as3 file download restrain? - actionscript-3

Question

I have a flash download on my site to download a pdf file.
var myfileReference:FileReference = new FileReference();
down_mc.visible = false;
down_comp.visible = false;
var myRequest:URLRequest = new URLRequest("GEORGIA INCORPORATED.pdf");
myfileReference.addEventListener(IOErrorEvent.IO_ERROR, ioError);
output_txt.text = "";
function ioError(event:ErrorEvent):void {
output_txt.text = "Sorry that there is an IO error during the file downloading. The error is:" + "\n" + event;
}
myfileReference.addEventListener(ProgressEvent.PROGRESS, fileDownloadProgress);
function fileDownloadProgress(event:ProgressEvent):void {
down_mc.visible = true;
}
myfileReference.addEventListener(Event.COMPLETE, fileDownloadCompleted);
function fileDownloadCompleted(evt:Event):void {
down_mc.visible = false;
down_comp.visible = true;
}
function downloadFile (event:MouseEvent):void {
try {
myfileReference.download(myRequest);
} catch (error:SecurityError) {
downloading. The error is:" + "\n" + error;
} catch (error:IllegalOperationError) {
downloading. The error is:" + "\n" + error;
}
}
b1.addEventListener(MouseEvent.CLICK, downloadFile);
the problem is some people want to change the name of the file they are downloading and changing the extension as well, the .pdf , thus making the file unusable. is there any way to restrain the clients from changing the extension?

Answer 1

In pure as3, you cannot force user to save a file under a specific extention. The only way to do it should be to use Air that let you have control on it through a FileStream Object (you can choose file name).
If you want to do it with Air, then you can do :
// Assuming you get your pdf raw data
var pdfData : ByteArray;
var f : File = File.desktopDirectory.resolvePath("myPdf.pdf");
// When user have select a file
f.addEventListener(Event.SELECT, function(e:Event):void{
var targetFile : File = e.target as File;
// Check if the selected file have pdf extension
if(targetFile.nativePath.substr(targetFile.nativePath.length - 4) != ".pdf")
// If not, add it
targetFile = new File(targetFile.nativePath + ".pdf");
// Save the file
var fs : FileStream = new FileStream();
fs.open(targetFile, FileMode.WRITE);
fs.writeBytes(pdfData);
fs.close();
});
// Ask user to save a file (by default on user desktop)
f.browseForSave("Save PDF");