盘点总结2023年Go并发库有哪些变化

func OnceFunc(f func()) func()
func OnceValue[T any](f func( "T any") T) func() T
func OnceValues[T1, T2 any](f func( "T1, T2 any") (T1, T2)) func() (T1, T2)

func TestOnce(t *testing.T) {
 var pool any
 var once sync.Once
 var initFn = func() {
  // init pool
  pool = 1
 }

 for i := 0; i < 10; i++ {
  once.Do(initFn)
  t.Log(pool)
 }
}

func TestOnceValue(t *testing.T) {
 var initPool = func() any {
  return 1
 }
 var poolGenerator = sync.OnceValue(initPool)

 for i := 0; i < 10; i++ {
  t.Log(poolGenerator())
 }
}

type Cond struct {
 noCopy noCopy
 // L is held while observing or changing the condition
 L Locker
 notify  notifyList
 checker copyChecker
}

func (c *copyChecker) check() {
 if uintptr(*c) != uintptr(unsafe.Pointer(c)) &&
  !atomic.CompareAndSwapUintptr((*uintptr)(c), 0, uintptr(unsafe.Pointer(c))) &&
  uintptr(*c) != uintptr(unsafe.Pointer(c)) {
  panic("sync.Cond is copied")
 }
}

func (c *copyChecker) check() {
 // Check if c has been copied in three steps:
 // 1. The first comparison is the fast-path. If c has been initialized and not copied, this will return immediately. Otherwise, c is either not initialized, or has been copied.
 // 2. Ensure c is initialized. If the CAS succeeds, we're done. If it fails, c was either initialized concurrently and we simply lost the race, or c has been copied.
 // 3. Do step 1 again. Now that c is definitely initialized, if this fails, c was copied.
 if uintptr(*c) != uintptr(unsafe.Pointer(c)) &&
  !atomic.CompareAndSwapUintptr((*uintptr)(c), 0, uintptr(unsafe.Pointer(c))) &&
  uintptr(*c) != uintptr(unsafe.Pointer(c)) {
  panic("sync.Cond is copied")
 }
}

func (m *Map) Range(f func(key, value any) bool) {
    ...
    if read.amended {
   read = readOnly{m: m.dirty}
   m.read.Store(&read)
   m.dirty = nil
   m.misses = 0
 }
    ...
}

func (m *Map) Range(f func(key, value any) bool) {
    ...
 if read.amended {
  read = readOnly{m: m.dirty}
  copyRead := read
  m.read.Store(&copyRead)
  m.dirty = nil
  m.misses = 0
 }
    ...
}

type Once struct {
 done uint32
 m    Mutex
}

type Once struct {
 done atomic.Uint32
 m    Mutex
}

func OnceFunc(f func()) func() {
 var (
  once  Once
  valid bool
  p     any
 )
 g := func() {
  defer func() {
   p = recover()
   if !valid {
    panic(p)
   }
  }()
  f()
  valid = true
 }
 return func() {
  once.Do(g)
  if !valid {
   panic(p)
  }
 }
}

func OnceFunc(f func()) func() {
 var (
  once  Once
  valid bool
  p     any
 )
 // Construct the inner closure just once to reduce costs on the fast path.
 g := func() {
  defer func() {
   p = recover()
   if !valid {
    // Re-panic immediately so on the first call the user gets a
    // complete stack trace into f.
    panic(p)
   }
  }()
  f()
  f = nil      // Do not keep f alive after invoking it.
  valid = true // Set only if f does not panic.
 }
 return func() {
  once.Do(g)
  if !valid {
   panic(p)
  }
 }
}

ctx, cancel := context.WithCancelCause(parent)
cancel(myError)
ctx.Err() // 返回 context.Canceled
context.Cause(ctx) // 返回 myError

func WithDeadlineCause(parent Context, d time.Time, cause error) (Context, CancelFunc)
func WithTimeoutCause(parent Context, timeout time.Duration, cause error) (Context, CancelFunc)

func AfterFunc(ctx Context, f func()) (stop func() bool)