imap: further speed up HEADER.FIELDS FETCH requests

Since headers are big and include a lot of lines MUAs don't
care about, we can skip the CRLF_HDR ops and just do the
CRLF conversion in partial_hdr_get and partial_hdr_not.
This is another 10-15% speedup for mutt w/o header caching.

1 files changed, 9 insertions, 2 deletions

diff --git a/lib/PublicInbox/IMAP.pm b/lib/PublicInbox/IMAP.pm
index 3cc68e66..fe3c7d1a 100644
--- a/lib/PublicInbox/IMAP.pm
+++ b/lib/PublicInbox/IMAP.pm
@@ -792,6 +792,7 @@ sub partial_hdr_not {
         }
         my $str = $eml->header_obj->as_string;
         $str =~ s/$hdrs_re//g;
+        $str =~ s/(?<!\r)\n/\r\n/sg;
         $str .= "\r\n";
 }
 
@@ -802,7 +803,9 @@ sub partial_hdr_get {
                 $eml = eml_body_idx($eml, $section_idx) or return;
         }
         my $str = $eml->header_obj->as_string;
-        join('', ($str =~ m/($hdrs_re)/g), "\r\n");
+        $str = join('', ($str =~ m/($hdrs_re)/g));
+        $str =~ s/(?<!\r)\n/\r\n/sg;
+        $str .= "\r\n";
 }
 
 sub partial_prepare ($$$$) {
@@ -828,7 +831,11 @@ sub partial_prepare ($$$$) {
                                                 : \&partial_hdr_get,
                                                 $1, undef, $4, $5 ];
                 $tmp->[2] = hdrs_regexp($3);
-                $$need |= CRLF_HDR|EML_HDR;
+
+                # don't emit CRLF_HDR instruction, here, partial_hdr_*
+                # will do CRLF conversion with only the extracted result
+                # and not waste time converting lines we don't care about.
+                $$need |= EML_HDR;
         } else {
                 undef;
         }