Potential problem with file_handle::extents on Windows

[tastewar]

We have a snippet of code that is intended to process sparse holes in files with a loop like this:

   std::vector<llfio::file_handle::extent_pair> ext = GetFileHandle().extents().value();
   uint32_t startBlock = 0, endBlock = 0, oldEndBlock = 0;
   for (auto it = ext.begin(); it != ext.end(); it++)
   {
   }

Seems to work fine on Linux, but in Windows, on a newly allocated 4096 byte file, we are getting back that there are 64 extents in the file. The first one looks correct, but the others all have 0xFFFFFFFF for both the beginning and length of the extent. Is this expected? Should we be ignoring any entries in the vector with 0xFFFFFFFF?

[ned14]

That's absolutely a bug. We never truncate the output vector to bytesout at https://github.com/ned14/llfio/blob/develop/include/llfio/v2.0/detail/impl/windows/file_handle.ipp#L388

[tastewar]

Thanks, Niall!

[ned14]

That bug should now be fixed.

[tastewar]

Thanks, Niall. Pulled this into our project and it has indeed fixed the issue.