Re: examples using Compress::Zlib ?

[grinder]

I was going to post my own SoPW on my troubles at getting Compress::Zlib to work, and Super Search pointed me here. Based on the code samples here, I was able to get my test case (a line-oriented zip/unzip) to work correctly.

Specifically, my problem was that I was creating a $gz handle using deflateInit(). So here's my code for future readers in the same predicament:

#! /usr/bin/perl -w

use strict;
use Compress::Zlib;

my $file = shift || 'testdata.gz';
my $gz   = gzopen( $file, 'wb' ) or die "Cannot open $file for gzwrite
+: $gzerrno\n";
my $line;

while( defined($line = <DATA>) ) {
    $gz->gzwrite( $line )
        or die "Could not write gzipped data to $file: $gzerrno\n";
}
$gz->gzclose();

$gz = gzopen( $file, 'rb' ) or die "Cannot open $file for gzread: $gze
+rrno\n";
while( $gz->gzreadline($line) > 0 ) {
    print $line;
}
die "Error reading from $file: [$gzerrno]\n" unless Z_STREAM_END == $g
+zerrno;
$gz->gzclose();

__DATA__
foo
bar
Judge my vow, sphinx of black quartz
__END__

I think it's pretty self-explanatory...

This does leave me with one question, however, and that is, how can I specify the that the writer uses different compression strategies, à la Z_BEST_SPEED and Z_BEST_COMPRESSION?

update: in reply to idnopheq's suggestion, despite have 512Mb RAM, I'd rather not have this hanging around in RAM, I actually want to dump it straight out onto tape. I initially used a deflateInit approach and wrote the output to a file myself, but I was unable to successfully read it back using gzopen on the resulting file.

--

g r i n d e r

[idnopheq]

If you go with the in-memory compression/decompression odel, you have more flexibility. From the perldoc for the deflateInit call:

-Level Defines the compression level. Valid values are 1 through 9, Z_BEST_SPEED, Z_BEST_COMPRESSION, and Z_DEFAULT_COMPRESSION. The default is -Level =>Z_DEFAULT_COMPRESSION.

So then:

deflateInit( -Bufsize => 300, 
                 -Level => Z_BEST_SPEED  ) ;

Then IIRC write the buffer to disk.

HTH
--
idnopheq
Apply yourself to new problems without preparation, develop confidence in your ability to to meet situations as they arrise.

~ Shunryu Suzuki