nntp: speed up XHDR for the Message-ID case

We can use our msgmap database to implement "XHDR Message-ID [range]"
commands quickly.  This helps immensely with slrnpull, which prefers
XHDR to LISTGROUP for some reason...

diff --git a/lib/PublicInbox/NNTP.pm b/lib/PublicInbox/NNTP.pm
index 8275ef087538c08e01a3a1024814cb1ce503261d..47b03e025269ef4d53fcf331ad495eba22d6f517 100644 (file)
--- a/lib/PublicInbox/NNTP.pm
+++ b/lib/PublicInbox/NNTP.pm
@@ -505,9 +505,45 @@ sub long_response ($$$$) {
        undef;
 }
 
+sub xhdr_message_id ($$) { # optimize XHDR Message-ID [range] for slrnpull.
+       my ($self, $range) = @_;
+
+       my $mm = $self->{ng}->mm;
+       if (defined $range && $range =~ /\A<(.+)>\z/) { # Message-ID
+               my $n = $mm->num_for($range);
+               more($self, '221 Header follows');
+               more($self, "<$range> <$range>") if defined $n;
+               '.';
+       } else { # numeric range
+               $range = $self->{article} unless defined $range;
+               my $r = get_range($self, $range);
+               return $r unless ref $r;
+               my ($beg, $end) = @$r;
+               more($self, '221 Header follows');
+               $self->long_response($beg, $end, sub {
+                       my ($i) = @_;
+                       my $mid = $mm->mid_for($$i);
+                       more($self, "$$i <$mid>") if defined $mid;
+               });
+       }
+}
+
 sub cmd_xhdr ($$;$) {
        my ($self, $header, $range) = @_;
        defined $self->{ng} or return '412 no news group currently selected';
+       my $sub = $header;
+       $sub =~ tr/A-Z-/a-z_/;
+       $sub = eval {
+               no strict 'refs';
+               $sub = *{'xhdr_'.$sub}{CODE};
+       };
+       return xhdr_slow($self, $header, $range) unless defined $sub;
+       $sub->($self, $range);
+}
+
+sub xhdr_slow ($$$) {
+       my ($self, $header, $range) = @_;
+
        if (defined $range && $range =~ /\A<(.+)>\z/) { # Message-ID
                my $r = $self->art_lookup($range, 2);
                return $r unless ref $r;