[Toybox] bunzip2 - bzcat as bunzip2

[Rob Landley]

On 10/15/14 23:53, Ashwini Sharma wrote:
> Hi Rob, List,
> 
> I was looking into 'bzcat' code. 
> Can't this be used as bunzip2 or as __base__ to bunzip2, as I am
> interested in
> bunzip2 utility.
> 
> At a glance it looked to me that it can be used, please share your opinion.

Yes, it can.

The only reason I haven't done so yet is busybox tar requires the gunzip
and bunzip it uses to be built-in, so I can't drop the decompression
utilities from the busybox config in aboriginal linux (my main test
harness for toybox) until I switch over to using toybox tar.

Also, I need to implement the relevant compression-side utilities. I
have about 1/3 of a gzip compressor implemented here (got distracted
while researching when to do dictionary resets; nobody quite seems to
agree on that one), and I did half a bzip2 implementation ages ago (the
fiddly bit is that the string sorting algorithms in the original are
kind of magic and unexplained; it seems to get constant time out of a
somewhat arbitrary set of sorting algorithms which give up and fall back
to the next one after doing a certain amount of work, but I don't
understand how/why it's set up that way. I need to stare at it some more.)

And then there's the whole "cleanup xz decompression, implement xz
compression" part to look forward to...

If you want to do a proper bunzip wrapper, be my guest. I did bzcat to
prove the engine works and left the rest on the todo list. I have a note
that loopfiles() needs a replace mode so bunzip and sed -i and maybe
patch can share code, but I can clean that up later. (And I need test
suite code to check that "bunzip blah.bz2" fails when blah already
exists...)

> Thanks,
> Ashwini

Rob

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