nntp: reduce syscalls for ARTICLE and BODY

Chances are we already have extra buffer space following the
expensive LF => CRLF conversion that we can safely append an
extra CRLF in those places without incurring a copy of the
full string buffer.

While we're at it, document where our pain points are in terms
of memory usage, since tracking/controlling memory use isn't
exactly obvious in high-level languages.

Perhaps we should start storing messages in git as CRLF...

diff --git a/lib/PublicInbox/NNTP.pm b/lib/PublicInbox/NNTP.pm
index 30d3dab69d973ad8eb971cb5158d6902d80af413..5a886a3c32be100b0d24f393b8792846d0fcfd24 100644 (file)
--- a/lib/PublicInbox/NNTP.pm
+++ b/lib/PublicInbox/NNTP.pm
@@ -521,10 +521,12 @@ found:
 
 sub msg_body_write ($$) {
        my ($self, $msg) = @_;
+
+       # these can momentarily double the memory consumption :<
        $$msg =~ s/^\./../smg;
-       $$msg =~ s/(?<!\r)\n/\r\n/sg;
+       $$msg =~ s/(?<!\r)\n/\r\n/sg; # Alpine barfs without this
+       $$msg .= "\r\n" unless $$msg =~ /\r\n\z/s;
        msg_more($self, $$msg);
-       msg_more($self, "\r\n") unless $$msg =~ /\r\n\z/s;
        '.'
 }
 
@@ -533,18 +535,19 @@ sub set_art {
        $self->{article} = $art if defined $art && $art =~ /\A[0-9]+\z/;
 }
 
-sub _header ($) {
-       my $hdr = $_[0]->as_string;
+sub msg_hdr_write ($$$) {
+       my ($self, $hdr, $body_follows) = @_;
+       $hdr = $hdr->as_string;
        utf8::encode($hdr);
-       $hdr =~ s/(?<!\r)\n/\r\n/sg;
+       $hdr =~ s/(?<!\r)\n/\r\n/sg; # Alpine barfs without this
 
        # for leafnode compatibility, we need to ensure Message-ID headers
        # are only a single line.  We can't subclass Email::Simple::Header
        # and override _default_fold_at in here, either; since that won't
        # affect messages already in the archive.
        $hdr =~ s/^(Message-ID:)[ \t]*\r\n[ \t]+([^\r]+)\r\n/$1 $2\r\n/igsm;
-
-       $hdr
+       $hdr .= "\r\n" if $body_follows;
+       msg_more($self, $hdr);
 }
 
 sub cmd_article ($;$) {
@@ -554,8 +557,7 @@ sub cmd_article ($;$) {
        my ($n, $mid, $msg, $hdr) = @$r;
        set_art($self, $art);
        more($self, "220 $n <$mid> article retrieved - head and body follow");
-       msg_more($self, _header($hdr));
-       msg_more($self, "\r\n");
+       msg_hdr_write($self, $hdr, 1);
        msg_body_write($self, $msg);
 }
 
@@ -566,7 +568,7 @@ sub cmd_head ($;$) {
        my ($n, $mid, undef, $hdr) = @$r;
        set_art($self, $art);
        more($self, "221 $n <$mid> article retrieved - head follows");
-       msg_more($self, _header($hdr));
+       msg_hdr_write($self, $hdr, 0);
        '.'
 }