add back() methods

2 files changed, 22 insertions, 0 deletions

diff --git a/vespalib/src/tests/small_vector/small_vector_test.cpp b/vespalib/src/tests/small_vector/small_vector_test.cpp
index 808571acef6..6d8238fefb4 100644
--- a/vespalib/src/tests/small_vector/small_vector_test.cpp
+++ b/vespalib/src/tests/small_vector/small_vector_test.cpp
@@ -243,4 +243,24 @@ TEST(SmallVectorTest, equal_operator) {
                   SmallVector<EqOnly>({EqOnly{1},EqOnly{5},EqOnly{3}}));
 }
 
+// to check "back() const"
+template<size_t N>
+int last_value_of(const SmallVector<int,N> &v) {
+    return v.back();
+}
+
+TEST(SmallVectorTest, check_back_method) {
+    SmallVector<int> vec;
+    for (int i = 0; i < 1000; ++i) {
+        vec.emplace_back(17);
+        EXPECT_EQ(vec.back(), 17);
+        EXPECT_EQ(last_value_of(vec), 17);
+        vec.back() = 42;
+        EXPECT_EQ(vec[i], 42);
+        vec.back() = i;
+        EXPECT_EQ(last_value_of(vec), i);
+    }
+    EXPECT_EQ(&vec.back(), vec.end() - 1);
+}
+
 GTEST_MAIN_RUN_ALL_TESTS()
diff --git a/vespalib/src/vespa/vespalib/util/small_vector.h b/vespalib/src/vespa/vespalib/util/small_vector.h
index 21a21fc2cbb..9cbc10951cf 100644
--- a/vespalib/src/vespa/vespalib/util/small_vector.h
+++ b/vespalib/src/vespa/vespalib/util/small_vector.h
@@ -186,6 +186,8 @@ public:
     const T *end() const { return (_data + _size); }
     T &operator[](size_t idx) { return _data[idx]; }
     const T &operator[](size_t idx) const { return _data[idx]; }
+    T &back() { return _data[_size - 1]; }
+    const T &back() const { return _data[_size - 1]; }
     void clear() {
         small_vector::destroy_objects(_data, _size);
         _size = 0;