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）

TxReadWriteSet结构体：

type TxReadWriteSet_DataModel int32const (    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）

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TxRwSetfunc (txRwSet *TxRwSet) FromProtoBytes(protoBytes []byte) error//构造KVReadfunc NewKVRead(key string, version *version.Height) *kvrwset.KVRead//构造version.Heightfunc NewVersion(protoVersion *kvrwset.Version) *version.Height//构造Versionfunc newProtoVersion(height *version.Height) *kvrwset.Version//构造KVWritefunc 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nsRWsfunc newNsRWs() *nsRWs//构造RWSetBuilderfunc NewRWSetBuilder() *RWSetBuilder//构造KVRead，并加入nsRWs.readMapfunc (rws *RWSetBuilder) AddToReadSet(ns string, key string, version *version.Height)//构造KVWrite，并加入nsRWs.writeMapfunc (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.rangeQueriesMapfunc (rws *RWSetBuilder) AddToRangeQuerySet(ns string, rqi *kvrwset.RangeQueryInfo)从RWSetBuilder构造TxRwSetfunc (rws *RWSetBuilder) GetTxReadWriteSet() *TxRwSet//获取或创建nsRWsfunc (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 uint32type Hash []byteconst 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merkleTreefunc 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QueryReadsMerkleSummaryfunc (m *merkleTree) getMaxLevel() MerkleTreeLevel //获取maxLevelfunc (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[][]bytefunc 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 := leafLevelfor {    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 Hashvar err errorfor 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merkleTreefunc NewRangeQueryResultsHelper(enableHashing bool, maxDegree uint32) (*RangeQueryResultsHelper, error)//添加KVRead加入pendingResults，如果pendingResults数量超过限额，执行processPendingResultsfunc (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QueryReadsMerkleSummaryfunc (helper *RangeQueryResultsHelper) GetMerkleSummary() *kvrwset.QueryReadsMerkleSummary//pendingResults序列化并哈希后，加入merkleTree，并清空pendingResultsfunc (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