nntp: use sysread to append to existing buffer

We already do this in PublicInbox::HTTP, as it's superior to
DS::read in this regard.  Initially (when I started writing
NNTP.pm, I wanted to use Danga::Socket's read buffering and
push_back_read (removed in DS) but quickly figured out it wasn't
useful at all for dealing with trickling clients.

1 files changed, 14 insertions, 7 deletions

diff --git a/lib/PublicInbox/NNTP.pm b/lib/PublicInbox/NNTP.pm
index 7729399a..5e66d077 100644
--- a/lib/PublicInbox/NNTP.pm
+++ b/lib/PublicInbox/NNTP.pm
@@ -954,13 +954,20 @@ sub event_write {
 sub event_read {
         my ($self) = @_;
         use constant LINE_MAX => 512; # RFC 977 section 2.3
-
-        if (index($self->{rbuf}, "\n") < 0) {
-                my $buf = $self->read(LINE_MAX) or return $self->close;
-                $self->{rbuf} .= $$buf;
+        my $rbuf = \($self->{rbuf});
+        my $r;
+
+        if (index($$rbuf, "\n") < 0) {
+                my $off = length($$rbuf);
+                $r = sysread($self->{sock}, $$rbuf, LINE_MAX, $off);
+                unless (defined $r) {
+                        return if $!{EAGAIN};
+                        return $self->close;
+                }
+                return $self->close if $r == 0;
         }
-        my $r = 1;
-        while ($r > 0 && $self->{rbuf} =~ s/\A[ \t\r\n]*([^\r\n]*)\r?\n//) {
+        $r = 1;
+        while ($r > 0 && $$rbuf =~ s/\A[ \t\r\n]*([^\r\n]*)\r?\n//) {
                 my $line = $1;
                 return $self->close if $line =~ /[[:cntrl:]]/s;
                 my $t0 = now();
@@ -972,7 +979,7 @@ sub event_read {
         }
 
         return $self->close if $r < 0;
-        my $len = length($self->{rbuf});
+        my $len = length($$rbuf);
         return $self->close if ($len >= LINE_MAX);
         update_idle_time($self);
 }