doc-view--buffer-file-name

doc-view--buffer-file-name is a variable defined in `doc-view.el'.
Its value is

nil

Documentation:
Only used internally.
The file name used for conversion. Normally it's the same as
`buffer-file-name', but for remote files, compressed files and
files inside an archive it is a temporary copy of
the (uncompressed, extracted) file residing in
`doc-view-cache-directory'.