Go语言小试牛刀---几个简单的例子
整理资料，发现之前手写的Go语言资料，现在贴过来。
第一个：Channel的使用，创建一个随机数
package main
import "fmt"
import "runtime"
func rand_generator_2() chan int{
out := make(chan int)
go func(){
for{
out<-rand.Int()
}
}()
return out
}
func main(){
rand_service_handler := rand_generator_2()
fmt.Printf("%d\n",<-rand_service_handler)
}
第二个：实现通过Channel通道求和的例子
package main
type NodeInterface interface {
receive(i int)
run() int
}
type Node struct {
name string
in_degree int
in_ch chan int
out_ch chan int
inode NodeInterface
}
func NewNode(name string, inode NodeInterface) *Node {
//创建一个Node，拥有两个channel
return &Node{name, 0, make(chan int), make(chan int), inode}
}
func (from *Node) ConnectTo(to *Node) {
to.in_degree++
go func() {
i := <- from.out_ch
to.in_ch <- i
}()
}
func (n *Node) Run() {
go func() {
defer func() {
if x := recover(); x != nil {
println(n.name, "panic with value ", x)
panic(x)
}
println(n.name, "finished");
}()
for n.in_degree > 0 {
received := <- n.in_ch
n.inode.receive(received)
n.in_degree--
}
ret := n.inode.run()
n.out_ch <- ret
}()
}
type DoubleNode struct {
data int
}
//创建一个新的Node
func NewDoubleNode(name string, data int) *Node {
return NewNode(name, &DoubleNode{data})
}
func (n *DoubleNode) receive(i int) {
}
func (n *DoubleNode) run() int {
return n.data * 2
}
type SumNode struct {
data int
}
func NewSumNode(name string) *Node {
return NewNode(name, &SumNode{0})
}
func (n *SumNode) receive(i int) {
n.data += i
}
func (n *SumNode) run() int {
return n.data
}
func main() {
sum := NewSumNode("sum")
sum.Run()
for _, num := range [5]int{1, 2, 3, 5, 6} {
node := NewDoubleNode("double", num)
node.ConnectTo(sum)
node.Run()
}
println(<- sum.out_ch)
}
第三个例子：Go语言的并发操作，go语言可以适配机器的cpu达到最大并发
package main
import (
"fmt"
"runtime"
)
var workers = runtime.NumCPU()
type Result struct {
jobname string
resultcode int
resultinfo string
}
type Job struct {
jobname string
results chan<- Result
}
func main() {
// go语言里大多数并发程序的开始处都有这一行代码, 但这行代码最终将会是多余的,
// 因为go语言的运行时系统会变得足够聪明以自动适配它所运行的机器
runtime.GOMAXPROCS(runtime.NumCPU())
// 返回当前处理器的数量
fmt.Println(runtime.GOMAXPROCS(0))
// 返回当前机器的逻辑处理器或者核心的数量
fmt.Println(runtime.NumCPU())
// 模拟8个工作任务
jobnames := []string{"gerry", "wcdj", "golang", "C++", "Lua", "perl", "python", "C"}
doRequest(jobnames)
}
func doRequest(jobnames []string) {
// 定义需要的channels切片
jobs := make(chan Job, workers)
results := make(chan Result, len(jobnames))
done := make(chan struct{}, workers)
// ---------------------------------------------
/*
* 下面是go协程并发处理的一个经典框架
*/
// 将需要并发处理的任务添加到jobs的channel中
go addJobs(jobs, jobnames, results) // Executes in its own goroutine
// 根据cpu的数量启动对应个数的goroutines从jobs争夺任务进行处理
for i := 0; i < workers; i++ {
go doJobs(done, jobs) // Each executes in its own goroutine
}
// 新创建一个接受结果的routine, 等待所有worker routiines的完成结果, 并将结果通知主routine
go awaitCompletion(done, results)
// 在主routine输出结果
processResults(results)
// ---------------------------------------------
}
func addJobs(jobs chan<- Job, jobnames []string, results chan<- Result) {
for _, jobname := range jobnames {
// 在channel中添加任务
jobs <- Job{jobname, results}
}
close(jobs)
}
func doJobs(done chan<- struct{}, jobs <-chan Job) {
// 在channel中取出任务并计算
for job := range jobs {
/*
* 定义类型自己的方法来处理业务逻辑, 实现框架和业务分离
*/
job.Do()
}
// 所有任务完成后的结束标志, 一个空结构体切片
done <- struct{}{}
}
// 方法是作用在自定义类型的值上的一类特殊函数
func (job Job) Do() {
// 打印当前处理的任务名称
fmt.Printf("... doing work in [%s]\n", job.jobname)
// 模拟处理结果
if job.jobname == "golang" {
job.results <- Result{job.jobname, 0, "OK"}
} else {
job.results <- Result{job.jobname, -1, "Error"}
}
}
func awaitCompletion(done <-chan struct{}, results chan Result) {
for i := 0; i < workers; i++ {
<-done
}
close(results)
}
func processResults(results <-chan Result) {
for result := range results {
fmt.Printf("done: %s,%d,%s\n", result.jobname, result.resultcode, result.resultinfo)
}
}
第四个：网络编程方面，基于Go实现Ping的操作，比较难，还未看明白
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// taken from http://golang.org/src/pkg/net/ipraw_test.go
package ping
import (
"bytes"
"errors"
"net"
"os"
"time"
)
const (
icmpv4EchoRequest = 8
icmpv4EchoReply = 0
icmpv6EchoRequest = 128
icmpv6EchoReply = 129
)
type icmpMessage struct {
Type int // type
Code int // code
Checksum int // checksum
Body icmpMessageBody // body
}
type icmpMessageBody interface {
Len() int
Marshal() ([]byte, error)
}
// Marshal returns the binary enconding of the ICMP echo request or
// reply message m.
func (m *icmpMessage) Marshal() ([]byte, error) {
b := []byte{byte(m.Type), byte(m.Code), 0, 0}
if m.Body != nil && m.Body.Len() != 0 {
mb, err := m.Body.Marshal()
if err != nil {
return nil, err
}
b = append(b, mb...)
}
switch m.Type {
case icmpv6EchoRequest, icmpv6EchoReply:
return b, nil
}
csumcv := len(b) - 1 // checksum coverage
s := uint32(0)
for i := 0; i < csumcv; i += 2 {
s += uint32(b[i+1])<<8 | uint32(b[i])
}
if csumcv&1 == 0 {
s += uint32(b[csumcv])
}
s = s>>16 + s&0xffff
s = s + s>>16
// Place checksum back in header; using ^= avoids the
// assumption the checksum bytes are zero.
b[2] ^= byte(^s & 0xff)
b[3] ^= byte(^s >> 8)
return b, nil
}
// parseICMPMessage parses b as an ICMP message.
func parseICMPMessage(b []byte) (*icmpMessage, error) {
msglen := len(b)
if msglen < 4 {
return nil, errors.New("message too short")
}
m := &icmpMessage{Type: int(b[0]), Code: int(b[1]), Checksum: int(b[2])<<8 | int(b[3])}
if msglen > 4 {
var err error
switch m.Type {
case icmpv4EchoRequest, icmpv4EchoReply, icmpv6EchoRequest, icmpv6EchoReply:
m.Body, err = parseICMPEcho(b[4:])
if err != nil {
return nil, err
}
}
}
return m, nil
}
// imcpEcho represenets an ICMP echo request or reply message body.
type icmpEcho struct {
ID int // identifier
Seq int // sequence number
Data []byte // data
}
func (p *icmpEcho) Len() int {
if p == nil {
return 0
}
return 4 + len(p.Data)
}
// Marshal returns the binary enconding of the ICMP echo request or
// reply message body p.
func (p *icmpEcho) Marshal() ([]byte, error) {
b := make([]byte, 4+len(p.Data))
b[0], b[1] = byte(p.ID>>8), byte(p.ID&0xff)
b[2], b[3] = byte(p.Seq>>8), byte(p.Seq&0xff)
copy(b[4:], p.Data)
return b, nil
}
// parseICMPEcho parses b as an ICMP echo request or reply message body.
func parseICMPEcho(b []byte) (*icmpEcho, error) {
bodylen := len(b)
p := &icmpEcho{ID: int(b[0])<<8 | int(b[1]), Seq: int(b[2])<<8 | int(b[3])}
if bodylen > 4 {
p.Data = make([]byte, bodylen-4)
copy(p.Data, b[4:])
}
return p, nil
}
func Ping(address string, timeout int) (alive bool) {
err := Pinger(address, timeout)
alive = err == nil
return
}
func Pinger(address string, timeout int) (err error) {
//拨号
c, err := net.Dial("ip4:icmp", address)
if err != nil {
return
}
//?
c.SetDeadline(time.Now().Add(time.Duration(timeout) * time.Second))
defer c.Close()
//>>
typ := icmpv4EchoRequest
xid, xseq := os.Getpid()&0xffff, 1
wb, err := (&icmpMessage{
Type: typ, Code: 0,
Body: &icmpEcho{
ID: xid, Seq: xseq,
Data: bytes.Repeat([]byte("Go Go Gadget Ping!!!"), 3),
},
}).Marshal()
if err != nil {
return
}
if _, err = c.Write(wb); err != nil {
return
}
var m *icmpMessage
rb := make([]byte, 20+len(wb))
for {
if _, err = c.Read(rb); err != nil {
return
}
rb = ipv4Payload(rb)
if m, err = parseICMPMessage(rb); err != nil {
return
}
switch m.Type {
case icmpv4EchoRequest, icmpv6EchoRequest:
continue
}
break
}
return
}
func ipv4Payload(b []byte) []byte {
if len(b) < 20 {
return b
}
hdrlen := int(b[0]&0x0f) << 2
return b[hdrlen:]
}