Re: big file warning if compressed

[Kevin Rodgers]

Richard Stallman wrote:
>     > That is because Emacs has no way of telling how big it is
>     > until after uncompressing it.
>
>     That's not really true: GNU zip has the --list option, which generates
>     output like:
>
>     compressed  uncompr. ratio uncompressed_name
>       12574759  58689536  78.5% foo.txt
>
> 1. How long does that take?  Does it get the info instantly
> or does it have to effectively uncompress the data to get the info?

gzip --list is fast: On that file, it took 15.9 seconds real time (3.0
user, 9.2 system) to run 1,000 iterations, compared to 7.1 seconds real
(6.3 user, 1.0 sys) for 1 iteration of gunzip --stdout | wc -l.

> 2. What about other compression formats?

According to http://www.gnu.org/software/gzip/manual/html_node/gzip_4.html

        The uncompressed size is given as `-1' for files not in gzip
        format, such as compressed `.Z' files

As far as the other compression programs supported by jka-compr.el,
neither compress/uncompress nor bzip2/bunzip2 seem to have this
feature.

> You can try working on this, but I'd rather save it for after the
> release.

OK.  (I've already got an untested patch to add support for it.)

--
Kevin