Fix CellId.ToInt64(depth) when depth <= m_Level.

2 files changed, 34 insertions, 10 deletions

diff --git a/geometry/cellid.hpp b/geometry/cellid.hpp
index f37054c328..ea1df53b5f 100644
--- a/geometry/cellid.hpp
+++ b/geometry/cellid.hpp
@@ -238,18 +238,24 @@ public:
   {
     ASSERT(0 < depth && depth <= DEPTH_LEVELS, (m_Bits, m_Level, depth));
     ASSERT(IsValid(), (m_Bits, m_Level));
-    uint64_t bits = m_Bits, res = 0;
-    for (int i = 0; i <= m_Level; ++i, bits >>= 2)
-      res += bits + 1;
-    bits = m_Bits;
-    for (int i = m_Level + 1; i < depth; ++i)
+
+    if (m_Level >= depth)
+      return AncestorAtLevel(depth - 1).ToInt64(depth);
+    else
     {
-      bits <<= 2;
-      res += bits;
+      uint64_t bits = m_Bits, res = 0;
+      for (int i = 0; i <= m_Level; ++i, bits >>= 2)
+        res += bits + 1;
+      bits = m_Bits;
+      for (int i = m_Level + 1; i < depth; ++i)
+      {
+        bits <<= 2;
+        res += bits;
+      }
+      ASSERT_GREATER(res, 0, (m_Bits, m_Level));
+      ASSERT_LESS_OR_EQUAL(res, TreeSizeForDepth(depth), (m_Bits, m_Level));
+      return static_cast<int64_t>(res);
     }
-    ASSERT_GREATER(res, 0, (m_Bits, m_Level));
-    ASSERT_LESS_OR_EQUAL(res, TreeSizeForDepth(depth), (m_Bits, m_Level));
-    return static_cast<int64_t>(res);
   }
 
   // Level order, numbering by Z-curve.
diff --git a/geometry/geometry_tests/cellid_test.cpp b/geometry/geometry_tests/cellid_test.cpp
index 07e7ed2ec7..a664f33e9e 100644
--- a/geometry/geometry_tests/cellid_test.cpp
+++ b/geometry/geometry_tests/cellid_test.cpp
@@ -49,6 +49,24 @@ UNIT_TEST(CellId_ToInt64)
   TEST_EQUAL(m2::CellId<3>("33").ToInt64(3), 21, ());
 }
 
+UNIT_TEST(CellId_ToInt64_LevelLessThanDepth)
+{
+  TEST_EQUAL(m2::CellId<3>("").ToInt64(2), 1, ());
+  TEST_EQUAL(m2::CellId<3>("0").ToInt64(2), 2, ());
+  TEST_EQUAL(m2::CellId<3>("1").ToInt64(2), 3, ());
+  TEST_EQUAL(m2::CellId<3>("2").ToInt64(2), 4, ());
+  TEST_EQUAL(m2::CellId<3>("3").ToInt64(2), 5, ());
+  TEST_EQUAL(m2::CellId<3>("00").ToInt64(2), 2, ());
+  TEST_EQUAL(m2::CellId<3>("01").ToInt64(2), 2, ());
+  TEST_EQUAL(m2::CellId<3>("03").ToInt64(2), 2, ());
+  TEST_EQUAL(m2::CellId<3>("10").ToInt64(2), 3, ());
+  TEST_EQUAL(m2::CellId<3>("20").ToInt64(2), 4, ());
+  TEST_EQUAL(m2::CellId<3>("23").ToInt64(2), 4, ());
+  TEST_EQUAL(m2::CellId<3>("30").ToInt64(2), 5, ());
+  TEST_EQUAL(m2::CellId<3>("31").ToInt64(2), 5, ());
+  TEST_EQUAL(m2::CellId<3>("33").ToInt64(2), 5, ());
+}
+
 UNIT_TEST(CellId_FromInt64)
 {
   TEST_EQUAL(m2::CellId<3>(""), m2::CellId<3>::FromInt64(1, 3), ());