Fiddlercore x-replywithfile over 2gb

Question

So I have an application that is caching local files with some code like this:

Fiddler.FiddlerApplication.BeforeRequest += delegate(Fiddler.Session oS)
{
    if (oS.url.StartsWith("foo.com/"))
    {
        oS.utilCreateResponseAndBypassServer();
        oS.oFlags["x-replywithfile"] = Path.GetFullPath(oS.url.Replace("foo.com/", "serve/"));
    }
}

This works fine for any files < 2GB. Above 2GB I get the error:

Fiddler - The requested file could not be read. The file is too long. This operation is currently limited to supporting files less than 2 gigabytes in size.   

I'm assuming internally Fiddler is using something like File.ReadAllBytes which is limited to 2gb because of maximum size of int. As far as I can tell there's no source code for FiddlerCore to open it up and change this... anyone know how to work around this limitation?

Answer 1

Cool scenario.

Yes, unfortunately the .NET Framework inherently limits all objects to a 2GB size, and as a consequence earlier versions of the AutoResponder could not return responses over 2gb. Update: Fiddler version 2.4.9.4 and later automatically detect huge files; any X-ReplyWithFile body over 262 megabytes (fiddler.memory.DropIfOver preference) will be streamed from the client and not stored in memory.

You could use Fiddler to return a HTTP/307 redirect to a different webserver and host the huge file there.

Your event handler could also directly stream the bytes of the file to the client in chunks (without using the x-replywithfile feature) using the oSession.oRequest.pipeClient.Send method, but this would involve a significant amount of code.