Support GetStringReference in SimpleProtobufReflection

commit_hash:f4cebea4a1e97ab52be1c0d3c91ec4a1a0de6a39

Author: bgaifullin

library/cpp/protobuf/util/simple_reflection.h

@@ -52,6 +52,16 @@ namespace NProtoBuf {
         template <typename T>
         inline typename TSelectCppType<T>::T Get(size_t index = 0) const;
 
+        inline TStringBuf GetStringReference(TString* scratch) const {
+            return GetStringReference(0, scratch);
+        }
+
+        inline TStringBuf GetStringReference(size_t index, TString* scratch) const {
+            Y_ASSERT(IsString());
+            return IsRepeated() ? Refl().GetRepeatedStringReference(Msg, Fd, index, scratch)
+                                : Refl().GetStringReference(Msg, Fd, scratch);
+        }
+
         template <typename TMsg>
         inline const TMsg* GetAs(size_t index = 0) const {
             // casting version of Get

library/cpp/protobuf/util/simple_reflection_ut.cpp

@@ -19,6 +19,21 @@ Y_UNIT_TEST_SUITE(ProtobufSimpleReflection) {
         return smf;
     }
 
+    Y_UNIT_TEST(GetStringReference) {
+        TSample src(GenSampleForMergeFrom());
+        const Descriptor* descr = src.GetDescriptor();
+        TString scratch;
+
+        TConstField srcOneStr(src, descr->FindFieldByName("OneStr"));
+        UNIT_ASSERT_VALUES_EQUAL("one str"_sb, srcOneStr.GetStringReference(&scratch));
+
+        src.ClearOneStr();
+        UNIT_ASSERT_VALUES_EQUAL(TStringBuf(), srcOneStr.GetStringReference(&scratch));
+
+        TConstField repStr(src, descr->FindFieldByName("RepStr"));
+        UNIT_ASSERT_VALUES_EQUAL("two rep str"_sb, repStr.GetStringReference(1, &scratch));
+    }
+
     Y_UNIT_TEST(MergeFromGeneric) {
         const TSample src(GenSampleForMergeFrom());
         TSample dst;