You have a tool called xsparse (https://www.gnu.org/software/tar/utils/xsparse.html) that is used to expand sparse files stored in GNU tar format.
The spec given
https://www.gnu.org/software/tar/manual/html_node/PAX-1.html#SEC193
Says that “The sparse map itself is stored in the file data block, preceding the actual file data. It consists of a series of
octal numbers of arbitrary length, delimited by newlines.”
However I think the xsparse tool interprets the number of holes, offsets and lengths as decimal rather than octal, so either
- the tool doesn’t meet the spec
- the spec is wrong
- or more likely I have the wrong end of the stick
😊