Tcl Source Code

Performing the example at the top of http://wiki.tcl.tk/4610 for generating a gzip file with 8.6b2 fails:

% set file critcl.kit 
critcl.kit
% set fin [open $file rb]
file5
% set header [dict create \
        filename $file time [file mtime $file] comment "Created by Tcl[info patchlevel]"]
filename critcl.kit time 1313070437 comment {Created by Tcl8.6b2}
% set fout [zlib push gzip [open $file.gz wb] -header $header]
file6
% fcopy $fin $fout
161266
% close $fin
% close $fout
% exit
rellis@d820:~/downloads/tcl86b2/inst/usr/local/bin$ gunzip -tv critcl.kit.gz 
critcl.kit.gz:
gzip: critcl.kit.gz: invalid compressed data--format violated

8.6b2 was compiled for, and running under, Slackware 13.1 64-bit.  GCC version is 4.4.4.

allow_comments - 1

Was completely broken, but a one-line fix (was returning the wrong length of written data from the transform guts). Note that _all_ compressing transforms were broken. Fixed in trunk tip.

Workaround is to read the binary data in and compress with [zlib gzip] *or* use the [zlib stream gzip] to make a compressing stream (so you can process the data a bit at a time). [substitute gzip with compress or deflate if you prefer]

File Added - 420930: testgzip.tcl

I also have to retract my report re. 32-bit linux.  The 32-bit system exhibits identical behavior to the 64-bit system on the test script.

Following up on the posting to comp.lang.tcl "zlib push creates corrupt file gz file when source size is equal or greater than 8092" this test script:

puts "Tcl[ info patchlevel ]"

set zeros [ open /dev/zero {RDONLY BINARY} ]

foreach size {8191 8192} {
  set data [ read $zeros $size ] 

  set fout [ open $size {WRONLY CREAT BINARY} ]
  puts -nonewline $fout $data
  close $fout

  set fin [open $size rb]
  set header [dict create filename $size time [file mtime $size] comment "Created by Tcl[info patchlevel]"]
  set fout [zlib push gzip [open $size.gz wb] -header $header]
  fcopy $fin $fout
  close $fin
  close $fout

}

close $zeros

Produces this result on 64-bit Linux - GCC 4.4.4:

rellis@d820:~/downloads/tcl86b2/inst/usr/local/bin$ ./tclsh8.6 testgzip.tcl 
Tcl8.6b2
rellis@d820:~/downloads/tcl86b2/inst/usr/local/bin$ gunzip -tv *gz
8191.gz:         OK
8192.gz:
gzip: 8192.gz: invalid compressed data--format violated

And produces these resulting files:
 8 -rw-r--r-- 1 rellis 8191 2011-08-11 21:22 8191
 4 -rw-r--r-- 1 rellis     72 2011-08-11 21:22 8191.gz
 8 -rw-r--r-- 1 rellis 8192 2011-08-11 21:22 8192
 8 -rw-r--r-- 1 rellis 4159 2011-08-11 21:22 8192.gz

Another data point:

The example from http://wiki.tcl.tk/4610 using 8.6b2 produces a proper gzip file on 32-bit Linux compiled with GCC 4.2.4.

Another test to narrow down the culprit:

% set file critcl.kit
critcl.kit
% set fin [open $file rb]  
file5
% set header [dict create filename $file time [file mtime $file] comment "Created by Tcl[info patchlevel]"]
filename critcl.kit time 1313079102 comment {Created by Tcl8.6b2}
% set fout [open $file.gz wb]
file6
% set comp [ zlib gzip $data -header $header ] ; list
% puts -nonewline $fout $comp
% close $fin
% close $fout
% exit
rellis@d820:~/downloads/tcl86b2/inst/usr/local/bin$ gunzip -tv critcl.kit.gz 
critcl.kit.gz:   OK

Not using zlib push gzip produces a correct gzip file.