msg_iter: pass $idx as a scalar, not array

This doesn't make any difference for most multipart
messages (or any single part messages).  However,
this starts having space savings when parts start
nesting.

It also slightly simplifies callers.

1 files changed, 4 insertions, 2 deletions

diff --git a/lib/PublicInbox/MsgIter.pm b/lib/PublicInbox/MsgIter.pm
index cd5a5d99..7c28d019 100644
--- a/lib/PublicInbox/MsgIter.pm
+++ b/lib/PublicInbox/MsgIter.pm
@@ -20,12 +20,14 @@ sub em_each_part ($$;$$) {
                 my $i = 0;
                 @parts = map { [ $_, 1, ++$i ] } @parts;
                 while (my $p = shift @parts) {
-                        my ($part, $depth, @idx) = @$p;
+                        my ($part, $depth, $idx) = @$p;
                         my @sub = $part->subparts;
                         if (@sub) {
                                 $depth++;
                                 $i = 0;
-                                @sub = map { [ $_, $depth, @idx, ++$i ] } @sub;
+                                @sub = map {
+                                        [ $_, $depth, "$idx.".(++$i) ]
+                                } @sub;
                                 @parts = (@sub, @parts);
                         } else {
                                 $cb->($p, $cb_arg);