mbox: split header and body processing

When dealing with ~30MB messages, we can save another ~30MB by
splitting the header and body processing and not appending the
body string back to the header.

We'll rely on buffering in gzip or kernel (via MSG_MORE)
to prevent silly packet sizes.

1 files changed, 33 insertions, 30 deletions

diff --git a/lib/PublicInbox/Mbox.pm b/lib/PublicInbox/Mbox.pm
index 1bf71c60..0c3e52fe 100644
--- a/lib/PublicInbox/Mbox.pm
+++ b/lib/PublicInbox/Mbox.pm
@@ -16,8 +16,8 @@ use Email::Simple;
 use Email::MIME::Encode;
 
 sub subject_fn ($) {
-        my ($simple) = @_;
-        my $fn = $simple->header('Subject');
+        my ($hdr) = @_;
+        my $fn = $hdr->header('Subject');
         return 'no-subject' unless defined($fn);
 
         # no need for full Email::MIME, here
@@ -36,20 +36,26 @@ sub mb_stream {
 }
 
 # called by PSGI server as body response
+# this gets called twice for every message, once to return the header,
+# once to retrieve the body
 sub getline {
         my ($more) = @_; # self
-        my ($ctx, $id, $prev, $next, $cur, $mref) = @$more;
-        if ($mref) { # first
-                pop @$more;
-                pop @$more;
-                return msg_str($ctx, $cur, $mref);
+        my ($ctx, $id, $prev, $next, $mref, $hdr) = @$more;
+        if ($hdr) { # first message hits this, only
+                pop @$more; # $hdr
+                return msg_hdr($ctx, $hdr);
         }
-        $cur = $next or return;
+        if ($mref) { # all messages hit this
+                pop @$more; # $mref
+                return msg_body($$mref);
+        }
+        my $cur = $next or return;
         my $ibx = $ctx->{-inbox};
         $next = $ibx->over->next_by_mid($ctx->{mid}, \$id, \$prev);
-        @$more = ($ctx, $id, $prev, $next); # $next may be undef, here
         $mref = $ibx->msg_by_smsg($cur) or return;
-        msg_str($ctx, Email::Simple->new($mref), $mref);
+        $hdr = Email::Simple->new($mref)->header_obj;
+        @$more = ($ctx, $id, $prev, $next, $mref); # $next may be undef, here
+        msg_hdr($ctx, $hdr); # all but first message hits this
 }
 
 sub close {} # noop
@@ -58,21 +64,17 @@ sub emit_raw {
         my ($ctx) = @_;
         my $mid = $ctx->{mid};
         my $ibx = $ctx->{-inbox};
-        my ($first, $mref, $more);
+        my ($mref, $more, $id, $prev, $next);
         if (my $over = $ibx->over) {
-                my ($id, $prev);
                 my $smsg = $over->next_by_mid($mid, \$id, \$prev) or return;
                 $mref = $ibx->msg_by_smsg($smsg) or return;
-                $first = Email::Simple->new($mref);
-                my $next = $over->next_by_mid($mid, \$id, \$prev);
-                # $more is for ->getline
-                $more = [ $ctx, $id, $prev, $next, $first, $mref ] if $next;
+                $next = $over->next_by_mid($mid, \$id, \$prev);
         } else {
                 $mref = $ibx->msg_by_mid($mid) or return;
-                $first = Email::Simple->new($mref);
         }
-        return unless defined $first;
-        my $fn = subject_fn($first);
+        my $hdr = Email::Simple->new($mref)->header_obj;
+        $more = [ $ctx, $id, $prev, $next, $mref, $hdr ]; # for ->getline
+        my $fn = subject_fn($hdr);
         my @hdr = ('Content-Type');
         if ($ibx->{obfuscate}) {
                 # obfuscation is stupid, but maybe scrapers are, too...
@@ -83,13 +85,11 @@ sub emit_raw {
                 $fn .= '.txt';
         }
         push @hdr, 'Content-Disposition', "inline; filename=$fn";
-        [ 200, \@hdr,
-                $more ? mb_stream($more) : [ msg_str($ctx, $first, $mref) ] ];
+        [ 200, \@hdr, mb_stream($more) ];
 }
 
-sub msg_str {
-        my ($ctx, $simple, $mref, $mid) = @_; # simple - Email::Simple object
-        my $header_obj = $simple->header_obj;
+sub msg_hdr ($$;$) {
+        my ($ctx, $header_obj, $mid) = @_;
 
         # drop potentially confusing headers, ssoma already should've dropped
         # Lines and Content-Length
@@ -121,12 +121,13 @@ sub msg_str {
                 $buf .= "$k: $v$crlf" if defined $v;
         }
         $buf .= $crlf;
+}
 
+sub msg_body ($) {
         # mboxrd quoting style
         # ref: http://www.qmail.org/man/man5/mbox.html
-        $$mref =~ s/^(>*From )/>$1/gm;
-        $buf .= $$mref;
-        $buf .= "\n";
+        $_[0] =~ s/^(>*From )/>$1/gm;
+        $_[0] .= "\n";
 }
 
 sub thread_mbox {
@@ -267,11 +268,13 @@ sub response {
 sub getline {
         my ($self) = @_;
         my $ctx = $self->{ctx} or return;
+        my $gz = $self->{gz};
         while (my $smsg = $self->{cb}->()) {
                 my $mref = $ctx->{-inbox}->msg_by_smsg($smsg) or next;
-                my $s = Email::Simple->new($mref);
-                $self->{gz}->write(PublicInbox::Mbox::msg_str($ctx, $s, $mref,
-                                $smsg->{mid}));
+                my $h = Email::Simple->new($mref)->header_obj;
+                $gz->write(PublicInbox::Mbox::msg_hdr($ctx, $h, $smsg->{mid}));
+                $gz->write(PublicInbox::Mbox::msg_body($$mref));
+
                 my $bref = $self->{buf};
                 if (length($$bref) >= 8192) {
                         my $ret = $$bref; # copy :<