Merge pull request #781 from cpunion/future-io

Future IO update

x/async/README.md

@@ -361,29 +361,83 @@ In some situations, you may want to get the first result of multiple async opera
 
 ## Design considerations in LLGo
 
-- Don't introduce `async`/`await` keywords to compatible with Go compiler (just compiling)
-- For performance reason don't implement async functions with goroutines
-- Avoid implementing `Promise` by using `chan` to avoid blocking the thread, but it can be wrapped as a `chan` to make it compatible `select` statement
+- Don't introduce `async`/`await` keywords to compatible with Go
+- For performance and memory reasons don't implement async functions with goroutines, coroutines, or other mechanisms that require per-task stack allocation
+- Avoid implementing async task by using `chan` that blocking the thread
 
 ## Design
 
-Introduce `async.IO[T]` type to represent an asynchronous operation, `async.Future[T]` type to represent the result of an asynchronous operation. `async.IO[T]` can be `bind` to a function that accepts `T` as an argument to chain multiple asynchronous operations. `async.IO[T]` can be `await` to get the value of the asynchronous operation.
+### `async.Future[T]` type
+
+Introduce `async.Future[T]` type to represent an eventual completion (or failure) of an asynchronous operation and its resulting value, similar to `Promise`/`Future` in other languages. Functions that return `async.Future[T]` are considered asynchronous functions.
+
+### Future creation
+
+`async.Future[T]` can be created by `async.Async[T]` function that takes a function that accepts a `resolve` function to produce a value of type `T`.
+
+### Future chaining (asynchronous callbacks style)
+
+`async.Future[T]` can be chained with `Then` method to add multiple callbacks to be executed when the operation is completed, it just runs once and calls every callbacks. Currently `Then` method can't be chained multiple times because Go doesn't support generics method (Need support `func (f Future[T]) Then[U any](f func(T) Future[U]) Future[U]`), maybe implements in Go+.
+
+### Future waiting (synchronous style)
+
+`async.Await[T]` function can be used to wait for the completion of a `Future[T]` and return the value produced by the operation. In LLGo, `async.Await[T]` is a blocking function that waits for the completion of the `Future[T]` and returns the value synchronously, it would be transformed to `Future.Then` callback in the frontend.
+
+### `async.Run[T]` function
+
+`async.Run[T]` function can be used to create an global asynchronous context and run async functions, and it would be hidden by the compiler in the future.
+
+Currently it will switch the callbacks to the goroutine that calls `async.Run[T]` function, this maybe changed in the future to reduce the overhead of switching goroutines and make it more parallel.
+
+### Prototype
 
 ```go
 package async
 
-type Future[T any] func() T
-type IO[T any] func() Future[T]
+type Future[T any] interface {
+  Then(f func(T))
+}
+
+func Async[T any](f func(resolve func(T))) Future[T]
+
+func Await[T any](future Future[T]) T
+```
+
+### Some async functions
+
+```go
+package async
+
+
+func Race[T1 any](futures ...Future[T1]) Future[T1]
+
+func All[T1 any](futures ...Future[T1]) Future[[]T1]
+
+```
+
+### Example
+
+```go
+package main
 
 func main() {
-  io := func() Future[string] {
-    return func() string {
-      return "Hello, World!"
-    }
+  async.Run(func() {
+  hello := func() async.Future[string] {
+    return async.Async(func(resolve func(string)) {
+      resolve("Hello, World!")
+    })
   }
 
-  future := io()
-  value := future()
-  println(value)
+  future := hello()
+  future.Then(func(value string) {
+    println("first callback:", value)
+  })
+  future.Then(func(value string) {
+    println("second callback:", value)
+  })
+
+  println("first await:", async.Await(future))
+  println("second await:", async.Await(future))
+  })
 }
 ```

x/async/TODO.md

@@ -0,0 +1,17 @@
+讨论：
+
+1. Future 用 interface 还是闭包：性能应该差不多，如果没有其他方法要暴露，感觉也没有换成 interface 的必要，interface 多一个对象分配。先添加 Then 方法方便未来替换。
+2. 几个方法提供不同参数个数的版本还是用 tuple：如果编译器不支持可变泛型参数个数和特化，我倾向用 tuple 先简化实现，tuple 的开销应该也容易被编译器优化掉。多个方法让用户选择 Await2/Await3 这种也恶心。
+3. 是否 Cancellable，暂时不加进去，多一个 context，也不一定能快速稳定下来，可以后面根据实践再改。
+4. Executor 可能会变化，目前提供的 Run 是阻塞的，也可以把它做成异步。
+5. 尽量再隐藏一些辅助类型，比如 TupleN，可能之提供 tuple 的构造和返回多值。内部的 libuv 如果隐藏可能要暴露同等接口，先不动了
+6. 性能可能做个简单测试，但不是关键，只要别太差。未来可能会尽量减少 executor 的切换、尽量多并行
+7. 异常兼容性：目前没考虑，这个要在回调里处理可能困难，要么就在 await 上处理，可以往后放一下，毕竟 golang 主要是以 error 为主
+8. 可能先看一下如何在 go+里面集成，判断目前的设计实现是否合理
+9. 多封装一些库看看通用性和易用性，\_demo 里几个简单例子基本符合预期，还需要更多检验
+
+TODO：
+
+[ ] 1. select 兼容 （可能把 Future 改为 interface 更合理？）
+[x] 2. Future 多个 Await 只会被执行一次
+[x] 3. Future 添加 Then 方法，不推荐直接当作函数调用，方便未来切换

x/async/_demo/all/all.go

@@ -3,6 +3,7 @@ package main
 import (
 	"fmt"
 	"os"
+	"sync/atomic"
 	"time"
 
 	"github.com/goplus/llgo/x/async"
@@ -32,26 +33,29 @@ func WriteFile(fileName string, content []byte) async.Future[error] {
 
 func sleep(i int, d time.Duration) async.Future[int] {
 	return async.Async(func(resolve func(int)) {
-		timeout.Timeout(d)(func(async.Void) {
+		timeout.Timeout(d).Then(func(async.Void) {
 			resolve(i)
 		})
 	})
 }
 
 func main() {
+	async.Run(func(resolve func(async.Void)) {
 		RunIO()
 		RunAllAndRace()
 		RunTimeout()
+		RunMultipleCallbacksNodelay()
+		RunMultipleCallbacksDelay()
 		RunSocket()
+	})
 }
 
 func RunIO() {
 	println("RunIO with Await")
 
 	// Hide `resolve` in Go+
-	async.Run(async.Async(func(resolve func(async.Void)) {
+
 	println("read file")
-		defer resolve(async.Void{})
 	content, err := async.Await(ReadFile("all.go")).Get()
 	if err != nil {
 		fmt.Printf("read err: %v\n", err)
@@ -64,32 +68,26 @@ func RunIO() {
 		return
 	}
 	fmt.Printf("write done\n")
-	}))
 
 	// Translated Await to BindIO in Go+:
 	println("RunIO with BindIO")
 
-	async.Run(async.Async(func(resolve func(async.Void)) {
-		ReadFile("all.go")(func(v tuple.Tuple2[[]byte, error]) {
+	ReadFile("all.go").Then(func(v tuple.Tuple2[[]byte, error]) {
 		content, err := v.Get()
 		if err != nil {
 			fmt.Printf("read err: %v\n", err)
-				resolve(async.Void{})
 			return
 		}
 		fmt.Printf("read content: %s\n", content)
-			WriteFile("2.out", content)(func(v error) {
+		WriteFile("2.out", content).Then(func(v error) {
 			err = v
 			if err != nil {
 				fmt.Printf("write err: %v\n", err)
-					resolve(async.Void{})
 				return
 			}
 			println("write done")
-				resolve(async.Void{})
 		})
 	})
-	}))
 }
 
 func RunAllAndRace() {
@@ -99,92 +97,139 @@ func RunAllAndRace() {
 
 	println("Run All with Await")
 
-	async.Run(async.Async(func(resolve func(async.Void)) {
-		async.All(sleep(1, ms200), sleep(2, ms100), sleep(3, ms300))(func(v []int) {
+	async.All(sleep(1, ms200), sleep(2, ms100), sleep(3, ms300)).Then(func(v []int) {
 		fmt.Printf("All: %v\n", v)
-			resolve(async.Void{})
 	})
-	}))
 
 	println("Run Race with Await")
 
-	async.Run(async.Async(func(resolve func(async.Void)) {
 	first := async.Race(sleep(1, ms200), sleep(2, ms100), sleep(3, ms300))
 	v := async.Await(first)
 	fmt.Printf("Race: %v\n", v)
-		resolve(async.Void{})
-	}))
 
 	// Translated to in Go+:
 
 	println("Run All with BindIO")
 
-	async.Run(async.Async(func(resolve func(async.Void)) {
-		async.All(sleep(1, ms200), sleep(2, ms100), sleep(3, ms300))(func(v []int) {
+	async.All(sleep(1, ms200), sleep(2, ms100), sleep(3, ms300)).Then(func(v []int) {
 		fmt.Printf("All: %v\n", v)
-			resolve(async.Void{})
 	})
-	}))
 
 	println("Run Race with BindIO")
 
-	async.Run(async.Async(func(resolve func(async.Void)) {
-		async.Race(sleep(1, ms200), sleep(2, ms100), sleep(3, ms300))(func(v int) {
+	async.Race(sleep(1, ms200), sleep(2, ms100), sleep(3, ms300)).Then(func(v int) {
 		fmt.Printf("Race: %v\n", v)
-			resolve(async.Void{})
 	})
-	}))
+
 }
 
 func RunTimeout() {
 	println("Run Timeout with Await")
 
-	async.Run(async.Async(func(resolve func(async.Void)) {
 	fmt.Printf("Start 100 ms timeout\n")
 	async.Await(timeout.Timeout(100 * time.Millisecond))
 	fmt.Printf("timeout\n")
-		resolve(async.Void{})
-	}))
 
 	// Translated to in Go+:
 
 	println("Run Timeout with BindIO")
 
-	async.Run(async.Async(func(resolve func(async.Void)) {
 	fmt.Printf("Start 100 ms timeout\n")
-		timeout.Timeout(100 * time.Millisecond)(func(async.Void) {
+	timeout.Timeout(100 * time.Millisecond).Then(func(async.Void) {
 		fmt.Printf("timeout\n")
-			resolve(async.Void{})
 	})
-	}))
+}
+
+func RunMultipleCallbacksNodelay() {
+	println("Run Multiple Callbacks")
+
+	runCnt := atomic.Int32{}
+
+	nodelay := async.Async(func(resolve func(async.Void)) {
+		println("nodelay")
+		runCnt.Add(1)
+	})
+
+	cbCnt := atomic.Int32{}
+	cb := func() {
+		if cbCnt.Add(1) == 2 {
+			if runCnt.Load() != 1 {
+				panic("runCnt != 1, got: " + fmt.Sprint(runCnt.Load()))
+			} else {
+				println("runCnt == 1")
+			}
+		}
+	}
+	nodelay.Then(func(async.Void) {
+		println("nodelay done")
+		cb()
+	})
+
+	nodelay.Then(func(async.Void) {
+		println("nodelay done again")
+		cb()
+	})
+}
+
+func RunMultipleCallbacksDelay() {
+	println("Run Multiple Callbacks")
+
+	runCnt := atomic.Int32{}
+
+	delay := async.Async(func(resolve func(async.Void)) {
+		timeout.Timeout(100 * time.Millisecond).Then(func(async.Void) {
+			println("delay")
+			runCnt.Add(1)
+		})
+	})
+
+	cbCnt := atomic.Int32{}
+	cb := func() {
+		if cbCnt.Add(1) == 2 {
+			if runCnt.Load() != 1 {
+				panic("runCnt != 1, got: " + fmt.Sprint(runCnt.Load()))
+			} else {
+				println("runCnt == 1")
+			}
+		}
+	}
+
+	delay.Then(func(async.Void) {
+		println("delay done")
+		cb()
+	})
+
+	delay.Then(func(async.Void) {
+		println("delay done again")
+		cb()
+	})
 }
 
 func RunSocket() {
 	println("Run Socket")
 
-	async.Run(async.Async(func(resolve func(async.Void)) {
 	println("RunServer")
 
-		RunServer()(func(async.Void) {
+	RunServer().Then(func(async.Void) {
 		println("RunServer done")
-			resolve(async.Void{})
 	})
 
 	println("RunClient")
 
-		timeout.Timeout(100 * time.Millisecond)(func(async.Void) {
-			RunClient()(func(async.Void) {
+	timeout.Timeout(100 * time.Millisecond).Then(func(async.Void) {
+		RunClient("Bob").Then(func(async.Void) {
+			println("RunClient done")
+		})
+		RunClient("Uncle").Then(func(async.Void) {
 			println("RunClient done")
-				resolve(async.Void{})
 		})
 	})
-	}))
 }
 
-func RunClient() async.Future[async.Void] {
+func RunClient(name string) async.Future[async.Void] {
 	return async.Async(func(resolve func(async.Void)) {
 		addr := "127.0.0.1:3927"
-		socketio.Connect("tcp", addr)(func(v tuple.Tuple2[*socketio.Conn, error]) {
+		socketio.Connect("tcp", addr).Then(func(v tuple.Tuple2[*socketio.Conn, error]) {
 			client, err := v.Get()
 			println("Connected", client, err)
 			if err != nil {
@@ -194,18 +239,18 @@ func RunClient() async.Future[async.Void] {
 			var loop func(client *socketio.Conn)
 			loop = func(client *socketio.Conn) {
 				counter++
-				data := fmt.Sprintf("Hello %d", counter)
-				client.Write([]byte(data))(func(err error) {
+				data := fmt.Sprintf("Hello from %s %d", name, counter)
+				client.Write([]byte(data)).Then(func(err error) {
 					if err != nil {
 						panic(err)
 					}
-					client.Read()(func(v tuple.Tuple2[[]byte, error]) {
+					client.Read().Then(func(v tuple.Tuple2[[]byte, error]) {
 						data, err := v.Get()
 						if err != nil {
 							panic(err)
 						}
 						println("Read from server:", string(data))
-						timeout.Timeout(1 * time.Second)(func(async.Void) {
+						timeout.Timeout(1 * time.Second).Then(func(async.Void) {
 							loop(client)
 						})
 					})
@@ -222,13 +267,13 @@ func RunServer() async.Future[async.Void] {
 			println("Client connected", client, err)
 			var loop func(client *socketio.Conn)
 			loop = func(client *socketio.Conn) {
-				client.Read()(func(v tuple.Tuple2[[]byte, error]) {
+				client.Read().Then(func(v tuple.Tuple2[[]byte, error]) {
 					data, err := v.Get()
 					if err != nil {
 						println("Read error", err)
 					} else {
 						println("Read from client:", string(data))
-						client.Write(data)(func(err error) {
+						client.Write(data).Then(func(err error) {
 							if err != nil {
 								println("Write error", err)
 							} else {

x/async/async.go

@@ -24,6 +24,10 @@ type Void = [0]byte
 
 type Future[T any] func(func(T))
 
+func (f Future[T]) Then(cb func(T)) {
+	f(cb)
+}
+
 // Just for pure LLGo/Go, transpile to callback in Go+
 func Await[T1 any](future Future[T1]) T1 {
 	return Run(future)

x/async/async_go.go

@@ -22,8 +22,25 @@ package async
 import "sync"
 
 func Async[T any](fn func(func(T))) Future[T] {
+	var once sync.Once
+	var result T
+	var wg sync.WaitGroup
+	wg.Add(1)
+
+	once.Do(func() {
+		go func() {
+			fn(func(v T) {
+				result = v
+				wg.Done()
+			})
+		}()
+	})
+
 	return func(chain func(T)) {
-		go fn(chain)
+		go func() {
+			wg.Wait()
+			chain(result)
+		}()
 	}
 }
 
@@ -34,7 +51,7 @@ func Race[T1 any](futures ...Future[T1]) Future[T1] {
 		ch := make(chan T1)
 		for _, future := range futures {
 			future := future
-			future(func(v T1) {
+			future.Then(func(v T1) {
 				defer func() {
 					// Avoid panic when the channel is closed.
 					_ = recover()
@@ -56,7 +73,7 @@ func All[T1 any](futures ...Future[T1]) Future[[]T1] {
 		wg.Add(n)
 		for i, future := range futures {
 			i := i
-			future(func(v T1) {
+			future.Then(func(v T1) {
 				results[i] = v
 				wg.Done()
 			})

x/async/async_llgo.go

@@ -20,6 +20,7 @@
 package async
 
 import (
+	"sync"
 	"sync/atomic"
 
 	"github.com/goplus/llgo/c/libuv"
@@ -27,23 +28,44 @@ import (
 )
 
 // Currently Async run chain a future that call chain in the goroutine running `async.Run`.
-// TODO(lijie): It would better to switch when needed.
 func Async[T any](fn func(func(T))) Future[T] {
-	return func(chain func(T)) {
+	var result T
+	var resultReady atomic.Bool
+	var callbacks []func(T)
+	var mutex sync.Mutex
 	loop := Exec().L
 
-		var result T
 	var a *libuv.Async
 	var cb libuv.AsyncCb
 	a, cb = cbind.BindF[libuv.Async, libuv.AsyncCb](func(a *libuv.Async) {
 		a.Close(nil)
-			chain(result)
+		mutex.Lock()
+		currentCallbacks := callbacks
+		callbacks = nil
+		mutex.Unlock()
+
+		for _, callback := range currentCallbacks {
+			callback(result)
+		}
 	})
 	loop.Async(a, cb)
+
+	// Execute fn immediately
 	fn(func(v T) {
 		result = v
+		resultReady.Store(true)
 		a.Send()
 	})
+
+	return func(chain func(T)) {
+		mutex.Lock()
+		if resultReady.Load() {
+			mutex.Unlock()
+			chain(result)
+		} else {
+			callbacks = append(callbacks, chain)
+			mutex.Unlock()
+		}
 	}
 }
 
@@ -53,7 +75,7 @@ func Race[T1 any](futures ...Future[T1]) Future[T1] {
 	return Async(func(resolve func(T1)) {
 		done := atomic.Bool{}
 		for _, future := range futures {
-			future(func(v T1) {
+			future.Then(func(v T1) {
 				if !done.Swap(true) {
 					// Just resolve the first one.
 					resolve(v)
@@ -70,7 +92,7 @@ func All[T1 any](futures ...Future[T1]) Future[[]T1] {
 		var done uint32
 		for i, future := range futures {
 			i := i
-			future(func(v T1) {
+			future.Then(func(v T1) {
 				results[i] = v
 				if atomic.AddUint32(&done, 1) == uint32(n) {
 					// All done.

x/async/executor_go.go

@@ -22,7 +22,7 @@ package async
 func Run[T any](future Future[T]) T {
 	ch := make(chan T)
 	go func() {
-		future(func(v T) {
+		future.Then(func(v T) {
 			ch <- v
 		})
 	}()

x/async/executor_llgo.go

@@ -59,7 +59,7 @@ func Run[T any](future Future[T]) T {
 	exec := &Executor{loop}
 	oldExec := setExec(exec)
 	var ret T
-	future(func(v T) {
+	future.Then(func(v T) {
 		ret = v
 	})
 	exec.Run()

x/socketio/socketio_llgo.go

@@ -104,7 +104,7 @@ func Listen(protocol, bindAddr string, listenCb func(client *Conn, err error)) {
 		listenCb(nil, err)
 		return
 	}
-	parseAddr(bindAddr)(func(v tuple.Tuple2[*net.SockAddr, error]) {
+	parseAddr(bindAddr).Then(func(v tuple.Tuple2[*net.SockAddr, error]) {
 		addr, err := v.Get()
 		if err != nil {
 			listenCb(nil, err)
@@ -167,7 +167,7 @@ func (l *Listener) accept() (client *Conn, err error) {
 
 func Connect(network, addr string) async.Future[tuple.Tuple2[*Conn, error]] {
 	return async.Async(func(resolve func(tuple.Tuple2[*Conn, error])) {
-		parseAddr(addr)(func(v tuple.Tuple2[*net.SockAddr, error]) {
+		parseAddr(addr).Then(func(v tuple.Tuple2[*net.SockAddr, error]) {
 			addr, err := v.Get()
 			if err != nil {
 				resolve(tuple.T2[*Conn, error]((*Conn)(nil), err))