Is there an asynchronous version of DirectoryInfo.GetFiles / Directory.GetDirectories in dotNet? I'd like to use them in an F# async block, and it'd be nice to have a version that can be called with AsyncCallbacks.
Problem is I'm trying to suck in a bunch of directories, probably on SMB mounts over slow network connections, and I don't want a bunch of thread pool threads sitting around waiting for network reads when they could be doing other work.
I didn't find an async version of GetFiles, however if you look at the sourcecode for other Async operations, they're defined as follows:
module FileExtensions =
let UnblockViaNewThread f =
async { //let ctxt = System.Threading.SynchronizationContext.Current
do! Async.SwitchToNewThread ()
let res = f()
do! Async.SwitchToThreadPool ()
//do! Async.SwitchTo ctxt
return res }
type System.IO.File with
static member AsyncOpenText(path) = UnblockViaNewThread (fun () -> System.IO.File.OpenText(path))
static member AsyncAppendText(path) = UnblockViaNewThread (fun () -> System.IO.File.AppendText(path))
static member AsyncOpenRead(path) = UnblockViaNewThread (fun () -> System.IO.File.OpenRead(path))
static member AsyncOpenWrite(path) = UnblockViaNewThread (fun () -> System.IO.File.OpenWrite(path))
static member AsyncOpen(path,mode,?access,?share) =
let access = match access with Some v -> v | None -> System.IO.FileAccess.ReadWrite
let share = match share with Some v -> v | None -> System.IO.FileShare.None
UnblockViaNewThread (fun () -> System.IO.File.Open(path,mode,access,share))
static member OpenTextAsync(path) = System.IO.File.AsyncOpenText(path)
static member AppendTextAsync(path) = System.IO.File.AsyncAppendText(path)
static member OpenReadAsync(path) = System.IO.File.AsyncOpenRead(path)
static member OpenWriteAsync(path) = System.IO.File.AsyncOpenWrite(path)
static member OpenAsync(path,mode,?access,?share) = System.IO.File.AsyncOpen(path, mode, ?access=access, ?share=share)
In other words, the Async file, streamreader, and WebClient operations are just wrappers around the syncronous operations, so you should be able to write your own wrapper around GetFiles/GetDirectories as follows:
module IOExtensions =
type System.IO.Directory with
static member AsyncGetFiles(directory) = async { return System.IO.Directory.GetFiles(directory) }
static member AsyncGetDirectories(path) = async { return System.IO.Directory.GetDirectories(path) }