兄弟连区块链教程Fabric1.0源代码分析Tx RWSet（读写集），2018年下半年，区块链行业正逐渐褪去发展之初的浮躁、回归理性，表面上看相关人才需求与身价似乎正在回落。但事实上，正是初期泡沫的渐退，让人们更多的关注点放在了区块链真正的技术之上。

Fabric 1.0源代码笔记 之 Tx #RWSet（读写集）

1、RWSet概述

在背书节点模拟Transaction期间，为交易准备了一个读写集合。
Read Set包含模拟Transaction读取的Key和版本的列表，Write Set包含Key、写入的新值、以及删除标记（是否删除Key）。

RWSet相关代码分布在protos/ledger/rwset、core/ledger/kvledger/txmgmt/rwsetutil目录下。目录结构如下：

• protos/ledger/rwset目录：
      * rwset.pb.go，TxReadWriteSet和NsReadWriteSet结构体定义。

    * kv_rwset.pb.go，KVRWSet、KVRead、KVWrite、Version、RangeQueryInfo结构体定义，以及isRangeQueryInfo_ReadsInfo接口定义。

• core/ledger/kvledger/txmgmt/rwsetutil目录：
      * rwset_proto_util.go，TxRwSet和NsRwSet结构体及方法。

    * rwset_builder.go，RWSetBuilder结构体及方法。
    * query_results_helper.go，RangeQueryResultsHelper结构体及方法。

2、TxReadWriteSet结构体（protos）

有个图5

TxReadWriteSet结构体：

type TxReadWriteSet_DataModel int32 const (     TxReadWriteSet_KV TxReadWriteSet_DataModel = 0 ) type TxReadWriteSet struct {     DataModel TxReadWriteSet_DataModel     NsRwset []*NsReadWriteSet } type NsReadWriteSet struct {     Namespace string     Rwset []byte //KVRWSet 序列化 } //代码在protos/ledger/rwset/rwset.pb.go

KVRWSet结构体：

type KVRWSet struct {     Reads []*KVRead     RangeQueriesInfo []*RangeQueryInfo     Writes []*KVWrite } type KVRead struct {     Key string     Version *Version } type KVWrite struct {     Key string     IsDelete bool     Value []byte } type Version struct {     BlockNum uint64     TxNum uint64 } type RangeQueryInfo struct {     StartKey string     EndKey string     ItrExhausted bool     ReadsInfo isRangeQueryInfo_ReadsInfo } 代码在protos/ledger/rwset/kvrwset/kv_rwset.pb.go

3、TxRwSet结构体及方法（core）

有个图6

type TxRwSet struct {     NsRwSets []*NsRwSet } type NsRwSet struct {     NameSpace string     KvRwSet *kvrwset.KVRWSet } //按TxRwSet构造TxReadWriteSet并序列化 func (txRwSet *TxRwSet) ToProtoBytes() ([]byte, error) //[]byte反序列化为TxReadWriteSet，按TxReadWriteSet构造TxRwSet func (txRwSet *TxRwSet) FromProtoBytes(protoBytes []byte) error //构造KVRead func NewKVRead(key string, version *version.Height) *kvrwset.KVRead //构造version.Height func NewVersion(protoVersion *kvrwset.Version) *version.Height //构造Version func newProtoVersion(height *version.Height) *kvrwset.Version //构造KVWrite func newKVWrite(key string, value []byte) *kvrwset.KVWrite //代码在core/ledger/kvledger/txmgmt/rwsetutil/rwset_proto_util.go

4、RWSetBuilder结构体及方法

RWSetBuilder结构体定义：

type RWSetBuilder struct {     rwMap map[string]*nsRWs //Namespace } type nsRWs struct {     readMap map[string]*kvrwset.KVRead //KVRead map     writeMap map[string]*kvrwset.KVWrite //KVWrite map     rangeQueriesMap map[rangeQueryKey]*kvrwset.RangeQueryInfo //RangeQueryInfo map     rangeQueriesKeys []rangeQueryKey //rangeQueryKey数组 } type rangeQueryKey struct {     startKey string     endKey string     itrExhausted bool //迭代器是否用尽 } //代码在core/ledger/kvledger/txmgmt/rwsetutil/rwset_builder.go

涉及方法如下：

//构造nsRWs func newNsRWs() *nsRWs //构造RWSetBuilder func NewRWSetBuilder() *RWSetBuilder //构造KVRead，并加入nsRWs.readMap func (rws *RWSetBuilder) AddToReadSet(ns string, key string, version *version.Height) //构造KVWrite，并加入nsRWs.writeMap func (rws *RWSetBuilder) AddToWriteSet(ns string, key string, value []byte) //用RangeQueryInfo构造rangeQueryKey，并将rangeQueryKey和RangeQueryInfo加入nsRWs.rangeQueriesKeys和nsRWs.rangeQueriesMap func (rws *RWSetBuilder) AddToRangeQuerySet(ns string, rqi *kvrwset.RangeQueryInfo) 从RWSetBuilder构造TxRwSet func (rws *RWSetBuilder) GetTxReadWriteSet() *TxRwSet //获取或创建nsRWs func (rws *RWSetBuilder) getOrCreateNsRW(ns string) *nsRWs //代码在core/ledger/kvledger/txmgmt/rwsetutil/rwset_builder.go

5、RangeQueryResultsHelper结构体及方法（什么用途呢？？？）

5.1、merkleTree（默克尔树）

Merkle Tree，也称Hash Tree，即存储hash值的一棵树。
Merkle树的叶子是数据块的hash值，非叶节点是其对应子节点串联字符串的hash。

type MerkleTreeLevel uint32 type Hash []byte const leafLevel = MerkleTreeLevel(1) type merkleTree struct {     tree map[MerkleTreeLevel][]Hash     maxLevel MerkleTreeLevel //1     maxDegree uint32 //单层最大个数 } //代码在core/ledger/kvledger/txmgmt/rwsetutil/query_results_helper.go

涉及方法如下：

//构造merkleTree func newMerkleTree(maxDegree uint32) (*merkleTree, error) //加入哈希，从第一层开始加，直至当前层哈希数量没有超过限额为止 func (m *merkleTree) update(nextLeafLevelHash Hash) error func (m *merkleTree) done() error func (m *merkleTree) getSummery() *kvrwset.QueryReadsMerkleSummary //构造QueryReadsMerkleSummary func (m *merkleTree) getMaxLevel() MerkleTreeLevel //获取maxLevel func (m *merkleTree) getMaxLevelHashes() []Hash //maxLevel层哈希数组 func (m *merkleTree) isEmpty() bool //maxLevel为1且第1层哈希数组为空 func (m *merkleTree) String() string //String //计算哈希数组合并后哈希 func computeCombinedHash(hashes []Hash) (Hash, error) //[]Hash转换为[][]byte func hashesToBytes(hashes []Hash) [][]byte //代码在core/ledger/kvledger/txmgmt/rwsetutil/query_results_helper.go

func (m *merkleTree) update(nextLeafLevelHash Hash) error代码如下:

//const leafLevel = MerkleTreeLevel(1) m.tree[leafLevel] = append(m.tree[leafLevel], nextLeafLevelHash) //先加入第一层 currentLevel := leafLevel for {     currentLevelHashes := m.tree[currentLevel]     //如果当前层数量没有超过限额，则返回，即Hash加到没有数量超出限额的层为止     if uint32(len(currentLevelHashes)) <= m.maxDegree {         return nil     }     //如果当前层数量超过限额     nextLevelHash, err := computeCombinedHash(currentLevelHashes) //计算当前层合并哈希     delete(m.tree, currentLevel) //删除当前层     nextLevel := currentLevel + 1 //进入更高一层     m.tree[nextLevel] = append(m.tree[nextLevel], nextLevelHash) //合并哈希加入更高一层     if nextLevel > m.maxLevel { //如果更高一层层高超过原定最大高度，则重置最大高度为更高一层层高         m.maxLevel = nextLevel     }     currentLevel = nextLevel //更新当前层为更高一层 } //代码在core/ledger/kvledger/txmgmt/rwsetutil/query_results_helper.go

func (m *merkleTree) done() error代码如下：

currentLevel := leafLevel //从第一层开始 var h Hash var err error for currentLevel < m.maxLevel { //循环至最高层     currentLevelHashes := m.tree[currentLevel]     switch len(currentLevelHashes) {     case 0: //当前层数量为0，进入更高一层         currentLevel++         continue     case 1: //当前层数量为1，获取当前值         h = currentLevelHashes[0]     default: //当前层数量1个，计算合并哈希         h, err = computeCombinedHash(currentLevelHashes)     }     delete(m.tree, currentLevel) //删除当前层     currentLevel++ //进入更高一层     m.tree[currentLevel] = append(m.tree[currentLevel], h) //前一层合并哈希加入本层 } finalHashes := m.tree[m.maxLevel] //最高一层 if uint32(len(finalHashes)) > m.maxDegree { //如果最高一层超出限额     delete(m.tree, m.maxLevel) //删除本层     m.maxLevel++ //进入更高一层     combinedHash, err := computeCombinedHash(finalHashes) //计算合并哈希     m.tree[m.maxLevel] = []Hash{combinedHash} //哈并哈希加入新的最高层 } return nil //代码在core/ledger/kvledger/txmgmt/rwsetutil/query_results_helper.go

5.2 RangeQueryResultsHelper

RangeQueryResultsHelper定义：

type RangeQueryResultsHelper struct {     pendingResults []*kvrwset.KVRead     mt *merkleTree //merkleTree     maxDegree uint32     hashingEnabled bool } //代码在core/ledger/kvledger/txmgmt/rwsetutil/query_results_helper.go

涉及方法如下：

//构造RangeQueryResultsHelper，如果启用哈希将构造merkleTree func NewRangeQueryResultsHelper(enableHashing bool, maxDegree uint32) (*RangeQueryResultsHelper, error) //添加KVRead加入pendingResults，如果pendingResults数量超过限额，执行processPendingResults func (helper *RangeQueryResultsHelper) AddResult(kvRead *kvrwset.KVRead) error //执行processPendingResults，并执行merkleTree.done() func (helper *RangeQueryResultsHelper) Done() ([]*kvrwset.KVRead, *kvrwset.QueryReadsMerkleSummary, error) //获取QueryReadsMerkleSummary func (helper *RangeQueryResultsHelper) GetMerkleSummary() *kvrwset.QueryReadsMerkleSummary //pendingResults序列化并哈希后，加入merkleTree，并清空pendingResults func (helper *RangeQueryResultsHelper) processPendingResults() error //KVRead序列化 func serializeKVReads(kvReads []*kvrwset.KVRead) ([]byte, error)

补充 QueryReadsMerkleSummary：

type QueryReadsMerkleSummary struct {     MaxDegree uint32     MaxLevel uint32     MaxLevelHashes [][]byte } //代码在protos/ledger/rwset/kvrwset/kv_rwset.pb.go