imap: support out-of-bounds ranges

"$UID_START:*" needs to return at least one message according
to RFC 3501 section 6.4.8.

While we're in the area, coerce ranges to (unsigned) integers by
adding zero ("+ 0") to reduce memory overhead.

1 files changed, 5 insertions, 3 deletions

diff --git a/lib/PublicInbox/IMAP.pm b/lib/PublicInbox/IMAP.pm
index 3815141a..ffa76bb0 100644
--- a/lib/PublicInbox/IMAP.pm
+++ b/lib/PublicInbox/IMAP.pm
@@ -455,11 +455,13 @@ sub range_step ($$) {
                 $$range_csv = undef;
         }
         if ($range =~ /\A([0-9]+):([0-9]+)\z/) {
-                ($beg, $end) = ($1, $2);
+                ($beg, $end) = ($1 + 0, $2 + 0);
         } elsif ($range =~ /\A([0-9]+):\*\z/) {
-                ($beg, $end) =  ($1, $ibx->mm->max // 0);
+                $beg = $1 + 0;
+                $end = $ibx->mm->max // 0;
+                $beg = $end if $beg > $end;
         } elsif ($range =~ /\A[0-9]+\z/) {
-                $beg = $end = $range;
+                $beg = $end = $range + 0;
         } else {
                 return 'BAD fetch range';
         }