64行代碼實現零拷貝go的TCP拆包粘包

這是一個建立於 的文章，其中的資訊可能已經有所發展或是發生改變。# 64行代碼實現零拷貝go的TCP拆包粘包### 前言這段時間想用go寫一個簡單IM系統，就思考了一下go語言TCP的拆包粘包。TCP的拆包粘包有一般有三種解決方案。#### 使用定長位元組實際使用中，少於固定字長的，要用字元去填充，空間使用率不夠高。#### 使用分隔字元一般用文本傳輸的，使用分隔字元，IM系統一般對效能要求高，不推薦使用文本傳輸。#### 用訊息的頭位元組標識訊息內容的長度可以使用二進位傳輸，效率高，推薦。下面看看怎麼實現。### 嘗試使用系統庫內建的bytes.Buffer實現代碼實現：```gopackage tcpimport ("fmt""net""log""bytes""encoding/binary")const (BYTES_SIZE uint16 = 1024HEAD_SIZE int = 2)func StartServer(address string) {listener, err := net.Listen("tcp", address)if err != nil {log.Println("Error listening", err.Error())return}for {conn, err := listener.Accept()fmt.Println(conn.RemoteAddr())if err != nil {fmt.Println("Error accepting", err.Error())return // 終止程式}go doConn(conn)}}func doConn(conn net.Conn) {var (buffer = bytes.NewBuffer(make([]byte, 0, BYTES_SIZE))bytes = make([]byte, BYTES_SIZE);isHead bool = truecontentSize inthead = make([]byte, HEAD_SIZE)content = make([]byte, BYTES_SIZE))for {readLen, err := conn.Read(bytes);if err != nil {log.Println("Error reading", err.Error())return}_, err = buffer.Write(bytes[0:readLen])if err != nil {log.Println("Error writing to buffer", err.Error())return}for {if isHead {if buffer.Len() >= HEAD_SIZE {_, err := buffer.Read(head)if err != nil {fmt.Println("Error reading", err.Error())return}contentSize = int(binary.BigEndian.Uint16(head))isHead = false} else {break}}if !isHead {if buffer.Len() >= contentSize {_, err := buffer.Read(content[:contentSize])if err != nil {fmt.Println("Error reading", err.Error())return}fmt.Println(string(content[:contentSize]))isHead = true} else {break}}}}}```測試案例：```gopackage tcpimport ("testing""net""fmt""encoding/binary")func TestStartServer(t *testing.T) {StartServer("localhost:50002")}func TestClient(t *testing.T) {conn, err := net.Dial("tcp", "localhost:50002")if err != nil {fmt.Println("Error dialing", err.Error())return // 終止程式}var headSize intvar headBytes = make([]byte, 2)s := "hello world"content := []byte(s)headSize = len(content)binary.BigEndian.PutUint16(headBytes, uint16(headSize))conn.Write(headBytes)conn.Write(content)s = "hello go"content = []byte(s)headSize = len(content)binary.BigEndian.PutUint16(headBytes, uint16(headSize))conn.Write(headBytes)conn.Write(content)s = "hello tcp"content = []byte(s)headSize = len(content)binary.BigEndian.PutUint16(headBytes, uint16(headSize))conn.Write(headBytes)conn.Write(content)}```執行結果```127.0.0.1:51062hello worldhello gohello tcp```用go系統庫的buffer，是不是感覺代碼特別彆扭，兩大缺點1.要寫大量的邏輯代碼，來彌補buffer對這個情境的不適用。2.效能不高，有三次次記憶體拷貝，coon->[]byte->Buffer->[]byte。### 自己實現既然輪子不合適，就自己造輪子，首先實現一個自己的Buffer,很簡單，只有六十幾行代碼，所有過程只有一次byte數組的拷貝，conn->buffer,剩下的全部操作都在原buffer的位元組數組裡面操作```gopackage tcpimport ("errors""io")type buffer struct {reader io.Readerbuf []bytestart intend int}func newBuffer(reader io.Reader, len int) buffer {buf := make([]byte, len)return buffer{reader, buf, 0, 0}}func (b *buffer) Len() int {return b.end - b.start}//將有用的位元組前移func (b *buffer) grow() {if b.start == 0 {return}copy(b.buf, b.buf[b.start:b.end])b.end -= b.startb.start = 0;}//從reader裡面讀取資料，如果reader阻塞，會發生阻塞func (b *buffer) readFromReader() (int, error) {b.grow()n, err := b.reader.Read(b.buf[b.end:])if (err != nil) {return n, err}b.end += nreturn n, nil}//返回n個位元組，而不產生移位func (b *buffer) seek(n int) ([]byte, error) {if b.end-b.start >= n {buf := b.buf[b.start:b.start+n]return buf, nil}return nil, errors.New("not enough")}//捨棄offset個欄位，讀取n個欄位func (b *buffer) read(offset, n int) ([]byte) {b.start += offsetbuf := b.buf[b.start:b.start+n]b.start += nreturn buf}```再看看怎樣使用它,將上面的doConn函數改成這樣就行了。```gofunc doConn(conn net.Conn) {var (buffer = newBuffer(conn, 16)headBuf []bytecontentSize intcontentBuf []byte)for {_, err := buffer.readFromReader()if err != nil {fmt.Println(err)return}for {headBuf, err = buffer.seek(HEAD_SIZE);if err != nil {break}contentSize = int(binary.BigEndian.Uint16(headBuf))if (buffer.Len() >= contentSize-HEAD_SIZE) {contentBuf = buffer.read(HEAD_SIZE, contentSize)fmt.Println(string(contentBuf))continue}break}}}```跑下測試案例，看下結果```127.0.0.1:51062hello worldhello gohello tcp```源碼地址：https://github.com/alberliu/goim你有更好的方式，可以郵箱我，alber_liu@qq.com,讓我學習一下1875 次點擊  ∙  2 贊