Async.FromBeginEnd<'T> Method (F#)
Creates an asynchronous computation in terms of a Begin/End pair of actions in the style used in CLI APIs.
Namespace/Module Path: Microsoft.FSharp.Control
Assembly: FSharp.Core (in FSharp.Core.dll)
// Signature: static member FromBeginEnd : (AsyncCallback * obj -> IAsyncResult) * (IAsyncResult -> 'T) * ?(unit -> unit) -> Async<'T> // Usage: Async.FromBeginEnd (beginAction, endAction) Async.FromBeginEnd (beginAction, endAction, cancelAction = cancelAction)
For example, the following code creates an asynchronous computation that wraps a web service call.
Async.FromBeginEnd(ws.BeginGetWeather,ws.EndGetWeather)
When the computation is run, beginFunc is executed, with a callback which represents the continuation of the computation. When the callback is invoked, the overall result is fetched using endFunc.
The computation will respond to cancellation while waiting for the completion of the operation. If a cancellation occurs, and cancelAction is specified, then it is executed, and the computation continues to wait for the completion of the operation. If cancelAction is not specified, cancellation causes the computation to stop immediately, and subsequent invocations of the callback are ignored.
The following code example shows how to create an F# asynchronous computation from a .NET asynchronous API that uses the Begin/End pattern. The example uses the .NET socket API in System.Net.Sockets. It is an implementation of a simple server application that accepts a connection, receives data from a client, and sends a response.
module SocketServer = open System.Net open System.Net.Sockets open System.Collections.Generic let toIList<'T> (data : 'T array) = let segment = new System.ArraySegment<'T>(data) let data = new List<System.ArraySegment<'T>>() :> IList<System.ArraySegment<'T>> data.Add(segment) data type Socket with member this.MyAcceptAsync() = Async.FromBeginEnd((fun (callback, state) -> this.BeginAccept(callback, state)), this.EndAccept) member this.MyConnectAsync(ipAddress : IPAddress, port : int) = Async.FromBeginEnd(ipAddress, port, (fun (ipAddress:IPAddress, port, callback, state) -> this.BeginConnect(ipAddress, port, callback, state)), this.EndConnect) member this.MySendAsync(data : byte array, flags : SocketFlags) = Async.FromBeginEnd(toIList data, flags, (fun (data : IList<System.ArraySegment<byte>>, flags : SocketFlags, callback, state) -> this.BeginSend(data, flags, callback, state)), this.EndSend) member this.MyReceiveAsync(data : byte array, flags : SocketFlags) = Async.FromBeginEnd(toIList data, flags, (fun (data : IList<System.ArraySegment<byte>>, flags : SocketFlags, callback, state) -> this.BeginReceive(data, flags, callback, state)), this.EndReceive) let port = 11000 let socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp) let ipHostInfo = Dns.Resolve(Dns.GetHostName()) let localIPAddress = ipHostInfo.AddressList.[0] let localEndPoint = new IPEndPoint(localIPAddress, port) socket.Bind(localEndPoint) let connectSendReceive (socket : Socket) = async { do! socket.MyConnectAsync(ipHostInfo.AddressList.[0], 11000) let buffer1 = [| 0uy .. 255uy |] let buffer2 = Array.zeroCreate<byte> 255 let flags = new SocketFlags() let! flag = socket.MySendAsync(buffer1, flags) let! result = socket.MyReceiveAsync(buffer2, flags) return buffer2 } let acceptReceiveSend (socket : Socket) = async { printfn "Listening..." socket.Listen(10) printfn "Accepting..." let! socket = socket.MyAcceptAsync() let buffer1 = Array.zeroCreate<byte> 256 let flags = new SocketFlags() printfn "Receiving..." let! nBytes = socket.MyReceiveAsync(buffer1, flags) printfn "Received %d bytes from client computer." nBytes let buffer2 = Array.rev buffer1 printfn "Sending..." let! flag = socket.MySendAsync(buffer2, flags) printfn "Completed." return buffer2 } let taskServer = Async.StartAsTask(acceptReceiveSend(socket)) taskServer.Wait() socket.Close()
Listening... Accepting... Receiving... Received 256 bytes from client computer. Sending... Completed.
The following code example shows the client code that can be used together with the server code in the previous example.
module SocketClient = open System.Net open System.Net.Sockets open System.Collections.Generic let toIList<'T> (data : 'T array) = let segment = new System.ArraySegment<'T>(data) let data = new List<System.ArraySegment<'T>>() :> IList<System.ArraySegment<'T>> data.Add(segment) data type Socket with member this.MyAcceptAsync(receiveSize) = Async.FromBeginEnd(receiveSize, (fun (receiveSize, callback, state) -> this.BeginAccept(receiveSize, callback, state)), this.EndConnect) member this.MyConnectAsync(ipAddress : IPAddress, port : int) = Async.FromBeginEnd(ipAddress, port, (fun (ipAddress:IPAddress, port, callback, state) -> this.BeginConnect(ipAddress, port, callback, state)), this.EndConnect) member this.MySendAsync(data, flags : SocketFlags) = Async.FromBeginEnd(toIList data, flags, (fun (data : IList<System.ArraySegment<byte>>, flags : SocketFlags, callback, state) -> this.BeginSend(data, flags, callback, state)), this.EndSend) member this.MyReceiveAsync(data, flags : SocketFlags) = Async.FromBeginEnd(toIList data, flags, (fun (data : IList<System.ArraySegment<byte>>, flags : SocketFlags, callback, state) -> this.BeginReceive(data, flags, callback, state)), this.EndReceive) let port = 11000 let socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp) let ipHostEntry = Dns.Resolve("hostname.contoso.com") printfn "Server address: %s" (ipHostEntry.AddressList.[0].ToString()) let connectSendReceive (socket : Socket) = async { do! socket.MyConnectAsync(ipHostEntry.AddressList.[0], 11000) printfn "Connected to remote host." let buffer1 = [| 0uy .. 255uy |] let buffer2 = Array.zeroCreate<byte> 255 let flags = new SocketFlags() printfn "Sending data..." let! flag = socket.MySendAsync(buffer1, flags) printfn "Receiving data..." let! result = socket.MyReceiveAsync(buffer2, flags) printfn "Received data from remote host." return buffer2 } let acceptReceiveSend (socket : Socket) = async { socket.Listen(1) do! socket.MyAcceptAsync(256) let buffer1 = Array.zeroCreate<byte> 255 let flags = new SocketFlags() let! flag = socket.MyReceiveAsync(buffer1, flags) let buffer2 = Array.rev buffer1 let! flag = socket.MySendAsync(buffer2, flags) return buffer2 } let taskClient = Async.StartAsTask(connectSendReceive(socket)) taskClient.Wait() taskClient.Result |> Array.iter (fun elem -> printf "%d " elem)
Sample Output
Server address: 10.80.57.8 Connected to remote host. Sending data... Receiving data... Received data from remote host. 255 254 253 252 251 250 249 248 247 246 ...
