intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 53 insertions, 0 deletions

diff --git a/library/cpp/protobuf/util/iterators.h b/library/cpp/protobuf/util/iterators.h
new file mode 100644
index 0000000000..6d53ac71b1
--- /dev/null
+++ b/library/cpp/protobuf/util/iterators.h
@@ -0,0 +1,53 @@
+#pragma once
+
+#include <google/protobuf/descriptor.h>
+
+namespace NProtoBuf {
+    class TFieldsIterator {
+    public:
+        explicit TFieldsIterator(const NProtoBuf::Descriptor* descriptor, int position = 0)
+        : Descriptor(descriptor)
+        , Position(position)
+        { }
+
+        TFieldsIterator& operator++() {
+            ++Position;
+            return *this;
+        }
+
+        TFieldsIterator& operator++(int) {
+            auto& ret = *this;
+            ++*this;
+            return ret;
+        }
+
+        const NProtoBuf::FieldDescriptor* operator*() const {
+            return Descriptor->field(Position);
+        }
+
+        bool operator== (const TFieldsIterator& other) const {
+            return Position == other.Position && Descriptor == other.Descriptor;
+        }
+
+        bool operator!= (const TFieldsIterator& other) const {
+            return !(*this == other);
+        }
+
+    private:
+        const NProtoBuf::Descriptor* Descriptor = nullptr;
+        int Position = 0;
+    };
+}
+
+// Namespaces required by `range-based for` ADL:
+namespace google {
+    namespace protobuf {
+        NProtoBuf::TFieldsIterator begin(const NProtoBuf::Descriptor& descriptor) {
+            return NProtoBuf::TFieldsIterator(&descriptor);
+        }
+
+        NProtoBuf::TFieldsIterator end(const NProtoBuf::Descriptor& descriptor) {
+            return NProtoBuf::TFieldsIterator(&descriptor, descriptor.field_count());
+        }
+    }
+}