apache2::filter.3

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.\" ========================================================================
.\"
.IX Title "mod_perl-2.0.2::docs::api::Apache2::Filter 3"
.TH mod_perl-2.0.2::docs::api::Apache2::Filter 3 "2005-10-21" "perl v5.10.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
Apache2::Filter \- Perl API for Apache 2.0 Filtering
.SH "Synopsis"
.IX Header "Synopsis"
.Vb 1
\&  use Apache2::Filter ();
\&  
\&  # filter attributes
\&  my $c = $f\->c;
\&  my $r = $f\->r;
\&  my $frec = $f\->frec();
\&  my $next_f = $f\->next;
\&  
\&  my $ctx = $f\->ctx;
\&  $f\->ctx($ctx);
\&  
\&  # bucket brigade filtering API
\&  $rc = $f\->next\->get_brigade($bb, $mode, $block, $readbytes);
\&  $rc = $f\->next\->pass_brigade($bb);
\&  $rc = $f\->fflush($bb);
\&  
\&  # streaming filtering API
\&  while ($filter\->read(my $buffer, $wanted)) {
\&      # transform $buffer here
\&      $filter\->print($buffer);
\&  }
\&  if ($f\->seen_eos) {
\&      $filter\->print("filter signature");
\&  }
\&  
\&  # filter manipulations
\&  $r\->add_input_filter(\e&callback);
\&  $c\->add_input_filter(\e&callback);
\&  $r\->add_output_filter(\e&callback);
\&  $c\->add_output_filter(\e&callback);
\&  $f\->remove;
.Ve
.SH "Description"
.IX Header "Description"
\&\f(CW\*(C`Apache2::Filter\*(C'\fR provides Perl \s-1API\s0 for Apache 2.0 filtering
framework.
.PP
Make sure to read \f(CW\*(C`the Filtering
tutorial|docs::2.0::user::handlers::filters\*(C'\fR.
.SH "Common Filter API"
.IX Header "Common Filter API"
The following methods can be called from any filter handler:
.ie n .Sh """c"""
.el .Sh "\f(CWc\fP"
.IX Subsection "c"
Get the current connection object from a connection or a request
filter:
.PP
.Vb 1
\&  $c = $f\->c;
.Ve
.ie n .IP "obj: $f\fR ( \f(CW""Apache2::Filter object"" )" 4
.el .IP "obj: \f(CW$f\fR ( \f(CWApache2::Filter object\fR )" 4
.IX Item "obj: $f ( Apache2::Filter object )"
.PD 0
.ie n .IP "ret: $c\fR ( \f(CW""Apache2::Connection object"" )" 4
.el .IP "ret: \f(CW$c\fR ( \f(CWApache2::Connection object\fR )" 4
.IX Item "ret: $c ( Apache2::Connection object )"
.IP "since: 2.0.00" 4
.IX Item "since: 2.0.00"
.PD
.ie n .Sh """ctx"""
.el .Sh "\f(CWctx\fP"
.IX Subsection "ctx"
Get/set the filter context data.
.PP
.Vb 2
\&  $ctx = $f\->ctx;
\&         $f\->ctx($ctx);
.Ve
.ie n .IP "obj: $f\fR ( \f(CW""Apache2::Filter object"" )" 4
.el .IP "obj: \f(CW$f\fR ( \f(CWApache2::Filter object\fR )" 4
.IX Item "obj: $f ( Apache2::Filter object )"
.PD 0
.ie n .IP "opt arg2: $ctx ( \s-1SCALAR\s0 )" 4
.el .IP "opt arg2: \f(CW$ctx\fR ( \s-1SCALAR\s0 )" 4
.IX Item "opt arg2: $ctx ( SCALAR )"
.PD
next context
.ie n .IP "ret: $ctx ( \s-1SCALAR\s0 )" 4
.el .IP "ret: \f(CW$ctx\fR ( \s-1SCALAR\s0 )" 4
.IX Item "ret: $ctx ( SCALAR )"
current context
.IP "since: 2.0.00" 4
.IX Item "since: 2.0.00"
.PP
A filter context is created before the filter is called for the first
time and it's destroyed at the end of the request. The context is
preserved between filter invocations of the same request. So if a
filter needs to store some data between invocations it should use the
filter context for that.  The filter context is initialized with the
\&\f(CW\*(C`undef\*(C'\fR value.
.PP
The \f(CW\*(C`ctx\*(C'\fR method accepts a single \s-1SCALAR\s0 argument. Therefore if you
want to store any other perl datastructure you should use a reference
to it.
.PP
For example you can store a hash reference:
.PP
.Vb 1
\&  $f\->ctx({ foo => \*(Aqbar\*(Aq });
.Ve
.PP
and then access it:
.PP
.Vb 1
\&  $foo = $f\->ctx\->{foo};
.Ve
.PP
if you access the context more than once it's more efficient to copy
it's value before using it:
.PP
.Vb 2
\&  my $ctx = $f\->ctx;
\&  $foo = $ctx\->{foo};
.Ve
.PP
to avoid redundant method calls. As of this writing \f(CW$ctx\fR is not a
tied variable, so if you modify it need to store it at the end:
.PP
.Vb 1
\&  $f\->ctx($ctx);
.Ve
.PP
\&\s-1META:\s0 later we might make it a TIEd-variable interface, so it'll be
stored automatically.
.PP
Besides its primary purpose of storing context data across multiple
filter invocations, this method is also useful when used as a
flag. For example here is how to ensure that something happens only
once during the filter's life:
.PP
.Vb 4
\&  unless ($f\->ctx) {
\&      do_something_once();
\&      $f\->ctx(1);
\&  }
.Ve
.ie n .Sh """frec"""
.el .Sh "\f(CWfrec\fP"
.IX Subsection "frec"
Get/set the \f(CW\*(C`Apache2::FilterRec\*(C'\fR
(filter record) object.
.PP
.Vb 1
\&  $frec = $f\->frec();
.Ve
.ie n .IP "obj: $f\fR ( \f(CW""Apache2::Filter object"" )" 4
.el .IP "obj: \f(CW$f\fR ( \f(CWApache2::Filter object\fR )" 4
.IX Item "obj: $f ( Apache2::Filter object )"
.PD 0
.ie n .IP "ret: $frec\fR ( \f(CW""Apache2::FilterRec object"" )" 4
.el .IP "ret: \f(CW$frec\fR ( \f(CWApache2::FilterRec object\fR )" 4
.IX Item "ret: $frec ( Apache2::FilterRec object )"
.IP "since: 2.0.00" 4
.IX Item "since: 2.0.00"
.PD
.PP
For example you can call
\&\f(CW\*(C`$frec\->name\*(C'\fR to get
filter's name.
.ie n .Sh """next"""
.el .Sh "\f(CWnext\fP"
.IX Subsection "next"
Return the \f(CW\*(C`Apache2::Filter\*(C'\fR object of the next filter in chain.
.PP
.Vb 1
\&  $next_f = $f\->next;
.Ve
.ie n .IP "obj: $f\fR ( \f(CW""Apache2::Filter object"" )" 4
.el .IP "obj: \f(CW$f\fR ( \f(CWApache2::Filter object\fR )" 4
.IX Item "obj: $f ( Apache2::Filter object )"
The current filter object
.ie n .IP "ret: $next_f\fR ( \f(CW""Apache2::Filter object"" )" 4
.el .IP "ret: \f(CW$next_f\fR ( \f(CWApache2::Filter object\fR )" 4
.IX Item "ret: $next_f ( Apache2::Filter object )"
The next filter object in chain
.IP "since: 2.0.00" 4
.IX Item "since: 2.0.00"
.PP
Since Apache inserts several core filters at the end of each chain,
normally this method always returns an object. However if it's not a
mod_perl filter handler, you can call only the following methods on
it: \f(CW\*(C`get_brigade\*(C'\fR,
\&\f(CW\*(C`pass_brigade\*(C'\fR, \f(CW\*(C`c\*(C'\fR, \f(CW\*(C`r\*(C'\fR,
\&\f(CW\*(C`frec\*(C'\fR and \f(CW\*(C`next\*(C'\fR. If you call other methods
the behavior is undefined.
.PP
The next filter can be a mod_perl one or not, it's easy to tell which
one is that by calling
\&\f(CW\*(C`$f\->frec\->name\*(C'\fR.
.ie n .Sh """r"""
.el .Sh "\f(CWr\fP"
.IX Subsection "r"
Inside an \s-1HTTP\s0 request filter retrieve the current request object:
.PP
.Vb 1
\&  $r = $f\->r;
.Ve
.ie n .IP "obj: $f\fR ( \f(CW""Apache2::Filter object"" )" 4
.el .IP "obj: \f(CW$f\fR ( \f(CWApache2::Filter object\fR )" 4
.IX Item "obj: $f ( Apache2::Filter object )"
.PD 0
.ie n .IP "ret: $r\fR ( \f(CW""Apache2::RequestRec object"" )" 4
.el .IP "ret: \f(CW$r\fR ( \f(CWApache2::RequestRec object\fR )" 4
.IX Item "ret: $r ( Apache2::RequestRec object )"
.IP "since: 2.0.00" 4
.IX Item "since: 2.0.00"
.PD
.PP
If a sub-request adds filters, then that sub-request object is
associated with the filter.
.ie n .Sh """remove"""
.el .Sh "\f(CWremove\fP"
.IX Subsection "remove"
Remove the current filter from the filter chain (for the current
request or connection).
.PP
.Vb 1
\&  $f\->remove;
.Ve
.ie n .IP "obj: $f\fR ( \f(CW""Apache2::Filter object"" )" 4
.el .IP "obj: \f(CW$f\fR ( \f(CWApache2::Filter object\fR )" 4
.IX Item "obj: $f ( Apache2::Filter object )"
.PD 0
.IP "ret: no return value" 4
.IX Item "ret: no return value"
.IP "since: 2.0.00" 4
.IX Item "since: 2.0.00"
.PD
.PP
Notice that you should either complete the current filter invocation
normally (by calling \f(CW\*(C`get_brigade\*(C'\fR or
\&\f(CW\*(C`pass_brigade\*(C'\fR depending on the filter kind) or
if nothing was done, return \f(CW\*(C`Apache2::Const::DECLINED\*(C'\fR and mod_perl will take