Virtual Cocoaheads merged with Virtual NSCoders & Newly Discovered macOS Image Capture Bug Can Fill Up Hard Drives With Empty Data

[David Phillip Oster]

For the last few weeks I've been attending the Tuesday 7pm to 9pm NSCoders meetup that normally meets at Orchard Cafe in Campbell, but during shelter in place, it is a Google Hangouts video conferencing . The hangouts URL is on the Meetup.com page: https://www.meetup.com/NSCoderNight-Silicon-Valley/events/bbxbslybcgblc/

https://www.macrumors.com/2020/04/28/macos-image-capture-bug-eats-storage/ published a story today on files read from iOS devices using ImageCapture have lots of zero padding.

I wrote a quick command line app to see if I had jgs with at least 500 bytes of trailing padding. I had 336, all since 2017.

Next step for me: since I have Tme Machine backups of this folder tree, is trimming back all such files to no more than 32 bytes of zero padding.

Here's the command line tool source code:

// Do I have any jpgs in my ~/Pictures or subdirectories such that they have more than 500 byts of trailing zero?

#import <Foundation/Foundation.h>

static BOOL HasEmptyTail(NSURL *url){

  NSData *data = [NSData dataWithContentsOfURL:url];

  if (501 < data.length) {

    uint8_t *p = (uint8_t *)data.bytes;

    p += data.length - 501;

    for (int i = 0; i < 500; ++i) {

      if (p[i]){

        return NO;

      }

    }

    return YES;

  }

  return NO;

}

static void TailZero() {

  NSFileManager *fm = [NSFileManager defaultManager];

  NSURL *url = [[fm URLsForDirectory:NSPicturesDirectory inDomains:NSUserDomainMask] firstObject];

  NSArray<NSURL *> *items = [fm contentsOfDirectoryAtURL:url includingPropertiesForKeys:nil options:0 error:NULL];

  for (NSURL *fileURL in items) {

    NSString *ext = [[fileURL pathExtension] lowercaseString];

    if ([ext isEqual:@"jpg"] || [ext isEqual:@"jpeg"]) {

      @autoreleasepool {

        if (HasEmptyTail(fileURL)) {

          fprintf(stderr, "%s\n", fileURL.path.fileSystemRepresentation);

        }

      }

    }

  }

}

int main(int argc, const char * argv[]) {

  @autoreleasepool {

    TailZero();

  }

  return 0;

}