func main() {
 //創(chuàng)建map
 m := make(map[int]string)
 //聲明一個(gè)長(zhǎng)度為2的倒計(jì)時(shí)門(mén)閂
 var wg sync.WaitGroup
 wg.Add(2)

 //協(xié)程1寫(xiě)
 go func() {
  for true {
   m[0] = "xiaoming"
  }
  wg.Done()
 }()

 //協(xié)程2讀
 go func() {
  for true {
   _ = m[0]
  }
  wg.Done()

 }()

 wg.Wait()
 fmt.Println("結(jié)束")
}

var mu sync.Mutex


func main() {
 //創(chuàng)建map
 m := make(map[int]string)
 
 var wg sync.WaitGroup
 wg.Add(2)

 //協(xié)程1上鎖后寫(xiě)
 go func() {

  for true {
   mu.Lock()
   m[0] = "xiaoming"
   mu.Unlock()
  }
  wg.Done()
 }()

 //協(xié)程2上鎖后讀
 go func() {
  for true {
   mu.Lock()
   _ = m[0]
   mu.Unlock()
  }
  wg.Done()

 }()

 wg.Wait()
 fmt.Println("結(jié)束")
}

func main() {
 //創(chuàng)建sync.Map
 var m sync.Map
 
 
 var wg sync.WaitGroup
 wg.Add(2)

 //協(xié)程1并發(fā)寫(xiě)
 go func() {

  for true {
   m.Store(1, "xiaoming")
  }
  wg.Done()
 }()

 //協(xié)程2并發(fā)讀
 go func() {
  for true {
   m.Load(1)
  }
  wg.Done()

 }()

 wg.Wait()
 fmt.Println("結(jié)束")
}

type Map struct {
 //重量級(jí)鎖
 mu Mutex
 //read指針，指向一個(gè)不可變的key數(shù)組
 read atomic.Pointer[readOnly]

 //dirty 指針指向可以進(jìn)行追加操作的key數(shù)組
 dirty map[any]*entry

 //當(dāng)前map讀寫(xiě)未命中次數(shù)
 misses int
}

func (m *Map) Store(key, value any) {
 _, _ = m.Swap(key, value)
}

func (m *Map) Swap(key, value any) (previous any, loaded bool) {
 //上read嘗試修改
 read := m.loadReadOnly()
 if e, ok := read.m[key]; ok {
  if v, ok := e.trySwap(&value); ok {
   if v == nil {
    return nil, false
   }
   return *v, true
  }
 }
 //上重量級(jí)鎖和read原子指針加載進(jìn)行修改
 m.mu.Lock()
 read = m.loadReadOnly()
 if e, ok := read.m[key]; ok {
  if e.unexpungeLocked() {
   
   m.dirty[key] = e
  }
  if v := e.swapLocked(&value); v != nil {
   loaded = true
   previous = *v
  }
 } else if e, ok := m.dirty[key]; ok { //如果在dirty數(shù)組發(fā)現(xiàn)則上swap鎖進(jìn)行修改
  if v := e.swapLocked(&value); v != nil {
   loaded = true
   previous = *v
  }
 } else {//上述情況都不符合則將amended 標(biāo)記為true后進(jìn)行追加
  if !read.amended {
   
   m.dirtyLocked()
   m.read.Store(&readOnly{m: read.m, amended: true})
  }
  m.dirty[key] = newEntry(value)
 }
 //解鎖返回
 m.mu.Unlock()
 return previous, loaded
}

func (m *Map) Load(key any) (value any, ok bool) {
 //加載讀原子變量
 read := m.loadReadOnly()
 //嘗試在read指針下讀取
 e, ok := read.m[key]
 //沒(méi)讀取到上mutex鎖到dirty下讀取，若發(fā)現(xiàn)則更新未命中數(shù)后返回結(jié)果
 if !ok && read.amended {
  m.mu.Lock()
  
  read = m.loadReadOnly()
  e, ok = read.m[key]
  if !ok && read.amended {
   e, ok = m.dirty[key]
   //更新未命中數(shù)
   m.missLocked()
  }
  m.mu.Unlock()
 }
 if !ok {
  return nil, false
 }
 return e.load()
}

func (m *Map) LoadAndDelete(key any) (value any, loaded bool) {
 //上讀鎖定位元素
 read := m.loadReadOnly()
 
 e, ok := read.m[key]
 //為命中則上重量級(jí)鎖到read和dirty下再次查找，找到了則刪除，若是在dirty下找到還需要額外更新一下未命中數(shù)
 if !ok && read.amended {
  m.mu.Lock()
  read = m.loadReadOnly()
  e, ok = read.m[key]
  if !ok && read.amended {
   e, ok = m.dirty[key]
   delete(m.dirty, key)
   //自增一次未命中數(shù)
   m.missLocked()
  }
  m.mu.Unlock()
 }
 if ok {
  return e.delete()
 }
 return nil, false
}

// Delete deletes the value for a key.
func (m *Map) Delete(key any) {
 m.LoadAndDelete(key)
}