Missing bytes??

stevee has asked for the wisdom of the Perl Monks concerning the following question:

Hi Venerable Monks, I am struggling with a corrupt zip archive (another story really!) but to help me in wading through the analysis I have written the following code:

open (FILE, "< i:\\lenova_2008-03-28.zip");
open (OUT, "> i:\\fullhexdump.txt");
binmode(FILE);
$count=0;
while (<FILE>) {
    $count++;
    read(FILE, $buf, 1);
    $byte = unpack "H*", $buf;
    print "$byte";
    print OUT "$byte ";
}
close FILE;
close OUT;
print "\n\n$count\n\n";
[download]

Now the zip archive is 5,914,271KB big, but running the above the count only gets to 22,780,549 bytes (giving a text output file of length 66,740KB). Obviously I am not reading the whole file in, but I can not see why. Does any Learned Brother or Sister have any idea?
Thanks
Stevee

Comment on Missing bytes?? Download Code

Replies are listed 'Best First'.
Re: Missing bytes?? by Corion (Patriarch) on Apr 06, 2008 at 15:36 UTC
You are reading from the file in two locations: `while (<FILE>) { ... read(FILE, $buf, 1);` [download] More likely you want `while (! eof FILE) {` instead of reading a line from `FILE` and then reading another byte from `FILE`.	[reply] [d/l] [select]
Re^2: Missing bytes?? by ikegami (Patriarch) on Apr 06, 2008 at 16:22 UTC
or `while (read(FILE, $buf, 1)) { ... }` [download]	[reply] [d/l]
Re^2: Missing bytes?? by stevee (Acolyte) on Apr 06, 2008 at 15:40 UTC
Thanks Corion, trying it now. Sadly I did not realise that while (<FILE>) read the file too!	[reply]
Re^3: Missing bytes?? by Anonymous Monk on Apr 07, 2008 at 09:26 UTC
interesting, what did you think ?	[reply]
Re: Missing bytes?? by jwkrahn (Abbot) on Apr 06, 2008 at 18:19 UTC
You don't have to read only one byte at a time: `open my $FILE, '<:raw', 'i:/lenova_2008-03-28.zip' or die "Cannot open + 'i:/lenova_2008-03-28.zip' $!"; open my $OUT, '>', 'i:/fullhexdump.txt' or die "Cannot open 'i:/fullhe +xdump.txt' $!"; $/ = \2048; my $count; while ( <$FILE> ) { $count += length; print $OUT unpack 'H*', $_; } close $FILE; close $OUT; print "\n\n$count\n\n";` [download]	[reply] [d/l]


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