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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