Re^2: CRC Error on ZIP Files

Hi AnomalousMonk,

thanks for your reply !
Warnings seem to be disabled somehow, since I am not receiving any of these
when running the script. Yet I am aware of the fact, that I should use "strict".
I must admit that I did not get rid of the bad habit of not declaring my
variables throughout all these years ...

To reply to your question: I think (!) I am not using FTP, since I am offering
and sending the file through the recipients browser. For that I am switching binary
mode on. Here is the critical code of the prescript running the download.

sub download {


use CGI;

$html=new CGI;


print $html->header(-type => 'application/octet-stream', -attachment =
+> $_[1]);
        
    open($peunter, "<", $_[0].$_[1]);
    binmode($peunter);
#     while (read($pointer,$bytes,1024)) {
#             print $bytes;
#     }
    @data = <$peunter>;
    
    close($peunter);
    
    print "@data";


}
[download]

Comment on Re^2: CRC Error on ZIP Files Download Code

Replies are listed 'Best First'.
Re^3: CRC Error on ZIP Files by Corion (Patriarch) on Mar 01, 2014 at 18:03 UTC
If you are on Windows, you really need to `binmode STDOUT;` [download] before printing. On all other operating systems, it's still good practice. Maybe try that, and alternatively, first create the ZIP file on disk, and manually download it through a trusted, different way, just to make sure that the ZIP file itself is not corrupted.	[reply] [d/l]
Re^4: CRC Error on ZIP Files by SearchigPerl (Acolyte) on Mar 01, 2014 at 19:22 UTC
Hi Corion, my deepest gratitude to you for your idea of testing the zip file on disk ! I have been assuming the zip file itself would be generated wrongly. Now I realize it's not ! The zip file, prior to downloading is working perfectly fine. The problem lies within the download-script. Yet having added the command binmode STDOUT; did not alter anything.	[reply]
Re^5: CRC Error on ZIP Files by Corion (Patriarch) on Mar 02, 2014 at 06:28 UTC
Did you look at the expected and actual file sizes? I note in your download subroutine that you never check whether open succeeds. Maybe the file you are trying to open does not exist? `my $filename= $_[0].$_[1]; open my $peunter, '<', $filename or die "Couldn't open '$filename': $!"; ...` [download]	[reply] [d/l]
Re^3: CRC Error on ZIP Files by graff (Chancellor) on Mar 01, 2014 at 19:56 UTC
Apart from Corion's suggestion to include `binmode STDOUT` (which I think really might be an issue, even if it's not the only issue), you may also want to try: `print $html->header(-type => 'application/zip', … );` [download] At least, according to Wikipedia, zip file format is "registered" as an official MIME type. Update: I actually don't know whether fixing the mime-type label will make any difference. I'm guessing that the issue is whether or not a carriage-return byte gets added before each line-feed byte, possibly at the receiving end, if not at the transmission end. Note the exact byte count for the original (working) zip file, then compare that to the exact byte count of a downloaded version; if the latter is bigger, there's something like a "unix2dos" filter kicking in at some point in the download process, and that will certainly screw up the zip file.	[reply] [d/l] [select]
Re^3: CRC Error on ZIP Files by aitap (Curate) on Mar 02, 2014 at 11:37 UTC
`print "@data";` This is your problem. Consider this code: `$ perl -E'@a=qw/1 2 3/; print "@a"' 1 2 3` [download] You wanted to print your lines joined by empty string, but "@array" joins array elements with space (read $" for more info on that). Your original, commented-out approach is better: just read your file by, say, 10 kilobytes and immediately send the data to client: `{ local $/ = \10240; print while <$peunter>; }` [download] In this example I tell Perl to read files with diamond operator (<$filehandle>) by 10240 bytes ($/) and loop printing the file pieces until I reach end-of-file. _{Edit: corrected typo}	[reply] [d/l] [select]
Re^3: CRC Error on ZIP Files by ww (Archbishop) on Mar 01, 2014 at 17:56 UTC
Perhaps it's a problem in your header. You specify the type (Ln 9)as 'application/octet-stream' but it should be 'application/zip' (according to http://en.wikipedia.org/wiki/MIME_type#Type_application ... yes, I know that's not the authoritative source, but it'll do as a hint). Come, let us reason together: Spirit of the Monastery	[reply]
Re^4: CRC Error on ZIP Files by SearchigPerl (Acolyte) on Mar 01, 2014 at 18:59 UTC
Hi ww, thanks for your hint, I changed the code accordingly (although I believe to have understood that "octet-stream" would be valid for all formats). Yet with the altered code the problem remains.	[reply]