我要评论golang切片有浅拷贝和深拷贝的区别
1、深拷贝（deep copy）
拷贝的是数据本身，创造一个样的新对象，新创建的对象与原对象不共享内存，新创建的对象在内存中开辟一个新的内存地址，新对象值修改时不会影响原对象值。既然内存地址不同，释放内存地址时，可分别释放。
值类型的数据，默认全部都是深复制，array、int、string、struct、float，bool。
2、浅拷贝（shallow copy）
拷贝的是数据地址，只复制指向的对象的指针，此时新对象和老对象指向的内存地址是一样的，新对象值修改时老对象也会变化。释放内存地址时，同时释放内存地址。
引用类型的数据，默认全部都是浅复制，slice，map。
去若是浅拷贝，原始的切片变化后所有的切片都会变化，无论切片是否在一个函数，还是一个goroutine中，都会发生变化
如下代码为例子
package main
import "fmt"
func main() {
// 创建一个切片
originalslice := []int{1, 2, 3, 4, 5}
// 使用切片[:]操作符创建浅拷贝
shallowcopy := originalslice[:]
shallowcopy2 := make([]int, len(shallowcopy))
copy(shallowcopy2, originalslice)
// 修改原始切片的元素
originalslice[0] = 100
// 输出原始切片和浅拷贝的切片
fmt.println("original slice:", originalslice)
fmt.println("shallow copy:", shallowcopy)
fmt.println("shallow copy2:", shallowcopy2)
}
如下代码问题困扰了好久，才发现是切片赋值的问题
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)
//可能一次读出来多个数据包 增加处理方式 @20240704
//直接在for循环中使用
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)
///此处经常出现问题
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
}
出现非常奇怪的问题切片内容经常莫名奇妙的改变，最后发现是切片赋值的问题
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: 1961452[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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