Re: [cgiapp] File Streaming

[Michael Peters]

Tobias Henoeckl wrote:
Hi, 

the CGI::Application documentation said, feature requests should be
sent to this mailing list, so that's why I'm posting here. Sorry if I
dont't know about recent topics here (is there a web archive
available anywhere?)
This is the place. The archives are at:
  http://www.mail-archive.com/cgiapp@lists.erlbaum.net/
  http://marc.theaimsgroup.com/?l=cgiapp&r=1&w=2
which it mentions at the bottom of each message from the list.
We stepped into memory problems using CGI::Application, as our
application had to deliver a file to the customer after doing some
calculations and access control. It worked well until our customer
started to serve *really* huge files, wich were slurped into memory
by the run mode handler and then returned for delivery.
As far as I could see there is no way supplied in CGI::Application to
stream a file directly from the file system to the user agent.
I fixed the problem with the attached patch, that allows to return not
only a string or string reference, but also a file handle. It should
be compatible with the previous version as far as I can see.
Using this patch I can now use the following code to deliver the
file, without having it in memory:
sub myhandler {
  my $self = shift;
  do_many_things();
  $self->header_props(
    -type                  => 'application/octet-stream',
    '-Content-length'      => -s $filename,
    -Application           => $filename,
    '-Content-Disposition' => "attachment; filename=\"$filename\"",
  );
  open my $fh, "</home/hoeni/Muenchen_10685x9166.jpg"
    || die;
  return $fh
}
I think that this is a really good idea. Although not necessary. You 
could alternatively do this:

  $self->header_type('none');
  print "Content-Type: application/octet-stream\n";
  #print the other headers here...
  open my $fh, "</home/hoeni/Muenchen_10685x9166.jpg"
        || die;
  while(my $line = <$fh>) { print $line };
  return;
at the end of your runmode. But I think I like your idea better.
The file is not given to cgiapp_postrun() with would make no sense
here.
Well, it might... what if I wanted to close the filehandle, or release 
on lock on it, etc.

If you implement this, it would be handy for the user of the lib to
have kind of $self->stream_file($filename, $optionalmimetype) method
which would do the above things and open and return a filehandle so
the above code could be reduced to:
do_many_things();
return($self->stream_file($filename, 'application/octet-stream'));
I think I like this idea the best, although I'm not sure it belongs in 
the the C::A core. If we implement the idea of returning a filehandle 
instead of just text, then I would encourage you to implement this as a 
plugin. CGI::Application::Plugin::Stream anyone? For information on 
plugins see http://twiki.med.yale.edu/twiki2/bin/view/CGIapp/Plugins on 
the wiki.


+        if (ref($body) ne 'GLOB') {
+            # Support scalar-ref for body return
+            $bodyref = (ref($body) eq 'SCALAR') ? $body : \$body;
One question: if you are just checking for a GLOB, will that catch class 
based file handles like the IO::* family?

--
Michael Peters
Developer
Plus Three, LP
---------------------------------------------------------------------
Web Archive:  http://www.mail-archive.com/cgiapp@lists.erlbaum.net/
             http://marc.theaimsgroup.com/?l=cgiapp&r=1&w=2
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]