/ go-winio Public
backuptar: Fix sparse file handling #221
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A recent OS change altered how sparse files are represented in backup
streams. This caused backuptar to no longer work with certain files. The
specific behavior that changed is as follows:
sparse block streams in the backup stream. Now, they will have a
data stream with size = 0, and no sparse block streams.
has the sparse attribute set) previously would not show as sparse in
the backup stream. Now, they will show as sparse.
The old backuptar behavior assumed that if the sparse flag was set on
the data stream, then there would always be a set of sparse blocks
following. These changes break this assumption, and so require special
It is unsupported to have a data stream, marked sparse, that contains
file content AND a series of sparse block streams following. As far as
I can tell this is not a valid case for backup streams.
This change also cleans up some code and error messages, and expands on
the test coverage for backuptar.
For more information on backup stream format see: https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-bkup/f67950c8-d583-469a-83dd-c4ff4cedf533
Signed-off-by: Kevin Parsons firstname.lastname@example.org