兄弟连区块链教程Fabric1.0源代码分析Peer DeliverClient（Deliver客户端），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。
# Fabric1.0源代码笔记之Peer DeliverClient（Deliver客户端）
## 1、DeliverClient概述
DeliverClient代码分布如下：
* peer/channel/deliverclient.go，deliverClientIntf接口定义及实现，以及DeliverClient工具函数。
* protos/orderer/ab.pb.go，AtomicBroadcast_DeliverClient接口定义和实现。
## 2、deliverClientIntf接口定义及实现
### 2.1、DeliverClient工具函数
```go
//构造deliverClient
func newDeliverClient(conn *grpc.ClientConn, client ab.AtomicBroadcast_DeliverClient, chainID string) *deliverClient
//代码在peer/channel/deliverclient.go
```
### 2.2、deliverClientIntf接口定义及实现
```go
type deliverClientIntf interface {
getSpecifiedBlock(num uint64) (*common.Block, error)
getOldestBlock() (*common.Block, error)
getNewestBlock() (*common.Block, error)
Close() error
}
type deliverClient struct {
conn *grpc.ClientConn
client ab.AtomicBroadcast_DeliverClient
chainID string
}
//构造查询Envelope
func seekHelper(chainID string, position *ab.SeekPosition) *common.Envelope
//r.client.Send(seekHelper(r.chainID, &ab.SeekPosition{Type: &ab.SeekPosition_Specified{Specified: &ab.SeekSpecified{Number: blockNumber}}}))
func (r *deliverClient) seekSpecified(blockNumber uint64) error
//r.client.Send(seekHelper(r.chainID, &ab.SeekPosition{Type: &ab.SeekPosition_Oldest{Oldest: &ab.SeekOldest{}}}))
func (r *deliverClient) seekOldest() error
//return r.client.Send(seekHelper(r.chainID, &ab.SeekPosition{Type: &ab.SeekPosition_Newest{Newest: &ab.SeekNewest{}}}))
func (r *deliverClient) seekNewest() error
//r.client.Recv()读取块
func (r *deliverClient) readBlock() (*common.Block, error)
//r.seekSpecified(num)和r.readBlock()
func (r *deliverClient) getSpecifiedBlock(num uint64) (*common.Block, error)
//r.seekOldest()和r.readBlock()
func (r *deliverClient) getOldestBlock() (*common.Block, error)
//r.seekNewest()和r.readBlock()
func (r *deliverClient) getNewestBlock() (*common.Block, error)
//r.conn.Close()
func (r *deliverClient) Close() error
//cf.DeliverClient.getSpecifiedBlock(0)获取创世区块
func getGenesisBlock(cf *ChannelCmdFactory) (*common.Block, error)
//代码在peer/channel/deliverclient.go
```
func seekHelper(chainID string, position *ab.SeekPosition) *common.Envelope代码如下：
```go
func seekHelper(chainID string, position *ab.SeekPosition) *common.Envelope {
seekInfo := &ab.SeekInfo{
Start: position,
Stop: position,
Behavior: ab.SeekInfo_BLOCK_UNTIL_READY,
}
msgVersion := int32(0)
epoch := uint64(0)
env, err := utils.CreateSignedEnvelope(common.HeaderType_CONFIG_UPDATE, chainID, localmsp.NewSigner(), seekInfo, msgVersion, epoch)
return env
}
//代码在peer/channel/deliverclient.go
```
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