# 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：
```go
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：
```go
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）
```go
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：
```go
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：
```go
//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。
```go
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：
```go
//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:
```go
//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：
```go
currentLevel := leafLevel
//从第一层开始
var h Hash
var err error
for currentLevel //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：
```go
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：
```go
//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：
```go
type
QueryReadsMerkleSummary
struct {
MaxDegree
uint32
MaxLevel
uint32
MaxLevelHashes [][]
byte
}
//代码在protos/ledger/rwset/kvrwset/kv_rwset.pb.go
```
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