libbb/archival: make setup_unzip_on_fd() return bytes read if not compressed

setup_unzip_on_fd() does not return the transformer structure, so the user
does not know how much to seek back (or alternatively what the signature was)
when compressor signature is not detected.

Currently not needed (the only user is tar which dies anyway).
However, rpm2cpio may need this if we extend it to extract the internal .cpio
even if cpio's compressions algo is not known.

function                                             old     new   delta
setup_unzip_on_fd                                     53      59      +6

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

0 files changed, 0 insertions, 0 deletions