static int stbi__decode_jpeg_header(stbi__jpeg *z, int scan)
{
   int m;
   z->jfif = 0;
   z->app14_color_transform = -1; // valid values are 0,1,2
   z->marker = STBI__MARKER_none; // initialize cached marker to empty
   m = stbi__get_marker(z);
   if (!stbi__SOI(m)) return stbi__err("no SOI","Corrupt JPEG");
   if (scan == STBI__SCAN_type) return 1;
   m = stbi__get_marker(z);
   while (!stbi__SOF(m)) {
      if (!stbi__process_marker(z,m)) return 0;
      m = stbi__get_marker(z);
      while (m == STBI__MARKER_none) {
         // some files have extra padding after their blocks, so ok, we'll scan
         if (stbi__at_eof(z->s)) return stbi__err("no SOF", "Corrupt JPEG");
         m = stbi__get_marker(z);
      }
   }
   z->progressive = stbi__SOF_progressive(m);
   if (!stbi__process_frame_header(z, scan)) return 0;
   return 1;
}
Unknown