package main

import "fmt"

type Person struct {
	age int
}

// 如果实现了接收者是指针类型的方法，会隐含地也实现了接收者是值类型的IncrAge1方法。
// 会修改age的值
func (p *Person) IncrAge1() {
	p.age += 1
}

// 如果实现了接收者是值类型的方法，会隐含地也实现了接收者是指针类型的IncrAge2方法。
// 不会修改age的值
func (p Person) IncrAge2() {
	p.age += 1
}

// 如果实现了接收者是值类型的方法，会隐含地也实现了接收者是指针类型的GetAge方法。
func (p Person) GetAge() int {
	return p.age
}

func main() {
	// p1 是值类型
	p := Person{age: 10}

	// 值类型 调用接收者是指针类型的方法
	p.IncrAge1()
	fmt.Println(p.GetAge())
	// 值类型 调用接收者是值类型的方法
	p.IncrAge2()
	fmt.Println(p.GetAge())

	// ----------------------

	// p2 是指针类型
	p2 := &Person{age: 20}

	// 指针类型 调用接收者是指针类型的方法
	p2.IncrAge1()
	fmt.Println(p2.GetAge())
	// 指针类型 调用接收者是值类型的方法
	p2.IncrAge2()
	fmt.Println(p2.GetAge())
}
/*
11
11
21
21
*/

package main

import "fmt"

func add(x, y int) *int {
	res := 0
	res = x + y
	return &res
}

func main() {
	fmt.Println(add(1, 2))
}

./main.go:6:2: res escapes to heap:
./main.go:6:2:   flow: ~r2 = &res:
./main.go:6:2:     from &res (address-of) at ./main.go:8:9
./main.go:6:2:     from return &res (return) at ./main.go:8:2
./main.go:6:2: moved to heap: res
./main.go:12:13: ... argument does not escape
0xc0000ae008

package main

import "fmt"

func main() {
    m := make(map[string]int)
    m["age"] = 8

    fmt.Printf("原始map的内存地址是：%p\n", &m)
    modifyMap(m)
    fmt.Printf("改动后的值是: %v\n", m)
}

func modifyMap(m map[string]int) {
    fmt.Printf("函数里接收到map的内存地址是：%p\n", &m)
    m["age"] = 9
}
/*
原始map的内存地址是：0xc00000e028
函数里接收到map的内存地址是：0xc00000e038
改动后的值是: map[age:9]
通过make函数创建的map变量本质是一个hmap类型的指针*hmap，所以函数内对形参的修改，会修改原内容数据(channel也如此)
*/

func A(i int) {
    defer A1(i, 2*i)
    if(i > 1) {
        defer A2("Hello", "eggo")
    }
    // code to do something
    return
}
func A1(a,b int) {
    //......
}
func A2(m,n string) {
    //......
}

func A(i int) {
        // code to do something
    if(i > 1){
       A2("Hello", "eggo")
    }
    A1(i, 2*i)
    return
}

package main

import "fmt"

// defer：延迟函数执行，先进后出
func main() {
    defer fmt.Println("defer1")
    defer fmt.Println("defer2")
    defer fmt.Println("defer3")
    defer fmt.Println("defer4")
    fmt.Println("11111")
}

// 11111
// defer4
// defer3
// defer2
// defer1

package main

import "fmt"

// panic后的defer函数不会被执行
func main() {
    defer fmt.Println("panic before")
    panic("发生panic")
    defer func() {
        fmt.Println("panic after")
    }()
}

// panic before
// panic: 发生panic

package main

import "fmt"

func F() {
    defer func() {
        fmt.Println("b")
    }()
    panic("a")
}

// 子函数抛出的panic没有recover时，上层函数时，程序直接异常终止
func main() {
    defer func() {
        fmt.Println("c")
    }()
    F()
    fmt.Println("继续执行")
}

// b
// c
// panic: a

package main

import "fmt"

func F() {
    defer func() {
        if err := recover(); err != nil {
            fmt.Println("捕获异常:", err)
        }
        fmt.Println("b")
    }()
    panic("a")
}

func main() {
    defer func() {
        fmt.Println("c")
    }()
    F()
    fmt.Println("继续执行")
}

// 捕获异常: a
// b
// 继续执行
// c

package main

import "fmt"

func main() {

	defer func() {
		if v := recover();v == 11 {
			fmt.Println("v:",v)
		}
		fmt.Printf("defer1...")
		}()

	defer func() {
		fmt.Printf("defer2...")
	}()

	array := [2]int{1,2}
	fmt.Println("array: ",array[1])
	panic(11)
}
//array:  2
//defer2...
//v:  11   
//defer1...

func foo() (ret int) {
    defer func() {
        ret++
    }()

    return 0
}

func a() {
    i := 0
    defer fmt.Println(i)
    i++
    return
}

func make(t Type, size ...IntegerType) Type

func new(Type) *Type

type slice struct {
    array unsafe.Pointer
    len   int
    cap   int
}

// 初始化方式1：直接声明
var slice1 []int

// 初始化方式2：使用字面量
slice2 := []int{1, 2, 3, 4}

// 初始化方式3：使用make创建slice
slice3 := make([]int, 3, 5)         

// 初始化方式4: 从切片或数组“截取”
slcie4 := arr[1:3]

package main

import "fmt"

func main() {
    slice := make([]int, 0)
    slice = append(slice, 1)
    fmt.Println(slice, len(slice), cap(slice))
}

func makeslice(et *_type, len, cap int) unsafe.Pointer {
    mem, overflow := math.MulUintptr(et.size, uintptr(cap))
    if overflow || mem > maxAlloc || len < 0 || len > cap {
        // NOTE: Produce a 'len out of range' error instead of a
        // 'cap out of range' error when someone does make([]T, bignumber).
        // 'cap out of range' is true too, but since the cap is only being
        // supplied implicitly, saying len is clearer.
        // See golang.org/issue/4085.
        mem, overflow := math.MulUintptr(et.size, uintptr(len))
        if overflow || mem > maxAlloc || len < 0 {
            panicmakeslicelen()
        }
        panicmakeslicecap()
    }

    return mallocgc(mem, et, true)
}

func main() {
    slice1 := []int{1, 2, 3, 4, 5}
    slice2 := make([]int, 5, 5)
    fmt.Printf("slice1: %v, %p\n", slice1, slice1)
    copy(slice2, slice1)
    fmt.Printf("slice2: %v, %p\n", slice2, slice2)
    slice3 := make([]int, 0, 5)
    for _, v := range slice1 {
        slice3 = append(slice3, v)
    }
    fmt.Printf("slice3: %v, %p\n", slice3, slice3)
}

slice1: [1 2 3 4 5], 0xc0000b0030
slice2: [1 2 3 4 5], 0xc0000b0060
slice3: [1 2 3 4 5], 0xc0000b0090

func main() {
    slice1 := []int{1, 2, 3, 4, 5}
    fmt.Printf("slice1: %v, %p\n", slice1, slice1)
    slice2 := slice1
    fmt.Printf("slice2: %v, %p\n", slice2, slice2)
}

slice1: [1 2 3 4 5], 0xc00001a120
slice2: [1 2 3 4 5], 0xc00001a120

/**
* 切片非并发安全
* 多次执行，每次得到的结果都不一样
* 可以考虑使用 channel 本身的特性 (阻塞) 来实现安全的并发读写
 */
func TestSliceConcurrencySafe(t *testing.T) {
 a := make([]int, 0)
 var wg sync.WaitGroup
 for i := 0; i < 10000; i++ {
  wg.Add(1)
  go func(i int) {
   a = append(a, i)
   wg.Done()
  }(i)
 }
 wg.Wait()
 t.Log(len(a)) 
 // not equal 10000
}

// A header for a Go map.
type hmap struct {
    count     int 
    // 代表哈希表中的元素个数，调用len(map)时，返回的就是该字段值。
    flags     uint8 
    // 状态标志（是否处于正在写入的状态等）
    B         uint8  
    // buckets（桶）的对数
    // 如果B=5，则buckets数组的长度 = 2^B=32，意味着有32个桶
    noverflow uint16 
    // 溢出桶的数量
    hash0     uint32 
    // 生成hash的随机数种子
    buckets    unsafe.Pointer 
    // 指向buckets数组的指针，数组大小为2^B，如果元素个数为0，它为nil。
    oldbuckets unsafe.Pointer 
    // 如果发生扩容，oldbuckets是指向老的buckets数组的指针，老的buckets数组大小是新的buckets的1/2;非扩容状态下，它为nil。
    nevacuate  uintptr        
    // 表示扩容进度，小于此地址的buckets代表已搬迁完成。
    extra *mapextra 
    // 存储溢出桶，这个字段是为了优化GC扫描而设计的，下面详细介绍
 }

// A bucket for a Go map.
type bmap struct {
    tophash [bucketCnt]uint8        
    // len为8的数组
    // 用来快速定位key是否在这个bmap中
    // 一个桶最多8个槽位，如果key所在的tophash值在tophash中，则代表该key在这个桶中
}

type bmap struct{
    tophash [8]uint8
    keys [8]keytype 
    // keytype 由编译器编译时候确定
    values [8]elemtype 
    // elemtype 由编译器编译时候确定
    overflow uintptr 
    // overflow指向下一个bmap，overflow是uintptr而不是*bmap类型，保证bmap完全不含指针，是为了减少gc，溢出桶存储到extra字段中
}

emptyRest      = 0 // 表明此桶单元为空，且更高索引的单元也是空
emptyOne       = 1 // 表明此桶单元为空
evacuatedX     = 2 // 用于表示扩容迁移到新桶前半段区间
evacuatedY     = 3 // 用于表示扩容迁移到新桶后半段区间
evacuatedEmpty = 4 // 用于表示此单元已迁移
minTopHash     = 5 // key的tophash值与桶状态值分割线值，小于此值的一定代表着桶单元的状态，大于此值的一定是key对应的tophash值

func tophash(hash uintptr) uint8 {
    top := uint8(hash >> (goarch.PtrSize*8 - 8))
    if top < minTopHash {
        top += minTopHash
    }
    return top
}

type mapextra struct {
    overflow    *[]*bmap
    // overflow 包含的是 hmap.buckets 的 overflow 的 buckets
    oldoverflow *[]*bma
   // oldoverflow 包含扩容时 hmap.oldbuckets 的 overflow 的 bucket
    nextOverflow *bmap 
     // 指向空闲的 overflow bucket 的指针
}

func TestMapRange(t *testing.T) {
    m := map[int]string{1: "a", 2: "b", 3: "c"}
    t.Log("first range:")
    for i, v := range m {
        t.Logf("m[%v]=%v ", i, v)
    }
    t.Log("\nsecond range:")
    for i, v := range m {
        t.Logf("m[%v]=%v ", i, v)
    }

    // 实现有序遍历
    var sl []int
    // 把 key 单独取出放到切片
    for k := range m {
        sl = append(sl, k)
    }
    // 排序切片
    sort.Ints(sl)
    // 以切片中的 key 顺序遍历 map 就是有序的了
    for _, k := range sl {
        t.Log(k, m[k])
    }
}

package main

import (
    "fmt"
    "time"
)

func main() {
    s := make(map[int]int)
    for i := 0; i < 100; i++ {
        go func(i int) {
            s[i] = i
        }(i)
    }
    for i := 0; i < 100; i++ {
        go func(i int) {
            fmt.Printf("map第%d个元素值是%d\n", i, s[i])
        }(i)
    }
    time.Sleep(1 * time.Second)
}

package main

import (
    "fmt"
    "sync"
    "time"
)

func main() {
    var lock sync.RWMutex
    s := make(map[int]int)
    for i := 0; i < 100; i++ {
        go func(i int) {
            lock.Lock()
            s[i] = i
            lock.Unlock()
        }(i)
    }
    for i := 0; i < 100; i++ {
        go func(i int) {
            lock.RLock()
            fmt.Printf("map第%d个元素值是%d\n", i, s[i])
            lock.RUnlock()
        }(i)
    }
    time.Sleep(1 * time.Second)
}

package main

import (
    "fmt"
    "sync"
    "time"
)

func main() {
    var m sync.Map
    for i := 0; i < 100; i++ {
        go func(i int) {
            m.Store(i, i)
        }(i)
    }
    for i := 0; i < 100; i++ {
        go func(i int) {
            v, ok := m.Load(i)
            fmt.Printf("Load: %v, %v\n", v, ok)
        }(i)
    }
    time.Sleep(1 * time.Second)
}

if h.flags&hashWriting != 0 {
    throw("concurrent map read and map write")
}

hash := t.hasher(key, uintptr(h.hash0))

hash := t.hasher(key, uintptr(h.hash0))
// 桶的个数m-1，即 1<<B-1,B=5时，则有0~31号桶
m := bucketMask(h.B)
// 计算哈希值对应的bucket
// t.bucketsize为一个bmap的大小，通过对哈希值和桶个数取模得到桶编号，通过对桶编号和buckets起始地址进行运算，获取哈希值对应的bucket
b := (*bmap)(add(h.buckets, (hash&m)*uintptr(t.bucketsize)))
// 是否在扩容
if c := h.oldbuckets; c != nil {
  // 桶个数已经发生增长一倍，则旧bucket的桶个数为当前桶个数的一半
    if !h.sameSizeGrow() {
        // There used to be half as many buckets; mask down one more power of two.
        m >>= 1
    }
    // 计算哈希值对应的旧bucket
    oldb := (*bmap)(add(c, (hash&m)*uintptr(t.bucketsize)))
    // 如果旧bucket的数据没有完成迁移，则使用旧bucket查找
    if !evacuated(oldb) {
        b = oldb
    }
}

top := tophash(hash)
func tophash(hash uintptr) uint8 {
    top := uint8(hash >> (goarch.PtrSize*8 - 8))
    if top < minTopHash {
        top += minTopHash
    }
    return top
}

for ; b != nil; b = b.overflow(t) {
        for i := uintptr(0); i < bucketCnt; i++ {
            if b.tophash[i] != top {
              // 未被使用的槽位，插入
                if b.tophash[i] == emptyRest {
                    break bucketloop
                }
                continue
            }
            // 找到tophash值对应的的key
            k := add(unsafe.Pointer(b), dataOffset+i*uintptr(t.keysize))
            if t.key.equal(key, k) {
                e := add(unsafe.Pointer(b), dataOffset+bucketCnt*uintptr(t.keysize)+i*uintptr(t.elemsize))
                return e
            }
        }
    }

// keys的偏移量
dataOffset = unsafe.Offsetof(struct{
  b bmap
  v int64
}{}.v)

// 一个bucket的元素个数
bucketCnt = 8

// key 定位公式
k :=add(unsafe.Pointer(b),dataOffset+i*uintptr(t.keysize))

// value 定位公式
v:= add(unsafe.Pointer(b),dataOffset+bucketCnt*uintptr(t.keysize)+i*uintptr(t.valuesize))

if inserti == nil {
        // all current buckets are full, allocate a new one.
        newb := h.newoverflow(t, b)
        // 创建一个新的溢出桶
        inserti = &newb.tophash[0]
        insertk = add(unsafe.Pointer(newb), dataOffset)
        elem = add(insertk, bucketCnt*uintptr(t.keysize))
}

if !h.growing() && (overLoadFactor(h.count+1, h.B) || tooManyOverflowBuckets(h.noverflow, h.B)) {
  hashGrow(t, h)
  goto again // Growing the table invalidates everything, so try again
}

// 判断是否在扩容
func (h *hmap) growing() bool {
    return h.oldbuckets != nil
}

func overLoadFactor(count int, B uint8) bool {
   return count > bucketCnt && uintptr(count) > loadFactor*bucketShift(B)
}

/*
其中 

bucketCnt = 8，一个桶可以装的最大元素个数
loadFactor = 6.5，负载因子，平均每个桶的元素个数
bucketShift(B): 桶的个数
*/

func tooManyOverflowBuckets(noverflow uint16, B uint8) bool {
    // If the threshold is too low, we do extraneous work.
    // If the threshold is too high, maps that grow and shrink can hold on to lots of unused memory.
    // "too many" means (approximately) as many overflow buckets as regular buckets.
    // See incrnoverflow for more details.
    if B > 15 {
        B = 15
    }
    // The compiler doesn't see here that B < 16; mask B to generate shorter shift code.
    return noverflow >= uint16(1)<<(B&15)
}

func hashGrow(t *maptype, h *hmap) {
   // 如果达到条件 1，那么将B值加1，相当于是原来的2倍
   // 否则对应条件 2，进行等量扩容，所以 B 不变
     bigger := uint8(1)
     if !overLoadFactor(h.count+1, h.B) {
         bigger = 0
         h.flags |= sameSizeGrow
     }
   // 记录老的buckets
    oldbuckets := h.buckets
  // 申请新的buckets空间
    newbuckets, nextOverflow := makeBucketArray(t, h.B+bigger, nil)
  // 注意&^ 运算符，这块代码的逻辑是转移标志位
    flags := h.flags &^ (iterator | oldIterator)
    if h.flags&iterator != 0 {
        flags |= oldIterator
    }
    // 提交grow (atomic wrt gc)
    h.B += bigger
    h.flags = flags
    h.oldbuckets = oldbuckets
    h.buckets = newbuckets
  // 搬迁进度为0
    h.nevacuate = 0
  // overflow buckets 数为0
    h.noverflow = 0

  // 如果发现hmap是通过extra字段 来存储 overflow buckets时
    if h.extra != nil && h.extra.overflow != nil {
        if h.extra.oldoverflow != nil {
            throw("oldoverflow is not nil")
        }
        h.extra.oldoverflow = h.extra.overflow
        h.extra.overflow = nil
    }
    if nextOverflow != nil {
        if h.extra == nil {
            h.extra = new(mapextra)
        }
        h.extra.nextOverflow = nextOverflow
    }
}

func growWork(t *maptype, h *hmap, bucket uintptr) {
    // 为了确认搬迁的 bucket 是我们正在使用的 bucket
    // 即如果当前key映射到老的bucket1，那么就搬迁该bucket1。
    evacuate(t, h, bucket&h.oldbucketmask())
    // 如果还未完成扩容工作，则再搬迁一个bucket。
    if h.growing() {
        evacuate(t, h, h.nevacuate)
    }
}

type Map struct {
   mu Mutex
   read atomic.Value // readOnly
   dirty map[interface{}]*entry
   misses int
}

type hchan struct {
 closed   uint32   // channel是否关闭的标志
 elemtype *_type   // channel中的元素类型
 
 // channel分为无缓冲和有缓冲两种。
 // 对于有缓冲的channel存储数据，使用了 ring buffer（环形缓冲区) 来缓存写入的数据，本质是循环数组
 // 为啥是循环数组？普通数组不行吗，普通数组容量固定更适合指定的空间，弹出元素时，普通数组需要全部都前移
 // 当下标超过数组容量后会回到第一个位置，所以需要有两个字段记录当前读和写的下标位置
 buf      unsafe.Pointer // 指向底层循环数组的指针（环形缓冲区）
 qcount   uint           // 循环数组中的元素数量
 dataqsiz uint           // 循环数组的长度
 elemsize uint16                 // 元素的大小
 sendx    uint           // 下一次写下标的位置
 recvx    uint           // 下一次读下标的位置
  
 // 尝试读取channel或向channel写入数据而被阻塞的goroutine
 recvq    waitq  // 读等待队列
 sendq    waitq  // 写等待队列

 lock mutex //互斥锁，保证读写channel时不存在并发竞争问题
}

type waitq struct {
   first *sudog
   last  *sudog
}

type sudog struct {
    g *g
    next *sudog
    prev *sudog
    elem unsafe.Pointer 
    c        *hchan 
    ...
}

func makechan64(t *chantype, size int64) *hchan {
    if int64(int(size)) != size {
        panic(plainError("makechan: size out of range"))
    }

    return makechan(t, int(size))
}

// 带缓冲
ch := make(chan int, 3)
// 不带缓冲
ch := make(chan int)

func chansend(c *hchan, ep unsafe.Pointer, block bool, callerpc uintptr) bool 

ch <- 10

select {
    case ch <- 10:
    ...

  default
}

func chanrecv(c *hchan, ep unsafe.Pointer, block bool) (selected, received bool) 

<ch

v := <ch

v, ok := <ch

// 当channel关闭时，for循环会自动退出，无需主动监测channel是否关闭，可以防止读取已经关闭的channel,造成读到数据为通道所存储的数据类型的零值
for i := range ch {
    fmt.Println(i)
}

select {
    case <-ch:
    ...

  default
}

close(ch)

func closechan(c *hchan) 

package main

import (
    "fmt"
    "time"
    "unsafe"
)

func main() {
  // ch是长度为4的带缓冲的channel
  // 初始hchan结构体重的buf为空，sendx和recvx均为0
    ch := make(chan string, 4)
    fmt.Println(ch, unsafe.Sizeof(ch))
    go sendTask(ch)
    go receiveTask(ch)
    time.Sleep(1 * time.Second)
}

// G1是发送者
// 当G1向ch里发送数据时，首先会对buf加锁，然后将task存储的数据copy到buf中，然后sendx++，然后释放对buf的锁
func sendTask(ch chan string) {
    taskList := []string{"this", "is", "a", "demo"}
    for _, task := range taskList {
        ch <- task //发送任务到channel
    }
}

// G2是接收者
// 当G2消费ch的时候，会首先对buf加锁，然后将buf中的数据copy到task变量对应的内存里，然后recvx++,并释放锁
func receiveTask(ch chan string) {
    for {
        task := <-ch                  //接收任务
        fmt.Println("received", task) //处理任务
    }
}

package main

import (
    "fmt"
    "time"
)

func loop(ch chan int) {
    for {
        select {
        case i := <-ch:
            fmt.Println("this  value of unbuffer channel", i)
        }
    }
}

func main() {
    ch := make(chan int)
    ch <- 1
    go loop(ch)
    time.Sleep(1 * time.Millisecond)
}

package main

import (
    "fmt"
    "time"
)

func loop(ch chan int) {
    for {
        select {
        case i := <-ch:
            fmt.Println("this  value of unbuffer channel", i)
        }
    }
}

func main() {
    ch := make(chan int,3)
    ch <- 1
    ch <- 2
    ch <- 3
    ch <- 4
    go loop(ch)
    time.Sleep(1 * time.Millisecond)
}

package main

import (
    "fmt"
    "sync"
    "time"
)

var wg sync.WaitGroup

func main() {
    ch1 := make(chan struct{}, 1)
    ch2 := make(chan struct{}, 1)
    ch3 := make(chan struct{}, 1)
    ch1 <- struct{}{}
    wg.Add(3)
    start := time.Now().Unix()
    go print("gorouine1", ch1, ch2)
    go print("gorouine2", ch2, ch3)
    go print("gorouine3", ch3, ch1)
    wg.Wait()
    end := time.Now().Unix()
    fmt.Printf("duration:%d\n", end-start)
}

func print(gorouine string, inputchan chan struct{}, outchan chan struct{}) {
    // 模拟内部操作耗时
    time.Sleep(1 * time.Second)
    select {
    case <-inputchan:
        fmt.Printf("%s\n", gorouine)
        outchan <- struct{}{}
    }
    wg.Done()
}
/*
gorouine1
gorouine2
gorouine3
duration:1
*/

func deadlock1() {
    ch := make(chan int) 
    ch <- 3 //  这里会发生一直阻塞的情况，执行不到下面一句
}

func deadlock2() {
    ch := make(chan int)
    ch <- 3  //  这里会发生一直阻塞的情况，执行不到下面一句
    num := <-ch
    fmt.Println("num=", num)
}

func deadlock2() {
    ch := make(chan int)
    ch <- 100 //  这里会发生一直阻塞的情况，执行不到下面一句
    go func() {
        num := <-ch
        fmt.Println("num=", num)
    }()
    time.Sleep(time.Second)
}

func deadlock3() {
    ch := make(chan int, 3)
    ch <- 3
    ch <- 4
    ch <- 5
    ch <- 6  //  这里会发生一直阻塞的情况
}

func deadlock4() {
    ch := make(chan int)
    // ch := make(chan int, 1)
    fmt.Println(<-ch)  //  这里会发生一直阻塞的情况
}

func deadlock5() {
    ch1 := make(chan int)
    ch2 := make(chan int)
    // 互相等对方造成死锁
    go func() {
        for {
            select {
            case num := <-ch1:
                fmt.Println("num=", num)
                ch2 <- 100
            }
        }
    }()

    for {
        select {
        case num := <-ch2:
            fmt.Println("num=", num)
            ch1 <- 300
        }
    }
}

type Mutex struct {  
     state int32  
     sema  uint32
 }

addr = &sema
func semroot(addr *uint32) *semaRoot {  
   return &semtable[(uintptr(unsafe.Pointer(addr))>>3)%semTabSize].root  
}
root := semroot(addr)
root.queue(addr, s, lifo)
root.dequeue(addr)

var semtable [251]struct {  
   root semaRoot  
   ...
}

type semaRoot struct {  
  lock  mutex  
  treap *sudog // root of balanced tree of unique waiters.  
  nwait uint32 // Number of waiters. Read w/o the lock.  
}

type sudog struct {
    g *g  
    next *sudog  
    prev *sudog
    elem unsafe.Pointer // 指向sema变量
    waitlink *sudog // g.waiting list or semaRoot  
    waittail *sudog // semaRoot
    ...
}

func (m *Mutex) Lock() {
    // Fast path: 幸运之路，一下就获取到了锁
    if atomic.CompareAndSwapInt32(&m.state, 0, mutexLocked) {
        return
    }
    // Slow path：缓慢之路，尝试自旋或阻塞获取锁
    m.lockSlow()
}

func (m *Mutex) Unlock() {  
   // Fast path: 幸运之路，解锁
   new := atomic.AddInt32(&m.state, -mutexLocked)  
   if new != 0 {  
            // Slow path：如果有等待的goroutine，唤醒等待的goroutine
            m.unlockSlow()
   }  
}

starving = runtime_nanotime()-waitStartTime > 1e6

delta := int32(mutexLocked - 1<<mutexWaiterShift)  
if !starving || old>>mutexWaiterShift == 1 {  
    delta -= mutexStarving
}
atomic.AddInt32(&m.state, delta)

if old&(mutexLocked|mutexStarving) == mutexLocked && runtime_canSpin(iter) {  
    ...
    runtime_doSpin()   
    continue  
}


func sync_runtime_canSpin(i int) bool {  
    if i >= active_spin 
    || ncpu <= 1 
    || gomaxprocs <= int32(sched.npidle+sched.nmspinning)+1 {  
          return false  
     }  
   if p := getg().m.p.ptr(); !runqempty(p) {  
      return false  
 }  
   return true  
}

func sync_runtime_doSpin() {
    procyield(active_spin_cnt)
}    

type RWMutex struct {
    w           Mutex  // 复用互斥锁
    writerSem   uint32 // 信号量，用于写等待读
    readerSem   uint32 // 信号量，用于读等待写
    readerCount int32  // 当前执行读的 goroutine 数量
    readerWait  int32  // 被阻塞的准备读的 goroutine 的数量
}

func (rw *RWMutex) RLock() // 加读锁
func (rw *RWMutex) RUnlock() // 释放读锁

func (rw *RWMutex) RLock() {
// 为什么readerCount会小于0呢？往下看发现writer的Lock()会对readerCount做减法操作（原子操作）
  if atomic.AddInt32(&rw.readerCount, 1) < 0 {
    // A writer is pending, wait for it.
    runtime_Semacquire(&rw.readerSem)
  }
}

func (rw *RWMutex) RUnlock() {
    if r := atomic.AddInt32(&rw.readerCount, -1); r < 0 {
        rw.rUnlockSlow(r)
    }
}

func (rw *RWMutex) rUnlockSlow(r int32) {
    // A writer is pending.
    if atomic.AddInt32(&rw.readerWait, -1) == 0 {
        // The last reader unblocks the writer.
        runtime_Semrelease(&rw.writerSem, false, 1)
    }
}

func (rw *RWMutex) Lock() // 加写锁
func (rw *RWMutex) Unlock() // 释放写锁

const rwmutexMaxReaders = 1 << 30

func (rw *RWMutex) Lock() {
    // First, resolve competition with other writers.
    rw.w.Lock()
    // Announce to readers there is a pending writer.
    r := atomic.AddInt32(&rw.readerCount, -rwmutexMaxReaders) + rwmutexMaxReaders
    // Wait for active readers.
    if r != 0 && atomic.AddInt32(&rw.readerWait, r) != 0 {
        runtime_Semacquire(&rw.writerSem)
    }
}

func (rw *RWMutex) Unlock() {
    // Announce to readers there is no active writer.
    r := atomic.AddInt32(&rw.readerCount, rwmutexMaxReaders)
    // Unblock blocked readers, if any.
    for i := 0; i < int(r); i++ {
        runtime_Semrelease(&rw.readerSem, false)
    }
    // Allow other writers to proceed.
    rw.w.Unlock()
}

package main

import (
    "bytes"
    "fmt"
    "runtime"
    "strconv"
    "sync"
    "sync/atomic"
)

type ReentrantLock struct {
    sync.Mutex
    recursion int32 // 这个goroutine 重入的次数
    owner     int64 // 当前持有锁的goroutine id
}

// Get returns the id of the current goroutine.
func GetGoroutineID() int64 {
    var buf [64]byte
    var s = buf[:runtime.Stack(buf[:], false)]
    s = s[len("goroutine "):]
    s = s[:bytes.IndexByte(s, ' ')]
    gid, _ := strconv.ParseInt(string(s), 10, 64)
    return gid
}

func NewReentrantLock() sync.Locker {
    res := &ReentrantLock{
        Mutex:     sync.Mutex{},
        recursion: 0,
        owner:     0,
    }
    return res
}

// ReentrantMutex 包装一个Mutex,实现可重入
type ReentrantMutex struct {
    sync.Mutex
    owner     int64 // 当前持有锁的goroutine id
    recursion int32 // 这个goroutine 重入的次数
}

func (m *ReentrantMutex) Lock() {
    gid := GetGoroutineID()
    // 如果当前持有锁的goroutine就是这次调用的goroutine,说明是重入
    if atomic.LoadInt64(&m.owner) == gid {
        m.recursion++
        return
    }
    m.Mutex.Lock()
    // 获得锁的goroutine第一次调用，记录下它的goroutine id,调用次数加1
    atomic.StoreInt64(&m.owner, gid)
    m.recursion = 1
}

func (m *ReentrantMutex) Unlock() {
    gid := GetGoroutineID()
    // 非持有锁的goroutine尝试释放锁，错误的使用
    if atomic.LoadInt64(&m.owner) != gid {
        panic(fmt.Sprintf("wrong the owner(%d): %d!", m.owner, gid))
    }
    // 调用次数减1
    m.recursion--
    if m.recursion != 0 { // 如果这个goroutine还没有完全释放，则直接返回
        return
    }
    // 此goroutine最后一次调用，需要释放锁
    atomic.StoreInt64(&m.owner, -1)
    m.Mutex.Unlock()
}

func main() {
    var mutex = &ReentrantMutex{}
    mutex.Lock()
    mutex.Lock()
    fmt.Println(111)
    mutex.Unlock()
    mutex.Unlock()
}

func AddInt32(addr *int32, delta int32) (new int32)

func AddInt64(addr *int64, delta int64) (new int64)

func AddUint32(addr *uint32, delta uint32) (new uint32)

func AddUint64(addr *uint64, delta uint64) (new uint64)

func AddUintptr(addr *uintptr, delta uintptr) (new uintptr)

func add(addr *int64, delta int64) {
    atomic.AddInt64(addr, delta) //加操作
    fmt.Println("add opts: ", *addr)
}

func LoadInt32(addr *int32) (val int32)

func LoadInt64(addr *int64) (val int64)

func LoadPointer(addr *unsafe.Pointer) (val unsafe.Pointer)

func LoadUint32(addr *uint32) (val uint32)

func LoadUint64(addr *uint64) (val uint64)

func LoadUintptr(addr *uintptr) (val uintptr)

// 特殊类型： Value类型，常用于配置变更
func (v *Value) Load() (x interface{}) {}

func load(addr *int64) {
    fmt.Println("load opts: ", atomic.LoadInt64(&opts))
}

func CompareAndSwapInt32(addr *int32, old, new int32) (swapped bool)

func CompareAndSwapInt64(addr *int64, old, new int64) (swapped bool)

func CompareAndSwapPointer(addr *unsafe.Pointer, old, new unsafe.Pointer) (swapped bool)

func CompareAndSwapUint32(addr *uint32, old, new uint32) (swapped bool)

func CompareAndSwapUint64(addr *uint64, old, new uint64) (swapped bool)

func CompareAndSwapUintptr(addr *uintptr, old, new uintptr) (swapped bool)