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golang切片拷貝的實(shí)現(xiàn)

 更新時(shí)間:2024年10月15日 10:22:37   作者:快刀一哥  
在Golang中,切片的淺拷貝只復(fù)制指向?qū)ο蟮闹羔?而深拷貝則復(fù)制數(shù)據(jù)本身,文中通過(guò)示例代碼介紹的非常詳細(xì),對(duì)大家的學(xué)習(xí)或者工作具有一定的參考學(xué)習(xí)價(jià)值,需要的朋友們下面隨著小編來(lái)一起學(xué)習(xí)學(xué)習(xí)吧

golang切片有淺拷貝和深拷貝的區(qū)別

1、深拷貝(Deep Copy)

拷貝的是數(shù)據(jù)本身,創(chuàng)造一個(gè)樣的新對(duì)象,新創(chuàng)建的對(duì)象與原對(duì)象不共享內(nèi)存,新創(chuàng)建的對(duì)象在內(nèi)存中開(kāi)辟一個(gè)新的內(nèi)存地址,新對(duì)象值修改時(shí)不會(huì)影響原對(duì)象值。既然內(nèi)存地址不同,釋放內(nèi)存地址時(shí),可分別釋放。

值類(lèi)型的數(shù)據(jù),默認(rèn)全部都是深復(fù)制,Array、Int、String、Struct、Float,Bool。

2、淺拷貝(Shallow Copy)

拷貝的是數(shù)據(jù)地址,只復(fù)制指向的對(duì)象的指針,此時(shí)新對(duì)象和老對(duì)象指向的內(nèi)存地址是一樣的,新對(duì)象值修改時(shí)老對(duì)象也會(huì)變化。釋放內(nèi)存地址時(shí),同時(shí)釋放內(nèi)存地址。

引用類(lèi)型的數(shù)據(jù),默認(rèn)全部都是淺復(fù)制,Slice,Map。

去若是淺拷貝,原始的切片變化后所有的切片都會(huì)變化,無(wú)論切片是否在一個(gè)函數(shù),還是一個(gè)goroutine中,都會(huì)發(fā)生變化

如下代碼為例子

package main

import "fmt"

func main() {
	
	// 創(chuàng)建一個(gè)切片
	originalSlice := []int{1, 2, 3, 4, 5}

	// 使用切片[:]操作符創(chuàng)建淺拷貝
	shallowCopy := originalSlice[:]
	shallowCopy2 := make([]int, len(shallowCopy))
	copy(shallowCopy2, originalSlice)

	// 修改原始切片的元素
	originalSlice[0] = 100

	// 輸出原始切片和淺拷貝的切片
	fmt.Println("Original Slice:", originalSlice)
	fmt.Println("Shallow Copy:", shallowCopy)
	fmt.Println("Shallow Copy2:", shallowCopy2)
}

如下代碼問(wèn)題困擾了好久,才發(fā)現(xiàn)是切片賦值的問(wèn)題

func (sf *ServerSession) running(ctx context.Context, subcom []uint8) {
	var err error
	var bytesRead int

	defer func() {
		sf.conn.Close()

	}()
	go sf.prehandler()

	raw := make([]byte, tcpAduMaxSize)

	for {
		select {
		case <-ctx.Done():
			err = errors.New("server active close")
			xlog.Errorln(err)
			return
		default:
		}

		err = sf.conn.SetReadDeadline(time.Now().Add(sf.readTimeout))
		if err != nil {
			xlog.Errorln("set read tcp data time deadline error:", err)
		}
		count, err := sf.conn.Read(raw)

		if err != nil {
			if err != io.EOF && err != io.ErrClosedPipe || strings.Contains(err.Error(), "use of closed network connection") {
				return
			}

			if e, ok := err.(net.Error); ok && !e.Temporary() {
				return
			}

			if bytesRead == 0 && err == io.EOF {
				err = fmt.Errorf("remote client closed, %v", err)
				xlog.Errorln(err)
				return
			}
			// cnt >0 do nothing
			// cnt == 0 && err != io.EOF continue do it next
		}
		adu := raw[:count]

		prodata := new(ProcessData)
		prodata.adu = make([]byte, len(adu))
		copy(prodata.adu, adu)
		prodata.count = count
		prodata.subcom = subcom
		Prodatach <- prodata

	}
}

func (sf *ServerSession) prehandler() {
	for {
		select {
		case prodata := <-Prodatach:
			go sf.prerunhandler(prodata)

		}
	}
}
func (sf *ServerSession) prerunhandler(prodata *ProcessData) {
	length := prodata.count
	adu := make([]byte, len(prodata.adu))
	copy(adu, prodata.adu)
	subcom := prodata.subcom
	xlog.Debug("run handler input1 out1 adu [% X] length is:%d\n", adu, length)
	//可能一次讀出來(lái)多個(gè)數(shù)據(jù)包 增加處理方式 @20240704
	//直接在for循環(huán)中使用
	for length > 0 {
		headdata := adu[:gaHeaderSize]
		head1 := new(gadataHeader)
		buf1 := bytes.NewReader(headdata)
		err := binary.Read(buf1, binary.BigEndian, head1)
		if err != nil {
			xlog.Errorln("ga server decode errr:", err)
		}
		xlog.Debugln("pre process packect SN:", head1.SN)
		galength := int(head1.Datalength) + gaHeaderSize

		if galength <= len(adu) {
			adu1 := adu[:galength]
			xlog.Debug("run handler input out adu [% X ],galength is:%d subcom is %d length is:%d\n", adu1, galength, subcom, length)
			sf.runhandler(adu1, galength, subcom)
			adu = adu[galength:]
			length -= galength

		} else {
			xlog.Debug("data length is %d, adu length is:%d\n", head1.Datalength, len(adu))
			break
		}

	}
}
func (sf *ServerSession) runhandler(adu []byte, count int, subcom []uint8) {
	if count < gaHeaderSize {
		return
	}
	xlog.Debug("run handler input adu [% X ],count is:%d subcom is %d", adu, count, subcom)
	// xlog.Debug("recive data [% x] count is % d \n", adu, count)
	head1 := new(gadataHeader)
	data := adu[:gaHeaderSize]
	buf1 := bytes.NewReader(data)
	err := binary.Read(buf1, binary.BigEndian, head1)
	if err != nil {
		xlog.Errorln("ga server decode errr:", err)
	}
	xlog.Debugln("gaserver head sn:", head1.SN)

	if !Find(subcom, head1.Subcomid) {
		xlog.Debug("subcom: %d is not in array %d \n", head1.Subcomid, subcom)
		return
	}
	// check head ProtocolIdentifier
	// if binary.BigEndian.Uint16(adu[2:]) != tcpProtocolIdentifier {
	// 	rdCnt, length = 0, tcpHeaderMbapSize
	// 	continue
	// }
	length := int(head1.Datalength) + gaHeaderSize
	if count == length {
		xlog.Debug("start decode packet SN is:%d subcom is %d data length is:%d\n", head1.SN, head1.Subcomid, head1.Datalength)
		if err = sf.frameHandler(adu); err != nil {
			xlog.Errorln("gaserver decode error:", err)
			return
		}
	} else {
		xlog.Debug("head data length: %d is not right %d \n", head1.Datalength, count)
		///此處經(jīng)常出現(xiàn)問(wèn)題
		xlog.Debug("adu data is [% X] \n", adu)
	}
}
func Find(subcoms []uint8, subcom uint8) bool {
	for i := 0; i < len(subcoms); i++ {
		if subcoms[i] == subcom {
			return true
		}
	}
	return false
}

出現(xiàn)非常奇怪的問(wèn)題切片內(nèi)容經(jīng)常莫名奇妙的改變,最后發(fā)現(xiàn)是切片賦值的問(wèn)題

1449[xx] 2024-07-05 16:28:03.428417 run handler input1 out1 adu [00 C4 11 0A 01 A3 00 0A 00 A1 42 79 08 20 1F 75 A0 00
 00 C5 11 06 01 A3 00 18 00 79 00 00 00 00 00 C0 C2 92 00 00 00 8D 42 95 85 C5 00 97 42 92 3D 71 ] length is:50
1450 [xx] 2024-07-05 16:28:03.428496 pre process packect SN: 196

1452[xx] 2024-07-05 16:28:03.448860 run handler input out adu [00 C6 11 40 01 A3 00 09 00 B6 00 05 53 65 76 65 6E 00 ],galength is:18 subcom is [17 41] length is:50
1453[xx] 2024-07-05 16:28:03.448985 run handler input adu [00 C6 11 40 01 A3 00 09 00 B6 00 05 53 65 76 65 6E 00 ],count is:18 subcom is [17 41]1454 [xx] 2024-07-05 16:28:03.449011 gaserver head sn: 198

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