From adc569af213fa6a95ff4ad6efcd1b66bd3980c0d Mon Sep 17 00:00:00 2001
From: Pavel Patsey <patsey.pavel@gmail.com>
Date: Thu, 23 Jan 2025 10:20:36 +0300
Subject: [PATCH] fix calc_dip

---
 tests/cidr4_merge/test_cidr4_merger.py  | 7 +++++++
 vpn_manager/cidr4_merge/cidr4_merger.py | 7 ++++---
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/tests/cidr4_merge/test_cidr4_merger.py b/tests/cidr4_merge/test_cidr4_merger.py
index 28acd42..319976b 100644
--- a/tests/cidr4_merge/test_cidr4_merger.py
+++ b/tests/cidr4_merge/test_cidr4_merger.py
@@ -88,6 +88,13 @@ def test_find_parent__with_exception():
 
 
 def test_calc_dip():
+    assert calc_dip(26, 26) == 0
+
     assert calc_dip(26, 27) == 67108864
+    assert calc_dip(27, 26) == 67108864
+
     assert calc_dip(26, 28) == 201326592
+    assert calc_dip(28, 26) == 201326592
+
     assert calc_dip(26, 29) == 469762048
+    assert calc_dip(29, 26) == 469762048
diff --git a/vpn_manager/cidr4_merge/cidr4_merger.py b/vpn_manager/cidr4_merge/cidr4_merger.py
index f92b9e2..a2d7802 100644
--- a/vpn_manager/cidr4_merge/cidr4_merger.py
+++ b/vpn_manager/cidr4_merge/cidr4_merger.py
@@ -44,9 +44,10 @@ def find_parent(a: Node, b: Node) -> Node:
 
 def calc_dip(mask_len_a: int, mask_len_b: int) -> int:
     dip = 0
-    while mask_len_a < mask_len_b:
-        dip += 1 << mask_len_a
-        mask_len_a += 1
+    len_min, len_max = sorted((mask_len_a, mask_len_b))
+    while len_min < len_max:
+        dip += 1 << len_min
+        len_min += 1
     return dip