10 Replies
      Latest reply on May 16, 2019 7:46 AM by wilsoncpw
      wilsoncpw Level 1 Level 1 (0 points)

        I've found that when I try to access a huge (several Gigabyte ,eg. a movie) file in an application compiled with Swift 5 / XCode 10.2, it no longer 'maps' the file.  Instead, it loads the entire thing - which causes my application to hang for several seconds.


        The file is a local file, so it should be able to map it fine.


        I was so suprised that I created a test app, the guts of it being...


        func openMappedFile (url: URL) throws {

                let data = try Data (contentsOf: url, options: .alwaysMapped)

                print (data.count)



        Sure enough, when I compile the test app with XCode 10.1/Swift 4.2, it behaves as expected, and immediately prints the count of the number of bytes in the file - without having to load the entire thing.


        But when I compile the same app with XCode 10.2/Swift 5, it hangs for several seconds, with lots of disk activity while it loads the file before printing 'count'


        Has anyone else been affected by this? Does anyone know of a workaround (while still using 'Data' - I don't want to have to fiddle round with Darwin APIs, mmap, etc.).  Or should I just go back to using XCode 10.1 until it's (hopefully) fixed.  I've already raised a bug for this in Bug Reporter.