[PATCH pve-access-control v5 1/7] permission: add acl tree node parent lookup without node creation

[David Riley <d.riley@proxmox.com>]

Add helper function to look up ACL nodes by path without creating
missing nodes along the path. This is necessary for safely locating
paths intended for deletion or migration without side effects.

This is in preparation for the following SDN resource ACL pruning and
VNet migration changes.

Signed-off-by: David Riley <d.riley@proxmox.com>
---
 src/PVE/AccessControl.pm | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/src/PVE/AccessControl.pm b/src/PVE/AccessControl.pm
index 0d632b3..e26dfce 100644
--- a/src/PVE/AccessControl.pm
+++ b/src/PVE/AccessControl.pm
@@ -1000,6 +1000,31 @@ sub find_acl_tree_node {
     return $node;
 }
 
+# finds an ACL node by path without autovivifying (creating) missing
+# nodes. returns a list containing the parent node, the final path
+# segment, and the target node itself.
+sub find_acl_tree_node_parent {
+    my ($root, $path) = @_;
+
+    my $current = $root;
+    my $parent = undef;
+    my $last_key = undef;
+
+    my @split_path = split('/', $path);
+
+    for my $segment (@split_path) {
+        if (defined($current->{children}) && defined($current->{children}->{$segment})) {
+            $parent = $current;
+            $last_key = $segment;
+            $current = $current->{children}->{$segment};
+        } else {
+            return (undef, undef, undef);
+        }
+    }
+
+    return ($parent, $last_key, $current);
+}
+
 sub add_user_group {
     my ($username, $usercfg, $group) = @_;
 
-- 
2.47.3