msg_iter: new internal API for iterating through MIME

Unlike Email::MIME::walk_parts, this is non-recursive and gives
depth + index offset information about the part for creating
links for later retrieval

It is intended for read-only access and changes are not
propagated to the parent; however future versions of it
may clobber bodies or the original version as it iterates
to reduce memory overhead.

It is intended for making it easy to locate attachments within a
message in the WWW view.

1 files changed, 36 insertions, 0 deletions

diff --git a/lib/PublicInbox/MsgIter.pm b/lib/PublicInbox/MsgIter.pm
new file mode 100644
index 00000000..d0dd82fb
--- /dev/null
+++ b/lib/PublicInbox/MsgIter.pm
@@ -0,0 +1,36 @@
+# Copyright (C) 2016 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+#
+package PublicInbox::MsgIter;
+use strict;
+use warnings;
+use base qw(Exporter);
+our @EXPORT = qw(msg_iter);
+
+# Like Email::MIME::walk_parts, but this is:
+# * non-recursive
+# * passes depth and indices to the iterator callback
+sub msg_iter ($$) {
+        my ($mime, $cb) = @_;
+        my @parts = $mime->subparts;
+        if (@parts) {
+                my $i = 0;
+                @parts = map { [ $_, 1, ++$i ] } @parts;
+                while (my $p = shift @parts) {
+                        my ($part, $depth, @idx) = @$p;
+                        my @sub = $part->subparts;
+                        if (@sub) {
+                                $depth++;
+                                $i = 0;
+                                @sub = map { [ $_, $depth, @idx, ++$i ] } @sub;
+                                @parts = (@sub, @parts);
+                        } else {
+                                $cb->($p);
+                        }
+                }
+        } else {
+                $cb->([$mime, 0, 0]);
+        }
+}
+
+1;