goConcurrency/channel.go

package goConcurrency

import (
	"fmt"
	"math/rand"
	"runtime"
	"sync"
	"time"
)

func ChannelOperate() {
	// 初始化
	ch := make(chan int) // 无缓冲的channel

	// send
	go func() {
		// send statement 发送语句
		ch <- 42 + 1024
	}()

	// receive
	go func() {
		// receive operation, 接收操作符
		v := <-ch
		println("Received from ch, value is ", v)
	}()

	time.Sleep(time.Second)

	// close
	close(ch)
}

func ChannelFor() {
	// 一，初始化部分数据
	ch := make(chan int) // 无缓冲的channel
	wg := sync.WaitGroup{}

	// 二，持续发送
	wg.Add(1)
	go func() {
		defer wg.Done()
		for i := 0; i < 5; i++ {
			// random send value
			ch <- rand.Intn(10)
		}
		// 关闭
		close(ch)
	}()

	// 三，持续接收，for range
	wg.Add(1)
	go func() {
		defer wg.Done()
		// 持续接收
		for e := range ch {
			println("received from ch, element is ", e)
		}
	}()

	wg.Wait()
}

func ChannelSync() {
	// 初始化内容
	ch := make(chan int)
	println("Len:", len(ch), ",Cap:", cap(ch))
	wg := sync.WaitGroup{}

	// 二，间隔发送
	wg.Add(1)
	go func() {
		defer wg.Done()
		for i := 0; i < 5; i++ {
			// send to ch
			ch <- i
			// .Format(layout) 格式化时间
			println("Send ", i, ".\tNow:", time.Now().Format("15:04:05.999999999"))
			// 间隔时间
			time.Sleep(1 * time.Second)
		}
		// close channel
		close(ch)
	}()

	// 三，间隔接收
	wg.Add(1)
	go func() {
		defer wg.Done()
		// receive from ch
		// until ch closed
		for v := range ch {
			println("Received ", v, ".\tNow:", time.Now().Format("15:04:05.999999999"))
			// 间隔时间，注意与send的间隔时间不同
			time.Sleep(3 * time.Second)
		}
	}()

	//
	wg.Wait()
}

func ChannelAsync() {
	// 初始化内容
	ch := make(chan int, 5)
	println("Len:", len(ch), ",Cap:", cap(ch))
	wg := sync.WaitGroup{}

	// 二，间隔发送
	wg.Add(1)
	go func() {
		defer wg.Done()
		for i := 0; i < 5; i++ {
			// send to ch
			ch <- i
			// .Format(layout) 格式化时间
			println("Send ", i, ".\tNow:", time.Now().Format("15:04:05.999999999"), ".Len:", len(ch), ",Cap:", cap(ch))
			// 间隔时间
			time.Sleep(1 * time.Second)
		}
		// close channel
		close(ch)
	}()

	// 三，间隔接收
	wg.Add(1)
	go func() {
		defer wg.Done()
		// receive from ch
		// until ch closed
		for v := range ch {
			println("Received ", v, ".\tNow:", time.Now().Format("15:04:05.999999999"), ".Len:", len(ch), ",Cap:", cap(ch))
			// 间隔时间，注意与send的间隔时间不同
			time.Sleep(3 * time.Second)
		}
	}()

	//
	wg.Wait()
}

func ChannelGoroutineNumCtl() {
	// 1 独立的goroutine输出goroutine数量
	go func() {
		for {
			fmt.Println("NumGoroutine:", runtime.NumGoroutine())
			time.Sleep(500 * time.Millisecond)
		}
	}()

	// 2 初始化channel，设置缓冲大小（并发规模）
	const size = 1024
	ch := make(chan struct{}, size)

	// 3 并发的goroutine
	for {
		// 一，启动goroutine前，执行 ch send
		// 当ch的缓冲已满时，阻塞
		ch <- struct{}{}
		go func() {
			time.Sleep(10 * time.Second)
			// 二，goroutine结束时，接收一个ch中的元素
			<-ch
		}()
	}
}

func ChannelDirectional() {
	// 初始化数据
	ch := make(chan int)    // 双向的channel
	wg := &sync.WaitGroup{} // *sync.WaitGroup

	// 单向channel函数go调用
	wg.Add(2)
	// 使用双向channel为单向channel赋值
	go getElement(ch, wg)
	go setElement(ch, 42, wg)

	//
	wg.Wait()
}

// only receive channel
// 语法即注释，使程序更加优雅
func getElement(ch <-chan int, wg *sync.WaitGroup) {
	defer wg.Done()
	//ch <- 10, 限制该操作不能执行

	println("received from ch, element is ", <-ch)
}

// only send channel
func setElement(ch chan<- int, v int, wg *sync.WaitGroup) {
	defer wg.Done()
	// <-ch 限制该操作不能执行
	ch <- v
	println("send to ch, element is ", v)
}