Go语言小试牛刀---几个简单的例子

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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:]
}