Add operator== for Finger

VersionedMap.cpp

@@ -449,6 +449,21 @@ struct Finger {
   Finger(Finger &&) = delete;
   Finger &operator=(Finger &&) = delete;
 
+  bool operator==(const Finger &other) const {
+    bool result = searchPathSize_ == other.searchPathSize_ &&
+                  (searchPathSize_ == 0 || backNode() == other.backNode());
+#ifndef NDEBUG
+    auto expected = searchPathSize_ == other.searchPathSize_ &&
+                    memcmp(searchPath, other.searchPath,
+                           searchPathSize_ * sizeof(searchPath[0])) == 0 &&
+                    (searchPathSize_ == 0 ||
+                     memcmp(direction + 1, other.direction + 1,
+                            (searchPathSize_ - 1) * sizeof(direction[0])) == 0);
+    assert(result == expected);
+#endif
+    return result;
+  }
+
 private:
   uint32_t searchPath[kPathLengthUpperBound];
   bool direction[kPathLengthUpperBound];
@@ -951,11 +966,7 @@ struct VersionedMap::Iterator::Impl {
   bool equals(const Impl &other) const {
     assert(map == other.map);
     assert(version == other.version);
-    if (finger.searchPathSize() == 0 || other.finger.searchPathSize() == 0) {
-      return finger.searchPathSize() == other.finger.searchPathSize();
-    }
-    return finger.backNode() == other.finger.backNode() &&
-           mutationIndex == other.mutationIndex;
+    return finger == other.finger && mutationIndex == other.mutationIndex;
   }
 };