package main

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

var lock sync.Mutex
var rwlock sync.RWMutex

func testSync() { //互斥锁
	var a map[int]int
	a = make(map[int]int)
	a[2] = 2 * 2
	a[3] = 3 * 3
	a[4] = 4 * 4
	a[5] = 5 * 5

	for i := 0; i < 2; i++ {
		go func(b map[int]int) {
			lock.Lock()
			b[2] = rand.Intn(100)
			fmt.Println(b)
			lock.Unlock()
		}(a)
	}
	time.Sleep(time.Second)

}
func testRWlock() {//读写锁的性能比互斥锁好上100倍，
	//读多写少的情况的用读写锁，可以有多个线程读，只有一个线程写
	var a map[int]int
	a = make(map[int]int)
	a[2] = 2 * 2
	a[3] = 3 * 3
	a[4] = 4 * 4
	a[5] = 5 * 5

	for i := 0; i < 2; i++ {
		go func(b map[int]int) {
			rwlock.Lock()
			b[2] = rand.Intn(100)
			time.Sleep(10*time.Millisecond)
			rwlock.Unlock()
		}(a)
	}
	var count int32
	for i := 0; i < 100; i++ {
		go func(b map[int]int) {
			for{
				// lock.Lock()
				rwlock.RLock()
				time.Sleep(time.Millisecond)
				// fmt.Println(b)
				rwlock.RUnlock()
				// lock.Unlock()
				atomic.AddInt32(&count,1)
			}
			
			
			
		}(a)
	}
	
	time.Sleep(time.Second*2)
	fmt.Println(atomic.LoadInt32(&count))
	

}
func main() {
	// testSync()
	testRWlock()
}