sharplispers / chipz Goto Github PK

Hello,

i tried the following code with an error :

From linux shell :

:~> echo "huge" | bzip2 - > huge.bz2
:~> file huge.bz2
huge.bz2: bzip2 compressed data, block size = 900k

Lisp Code (according to the doc) :

(with-open-file (stream "huge.bz2"  :element-type '(unsigned-byte 8))
           (chipz:decompress nil 'chipz:bzip2 stream))

Error (SIMPLE-ERROR) during printing: #<CHIPZ:INVALID-BZIP2-DATA {1006A7BB43}>

With a little help from comp.lang.lisp, i think there is an error in the bzip2.lisp file.
In the following function :

(bzip2-selector1 (state)
               (declare (type bzip2-state state))
               (let ((n-groups (ensure-and-read-bits 3 state)))
                 (unless (<= 3 n-groups 6)
                   (error 'invalid-bzip2-data))
                 (setf (bzip2-state-n-groups state) n-groups)
(transition-to bzip2-selector2)))

the n-groups value is tested between 3 and 6.
But in the C code version (decompress.c v1.0.6) the test is between 2 and 6.
if (nGroups < 2 || nGroups > 6) RETURN(BZ_DATA_ERROR); (line 288)

With 2 instead of 3, no more error in the test.

Thanks

Following has a reasonable chance (30%+) of triggering EOF error from chipz:

(ql:quickload '(chipz salza2))

(let* ((d (map-into (make-array (expt 2 8) :element-type '(unsigned-byte 8))
                    (lambda () (random 255))))
       (v (salza2:compress-data d 'salza2:deflate-compressor)))
  (with-simple-restart (continue "continue")
    (let ((x (time (chipz:decompress nil 'chipz:deflate v))))
      (assert (equalp d x)))))

Not completely sure it is chipz rather than salza2, but other decompressors don't seem to object to the same data.

I'm not sure what the protocol is for something like this, could someone place this into ultralisp?

If it is something I can do via a mirroring fork, then I'll do it. If a sharplisper member is empowered to do so then I request that it be so.

And if there is good reason to avoid it, I'm all ears.

cheers