurn) == 0 {
+		// It's not our turn explicitly to sign, delay it a bit
+		wiggle := time.Duration(len(snap.Signers)/2+1) * wiggleTime
+		delay += time.Duration(rand.Int63n(int64(wiggle)))
+
+		log.Trace("Out-of-turn signing requested", "wiggle", common.PrettyDuration(wiggle))
+	}
+```
+
+
+
+
+CalcDifficulty
+计算难度。
+难度根据前一个块和当前signer计算。
+即不同signer的序号不同，是否轮到当前signer出块会导致不同的出块难度。
+
+返回上一个块的哈希
+```
+// SealHash returns the hash of a block prior to it being sealed.
+func (c *Clique) SealHash(header *types.Header) common.Hash {
+	return SealHash(header)
+}
+```