emplace_back() with arguments support + return reference for consistency with TVector

2 files changed, 39 insertions, 3 deletions

diff --git a/library/cpp/containers/paged_vector/paged_vector.h b/library/cpp/containers/paged_vector/paged_vector.h
index 62a8574476..0a6dd8f83c 100644
--- a/library/cpp/containers/paged_vector/paged_vector.h
+++ b/library/cpp/containers/paged_vector/paged_vector.h
@@ -7,7 +7,7 @@
 #include <iterator>
 
 namespace NPagedVector {
-    template <class T, ui32 PageSize = 1u << 20, class A = std::allocator<T>>
+    template <class T, ui32 PageSize = 1u << 20u, class A = std::allocator<T>>
     class TPagedVector;
 
     namespace NPrivate {
@@ -263,9 +263,10 @@ namespace NPagedVector {
             return !empty();
         }
 
-        void emplace_back() {
+        template<typename... Args>
+        reference emplace_back(Args&&... args) {
             PrepareAppend();
-            CurrentPage().emplace_back();
+            return CurrentPage().emplace_back(std::forward<Args>(args)...);
         }
 
         void push_back(const_reference t) {
diff --git a/library/cpp/containers/paged_vector/ut/paged_vector_ut.cpp b/library/cpp/containers/paged_vector/ut/paged_vector_ut.cpp
index e867808ee4..d059ce34ec 100644
--- a/library/cpp/containers/paged_vector/ut/paged_vector_ut.cpp
+++ b/library/cpp/containers/paged_vector/ut/paged_vector_ut.cpp
@@ -16,6 +16,8 @@ class TPagedVectorTest: public TTestBase {
     UNIT_TEST(TestAt)
     UNIT_TEST(TestAutoRef)
     UNIT_TEST(TestIterators)
+    UNIT_TEST(TestEmplaceBack1)
+    UNIT_TEST(TestEmplaceBack2)
     //UNIT_TEST(TestEbo)
     UNIT_TEST_SUITE_END();
 
@@ -341,6 +343,39 @@ private:
         UNIT_ASSERT(crvint.rbegin() != crvint.rend());
     }
 
+    void TestEmplaceBack1() {
+        NPagedVector::TPagedVector<int, 3> vint;
+
+        for (int i = 0; i < 55; ++i) {
+            UNIT_ASSERT_EQUAL(vint.emplace_back(i), i);
+        }
+
+        UNIT_ASSERT_EQUAL(vint.size(), 55);
+
+        for (int i = 0; i < 55; ++i) {
+            UNIT_ASSERT_EQUAL(vint[i], i);
+        }
+    }
+
+    void TestEmplaceBack2() {
+        using TPair = std::pair<int, TString>;
+        NPagedVector::TPagedVector<TPair, 5> arr;
+
+        for (int i = 0; i < 55; ++i) {
+            auto s = ToString(i);
+            auto& element = arr.emplace_back(i, s);
+            UNIT_ASSERT_EQUAL(element, std::make_pair(i, s));
+            UNIT_ASSERT_UNEQUAL(element, std::make_pair(i + 1, s));
+        }
+
+        UNIT_ASSERT_EQUAL(arr.size(), 55);
+
+        for (int i = 0; i < 55; ++i) {
+            UNIT_ASSERT_EQUAL(arr[i].first, i);
+            UNIT_ASSERT_EQUAL(arr[i].second, ToString(i));
+        }
+    }
+
     /* This test check a potential issue with empty base class
          * optimization. Some compilers (VC6) do not implement it
          * correctly resulting ina wrong behavior. */