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From: Eric Wong <e@yhbt.net>
To: meta@public-inbox.org
Subject: [PATCH 24/43] www: start making gzipfilter the parent response class
Date: Sun,  5 Jul 2020 23:27:40 +0000
Message-Id: <20200705232759.3161-25-e@yhbt.net>
In-Reply-To: <20200705232759.3161-1-e@yhbt.net>
References: <20200705232759.3161-1-e@yhbt.net>
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List-Id: <meta.public-inbox.org>

Virtually all of our responses are going to be gzipped, anyways.
This will allow us to utilize zlib as a buffering layer and
share common code for async blob retrieval responses.

To streamline this and allow GzipFilter to be a parent class,
we'll replace the NoopFilter with a similar CompressNoop class
which emulates the two Compress::Raw::Zlib::Deflate methods we
use.

This drops a bunch of redundant code and will hopefully make
upcoming WwwStream changes easier to reason about.
---
 MANIFEST                         |  2 +-
 lib/PublicInbox/CompressNoop.pm  | 22 +++++++
 lib/PublicInbox/GzipFilter.pm    | 75 +++++++++++++++++++-----
 lib/PublicInbox/Mbox.pm          | 90 ++++++++---------------------
 lib/PublicInbox/MboxGz.pm        | 71 +++++------------------
 lib/PublicInbox/NoopFilter.pm    | 24 --------
 lib/PublicInbox/WwwAtomStream.pm | 98 ++++++++------------------------
 lib/PublicInbox/WwwListing.pm    |  3 +-
 lib/PublicInbox/WwwStatic.pm     |  3 +-
 9 files changed, 148 insertions(+), 240 deletions(-)
 create mode 100644 lib/PublicInbox/CompressNoop.pm
 delete mode 100644 lib/PublicInbox/NoopFilter.pm

diff --git a/MANIFEST b/MANIFEST
index 9b0f50203..963caad02 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -100,6 +100,7 @@ lib/PublicInbox/Admin.pm
 lib/PublicInbox/AdminEdit.pm
 lib/PublicInbox/AltId.pm
 lib/PublicInbox/Cgit.pm
+lib/PublicInbox/CompressNoop.pm
 lib/PublicInbox/Config.pm
 lib/PublicInbox/ContentHash.pm
 lib/PublicInbox/DS.pm
@@ -159,7 +160,6 @@ lib/PublicInbox/NNTP.pm
 lib/PublicInbox/NNTPD.pm
 lib/PublicInbox/NNTPdeflate.pm
 lib/PublicInbox/NewsWWW.pm
-lib/PublicInbox/NoopFilter.pm
 lib/PublicInbox/Over.pm
 lib/PublicInbox/OverIdx.pm
 lib/PublicInbox/ParentPipe.pm
diff --git a/lib/PublicInbox/CompressNoop.pm b/lib/PublicInbox/CompressNoop.pm
new file mode 100644
index 000000000..fe73c2d10
--- /dev/null
+++ b/lib/PublicInbox/CompressNoop.pm
@@ -0,0 +1,22 @@
+# Copyright (C) 2020 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+
+# Provide the same methods as Compress::Raw::Zlib::Deflate but
+# does no transformation of outgoing data
+package PublicInbox::CompressNoop;
+use strict;
+use Compress::Raw::Zlib qw(Z_OK);
+
+sub new { bless \(my $self), __PACKAGE__ }
+
+sub deflate { # ($self, $input, $output)
+	$_[2] .= $_[1];
+	Z_OK;
+}
+
+sub flush { # ($self, $output, $flags = Z_FINISH)
+	$_[1] //= '';
+	Z_OK;
+}
+
+1;
diff --git a/lib/PublicInbox/GzipFilter.pm b/lib/PublicInbox/GzipFilter.pm
index 0a6c56a5d..99d43cf04 100644
--- a/lib/PublicInbox/GzipFilter.pm
+++ b/lib/PublicInbox/GzipFilter.pm
@@ -6,6 +6,10 @@ package PublicInbox::GzipFilter;
 use strict;
 use parent qw(Exporter);
 use Compress::Raw::Zlib qw(Z_FINISH Z_OK);
+use PublicInbox::CompressNoop;
+use PublicInbox::Eml;
+use PublicInbox::GitAsyncCat;
+
 our @EXPORT_OK = qw(gzf_maybe);
 my %OPT = (-WindowBits => 15 + 16, -AppendOutput => 1);
 my @GZIP_HDRS = qw(Vary Accept-Encoding Content-Encoding gzip);
@@ -14,22 +18,41 @@ sub new { bless {}, shift }
 
 # for Qspawn if using $env->{'pi-httpd.async'}
 sub attach {
-	my ($self, $fh) = @_;
-	$self->{fh} = $fh;
+	my ($self, $http_out) = @_;
+	$self->{http_out} = $http_out;
 	$self
 }
 
-# returns `0' and not `undef' on failure (see Www*Stream)
-sub gzf_maybe ($$) {
+sub gz_or_noop {
 	my ($res_hdr, $env) = @_;
-	return 0 if (($env->{HTTP_ACCEPT_ENCODING}) // '') !~ /\bgzip\b/;
-	my ($gz, $err) = Compress::Raw::Zlib::Deflate->new(%OPT);
-	return 0 if $err != Z_OK;
+	if (($env->{HTTP_ACCEPT_ENCODING} // '') =~ /\bgzip\b/) {
+		$env->{'plack.skip-deflater'} = 1;
+		push @$res_hdr, @GZIP_HDRS;
+		gzip_or_die();
+	} else {
+		PublicInbox::CompressNoop::new();
+	}
+}
 
-	# in case Plack::Middleware::Deflater is loaded:
-	$env->{'plack.skip-deflater'} = 1;
-	push @$res_hdr, @GZIP_HDRS;
-	bless { gz => $gz }, __PACKAGE__;
+sub gzf_maybe ($$) { bless { gz => gz_or_noop(@_) }, __PACKAGE__ }
+
+sub psgi_response {
+	my ($self, $code, $res_hdr, $next_cb, $eml_cb) = @_;
+	my $env = $self->{env};
+	$self->{gz} //= gz_or_noop($res_hdr, $env);
+	if ($env->{'pi-httpd.async'}) {
+		$self->{async_next} = $next_cb;
+		$self->{async_eml} = $eml_cb;
+		my $http = $env->{'psgix.io'}; # PublicInbox::HTTP
+		$http->{forward} = $self;
+		sub {
+			my ($wcb) = @_; # -httpd provided write callback
+			$self->{http_out} = $wcb->([$code, $res_hdr]);
+			$next_cb->($http); # start stepping
+		};
+	} else { # generic PSGI code path
+		[ $code, $res_hdr, $self ];
+	}
 }
 
 sub qsp_maybe ($$) {
@@ -80,7 +103,7 @@ sub translate ($$) {
 
 sub write {
 	# my $ret = bytes::length($_[1]); # XXX does anybody care?
-	$_[0]->{fh}->write(translate($_[0], $_[1]));
+	$_[0]->{http_out}->write(translate($_[0], $_[1]));
 }
 
 # similar to ->translate; use this when we're sure we know we have
@@ -109,9 +132,31 @@ sub zflush ($;$) {
 
 sub close {
 	my ($self) = @_;
-	my $fh = delete $self->{fh};
-	$fh->write(zflush($self));
-	$fh->close;
+	if (my $http_out = delete $self->{http_out}) {
+		$http_out->write(zflush($self));
+		$http_out->close;
+	}
+}
+
+# this is public-inbox-httpd-specific
+sub async_blob_cb { # git->cat_async callback
+	my ($bref, $oid, $type, $size, $self) = @_;
+	my $http = $self->{env}->{'psgix.io'} or return; # client abort
+	my $smsg = $self->{smsg} or die 'BUG: no smsg';
+	if (!defined($oid)) {
+		# it's possible to have TOCTOU if an admin runs
+		# public-inbox-(edit|purge), just move onto the next message
+		return $http->next_step($self->{async_next});
+	}
+	$smsg->{blob} eq $oid or die "BUG: $smsg->{blob} != $oid";
+	$self->{async_eml}->($self, PublicInbox::Eml->new($bref));
+	$http->next_step($self->{async_next});
+}
+
+sub smsg_blob {
+	my ($self, $smsg) = @_;
+	git_async_cat($self->{-inbox}->git, $smsg->{blob},
+			\&async_blob_cb, $self);
 }
 
 1;
diff --git a/lib/PublicInbox/Mbox.pm b/lib/PublicInbox/Mbox.pm
index 895f828c5..abdf43c93 100644
--- a/lib/PublicInbox/Mbox.pm
+++ b/lib/PublicInbox/Mbox.pm
@@ -9,13 +9,11 @@
 # more common "push" model)
 package PublicInbox::Mbox;
 use strict;
-use warnings;
+use parent 'PublicInbox::GzipFilter';
 use PublicInbox::MID qw/mid_escape/;
 use PublicInbox::Hval qw/to_filename/;
 use PublicInbox::Smsg;
 use PublicInbox::Eml;
-use PublicInbox::GitAsyncCat;
-use PublicInbox::GzipFilter qw(gzf_maybe);
 
 # called by PSGI server as body response
 # this gets called twice for every message, once to return the header,
@@ -25,49 +23,35 @@ sub getline {
 	my $smsg = $ctx->{smsg} or return;
 	my $ibx = $ctx->{-inbox};
 	my $eml = $ibx->smsg_eml($smsg) or return;
-	$ctx->{smsg} = $ibx->over->next_by_mid($ctx->{mid}, @{$ctx->{id_prev}});
-	msg_hdr($ctx, $eml, $smsg->{mid}) . msg_body($eml);
-}
-
-sub close { !!delete($_[0]->{http_out}) }
-
-sub mbox_async_step ($) { # public-inbox-httpd-only
-	my ($ctx) = @_;
-	if (my $smsg = $ctx->{smsg}) {
-		git_async_cat($ctx->{-inbox}->git, $smsg->{blob},
-				\&mbox_blob_cb, $ctx);
-	} elsif (my $out = delete $ctx->{http_out}) {
-		$out->close;
+	my $n = $ctx->{smsg} = $ibx->over->next_by_mid(@{$ctx->{next_arg}});
+	$ctx->zmore(msg_hdr($ctx, $eml, $smsg->{mid}));
+	if ($n) {
+		$ctx->translate(msg_body($eml));
+	} else { # last message
+		$ctx->zmore(msg_body($eml));
+		$ctx->zflush;
 	}
 }
 
 # called by PublicInbox::DS::write
-sub mbox_async_next {
+sub async_next {
 	my ($http) = @_; # PublicInbox::HTTP
 	my $ctx = $http->{forward} or return; # client aborted
 	eval {
-		$ctx->{smsg} = $ctx->{-inbox}->over->next_by_mid(
-					$ctx->{mid}, @{$ctx->{id_prev}});
-		mbox_async_step($ctx);
+		my $smsg = $ctx->{smsg} or return $ctx->close;
+		$ctx->smsg_blob($smsg);
 	};
+	warn "E: $@" if $@;
 }
 
-# this is public-inbox-httpd-specific
-sub mbox_blob_cb { # git->cat_async callback
-	my ($bref, $oid, $type, $size, $ctx) = @_;
-	my $http = $ctx->{env}->{'psgix.io'} or return; # client abort
-	my $smsg = delete $ctx->{smsg} or die 'BUG: no smsg';
-	if (!defined($oid)) {
-		# it's possible to have TOCTOU if an admin runs
-		# public-inbox-(edit|purge), just move onto the next message
-		return $http->next_step(\&mbox_async_next);
-	} else {
-		$smsg->{blob} eq $oid or die "BUG: $smsg->{blob} != $oid";
-	}
-	my $eml = PublicInbox::Eml->new($bref);
-	$ctx->{http_out}->write(msg_hdr($ctx, $eml, $smsg->{mid}));
-	$ctx->{http_out}->write(msg_body($eml));
-	$http->next_step(\&mbox_async_next);
+sub async_eml { # ->{async_eml} for async_blob_cb
+	my ($ctx, $eml) = @_;
+	my $smsg = delete $ctx->{smsg};
+	# next message
+	$ctx->{smsg} = $ctx->{-inbox}->over->next_by_mid(@{$ctx->{next_arg}});
+
+	$ctx->zmore(msg_hdr($ctx, $eml, $smsg->{mid}));
+	$ctx->{http_out}->write($ctx->translate(msg_body($eml)));
 }
 
 sub res_hdr ($$) {
@@ -97,41 +81,17 @@ sub no_over_raw ($) {
 		[ msg_hdr($ctx, $eml, $ctx->{mid}) . msg_body($eml) ] ]
 }
 
-sub stream_raw { # MboxGz response callback
-	my ($ctx) = @_;
-	delete($ctx->{smsg}) //
-		$ctx->{-inbox}->over->next_by_mid($ctx->{mid},
-						@{$ctx->{id_prev}});
-}
-
 # /$INBOX/$MESSAGE_ID/raw
 sub emit_raw {
 	my ($ctx) = @_;
-	my $env = $ctx->{env};
-	$ctx->{base_url} = $ctx->{-inbox}->base_url($env);
+	$ctx->{base_url} = $ctx->{-inbox}->base_url($ctx->{env});
 	my $over = $ctx->{-inbox}->over or return no_over_raw($ctx);
 	my ($id, $prev);
-	my $smsg = $over->next_by_mid($ctx->{mid}, \$id, \$prev) or return;
-	$ctx->{smsg} = $smsg;
+	my $mip = $ctx->{next_arg} = [ $ctx->{mid}, \$id, \$prev ];
+	my $smsg = $ctx->{smsg} = $over->next_by_mid(@$mip) or return;
 	my $res_hdr = res_hdr($ctx, $smsg->{subject});
-	$ctx->{id_prev} = [ \$id, \$prev ];
-
-	if (my $gzf = gzf_maybe($res_hdr, $env)) {
-		$ctx->{gz} = delete $gzf->{gz};
-		require PublicInbox::MboxGz;
-		PublicInbox::MboxGz::response($ctx, \&stream_raw, $res_hdr);
-	} elsif ($env->{'pi-httpd.async'}) {
-		sub {
-			my ($wcb) = @_; # -httpd provided write callback
-			$ctx->{http_out} = $wcb->([200, $res_hdr]);
-			$ctx->{env}->{'psgix.io'}->{forward} = $ctx;
-			bless $ctx, __PACKAGE__;
-			mbox_async_step($ctx); # start stepping
-		};
-	} else { # generic PSGI code path
-		bless $ctx, __PACKAGE__; # respond to ->getline
-		[ 200, $res_hdr, $ctx ];
-	}
+	bless $ctx, __PACKAGE__;
+	$ctx->psgi_response(200, $res_hdr, \&async_next, \&async_eml);
 }
 
 sub msg_hdr ($$;$) {
diff --git a/lib/PublicInbox/MboxGz.pm b/lib/PublicInbox/MboxGz.pm
index 716bf7b19..fdd16f68e 100644
--- a/lib/PublicInbox/MboxGz.pm
+++ b/lib/PublicInbox/MboxGz.pm
@@ -6,77 +6,32 @@ use parent 'PublicInbox::GzipFilter';
 use PublicInbox::Eml;
 use PublicInbox::Hval qw/to_filename/;
 use PublicInbox::Mbox;
-use PublicInbox::GitAsyncCat;
 *msg_hdr = \&PublicInbox::Mbox::msg_hdr;
 *msg_body = \&PublicInbox::Mbox::msg_body;
 
-# this is public-inbox-httpd-specific
-sub mboxgz_blob_cb { # git->cat_async callback
-	my ($bref, $oid, $type, $size, $self) = @_;
-	my $http = $self->{env}->{'psgix.io'} or return; # client abort
-	my $smsg = delete $self->{smsg} or die 'BUG: no smsg';
-	if (!defined($oid)) {
-		# it's possible to have TOCTOU if an admin runs
-		# public-inbox-(edit|purge), just move onto the next message
-		return $http->next_step(\&mboxgz_async_next);
-	} else {
-		$smsg->{blob} eq $oid or die "BUG: $smsg->{blob} != $oid";
-	}
-	my $eml = PublicInbox::Eml->new($bref);
-	$self->zmore(msg_hdr($self, $eml, $smsg->{mid}));
-
-	# PublicInbox::HTTP::{Chunked,Identity}::write
-	$self->{http_out}->write($self->translate(msg_body($eml)));
-
-	$http->next_step(\&mboxgz_async_next);
-}
-
-# this is public-inbox-httpd-specific
-sub mboxgz_async_step ($) {
-	my ($self) = @_;
-	if (my $smsg = $self->{smsg} = $self->{cb}->($self)) {
-		git_async_cat($self->{-inbox}->git, $smsg->{blob},
-				\&mboxgz_blob_cb, $self);
-	} elsif (my $out = delete $self->{http_out}) {
-		$out->write($self->zflush);
-		$out->close;
-	}
-}
-
-# called by PublicInbox::DS::write
-sub mboxgz_async_next {
+sub async_next ($) {
 	my ($http) = @_; # PublicInbox::HTTP
-	mboxgz_async_step($http->{forward});
-}
-
-# called by PublicInbox::HTTP::close, or any other PSGI server
-sub close { !!delete($_[0]->{http_out}) }
-
-sub response {
-	my ($self, $cb, $res_hdr) = @_;
-	$self->{cb} = $cb;
-	bless $self, __PACKAGE__;
-	if ($self->{env}->{'pi-httpd.async'}) {
-		sub {
-			my ($wcb) = @_; # -httpd provided write callback
-			$self->{http_out} = $wcb->([200, $res_hdr]);
-			$self->{env}->{'psgix.io'}->{forward} = $self;
-			mboxgz_async_step($self); # start stepping
-		};
-	} else { # generic PSGI
-		[ 200, $res_hdr, $self ];
-	}
+	my $ctx = $http->{forward} or return;
+	eval {
+		$ctx->{smsg} = $ctx->{cb}->($ctx) or return $ctx->close;
+		$ctx->smsg_blob($ctx->{smsg});
+	};
+	warn "E: $@" if $@;
 }
 
 sub mbox_gz {
 	my ($self, $cb, $fn) = @_;
+	$self->{cb} = $cb;
 	$self->{base_url} = $self->{-inbox}->base_url($self->{env});
 	$self->{gz} = PublicInbox::GzipFilter::gzip_or_die();
 	$fn = to_filename($fn // 'no-subject');
 	$fn = 'no-subject' if $fn eq '';
 	# http://www.iana.org/assignments/media-types/application/gzip
-	response($self, $cb, [ qw(Content-Type application/gzip),
-		'Content-Disposition', "inline; filename=$fn.mbox.gz" ]);
+	bless $self, __PACKAGE__;
+	my $res_hdr = [ 'Content-Type' => 'application/gzip',
+		'Content-Disposition' => "inline; filename=$fn.mbox.gz" ];
+	$self->psgi_response(200, $res_hdr, \&async_next,
+				\&PublicInbox::Mbox::async_eml);
 }
 
 # called by Plack::Util::foreach or similar (generic PSGI)
diff --git a/lib/PublicInbox/NoopFilter.pm b/lib/PublicInbox/NoopFilter.pm
deleted file mode 100644
index a97dbde64..000000000
--- a/lib/PublicInbox/NoopFilter.pm
+++ /dev/null
@@ -1,24 +0,0 @@
-# Copyright (C) 2020 all contributors <meta@public-inbox.org>
-# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
-
-package PublicInbox::NoopFilter;
-use strict;
-
-sub new { bless \(my $self = ''), __PACKAGE__ }
-
-# noop workalike for PublicInbox::GzipFilter methods
-sub translate {
-	my $self = $_[0];
-	my $ret = $$self .= ($_[1] // '');
-	$$self = '';
-	$ret;
-}
-
-sub zmore {
-	${$_[0]} .= $_[1];
-	undef;
-}
-
-sub zflush { translate($_[0], $_[1]) }
-
-1;
diff --git a/lib/PublicInbox/WwwAtomStream.pm b/lib/PublicInbox/WwwAtomStream.pm
index 583309228..073df1dfa 100644
--- a/lib/PublicInbox/WwwAtomStream.pm
+++ b/lib/PublicInbox/WwwAtomStream.pm
@@ -7,107 +7,59 @@
 # more common "push" model)
 package PublicInbox::WwwAtomStream;
 use strict;
-use warnings;
+use parent 'PublicInbox::GzipFilter';
 
 use POSIX qw(strftime);
 use Digest::SHA qw(sha1_hex);
 use PublicInbox::Address;
 use PublicInbox::Hval qw(ascii_html mid_href);
 use PublicInbox::MsgTime qw(msg_timestamp);
-use PublicInbox::GzipFilter qw(gzf_maybe);
-use PublicInbox::GitAsyncCat;
-
-# called by generic PSGI server after getline,
-# and also by PublicInbox::HTTP::close
-sub close { !!delete($_[0]->{http_out}) }
 
 sub new {
 	my ($class, $ctx, $cb) = @_;
 	$ctx->{feed_base_url} = $ctx->{-inbox}->base_url($ctx->{env});
-	$ctx->{cb} = $cb || \&close;
+	$ctx->{cb} = $cb || \&PublicInbox::GzipFilter::close;
 	$ctx->{emit_header} = 1;
 	bless $ctx, $class;
 }
 
-# called by PublicInbox::DS::write
-sub atom_async_next {
+sub async_next ($) {
 	my ($http) = @_; # PublicInbox::HTTP
-	atom_async_step($http->{forward});
-}
-
-# this is public-inbox-httpd-specific
-sub atom_blob_cb { # git->cat_async callback
-	my ($bref, $oid, $type, $size, $ctx) = @_;
-	my $http = $ctx->{env}->{'psgix.io'} or return; # client abort
-	my $smsg = delete $ctx->{smsg} or die 'BUG: no smsg';
-	if (!defined($oid)) {
-		# it's possible to have TOCTOU if an admin runs
-		# public-inbox-(edit|purge), just move onto the next message
-		return $http->next_step(\&atom_async_next);
-	} else {
-		$smsg->{blob} eq $oid or die "BUG: $smsg->{blob} != $oid";
-	}
-	my $buf = feed_entry($ctx, $smsg, PublicInbox::Eml->new($bref));
-	if (my $gzf = $ctx->{gzf}) {
-		$buf = $gzf->translate($buf);
-	}
-	# PublicInbox::HTTP::{Chunked,Identity}::write
-	$ctx->{http_out}->write($buf);
-
-	$http->next_step(\&atom_async_next);
+	my $ctx = $http->{forward} or return;
+	eval {
+		if (my $smsg = $ctx->{smsg} = $ctx->{cb}->($ctx)) {
+			$ctx->smsg_blob($smsg);
+		} else {
+			$ctx->{http_out}->write($ctx->translate('</feed>'));
+			$ctx->close;
+		}
+	};
+	warn "E: $@" if $@;
 }
 
-sub atom_async_step { # this is public-inbox-httpd-specific
-	my ($ctx) = @_;
-	if (my $smsg = $ctx->{smsg} = $ctx->{cb}->($ctx)) {
-		git_async_cat($ctx->{-inbox}->git, $smsg->{blob},
-				\&atom_blob_cb, $ctx);
-	} elsif (my $out = delete $ctx->{http_out}) {
-		if (my $gzf = delete $ctx->{gzf}) {
-			$out->write($gzf->zflush);
-		}
-		$out->close;
-	}
+sub async_eml { # ->{async_eml} for async_blob_cb
+	my ($ctx, $eml) = @_;
+	my $smsg = delete $ctx->{smsg};
+	$ctx->{http_out}->write($ctx->translate(feed_entry($ctx, $smsg, $eml)))
 }
 
 sub response {
 	my ($class, $ctx, $code, $cb) = @_;
 	my $res_hdr = [ 'Content-Type' => 'application/atom+xml' ];
 	$class->new($ctx, $cb);
-	$ctx->{gzf} = gzf_maybe($res_hdr, $ctx->{env});
-	if ($ctx->{env}->{'pi-httpd.async'}) {
-		sub {
-			my ($wcb) = @_; # -httpd provided write callback
-			$ctx->{http_out} = $wcb->([200, $res_hdr]);
-			$ctx->{env}->{'psgix.io'}->{forward} = $ctx;
-			atom_async_step($ctx); # start stepping
-		};
-	} else {
-		[ $code, $res_hdr, $ctx ];
-	}
+	$ctx->psgi_response($code, $res_hdr, \&async_next, \&async_eml);
 }
 
 # called once for each message by PSGI server
 sub getline {
 	my ($self) = @_;
-	my $buf = do {
-		if (my $middle = $self->{cb}) {
-			if (my $smsg = $middle->($self)) {
-				my $eml = $self->{-inbox}->smsg_eml($smsg) or
-						return '';
-				feed_entry($self, $smsg, $eml);
-			} else {
-				undef;
-			}
-		}
-	} // (delete($self->{cb}) ? '</feed>' : undef);
-
-	# gzf may be GzipFilter, `undef' or `0'
-	my $gzf = $self->{gzf} or return $buf;
-
-	return $gzf->translate($buf) if defined $buf;
-	$self->{gzf} = 0; # next call to ->getline returns $buf (== undef)
-	$gzf->translate(undef);
+	my $cb = $self->{cb} or return;
+	while (my $smsg = $cb->($self)) {
+		my $eml = $self->{-inbox}->smsg_eml($smsg) or next;
+		return $self->translate(feed_entry($self, $smsg, $eml));
+	}
+	delete $self->{cb};
+	$self->zflush('</feed>');
 }
 
 # private
diff --git a/lib/PublicInbox/WwwListing.pm b/lib/PublicInbox/WwwListing.pm
index d641e6d5c..5f85e3464 100644
--- a/lib/PublicInbox/WwwListing.pm
+++ b/lib/PublicInbox/WwwListing.pm
@@ -10,7 +10,6 @@ use PublicInbox::Hval qw(ascii_html prurl);
 use PublicInbox::Linkify;
 use PublicInbox::View;
 use PublicInbox::Inbox;
-use PublicInbox::NoopFilter;
 use PublicInbox::GzipFilter qw(gzf_maybe);
 use bytes (); # bytes::length
 use HTTP::Date qw(time2str);
@@ -108,7 +107,7 @@ sub html ($$) {
 	my ($env, $list) = @_;
 	my $h = [ 'Content-Type', 'text/html; charset=UTF-8',
 			'Content-Length', undef ];
-	my $gzf = gzf_maybe($h, $env) || PublicInbox::NoopFilter::new();
+	my $gzf = gzf_maybe($h, $env);
 	$gzf->zmore('<html><head><title>' .
 				'public-inbox listing</title>' .
 				'</head><body><pre>');
diff --git a/lib/PublicInbox/WwwStatic.pm b/lib/PublicInbox/WwwStatic.pm
index d0611949d..051d2e039 100644
--- a/lib/PublicInbox/WwwStatic.pm
+++ b/lib/PublicInbox/WwwStatic.pm
@@ -17,7 +17,6 @@ use HTTP::Date qw(time2str);
 use HTTP::Status qw(status_message);
 use Errno qw(EACCES ENOTDIR ENOENT);
 use URI::Escape qw(uri_escape_utf8);
-use PublicInbox::NoopFilter;
 use PublicInbox::GzipFilter qw(gzf_maybe);
 use PublicInbox::Hval qw(ascii_html);
 use Plack::MIME;
@@ -313,7 +312,7 @@ sub dir_response ($$$) {
 
 	my $path_info_html = ascii_html($path_info);
 	my $h = [qw(Content-Type text/html Content-Length), undef];
-	my $gzf = gzf_maybe($h, $env) || PublicInbox::NoopFilter::new();
+	my $gzf = gzf_maybe($h, $env);
 	$gzf->zmore("<html><head><title>Index of $path_info_html</title>" .
 		${$self->{style}} .
 		"</head><body><pre>Index of $path_info_html</pre><hr><pre>\n");