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blog/golang/golang-concurrency-Mutex.md 0 → 100644
浏览文件 @ 070bdd8d
# Golang 并发编程-Mutex 互斥锁实现同步
Mutex 互斥锁实现同步
示例
```go
package main
import (
"fmt"
"sync"
"time"
)
var value = 100
var wg sync.WaitGroup
var lock sync.Mutex
func add() {
defer wg.Done()
lock.Lock()
time.Sleep(time.Millisecond * 2)
value += 1
fmt.Printf("i++: %v\n", value)
lock.Unlock()
}
func sub() {
defer wg.Done()
lock.Lock()
time.Sleep(time.Millisecond * 10)
value -= 1
fmt.Printf("i--: %v\n", value)
lock.Unlock()
}
func main() {
for i := 0; i < 100; i++ {
wg.Add(1)
go add()
wg.Add(1)
go sub()
}
wg.Wait()
fmt.Printf("end: %v\n", value)
}
```
blog/golang/golang-concurrency-Ticker.md 0 → 100644
浏览文件 @ 070bdd8d
# Golang 并发编程-Ticker 周期执行
Timer 只执行一次，Ticker 可以周期的执行
示例
```go
package main
import (
"fmt"
"time"
)
func main() {
// 执行五次打印
ticker := time.NewTicker(time.Second)
count := 0
for _ = range ticker.C {
fmt.Println("ticker")
count++
if count >= 5 {
ticker.Stop()
break
}
}
}
```
示例
```go
package main
import (
"fmt"
"time"
)
func main() {
ticker := time.NewTicker(time.Second)
chanInt := make(chan int)
// 定时向管道随机发送一个数
go func() {
for _ = range ticker.C {
select {
case chanInt <- 1:
case chanInt <- 2:
case chanInt <- 3:
}
}
}()
// 接收管道数据
sum := 0
for v := range chanInt {
fmt.Printf("v: %v\n", v)
sum += v
if sum >= 10 {
break
}
}
}
```
blog/golang/golang-concurrency-Timer.md 0 → 100644
浏览文件 @ 070bdd8d
# Golang 并发编程-Timer定时器
定时器，可以实现一些定时操作，内部通过 channel 实现
示例
```go
package main
import (
"fmt"
"time"
)
func main() {
timer := time.NewTimer(time.Second * 2)
fmt.Printf("time.Now(): %v\n", time.Now())
// time.Now(): 2022-09-29 22:31:16.348683 +0800 CST m=+0.000252176
// 阻塞，直到到达指定时间
c := <-timer.C
fmt.Printf("c: %v\n", c)
// c: 2022-09-29 22:31:18.35269 +0800 CST m=+2.004256507
}
```
示例
```go
package main
import (
"fmt"
"time"
)
func main() {
timer := time.NewTimer(time.Second * 2)
fmt.Printf("time.Now(): %v\n", time.Now())
// time.Now(): 2022-09-29 22:32:25.585226 +0800 CST m=+0.000134248
// 阻塞，直到到达指定时间
<-timer.C
fmt.Printf("time.Now(): %v\n", time.Now())
// time.Now(): 2022-09-29 22:32:27.585439 +0800 CST m=+2.000219266
}
```
示例
```go
package main
import (
"fmt"
"time"
)
func main() {
fmt.Printf("time.Now(): %v\n", time.Now())
// time.Now(): 2022-09-29 22:34:08.764178 +0800 CST m=+0.000082405
time.Sleep(time.Second * 2)
fmt.Printf("time.Now(): %v\n", time.Now())
// time.Now(): 2022-09-29 22:34:10.765022 +0800 CST m=+2.000924537
}
```
示例
```go
package main
import (
"fmt"
"time"
)
func main() {
fmt.Printf("time.Now(): %v\n", time.Now())
// time.Now(): 2022-09-29 22:34:41.029391 +0800 CST m=+0.000077713
<-time.After(time.Second * 2)
fmt.Printf("time.Now(): %v\n", time.Now())
// time.Now(): 2022-09-29 22:34:43.031081 +0800 CST m=+2.001766091
}
```
示例
```go
package main
import (
"fmt"
"time"
)
func main() {
timer := time.NewTimer(time.Second * 1)
go func() {
<-timer.C
fmt.Println("func")
}()
// 停止定时器
stop := timer.Stop()
if stop {
fmt.Println("stop")
}
time.Sleep(time.Second * 2)
}
```
示例
```go
package main
import (
"fmt"
"time"
)
func main() {
timer := time.NewTimer(time.Second * 5)
// 重新设置定时器时间
timer.Reset(time.Second * 1)
<-timer.C
fmt.Println("end")
}
```
blog/golang/golang-concurrency-WaitGroup.md 0 → 100644
浏览文件 @ 070bdd8d
# Golang 并发编程-WaitGroup实现同步
示例1
```go
package main
import (
"fmt"
)
func showMessage(i int) {
fmt.Printf("i: %v\n", i)
}
func main() {
for i := 0; i < 10; i++ {
showMessage(i)
}
}
```
输出
```go
i: 0
i: 1
i: 2
i: 3
i: 4
i: 5
i: 6
i: 7
i: 8
i: 9
```
示例 2
```go
package main
import (
"fmt"
)
func showMessage(i int) {
fmt.Printf("i: %v\n", i)
}
func main() {
for i := 0; i < 10; i++ {
// 启动协程来执行
go showMessage(i)
}
// 主协程执行结束
fmt.Println("end")
}
```
输出
```go
i: 0
end
```
示例 3
```go
package main
import (
"fmt"
"sync"
)
var wp sync.WaitGroup
func showMessage(i int) {
defer wp.Done()
fmt.Printf("i: %v\n", i)
}
func main() {
for i := 0; i < 10; i++ {
go showMessage(i)
wp.Add(1)
}
wp.Wait()
fmt.Println("end")
}
```
输出
```
i: 4
i: 1
i: 0
i: 5
i: 7
i: 8
i: 2
i: 3
i: 9
i: 6
end
```
blog/golang/golang-concurrency-atomic.md 0 → 100644
浏览文件 @ 070bdd8d
# Golang 并发编程-atomic原子操作
## 原子变量
不加锁示例
```go
package main
import (
"fmt"
"time"
)
var value = 100
func add() {
value++
}
func sub() {
value--
}
func main() {
for i := 0; i < 100; i++ {
go add()
go sub()
}
time.Sleep(time.Second * 2)
fmt.Printf("value: %v\n", value)
// value: 101
}
```
加锁示例
```go
package main
import (
"fmt"
"sync"
"time"
)
var value = 100
var lock sync.Mutex
func add() {
lock.Lock()
value++
lock.Unlock()
}
func sub() {
lock.Lock()
value--
lock.Unlock()
}
func main() {
for i := 0; i < 100; i++ {
go add()
go sub()
}
time.Sleep(time.Second * 2)
fmt.Printf("value: %v\n", value)
// value: 100
}
```
atomic示例
cas: compare and swap (old new)
```go
package main
import (
"fmt"
"sync/atomic"
"time"
)
var value int32 = 100
func add() {
atomic.AddInt32(&value, 1)
}
func sub() {
atomic.AddInt32(&value, -1)
}
func main() {
for i := 0; i < 100; i++ {
go add()
go sub()
}
time.Sleep(time.Second * 2)
fmt.Printf("value: %v\n", value)
// value: 100
}
```
## 原子操作详解
atomic 提供的原子操作能够确保任一时刻，只有一个goroutine对变量进行操作
善用atomic能够避免程序中出现大量的锁操作
atomic常见的操作有：
- 增减
- 载入 read
- 比较并交换cas
- 交换
- 存储 write
### 增减
```go
package main
import (
"fmt"
"sync/atomic"
)
func main() {
var value int32 = 100
atomic.AddInt32(&value, 1)
fmt.Printf("value: %v\n", value)
// value: 101
atomic.AddInt32(&value, -1)
fmt.Printf("value: %v\n", value)
// value: 100
}
```
### 读写
```go
package main
import (
"fmt"
"sync/atomic"
)
func main() {
var value int32 = 100
// read
atomic.LoadInt32(&value)
fmt.Printf("value: %v\n", value)
// value: 100
// write
atomic.StoreInt32(&value, 200)
fmt.Printf("value: %v\n", value)
// value: 200
}
```
### 比较并交换cas
```go
package main
import (
"fmt"
"sync/atomic"
)
func main() {
var value int32 = 100
// cas
ret := atomic.CompareAndSwapInt32(&value, 100, 200)
fmt.Printf("ret: %v\n", ret)
// ret: true
fmt.Printf("value: %v\n", value)
// value: 200
}
```
### 交换
```go
package main
import (
"fmt"
"sync/atomic"
)
func main() {
var value int32 = 100
// 直接交换
atomic.SwapInt32(&value, 200)
fmt.Printf("value: %v\n", value)
// value: 200
}
```
blog/golang/golang-concurrency-channel.md 0 → 100644
浏览文件 @ 070bdd8d
# Golang 并发编程-channel
Go 提供了一种通道机制，用于 goroutine 之间`共享数据`
通道需要指定`数据类型`
通道分类：
- 无缓冲通道 同步通讯
- 缓冲通道 异步通讯
语法
```go
// 整型无缓冲通道，默认零值
Unbuffered := make(chan int)
// 整型缓冲通道
buffered := make(chan int, 10)
```
通道数据交换
```go
channel := make(chan string, 5)
// 将值发送到通道
channel <- "hello"
// 从通道接收值
data := <- channel
```
通道的发送和接收特性
- 同一通道，发送操作之间是互斥的，接收操作之间也是互斥的
- 发送操作和接收操作中对元素值的处理都是不可分割的
- 发送操作在完全完成之前会被阻塞，接收操作也是如此
示例
```go
package main
import (
"fmt"
"math/rand"
"time"
)
// 创建一个int类型的通道
var value = make(chan int)
func send() {
// 向通道发送一个随机值
rand.Seed(time.Now().UnixNano())
v := rand.Intn(10)
time.Sleep(time.Second * 3)
value <- v
}
func main() {
// 关闭通道
defer close(value)
go send()
fmt.Println("wait...")
// 从通道接收值
v := <-value
fmt.Printf("v: %v\n", v)
}
```
## Channel遍历
示例
```go
package main
import "fmt"
var c = make(chan int)
func main() {
go func() {
for i := 0; i < 2; i++ {
c <- i
}
// 不关闭可能出现死锁
close(c)
}()
// 方式一
// for i := 0; i < 2; i++ {
// v := <-c
// fmt.Printf("v: %v\n", v)
// }
// 方式二
// for v := range c {
// fmt.Printf("v: %v\n", v)
// }
// 方式三
for {
v, ok := <-c
if ok {
fmt.Printf("v: %v\n", v)
} else {
break
}
}
}
```
blog/golang/golang-concurrency-goroutines.md 0 → 100644
浏览文件 @ 070bdd8d
# Golang 并发编程-协程
共语言中的并发是`函数`相互独立运行的能力。goroutines 是并发运行的函数
创建协程
```go
go task()
```
示例 1
```go
package main
import (
"fmt"
"time"
)
func showMessage(message string) {
for i := 0; i < 5; i++ {
fmt.Println(message)
time.Sleep(time.Millisecond * 100)
}
}
func main() {
showMessage("Tom")
showMessage("Jack")
}
```
输出
```
Tom
Tom
Tom
Tom
Tom
Jack
Jack
Jack
Jack
Jack
```
```go
func main() {
go showMessage("Tom")
showMessage("Jack")
}
```
输出
```go
Jack
Tom
Tom
Jack
Jack
Tom
Tom
Jack
Jack
Tom
```
示例 2
```go
package main
import (
"fmt"
"io/ioutil"
"log"
"net/http"
"time"
)
func responseSize(url string) {
fmt.Println("step1: ", url)
response, err := http.Get(url)
if err != nil {
log.Fatal(err)
}
fmt.Println("step2: ", url)
defer response.Body.Close()
fmt.Println("step3: ", url)
body, err := ioutil.ReadAll(response.Body)
if err != nil {
log.Fatal(err)
}
fmt.Println("step4: ", len(body))
}
func main() {
go responseSize("https://www.baidu.com/")
go responseSize("https://www.jd.com/")
go responseSize("https://www.taobao.com/")
time.Sleep(time.Second * 10)
}
```
输出
```
step1: https://www.baidu.com/
step1: https://www.jd.com/
step1: https://www.taobao.com/
step2: https://www.jd.com/
step3: https://www.jd.com/
step4: 160260
step2: https://www.baidu.com/
step3: https://www.baidu.com/
step4: 227
step2: https://www.taobao.com/
step3: https://www.taobao.com/
step4: 87347
```
blog/golang/golang-concurrency-runtime.md 0 → 100644
浏览文件 @ 070bdd8d
# Golang 并发编程-runtime包
runtime定义了协程管理的包
## Gosched
让出执行权限
示例
```go
package main
import (
"fmt"
)
func show() {
for i := 0; i < 2; i++ {
fmt.Printf("show i: %v\n", i)
}
}
func main() {
go show()
for i := 0; i < 2; i++ {
fmt.Printf("main i: %v\n", i)
}
fmt.Println("end")
}
```
输出
```
main i: 0
main i: 1
end
```
示例 2
```go
package main
import (
"fmt"
"runtime"
)
func show() {
for i := 0; i < 2; i++ {
fmt.Printf("show i: %v\n", i)
}
}
func main() {
go show()
for i := 0; i < 2; i++ {
// 让出执行权限，给其他子协程执行
runtime.Gosched()
fmt.Printf("main i: %v\n", i)
}
fmt.Println("end")
}
```
输出
```
show i: 0
main i: 0
main i: 1
end
```
## Goexit
退出当前协程
示例
```go
package main
import (
"fmt"
"runtime"
"time"
)
func show() {
for i := 0; i < 10; i++ {
fmt.Printf("show i: %v\n", i)
if i >= 5 {
runtime.Goexit()
}
}
}
func main() {
go show()
time.Sleep(time.Second)
fmt.Println("end")
}
```
输出
```
show i: 0
show i: 1
show i: 2
show i: 3
show i: 4
show i: 5
end
```
## GOMAXPROCS
设置CPU数量
```go
package main
import (
"fmt"
"runtime"
"time"
)
func show(name string) {
for i := 0; i < 10; i++ {
fmt.Printf("%v i: %v\n", name, i)
}
}
func main() {
// 查看CPU核数
fmt.Printf("runtime.NumCPU(): %v\n", runtime.NumCPU())
// runtime.NumCPU(): 8
// 设置CPU数量
runtime.GOMAXPROCS(2)
go show("A")
go show("B")
time.Sleep(time.Second)
fmt.Println("end")
}
```
blog/golang/golang-concurrency-select-switch.md 0 → 100644
浏览文件 @ 070bdd8d
# Golang 并发编程-select switch
select 是go中的一个控制结构，类似于switch语句，用于处理异步IO操作
select 会监听case语句中channel的读写操作，当case中channel读写操作为非阻塞状态（即能读写）时，将会触发相应的动作
sekect 中的case语句必须是一个channel操作
select 中的default子句总是可运行的
如果有多个case都可以运行，select会`随机`公平地选出一个执行，其他不会执行
如果没有可运行的case语句，且有default语句，那么就会执行default语句
如果没有可运行的case语句，且没有default语句，select将`阻塞`，知道某个case通信可以运行
示例
```go
package main
import (
"fmt"
"time"
)
var chanInt = make(chan int)
var chanString = make(chan string)
func main() {
go func() {
chanInt <- 10
chanString <- "Tom"
defer close(chanInt)
defer close(chanString)
}()
for {
select {
case i := <-chanInt:
fmt.Printf("int: %v\n", i)
case i := <-chanString:
fmt.Printf("string: %v\n", i)
default:
fmt.Println("default")
}
time.Sleep(time.Second)
}
}
```
blog/golang/golang-concurrency.md 已删除 100644 → 0
浏览文件 @ b28d0c5b
# 第二十章 Golang 并发编程
## 协程
共语言中的并发是`函数`相互独立运行的能力。goroutines 是并发运行的函数
创建协程
```go
go task()
```
示例 1
```go
package main
import (
"fmt"
"time"
)
func showMessage(message string) {
for i := 0; i < 5; i++ {
fmt.Println(message)
time.Sleep(time.Millisecond * 100)
}
}
func main() {
showMessage("Tom")
showMessage("Jack")
}
```
输出
```
Tom
Tom
Tom
Tom
Tom
Jack
Jack
Jack
Jack
Jack
```
```go
func main() {
go showMessage("Tom")
showMessage("Jack")
}
```
输出
```go
Jack
Tom
Tom
Jack
Jack
Tom
Tom
Jack
Jack
Tom
```
示例 2
```go
package main
import (
"fmt"
"io/ioutil"
"log"
"net/http"
"time"
)
func responseSize(url string) {
fmt.Println("step1: ", url)
response, err := http.Get(url)
if err != nil {
log.Fatal(err)
}
fmt.Println("step2: ", url)
defer response.Body.Close()
fmt.Println("step3: ", url)
body, err := ioutil.ReadAll(response.Body)
if err != nil {
log.Fatal(err)
}
fmt.Println("step4: ", len(body))
}
func main() {
go responseSize("https://www.baidu.com/")
go responseSize("https://www.jd.com/")
go responseSize("https://www.taobao.com/")
time.Sleep(time.Second * 10)
}
```
输出
```
step1: https://www.baidu.com/
step1: https://www.jd.com/
step1: https://www.taobao.com/
step2: https://www.jd.com/
step3: https://www.jd.com/
step4: 160260
step2: https://www.baidu.com/
step3: https://www.baidu.com/
step4: 227
step2: https://www.taobao.com/
step3: https://www.taobao.com/
step4: 87347
```
## channel
Go提供了一种通道机制，用于goroutine之间`共享数据`
通道需要指定`数据类型`
通道分类：
- 无缓冲通道 同步通讯
- 缓冲通道 异步通讯
语法
```go
// 整型无缓冲通道，默认零值
Unbuffered := make(chan int)
// 整型缓冲通道
buffered := make(chan int, 10)
```
通道数据交换
```go
channel := make(chan string, 5)
// 将值发送到通道
channel <- "hello"
// 从通道接收值
data := <- channel
```
通道的发送和接收特性
- 同一通道，发送操作之间是互斥的，接收操作之间也是互斥的
- 发送操作和接收操作中对元素值的处理都是不可分割的
- 发送操作在完全完成之前会被阻塞，接收操作也是如此
示例
```go
package main
import (
"fmt"
"math/rand"
"time"
)
// 创建一个int类型的通道
var value = make(chan int)
func send() {
// 向通道发送一个随机值
rand.Seed(time.Now().UnixNano())
v := rand.Intn(10)
time.Sleep(time.Second * 3)
value <- v
}
func main() {
// 关闭通道
defer close(value)
go send()
fmt.Println("wait...")
// 从通道接收值
v := <-value
fmt.Printf("v: %v\n", v)
}
```
## WaitGroup实现同步
示例1
```go
package main
import (
"fmt"
)
func showMessage(i int) {
fmt.Printf("i: %v\n", i)
}
func main() {
for i := 0; i < 10; i++ {
showMessage(i)
}
}
```
输出
```go
i: 0
i: 1
i: 2
i: 3
i: 4
i: 5
i: 6
i: 7
i: 8
i: 9
```
示例 2
```go
package main
import (
"fmt"
)
func showMessage(i int) {
fmt.Printf("i: %v\n", i)
}
func main() {
for i := 0; i < 10; i++ {
// 启动协程来执行
go showMessage(i)
}
// 主协程执行结束
fmt.Println("end")
}
```
输出
```go
i: 0
end
```
示例 3
```go
package main
import (
"fmt"
"sync"
)
var wp sync.WaitGroup
func showMessage(i int) {
defer wp.Done()
fmt.Printf("i: %v\n", i)
}
func main() {
for i := 0; i < 10; i++ {
go showMessage(i)
wp.Add(1)
}
wp.Wait()
fmt.Println("end")
}
```
输出
```
i: 4
i: 1
i: 0
i: 5
i: 7
i: 8
i: 2
i: 3
i: 9
i: 6
end
```
## runtime包
runtime定义了协程管理的包
### Gosched
让出执行权限
示例
```go
package main
import (
"fmt"
)
func show() {
for i := 0; i < 2; i++ {
fmt.Printf("show i: %v\n", i)
}
}
func main() {
go show()
for i := 0; i < 2; i++ {
fmt.Printf("main i: %v\n", i)
}
fmt.Println("end")
}
```
输出
```
main i: 0
main i: 1
end
```
示例 2
```go
package main
import (
"fmt"
"runtime"
)
func show() {
for i := 0; i < 2; i++ {
fmt.Printf("show i: %v\n", i)
}
}
func main() {
go show()
for i := 0; i < 2; i++ {
// 让出执行权限，给其他子协程执行
runtime.Gosched()
fmt.Printf("main i: %v\n", i)
}
fmt.Println("end")
}
```
输出
```
show i: 0
main i: 0
main i: 1
end
```
### Goexit
退出当前协程
示例
```go
package main
import (
"fmt"
"runtime"
"time"
)
func show() {
for i := 0; i < 10; i++ {
fmt.Printf("show i: %v\n", i)
if i >= 5 {
runtime.Goexit()
}
}
}
func main() {
go show()
time.Sleep(time.Second)
fmt.Println("end")
}
```
输出
```
show i: 0
show i: 1
show i: 2
show i: 3
show i: 4
show i: 5
end
```
### GOMAXPROCS
设置CPU数量
```go
package main
import (
"fmt"
"runtime"
"time"
)
func show(name string) {
for i := 0; i < 10; i++ {
fmt.Printf("%v i: %v\n", name, i)
}
}
func main() {
// 查看CPU核数
fmt.Printf("runtime.NumCPU(): %v\n", runtime.NumCPU())
// runtime.NumCPU(): 8
// 设置CPU数量
runtime.GOMAXPROCS(2)
go show("A")
go show("B")
time.Sleep(time.Second)
fmt.Println("end")
}
```
## Mutex 互斥锁实现同步
示例
```go
package main
import (
"fmt"
"sync"
"time"
)
var value = 100
var wg sync.WaitGroup
var lock sync.Mutex
func add() {
defer wg.Done()
lock.Lock()
time.Sleep(time.Millisecond * 2)
value += 1
fmt.Printf("i++: %v\n", value)
lock.Unlock()
}
func sub() {
defer wg.Done()
lock.Lock()
time.Sleep(time.Millisecond * 10)
value -= 1
fmt.Printf("i--: %v\n", value)
lock.Unlock()
}
func main() {
for i := 0; i < 100; i++ {
wg.Add(1)
go add()
wg.Add(1)
go sub()
}
wg.Wait()
fmt.Printf("end: %v\n", value)
}
```
## Channel遍历
示例
```go
package main
import "fmt"
var c = make(chan int)
func main() {
go func() {
for i := 0; i < 2; i++ {
c <- i
}
// 不关闭可能出现死锁
close(c)
}()
// 方式一
// for i := 0; i < 2; i++ {
// v := <-c
// fmt.Printf("v: %v\n", v)
// }
// 方式二
// for v := range c {
// fmt.Printf("v: %v\n", v)
// }
// 方式三
for {
v, ok := <-c
if ok {
fmt.Printf("v: %v\n", v)
} else {
break
}
}
}
```
## select switch
select 是go中的一个控制结构，类似于switch语句，用于处理异步IO操作
select 会监听case语句中channel的读写操作，当case中channel读写操作为非阻塞状态（即能读写）时，将会触发相应的动作
sekect 中的case语句必须是一个channel操作
select 中的default子句总是可运行的
如果有多个case都可以运行，select会`随机`公平地选出一个执行，其他不会执行
如果没有可运行的case语句，且有default语句，那么就会执行default语句
如果没有可运行的case语句，且没有default语句，select将`阻塞`，知道某个case通信可以运行
示例
```go
package main
import (
"fmt"
"time"
)
var chanInt = make(chan int)
var chanString = make(chan string)
func main() {
go func() {
chanInt <- 10
chanString <- "Tom"
defer close(chanInt)
defer close(chanString)
}()
for {
select {
case i := <-chanInt:
fmt.Printf("int: %v\n", i)
case i := <-chanString:
fmt.Printf("string: %v\n", i)
default:
fmt.Println("default")
}
time.Sleep(time.Second)
}
}
```
## Timer
定时器，可以实现一些定时操作，内部通过channel实现
示例
```go
package main
import (
"fmt"
"time"
)
func main() {
timer := time.NewTimer(time.Second * 2)
fmt.Printf("time.Now(): %v\n", time.Now())
// time.Now(): 2022-09-29 22:31:16.348683 +0800 CST m=+0.000252176
// 阻塞，直到到达指定时间
c := <-timer.C
fmt.Printf("c: %v\n", c)
// c: 2022-09-29 22:31:18.35269 +0800 CST m=+2.004256507
}
```
示例
```go
package main
import (
"fmt"
"time"
)
func main() {
timer := time.NewTimer(time.Second * 2)
fmt.Printf("time.Now(): %v\n", time.Now())
// time.Now(): 2022-09-29 22:32:25.585226 +0800 CST m=+0.000134248
// 阻塞，直到到达指定时间
<-timer.C
fmt.Printf("time.Now(): %v\n", time.Now())
// time.Now(): 2022-09-29 22:32:27.585439 +0800 CST m=+2.000219266
}
```
示例
```go
package main
import (
"fmt"
"time"
)
func main() {
fmt.Printf("time.Now(): %v\n", time.Now())
// time.Now(): 2022-09-29 22:34:08.764178 +0800 CST m=+0.000082405
time.Sleep(time.Second * 2)
fmt.Printf("time.Now(): %v\n", time.Now())
// time.Now(): 2022-09-29 22:34:10.765022 +0800 CST m=+2.000924537
}
```
示例
```go
package main
import (
"fmt"
"time"
)
func main() {
fmt.Printf("time.Now(): %v\n", time.Now())
// time.Now(): 2022-09-29 22:34:41.029391 +0800 CST m=+0.000077713
<-time.After(time.Second * 2)
fmt.Printf("time.Now(): %v\n", time.Now())
// time.Now(): 2022-09-29 22:34:43.031081 +0800 CST m=+2.001766091
}
```
示例
```go
package main
import (
"fmt"
"time"
)
func main() {
timer := time.NewTimer(time.Second * 1)
go func() {
<-timer.C
fmt.Println("func")
}()
// 停止定时器
stop := timer.Stop()
if stop {
fmt.Println("stop")
}
time.Sleep(time.Second * 2)
}
```
示例
```go
package main
import (
"fmt"
"time"
)
func main() {
timer := time.NewTimer(time.Second * 5)
// 重新设置定时器时间
timer.Reset(time.Second * 1)
<-timer.C
fmt.Println("end")
}
```
## Ticker
Timer只执行一次，Ticker可以周期的执行
示例
```go
package main
import (
"fmt"
"time"
)
func main() {
// 执行五次打印
ticker := time.NewTicker(time.Second)
count := 0
for _ = range ticker.C {
fmt.Println("ticker")
count++
if count >= 5 {
ticker.Stop()
break
}
}
}
```
示例
```go
package main
import (
"fmt"
"time"
)
func main() {
ticker := time.NewTicker(time.Second)
chanInt := make(chan int)
// 定时向管道随机发送一个数
go func() {
for _ = range ticker.C {
select {
case chanInt <- 1:
case chanInt <- 2:
case chanInt <- 3:
}
}
}()
// 接收管道数据
sum := 0
for v := range chanInt {
fmt.Printf("v: %v\n", v)
sum += v
if sum >= 10 {
break
}
}
}
```
## 原子变量
不加锁示例
```go
package main
import (
"fmt"
"time"
)
var value = 100
func add() {
value++
}
func sub() {
value--
}
func main() {
for i := 0; i < 100; i++ {
go add()
go sub()
}
time.Sleep(time.Second * 2)
fmt.Printf("value: %v\n", value)
// value: 101
}
```
加锁示例
```go
package main
import (
"fmt"
"sync"
"time"
)
var value = 100
var lock sync.Mutex
func add() {
lock.Lock()
value++
lock.Unlock()
}
func sub() {
lock.Lock()
value--
lock.Unlock()
}
func main() {
for i := 0; i < 100; i++ {
go add()
go sub()
}
time.Sleep(time.Second * 2)
fmt.Printf("value: %v\n", value)
// value: 100
}
```
atomic示例
cas: compare and swap (old new)
```go
package main
import (
"fmt"
"sync/atomic"
"time"
)
var value int32 = 100
func add() {
atomic.AddInt32(&value, 1)
}
func sub() {
atomic.AddInt32(&value, -1)
}
func main() {
for i := 0; i < 100; i++ {
go add()
go sub()
}
time.Sleep(time.Second * 2)
fmt.Printf("value: %v\n", value)
// value: 100
}
```
## 原子操作详解
atomic 提供的原子操作能够确保任一时刻，只有一个goroutine对变量进行操作
善用atomic能够避免程序中出现大量的锁操作
atomic常见的操作有：
- 增减
- 载入 read
- 比较并交换cas
- 交换
- 存储 write
### 增减
```go
package main
import (
"fmt"
"sync/atomic"
)
func main() {
var value int32 = 100
atomic.AddInt32(&value, 1)
fmt.Printf("value: %v\n", value)
// value: 101
atomic.AddInt32(&value, -1)
fmt.Printf("value: %v\n", value)
// value: 100
}
```
### 读写
```go
package main
import (
"fmt"
"sync/atomic"
)
func main() {
var value int32 = 100
// read
atomic.LoadInt32(&value)
fmt.Printf("value: %v\n", value)
// value: 100
// write
atomic.StoreInt32(&value, 200)
fmt.Printf("value: %v\n", value)
// value: 200
}
```
### 比较并交换cas
```go
package main
import (
"fmt"
"sync/atomic"
)
func main() {
var value int32 = 100
// cas
ret := atomic.CompareAndSwapInt32(&value, 100, 200)
fmt.Printf("ret: %v\n", ret)
// ret: true
fmt.Printf("value: %v\n", value)
// value: 200
}
```
### 交换
```go
package main
import (
"fmt"
"sync/atomic"
)
func main() {
var value int32 = 100
// 直接交换
atomic.SwapInt32(&value, 200)
fmt.Printf("value: %v\n", value)
// value: 200
}
```
blog/golang/index.md
浏览文件 @ 070bdd8d
......@@ -46,7 +46,17 @@
[第十九章 Golang包 package](/blog/golang/golang-package.md)
[第二十章 Golang 并发编程](/blog/golang/golang-concurrency.md)
第二十章 Golang 并发编程
- [Golang 并发编程-协程](/blog/golang/golang-concurrency-goroutines.md)
- [Golang 并发编程-channel](/blog/golang/golang-concurrency-channel.md)
- [Golang 并发编程-WaitGroup实现同步](/blog/golang/golang-concurrency-WaitGroup.md)
- [Golang 并发编程-runtime包](/blog/golang/golang-concurrency-runtime.md)
- [Golang 并发编程-Mutex 互斥锁实现同步](/blog/golang/golang-concurrency-Mutex.md)
- [Golang 并发编程-atomic原子操作](/blog/golang/golang-concurrency-atomic.md)
- [Golang 并发编程-select switch](/blog/golang/golang-concurrency-select-switch.md)
- [Golang 并发编程-Timer定时器](/blog/golang/golang-concurrency-Timer.md)
- [Golang 并发编程-Ticker 周期执行](/blog/golang/golang-concurrency-Ticker.md)
第二十一章 Golang标准库
......
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