On Wed 08 Apr 2009, André Warnier wrote:
> I want to write a mod_perl input filter, which essentially would
> replace some characters from form-posted input on the fly, before
> letting the request go to the real application.
> The requests are POST, with content encoded in one long string,
> URL-encoded. I am thinking of writing this as a FilterRequestHandler
> filter, grabbing the content, splitting it on "&", URL-decoding the
> so-splitted query parameters individually, then in the value
> performing the character substitutions, then re-URL-encoding the
> query parameters, re-joining them with "&", and essentially et voilà.
>
> Basically, the type shown here :
> http://perl.apache.org/docs/2.0/user/handlers/filters.html#toc_Stream
>_oriented_Input_Filters
>
> Is the above a realistic view, or am I missing something essential ?
Remember the request can consist of multiple brigades. Each filter
invocation gets one brigade. That means you have to be prepared to
store some context (store the /[^&;]*$/ part in $f->ctx). Don't try to
read in the whole request. Operate on each part of it.
For example try the following PerlInputFilterHandler:
sub handler {
my ($f)=...@_;
$f->print("\n###########\n");
my $buf;
while($f->read($buf, 1024)) {
$f->print("\n>>>$buf<<<\n");
undef $buf;
}
$f->print("\n:::::::::::\n");
return Apache2::Const::OK;
}
with this PerlResponseHandler:
sub handler {
my ($r)=...@_;
$r->content_type('text/plain');
my $buf;
while($r->read($buf, 15000)) {
$r->print($buf);
undef $buf;
}
return Apache2::Const::OK;
}
and feed it with more than 8000 bytes:
perl -e 'print "x"x10000' | curl -qs -d @- http://localhost/iftest
You'll see multiple blocks wrapped in >>> ... <<< from the filter loop.
But you'll also see 2 blocks of ######### ... :::::::::: that mark the
filter invocations.
BTW, the buffer size in the response handler is that large because is
must be able to store a whole brigade's content due to a modperl bug,
see "XXX:" comment in modperl_request_read(). So, don't $f->print much
in one filter invocation.
Torsten
--
Need professional mod_perl support?
Just hire me: torsten.foert...@gmx.net
