Restoring authorship annotation for Alexander Rutkovsky <alexvru@mail.ru>. Commit 2 of 2.

1 files changed, 1000 insertions, 1000 deletions

diff --git a/library/cpp/actors/util/rope.h b/library/cpp/actors/util/rope.h
index 9d3c3896c8..f5595efbaa 100644
--- a/library/cpp/actors/util/rope.h
+++ b/library/cpp/actors/util/rope.h
@@ -1,998 +1,998 @@
-#pragma once 
- 
-#include <util/generic/ptr.h> 
-#include <util/generic/string.h> 
-#include <util/generic/hash_set.h> 
-#include <util/stream/str.h> 
+#pragma once
+
+#include <util/generic/ptr.h>
+#include <util/generic/string.h>
+#include <util/generic/hash_set.h>
+#include <util/stream/str.h>
 #include <util/system/sanitizers.h>
 #include <util/system/valgrind.h>
- 
-// exactly one of them must be included 
-#include "rope_cont_list.h" 
-//#include "rope_cont_deque.h" 
- 
-struct IRopeChunkBackend : TThrRefBase { 
-    using TData = std::tuple<const char*, size_t>; 
-    virtual ~IRopeChunkBackend() = default; 
-    virtual TData GetData() const = 0; 
-    virtual size_t GetCapacity() const = 0; 
-    using TPtr = TIntrusivePtr<IRopeChunkBackend>; 
-}; 
- 
-class TRopeAlignedBuffer : public IRopeChunkBackend { 
-    static constexpr size_t Alignment = 16; 
-    static constexpr size_t MallocAlignment = sizeof(size_t); 
- 
-    ui32 Size; 
-    const ui32 Capacity; 
-    const ui32 Offset; 
-    alignas(Alignment) char Data[]; 
- 
-    TRopeAlignedBuffer(size_t size) 
-        : Size(size) 
-        , Capacity(size) 
-        , Offset((Alignment - reinterpret_cast<uintptr_t>(Data)) & (Alignment - 1)) 
-    { 
-        Y_VERIFY(Offset <= Alignment - MallocAlignment); 
-    } 
- 
-public: 
-    static TIntrusivePtr<TRopeAlignedBuffer> Allocate(size_t size) { 
-        return new(malloc(sizeof(TRopeAlignedBuffer) + size + Alignment - MallocAlignment)) TRopeAlignedBuffer(size); 
-    } 
- 
-    void *operator new(size_t) { 
-        Y_FAIL(); 
-    } 
- 
-    void *operator new(size_t, void *ptr) { 
-        return ptr; 
-    } 
- 
-    void operator delete(void *ptr) { 
-        free(ptr); 
-    } 
- 
+
+// exactly one of them must be included
+#include "rope_cont_list.h"
+//#include "rope_cont_deque.h"
+
+struct IRopeChunkBackend : TThrRefBase {
+    using TData = std::tuple<const char*, size_t>;
+    virtual ~IRopeChunkBackend() = default;
+    virtual TData GetData() const = 0;
+    virtual size_t GetCapacity() const = 0;
+    using TPtr = TIntrusivePtr<IRopeChunkBackend>;
+};
+
+class TRopeAlignedBuffer : public IRopeChunkBackend {
+    static constexpr size_t Alignment = 16;
+    static constexpr size_t MallocAlignment = sizeof(size_t);
+
+    ui32 Size;
+    const ui32 Capacity;
+    const ui32 Offset;
+    alignas(Alignment) char Data[];
+
+    TRopeAlignedBuffer(size_t size)
+        : Size(size)
+        , Capacity(size)
+        , Offset((Alignment - reinterpret_cast<uintptr_t>(Data)) & (Alignment - 1))
+    {
+        Y_VERIFY(Offset <= Alignment - MallocAlignment);
+    }
+
+public:
+    static TIntrusivePtr<TRopeAlignedBuffer> Allocate(size_t size) {
+        return new(malloc(sizeof(TRopeAlignedBuffer) + size + Alignment - MallocAlignment)) TRopeAlignedBuffer(size);
+    }
+
+    void *operator new(size_t) {
+        Y_FAIL();
+    }
+
+    void *operator new(size_t, void *ptr) {
+        return ptr;
+    }
+
+    void operator delete(void *ptr) {
+        free(ptr);
+    }
+
     void operator delete(void* p, void* ptr) {
         Y_UNUSED(p);
         Y_UNUSED(ptr);
     }
 
-    TData GetData() const override { 
-        return {Data + Offset, Size}; 
-    } 
- 
-    size_t GetCapacity() const override { 
-        return Capacity; 
-    } 
- 
-    char *GetBuffer() { 
-        return Data + Offset; 
-    } 
- 
-    void AdjustSize(size_t size) { 
-        Y_VERIFY(size <= Capacity); 
-        Size = size; 
-    } 
-}; 
- 
-namespace NRopeDetails { 
- 
-    template<bool IsConst, typename TRope, typename TList> 
-    struct TIteratorTraits; 
- 
-    template<typename TRope, typename TList> 
-    struct TIteratorTraits<true, TRope, TList> { 
-        using TRopePtr = const TRope*; 
-        using TListIterator = typename TList::const_iterator; 
-    }; 
- 
-    template<typename TRope, typename TList> 
-    struct TIteratorTraits<false, TRope, TList> { 
-        using TRopePtr = TRope*; 
-        using TListIterator = typename TList::iterator; 
-    }; 
- 
-} // NRopeDetails 
- 
-class TRopeArena; 
- 
-template<typename T> 
-struct always_false : std::false_type {}; 
- 
-class TRope { 
-    friend class TRopeArena; 
- 
-    struct TChunk 
-    { 
-        class TBackend { 
-            enum class EType : uintptr_t { 
-                STRING, 
-                ROPE_CHUNK_BACKEND, 
-            }; 
- 
-            uintptr_t Owner = 0; // lower bits contain type of the owner 
- 
-        public: 
-            TBackend() = delete; 
- 
-            TBackend(const TBackend& other) 
-                : Owner(Clone(other.Owner)) 
-            {} 
- 
-            TBackend(TBackend&& other) 
-                : Owner(std::exchange(other.Owner, 0)) 
-            {} 
- 
-            TBackend(TString s) 
-                : Owner(Construct<TString>(EType::STRING, std::move(s))) 
-            {} 
- 
-            TBackend(IRopeChunkBackend::TPtr backend) 
-                : Owner(Construct<IRopeChunkBackend::TPtr>(EType::ROPE_CHUNK_BACKEND, std::move(backend))) 
-            {} 
- 
-            ~TBackend() { 
-                if (Owner) { 
-                    Destroy(Owner); 
-                } 
-            } 
- 
-            TBackend& operator =(const TBackend& other) { 
-                if (Owner) { 
-                    Destroy(Owner); 
-                } 
-                Owner = Clone(other.Owner); 
-                return *this; 
-            } 
- 
-            TBackend& operator =(TBackend&& other) { 
-                if (Owner) { 
-                    Destroy(Owner); 
-                } 
-                Owner = std::exchange(other.Owner, 0); 
-                return *this; 
-            } 
- 
-            bool operator ==(const TBackend& other) const { 
-                return Owner == other.Owner; 
-            } 
- 
-            const void *UniqueId() const { 
-                return reinterpret_cast<const void*>(Owner); 
-            } 
- 
-            const IRopeChunkBackend::TData GetData() const { 
-                return Visit(Owner, [](EType, auto& value) -> IRopeChunkBackend::TData { 
-                    using T = std::decay_t<decltype(value)>; 
-                    if constexpr (std::is_same_v<T, TString>) { 
-                        return {value.data(), value.size()}; 
-                    } else if constexpr (std::is_same_v<T, IRopeChunkBackend::TPtr>) { 
-                        return value->GetData(); 
-                    } else { 
-                        return {}; 
-                    } 
-                }); 
-            } 
- 
-            size_t GetCapacity() const { 
-                return Visit(Owner, [](EType, auto& value) { 
-                    using T = std::decay_t<decltype(value)>; 
-                    if constexpr (std::is_same_v<T, TString>) { 
-                        return value.capacity(); 
-                    } else if constexpr (std::is_same_v<T, IRopeChunkBackend::TPtr>) { 
-                        return value->GetCapacity(); 
-                    } else { 
-                        Y_FAIL(); 
-                    } 
-                }); 
-            } 
- 
-        private: 
-            static constexpr uintptr_t TypeMask = (1 << 3) - 1; 
-            static constexpr uintptr_t ValueMask = ~TypeMask; 
- 
-            template<typename T> 
-            struct TObjectHolder { 
-                struct TWrappedObject : TThrRefBase { 
-                    T Value; 
-                    TWrappedObject(T&& value) 
-                        : Value(std::move(value)) 
-                    {} 
-                }; 
-                TIntrusivePtr<TWrappedObject> Object; 
- 
-                TObjectHolder(T&& object) 
-                    : Object(MakeIntrusive<TWrappedObject>(std::move(object))) 
-                {} 
-            }; 
- 
-            template<typename TObject> 
-            static uintptr_t Construct(EType type, TObject object) { 
-                if constexpr (sizeof(TObject) <= sizeof(uintptr_t)) { 
-                    uintptr_t res = 0; 
-                    new(&res) TObject(std::move(object)); 
-                    Y_VERIFY_DEBUG((res & ValueMask) == res); 
-                    return res | static_cast<uintptr_t>(type); 
-                } else { 
-                    return Construct<TObjectHolder<TObject>>(type, TObjectHolder<TObject>(std::move(object))); 
-                } 
-            } 
- 
-            template<typename TCallback> 
-            static std::invoke_result_t<TCallback, EType, TString&> VisitRaw(uintptr_t value, TCallback&& callback) { 
-                Y_VERIFY_DEBUG(value); 
-                const EType type = static_cast<EType>(value & TypeMask); 
-                value &= ValueMask; 
-                auto caller = [&](auto& value) { return std::invoke(std::forward<TCallback>(callback), type, value); }; 
-                auto wrapper = [&](auto& value) { 
-                    using T = std::decay_t<decltype(value)>; 
-                    if constexpr (sizeof(T) <= sizeof(uintptr_t)) { 
-                        return caller(value); 
-                    } else { 
-                        return caller(reinterpret_cast<TObjectHolder<T>&>(value)); 
-                    } 
-                }; 
-                switch (type) { 
-                    case EType::STRING:             return wrapper(reinterpret_cast<TString&>(value)); 
-                    case EType::ROPE_CHUNK_BACKEND: return wrapper(reinterpret_cast<IRopeChunkBackend::TPtr&>(value)); 
-                } 
+    TData GetData() const override {
+        return {Data + Offset, Size};
+    }
+
+    size_t GetCapacity() const override {
+        return Capacity;
+    }
+
+    char *GetBuffer() {
+        return Data + Offset;
+    }
+
+    void AdjustSize(size_t size) {
+        Y_VERIFY(size <= Capacity);
+        Size = size;
+    }
+};
+
+namespace NRopeDetails {
+
+    template<bool IsConst, typename TRope, typename TList>
+    struct TIteratorTraits;
+
+    template<typename TRope, typename TList>
+    struct TIteratorTraits<true, TRope, TList> {
+        using TRopePtr = const TRope*;
+        using TListIterator = typename TList::const_iterator;
+    };
+
+    template<typename TRope, typename TList>
+    struct TIteratorTraits<false, TRope, TList> {
+        using TRopePtr = TRope*;
+        using TListIterator = typename TList::iterator;
+    };
+
+} // NRopeDetails
+
+class TRopeArena;
+
+template<typename T>
+struct always_false : std::false_type {};
+
+class TRope {
+    friend class TRopeArena;
+
+    struct TChunk
+    {
+        class TBackend {
+            enum class EType : uintptr_t {
+                STRING,
+                ROPE_CHUNK_BACKEND,
+            };
+
+            uintptr_t Owner = 0; // lower bits contain type of the owner
+
+        public:
+            TBackend() = delete;
+
+            TBackend(const TBackend& other)
+                : Owner(Clone(other.Owner))
+            {}
+
+            TBackend(TBackend&& other)
+                : Owner(std::exchange(other.Owner, 0))
+            {}
+
+            TBackend(TString s)
+                : Owner(Construct<TString>(EType::STRING, std::move(s)))
+            {}
+
+            TBackend(IRopeChunkBackend::TPtr backend)
+                : Owner(Construct<IRopeChunkBackend::TPtr>(EType::ROPE_CHUNK_BACKEND, std::move(backend)))
+            {}
+
+            ~TBackend() {
+                if (Owner) {
+                    Destroy(Owner);
+                }
+            }
+
+            TBackend& operator =(const TBackend& other) {
+                if (Owner) {
+                    Destroy(Owner);
+                }
+                Owner = Clone(other.Owner);
+                return *this;
+            }
+
+            TBackend& operator =(TBackend&& other) {
+                if (Owner) {
+                    Destroy(Owner);
+                }
+                Owner = std::exchange(other.Owner, 0);
+                return *this;
+            }
+
+            bool operator ==(const TBackend& other) const {
+                return Owner == other.Owner;
+            }
+
+            const void *UniqueId() const {
+                return reinterpret_cast<const void*>(Owner);
+            }
+
+            const IRopeChunkBackend::TData GetData() const {
+                return Visit(Owner, [](EType, auto& value) -> IRopeChunkBackend::TData {
+                    using T = std::decay_t<decltype(value)>;
+                    if constexpr (std::is_same_v<T, TString>) {
+                        return {value.data(), value.size()};
+                    } else if constexpr (std::is_same_v<T, IRopeChunkBackend::TPtr>) {
+                        return value->GetData();
+                    } else {
+                        return {};
+                    }
+                });
+            }
+
+            size_t GetCapacity() const {
+                return Visit(Owner, [](EType, auto& value) {
+                    using T = std::decay_t<decltype(value)>;
+                    if constexpr (std::is_same_v<T, TString>) {
+                        return value.capacity();
+                    } else if constexpr (std::is_same_v<T, IRopeChunkBackend::TPtr>) {
+                        return value->GetCapacity();
+                    } else {
+                        Y_FAIL();
+                    }
+                });
+            }
+
+        private:
+            static constexpr uintptr_t TypeMask = (1 << 3) - 1;
+            static constexpr uintptr_t ValueMask = ~TypeMask;
+
+            template<typename T>
+            struct TObjectHolder {
+                struct TWrappedObject : TThrRefBase {
+                    T Value;
+                    TWrappedObject(T&& value)
+                        : Value(std::move(value))
+                    {}
+                };
+                TIntrusivePtr<TWrappedObject> Object;
+
+                TObjectHolder(T&& object)
+                    : Object(MakeIntrusive<TWrappedObject>(std::move(object)))
+                {}
+            };
+
+            template<typename TObject>
+            static uintptr_t Construct(EType type, TObject object) {
+                if constexpr (sizeof(TObject) <= sizeof(uintptr_t)) {
+                    uintptr_t res = 0;
+                    new(&res) TObject(std::move(object));
+                    Y_VERIFY_DEBUG((res & ValueMask) == res);
+                    return res | static_cast<uintptr_t>(type);
+                } else {
+                    return Construct<TObjectHolder<TObject>>(type, TObjectHolder<TObject>(std::move(object)));
+                }
+            }
+
+            template<typename TCallback>
+            static std::invoke_result_t<TCallback, EType, TString&> VisitRaw(uintptr_t value, TCallback&& callback) {
+                Y_VERIFY_DEBUG(value);
+                const EType type = static_cast<EType>(value & TypeMask);
+                value &= ValueMask;
+                auto caller = [&](auto& value) { return std::invoke(std::forward<TCallback>(callback), type, value); };
+                auto wrapper = [&](auto& value) {
+                    using T = std::decay_t<decltype(value)>;
+                    if constexpr (sizeof(T) <= sizeof(uintptr_t)) {
+                        return caller(value);
+                    } else {
+                        return caller(reinterpret_cast<TObjectHolder<T>&>(value));
+                    }
+                };
+                switch (type) {
+                    case EType::STRING:             return wrapper(reinterpret_cast<TString&>(value));
+                    case EType::ROPE_CHUNK_BACKEND: return wrapper(reinterpret_cast<IRopeChunkBackend::TPtr&>(value));
+                }
                 Y_FAIL("Unexpected type# %" PRIu64, static_cast<ui64>(type));
-            } 
- 
-            template<typename TCallback> 
-            static std::invoke_result_t<TCallback, EType, TString&> Visit(uintptr_t value, TCallback&& callback) { 
-                return VisitRaw(value, [&](EType type, auto& value) { 
-                    return std::invoke(std::forward<TCallback>(callback), type, Unwrap(value)); 
-                }); 
-            } 
- 
-            template<typename T> static T& Unwrap(T& object) { return object; } 
-            template<typename T> static T& Unwrap(TObjectHolder<T>& holder) { return holder.Object->Value; } 
- 
-            static uintptr_t Clone(uintptr_t value) { 
-                return VisitRaw(value, [](EType type, auto& value) { return Construct(type, value); }); 
-            } 
- 
-            static void Destroy(uintptr_t value) { 
-                VisitRaw(value, [](EType, auto& value) { CallDtor(value); }); 
-            } 
- 
-            template<typename T> 
-            static void CallDtor(T& value) { 
-                value.~T(); 
-            } 
-        }; 
- 
-        TBackend Backend; // who actually holds the data 
-        const char *Begin; // data start 
-        const char *End; // data end 
- 
-        static constexpr struct TSlice {} Slice{}; 
- 
-        template<typename T> 
-        TChunk(T&& backend, const IRopeChunkBackend::TData& data) 
-            : Backend(std::move(backend)) 
-            , Begin(std::get<0>(data)) 
-            , End(Begin + std::get<1>(data)) 
-        { 
-            Y_VERIFY_DEBUG(Begin != End); 
-        } 
- 
-        TChunk(TString s) 
-            : Backend(std::move(s)) 
-        { 
-            size_t size; 
-            std::tie(Begin, size) = Backend.GetData(); 
-            End = Begin + size; 
-        } 
- 
-        TChunk(IRopeChunkBackend::TPtr backend) 
-            : TChunk(backend, backend->GetData()) 
-        {} 
- 
-        TChunk(TSlice, const char *data, size_t size, const TChunk& from) 
-            : TChunk(from.Backend, {data, size}) 
-        {} 
- 
-        TChunk(TSlice, const char *begin, const char *end, const TChunk& from) 
-            : TChunk(Slice, begin, end - begin, from) 
-        {} 
- 
-        explicit TChunk(const TChunk& other) 
-            : Backend(other.Backend) 
-            , Begin(other.Begin) 
-            , End(other.End) 
-        {} 
- 
-        TChunk(TChunk&& other) 
-            : Backend(std::move(other.Backend)) 
-            , Begin(other.Begin) 
-            , End(other.End) 
-        {} 
- 
-        TChunk& operator =(const TChunk&) = default; 
-        TChunk& operator =(TChunk&&) = default; 
- 
-        size_t GetSize() const { 
-            return End - Begin; 
-        } 
- 
-        static void Clear(TChunk& chunk) { 
-            chunk.Begin = nullptr; 
-        } 
- 
-        static bool IsInUse(const TChunk& chunk) { 
-            return chunk.Begin != nullptr; 
-        } 
- 
-        size_t GetCapacity() const { 
-            return Backend.GetCapacity(); 
-        } 
-    }; 
- 
-    using TChunkList = NRopeDetails::TChunkList<TChunk>; 
- 
-private: 
-    // we use list here to store chain items as we have to keep valid iterators when erase/insert operations are invoked; 
-    // iterator uses underlying container's iterator, so we have to use container that keeps valid iterators on delete, 
-    // thus, the list 
-    TChunkList Chain; 
-    size_t Size = 0; 
- 
-private: 
-    template<bool IsConst> 
-    class TIteratorImpl { 
-        using TTraits = NRopeDetails::TIteratorTraits<IsConst, TRope, TChunkList>; 
- 
-        typename TTraits::TRopePtr Rope; 
-        typename TTraits::TListIterator Iter; 
-        const char *Ptr; // ptr is always nullptr when iterator is positioned at the rope end 
- 
-#ifndef NDEBUG 
-        ui32 ValidityToken; 
-#endif 
- 
-    private: 
-        TIteratorImpl(typename TTraits::TRopePtr rope, typename TTraits::TListIterator iter, const char *ptr = nullptr) 
-            : Rope(rope) 
-            , Iter(iter) 
-            , Ptr(ptr) 
-#ifndef NDEBUG 
-            , ValidityToken(Rope->GetValidityToken()) 
-#endif 
-        {} 
- 
-    public: 
-        TIteratorImpl() 
-            : Rope(nullptr) 
-            , Ptr(nullptr) 
-        {} 
- 
-        template<bool IsOtherConst> 
-        TIteratorImpl(const TIteratorImpl<IsOtherConst>& other) 
-            : Rope(other.Rope) 
-            , Iter(other.Iter) 
-            , Ptr(other.Ptr) 
-#ifndef NDEBUG 
-            , ValidityToken(other.ValidityToken) 
-#endif 
-        {} 
- 
-        void CheckValid() const { 
-#ifndef NDEBUG 
-            Y_VERIFY(ValidityToken == Rope->GetValidityToken()); 
-#endif 
-        } 
- 
-        TIteratorImpl& operator +=(size_t amount) { 
-            CheckValid(); 
- 
-            while (amount) { 
-                Y_VERIFY_DEBUG(Valid()); 
-                const size_t max = ContiguousSize(); 
-                const size_t num = std::min(amount, max); 
-                amount -= num; 
-                Ptr += num; 
-                if (Ptr == Iter->End) { 
-                    AdvanceToNextContiguousBlock(); 
-                } 
-            } 
- 
-            return *this; 
-        } 
- 
-        TIteratorImpl operator +(size_t amount) const { 
-            CheckValid(); 
- 
-            return TIteratorImpl(*this) += amount; 
-        } 
- 
-        TIteratorImpl& operator -=(size_t amount) { 
-            CheckValid(); 
- 
-            while (amount) { 
-                const size_t num = Ptr ? std::min<size_t>(amount, Ptr - Iter->Begin) : 0; 
-                amount -= num; 
-                Ptr -= num; 
-                if (amount) { 
-                    Y_VERIFY_DEBUG(Iter != GetChainBegin()); 
-                    --Iter; 
-                    Ptr = Iter->End; 
-                } 
-            } 
- 
-            return *this; 
-        } 
- 
-        TIteratorImpl operator -(size_t amount) const { 
-            CheckValid(); 
-            return TIteratorImpl(*this) -= amount; 
-        } 
- 
-        std::pair<const char*, size_t> operator *() const { 
-            return {ContiguousData(), ContiguousSize()}; 
-        } 
- 
-        TIteratorImpl& operator ++() { 
-            AdvanceToNextContiguousBlock(); 
-            return *this; 
-        } 
- 
-        TIteratorImpl operator ++(int) const { 
-            auto it(*this); 
-            it.AdvanceToNextContiguousBlock(); 
-            return it; 
-        } 
- 
-        //////////////////////////////////////////////////////////////////////////////////////////////////////////////// 
-        // Operation with contiguous data 
-        //////////////////////////////////////////////////////////////////////////////////////////////////////////////// 
- 
-        // Get the pointer to the contiguous block of data; valid locations are [Data; Data + Size). 
-        const char *ContiguousData() const { 
-            CheckValid(); 
-            return Ptr; 
-        } 
- 
-        // Get the amount of contiguous block. 
-        size_t ContiguousSize() const { 
-            CheckValid(); 
-            return Ptr ? Iter->End - Ptr : 0; 
-        } 
- 
+            }
+
+            template<typename TCallback>
+            static std::invoke_result_t<TCallback, EType, TString&> Visit(uintptr_t value, TCallback&& callback) {
+                return VisitRaw(value, [&](EType type, auto& value) {
+                    return std::invoke(std::forward<TCallback>(callback), type, Unwrap(value));
+                });
+            }
+
+            template<typename T> static T& Unwrap(T& object) { return object; }
+            template<typename T> static T& Unwrap(TObjectHolder<T>& holder) { return holder.Object->Value; }
+
+            static uintptr_t Clone(uintptr_t value) {
+                return VisitRaw(value, [](EType type, auto& value) { return Construct(type, value); });
+            }
+
+            static void Destroy(uintptr_t value) {
+                VisitRaw(value, [](EType, auto& value) { CallDtor(value); });
+            }
+
+            template<typename T>
+            static void CallDtor(T& value) {
+                value.~T();
+            }
+        };
+
+        TBackend Backend; // who actually holds the data
+        const char *Begin; // data start
+        const char *End; // data end
+
+        static constexpr struct TSlice {} Slice{};
+
+        template<typename T>
+        TChunk(T&& backend, const IRopeChunkBackend::TData& data)
+            : Backend(std::move(backend))
+            , Begin(std::get<0>(data))
+            , End(Begin + std::get<1>(data))
+        {
+            Y_VERIFY_DEBUG(Begin != End);
+        }
+
+        TChunk(TString s)
+            : Backend(std::move(s))
+        {
+            size_t size;
+            std::tie(Begin, size) = Backend.GetData();
+            End = Begin + size;
+        }
+
+        TChunk(IRopeChunkBackend::TPtr backend)
+            : TChunk(backend, backend->GetData())
+        {}
+
+        TChunk(TSlice, const char *data, size_t size, const TChunk& from)
+            : TChunk(from.Backend, {data, size})
+        {}
+
+        TChunk(TSlice, const char *begin, const char *end, const TChunk& from)
+            : TChunk(Slice, begin, end - begin, from)
+        {}
+
+        explicit TChunk(const TChunk& other)
+            : Backend(other.Backend)
+            , Begin(other.Begin)
+            , End(other.End)
+        {}
+
+        TChunk(TChunk&& other)
+            : Backend(std::move(other.Backend))
+            , Begin(other.Begin)
+            , End(other.End)
+        {}
+
+        TChunk& operator =(const TChunk&) = default;
+        TChunk& operator =(TChunk&&) = default;
+
+        size_t GetSize() const {
+            return End - Begin;
+        }
+
+        static void Clear(TChunk& chunk) {
+            chunk.Begin = nullptr;
+        }
+
+        static bool IsInUse(const TChunk& chunk) {
+            return chunk.Begin != nullptr;
+        }
+
+        size_t GetCapacity() const {
+            return Backend.GetCapacity();
+        }
+    };
+
+    using TChunkList = NRopeDetails::TChunkList<TChunk>;
+
+private:
+    // we use list here to store chain items as we have to keep valid iterators when erase/insert operations are invoked;
+    // iterator uses underlying container's iterator, so we have to use container that keeps valid iterators on delete,
+    // thus, the list
+    TChunkList Chain;
+    size_t Size = 0;
+
+private:
+    template<bool IsConst>
+    class TIteratorImpl {
+        using TTraits = NRopeDetails::TIteratorTraits<IsConst, TRope, TChunkList>;
+
+        typename TTraits::TRopePtr Rope;
+        typename TTraits::TListIterator Iter;
+        const char *Ptr; // ptr is always nullptr when iterator is positioned at the rope end
+
+#ifndef NDEBUG
+        ui32 ValidityToken;
+#endif
+
+    private:
+        TIteratorImpl(typename TTraits::TRopePtr rope, typename TTraits::TListIterator iter, const char *ptr = nullptr)
+            : Rope(rope)
+            , Iter(iter)
+            , Ptr(ptr)
+#ifndef NDEBUG
+            , ValidityToken(Rope->GetValidityToken())
+#endif
+        {}
+
+    public:
+        TIteratorImpl()
+            : Rope(nullptr)
+            , Ptr(nullptr)
+        {}
+
+        template<bool IsOtherConst>
+        TIteratorImpl(const TIteratorImpl<IsOtherConst>& other)
+            : Rope(other.Rope)
+            , Iter(other.Iter)
+            , Ptr(other.Ptr)
+#ifndef NDEBUG
+            , ValidityToken(other.ValidityToken)
+#endif
+        {}
+
+        void CheckValid() const {
+#ifndef NDEBUG
+            Y_VERIFY(ValidityToken == Rope->GetValidityToken());
+#endif
+        }
+
+        TIteratorImpl& operator +=(size_t amount) {
+            CheckValid();
+
+            while (amount) {
+                Y_VERIFY_DEBUG(Valid());
+                const size_t max = ContiguousSize();
+                const size_t num = std::min(amount, max);
+                amount -= num;
+                Ptr += num;
+                if (Ptr == Iter->End) {
+                    AdvanceToNextContiguousBlock();
+                }
+            }
+
+            return *this;
+        }
+
+        TIteratorImpl operator +(size_t amount) const {
+            CheckValid();
+
+            return TIteratorImpl(*this) += amount;
+        }
+
+        TIteratorImpl& operator -=(size_t amount) {
+            CheckValid();
+
+            while (amount) {
+                const size_t num = Ptr ? std::min<size_t>(amount, Ptr - Iter->Begin) : 0;
+                amount -= num;
+                Ptr -= num;
+                if (amount) {
+                    Y_VERIFY_DEBUG(Iter != GetChainBegin());
+                    --Iter;
+                    Ptr = Iter->End;
+                }
+            }
+
+            return *this;
+        }
+
+        TIteratorImpl operator -(size_t amount) const {
+            CheckValid();
+            return TIteratorImpl(*this) -= amount;
+        }
+
+        std::pair<const char*, size_t> operator *() const {
+            return {ContiguousData(), ContiguousSize()};
+        }
+
+        TIteratorImpl& operator ++() {
+            AdvanceToNextContiguousBlock();
+            return *this;
+        }
+
+        TIteratorImpl operator ++(int) const {
+            auto it(*this);
+            it.AdvanceToNextContiguousBlock();
+            return it;
+        }
+
+        ////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+        // Operation with contiguous data
+        ////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+
+        // Get the pointer to the contiguous block of data; valid locations are [Data; Data + Size).
+        const char *ContiguousData() const {
+            CheckValid();
+            return Ptr;
+        }
+
+        // Get the amount of contiguous block.
+        size_t ContiguousSize() const {
+            CheckValid();
+            return Ptr ? Iter->End - Ptr : 0;
+        }
+
         size_t ChunkOffset() const {
             return Ptr ? Ptr - Iter->Begin : 0;
         }
 
-        // Advance to next contiguous block of data. 
-        void AdvanceToNextContiguousBlock() { 
-            CheckValid(); 
-            Y_VERIFY_DEBUG(Valid()); 
-            ++Iter; 
-            Ptr = Iter != GetChainEnd() ? Iter->Begin : nullptr; 
-        } 
- 
-        // Extract some data and advance. Size is not checked here, to it must be provided valid. 
-        void ExtractPlainDataAndAdvance(void *buffer, size_t len) { 
-            CheckValid(); 
- 
-            while (len) { 
-                Y_VERIFY_DEBUG(Ptr); 
- 
-                // calculate amount of bytes we need to move 
-                const size_t max = ContiguousSize(); 
-                const size_t num = std::min(len, max); 
- 
-                // copy data to the buffer and advance buffer pointers 
-                memcpy(buffer, Ptr, num); 
-                buffer = static_cast<char*>(buffer) + num; 
-                len -= num; 
- 
-                // advance iterator itself 
-                Ptr += num; 
-                if (Ptr == Iter->End) { 
-                    AdvanceToNextContiguousBlock(); 
-                } 
-            } 
-        } 
- 
-        // Checks if the iterator points to the end of the rope or not. 
-        bool Valid() const { 
-            CheckValid(); 
-            return Ptr; 
-        } 
- 
-        template<bool IsOtherConst> 
-        bool operator ==(const TIteratorImpl<IsOtherConst>& other) const { 
-            Y_VERIFY_DEBUG(Rope == other.Rope); 
-            CheckValid(); 
-            other.CheckValid(); 
-            return Iter == other.Iter && Ptr == other.Ptr; 
-        } 
- 
-        template<bool IsOtherConst> 
-        bool operator !=(const TIteratorImpl<IsOtherConst>& other) const { 
-            CheckValid(); 
-            other.CheckValid(); 
-            return !(*this == other); 
-        } 
- 
-    private: 
-        friend class TRope; 
- 
-        typename TTraits::TListIterator operator ->() const { 
-            CheckValid(); 
-            return Iter; 
-        } 
- 
-        const TChunk& GetChunk() const { 
-            CheckValid(); 
-            return *Iter; 
-        } 
- 
-        typename TTraits::TListIterator GetChainBegin() const { 
-            CheckValid(); 
-            return Rope->Chain.begin(); 
-        } 
- 
-        typename TTraits::TListIterator GetChainEnd() const { 
-            CheckValid(); 
-            return Rope->Chain.end(); 
-        } 
- 
-        bool PointsToChunkMiddle() const { 
-            CheckValid(); 
-            return Ptr && Ptr != Iter->Begin; 
-        } 
-    }; 
- 
-public: 
-#ifndef NDEBUG 
-    ui32 ValidityToken = 0; 
-    ui32 GetValidityToken() const { return ValidityToken; } 
-    void InvalidateIterators() { ++ValidityToken; } 
-#else 
-    void InvalidateIterators() {} 
-#endif 
- 
-public: 
-    using TConstIterator = TIteratorImpl<true>; 
-    using TIterator = TIteratorImpl<false>; 
- 
-public: 
-    TRope() = default; 
-    TRope(const TRope& rope) = default; 
- 
-    TRope(TRope&& rope) 
-        : Chain(std::move(rope.Chain)) 
-        , Size(std::exchange(rope.Size, 0)) 
-    { 
-        rope.InvalidateIterators(); 
-    } 
- 
-    TRope(TString s) { 
-        if (s) { 
-            Size = s.size(); 
+        // Advance to next contiguous block of data.
+        void AdvanceToNextContiguousBlock() {
+            CheckValid();
+            Y_VERIFY_DEBUG(Valid());
+            ++Iter;
+            Ptr = Iter != GetChainEnd() ? Iter->Begin : nullptr;
+        }
+
+        // Extract some data and advance. Size is not checked here, to it must be provided valid.
+        void ExtractPlainDataAndAdvance(void *buffer, size_t len) {
+            CheckValid();
+
+            while (len) {
+                Y_VERIFY_DEBUG(Ptr);
+
+                // calculate amount of bytes we need to move
+                const size_t max = ContiguousSize();
+                const size_t num = std::min(len, max);
+
+                // copy data to the buffer and advance buffer pointers
+                memcpy(buffer, Ptr, num);
+                buffer = static_cast<char*>(buffer) + num;
+                len -= num;
+
+                // advance iterator itself
+                Ptr += num;
+                if (Ptr == Iter->End) {
+                    AdvanceToNextContiguousBlock();
+                }
+            }
+        }
+
+        // Checks if the iterator points to the end of the rope or not.
+        bool Valid() const {
+            CheckValid();
+            return Ptr;
+        }
+
+        template<bool IsOtherConst>
+        bool operator ==(const TIteratorImpl<IsOtherConst>& other) const {
+            Y_VERIFY_DEBUG(Rope == other.Rope);
+            CheckValid();
+            other.CheckValid();
+            return Iter == other.Iter && Ptr == other.Ptr;
+        }
+
+        template<bool IsOtherConst>
+        bool operator !=(const TIteratorImpl<IsOtherConst>& other) const {
+            CheckValid();
+            other.CheckValid();
+            return !(*this == other);
+        }
+
+    private:
+        friend class TRope;
+
+        typename TTraits::TListIterator operator ->() const {
+            CheckValid();
+            return Iter;
+        }
+
+        const TChunk& GetChunk() const {
+            CheckValid();
+            return *Iter;
+        }
+
+        typename TTraits::TListIterator GetChainBegin() const {
+            CheckValid();
+            return Rope->Chain.begin();
+        }
+
+        typename TTraits::TListIterator GetChainEnd() const {
+            CheckValid();
+            return Rope->Chain.end();
+        }
+
+        bool PointsToChunkMiddle() const {
+            CheckValid();
+            return Ptr && Ptr != Iter->Begin;
+        }
+    };
+
+public:
+#ifndef NDEBUG
+    ui32 ValidityToken = 0;
+    ui32 GetValidityToken() const { return ValidityToken; }
+    void InvalidateIterators() { ++ValidityToken; }
+#else
+    void InvalidateIterators() {}
+#endif
+
+public:
+    using TConstIterator = TIteratorImpl<true>;
+    using TIterator = TIteratorImpl<false>;
+
+public:
+    TRope() = default;
+    TRope(const TRope& rope) = default;
+
+    TRope(TRope&& rope)
+        : Chain(std::move(rope.Chain))
+        , Size(std::exchange(rope.Size, 0))
+    {
+        rope.InvalidateIterators();
+    }
+
+    TRope(TString s) {
+        if (s) {
+            Size = s.size();
             s.reserve(32);
-            Chain.PutToEnd(std::move(s)); 
-        } 
-    } 
- 
-    TRope(IRopeChunkBackend::TPtr item) { 
-        std::tie(std::ignore, Size) = item->GetData(); 
-        Chain.PutToEnd(std::move(item)); 
-    } 
- 
-    TRope(TConstIterator begin, TConstIterator end) { 
-        Y_VERIFY_DEBUG(begin.Rope == end.Rope); 
-        if (begin.Rope == this) { 
-            TRope temp(begin, end); 
-            *this = std::move(temp); 
-            return; 
-        } 
- 
-        while (begin.Iter != end.Iter) { 
-            const size_t size = begin.ContiguousSize(); 
-            Chain.PutToEnd(TChunk::Slice, begin.ContiguousData(), size, begin.GetChunk()); 
-            begin.AdvanceToNextContiguousBlock(); 
-            Size += size; 
-        } 
- 
-        if (begin != end && end.PointsToChunkMiddle()) { 
-            Chain.PutToEnd(TChunk::Slice, begin.Ptr, end.Ptr, begin.GetChunk()); 
-            Size += end.Ptr - begin.Ptr; 
-        } 
-    } 
- 
-    ~TRope() { 
-    } 
- 
-    // creates a copy of rope with chunks with inefficient storage ratio being copied with arena allocator 
-    static TRope CopySpaceOptimized(TRope&& origin, size_t worstRatioPer1k, TRopeArena& arena); 
- 
-    TRope& operator=(const TRope& other) { 
-        Chain = other.Chain; 
-        Size = other.Size; 
-        return *this; 
-    } 
- 
-    TRope& operator=(TRope&& other) { 
-        Chain = std::move(other.Chain); 
-        Size = std::exchange(other.Size, 0); 
-        InvalidateIterators(); 
-        other.InvalidateIterators(); 
-        return *this; 
-    } 
- 
-    size_t GetSize() const { 
-        return Size; 
-    } 
- 
-    bool IsEmpty() const { 
-        return !Size; 
-    } 
- 
-    operator bool() const { 
-        return Chain; 
-    } 
- 
-    TIterator Begin() { 
-        return *this ? TIterator(this, Chain.begin(), Chain.GetFirstChunk().Begin) : End(); 
-    } 
- 
-    TIterator End() { 
-        return TIterator(this, Chain.end()); 
-    } 
- 
-    TIterator Iterator(TChunkList::iterator it) { 
-        return TIterator(this, it, it != Chain.end() ? it->Begin : nullptr); 
-    } 
- 
-    TIterator Position(size_t index) { 
-        return Begin() + index; 
-    } 
- 
-    TConstIterator Begin() const { 
-        return *this ? TConstIterator(this, Chain.begin(), Chain.GetFirstChunk().Begin) : End(); 
-    } 
- 
-    TConstIterator End() const { 
-        return TConstIterator(this, Chain.end()); 
-    } 
- 
-    TConstIterator Position(size_t index) const { 
-        return Begin() + index; 
-    } 
- 
-    TConstIterator begin() const { return Begin(); } 
-    TConstIterator end() const { return End(); } 
- 
-    void Erase(TIterator begin, TIterator end) { 
-        Cut(begin, end, nullptr); 
-    } 
- 
-    TRope Extract(TIterator begin, TIterator end) { 
-        TRope res; 
-        Cut(begin, end, &res); 
-        return res; 
-    } 
- 
-    void ExtractFront(size_t num, TRope *dest) { 
-        Y_VERIFY(Size >= num); 
-        if (num == Size && !*dest) { 
-            *dest = std::move(*this); 
-            return; 
-        } 
-        Size -= num; 
-        dest->Size += num; 
-        TChunkList::iterator it, first = Chain.begin(); 
-        for (it = first; num && num >= it->GetSize(); ++it) { 
-            num -= it->GetSize(); 
-        } 
-        if (it != first) { 
-            if (dest->Chain) { 
-                auto& last = dest->Chain.GetLastChunk(); 
-                if (last.Backend == first->Backend && last.End == first->Begin) { 
-                    last.End = first->End; 
-                    first = Chain.Erase(first); // TODO(alexvru): "it" gets invalidated here on some containers 
-                } 
-            } 
-            dest->Chain.Splice(dest->Chain.end(), Chain, first, it); 
-        } 
-        if (num) { 
-            auto it = Chain.begin(); 
-            if (dest->Chain) { 
-                auto& last = dest->Chain.GetLastChunk(); 
-                if (last.Backend == first->Backend && last.End == first->Begin) { 
-                    first->Begin += num; 
-                    last.End = first->Begin; 
-                    return; 
-                } 
-            } 
-            dest->Chain.PutToEnd(TChunk::Slice, it->Begin, it->Begin + num, *it); 
-            it->Begin += num; 
-        } 
-    } 
- 
-    void Insert(TIterator pos, TRope&& rope) { 
-        Y_VERIFY_DEBUG(this == pos.Rope); 
-        Y_VERIFY_DEBUG(this != &rope); 
- 
-        if (!rope) { 
-            return; // do nothing for empty rope 
-        } 
- 
-        // adjust size 
-        Size += std::exchange(rope.Size, 0); 
- 
-        // check if we have to split the block 
-        if (pos.PointsToChunkMiddle()) { 
-            pos.Iter = Chain.InsertBefore(pos.Iter, TChunk::Slice, pos->Begin, pos.Ptr, pos.GetChunk()); 
-            ++pos.Iter; 
-            pos->Begin = pos.Ptr; 
-        } 
- 
-        // perform glueing if possible 
-        TChunk *ropeLeft = &rope.Chain.GetFirstChunk(); 
-        TChunk *ropeRight = &rope.Chain.GetLastChunk(); 
-        bool gluedLeft = false, gluedRight = false; 
-        if (pos.Iter != Chain.begin()) { // glue left part whenever possible 
-            // obtain iterator to previous chunk 
-            auto prev(pos.Iter); 
-            --prev; 
-            if (prev->End == ropeLeft->Begin && prev->Backend == ropeLeft->Backend) { // it is glueable 
-                prev->End = ropeLeft->End; 
-                gluedLeft = true; 
-            } 
-        } 
-        if (pos.Iter != Chain.end() && ropeRight->End == pos->Begin && ropeRight->Backend == pos->Backend) { 
-            pos->Begin = ropeRight->Begin; 
-            gluedRight = true; 
-        } 
-        if (gluedLeft) { 
-            rope.Chain.EraseFront(); 
-        } 
-        if (gluedRight) { 
-            if (rope) { 
-                rope.Chain.EraseBack(); 
-            } else { // it looks like double-glueing for the same chunk, we have to drop previous one 
-                auto prev(pos.Iter); 
-                --prev; 
-                pos->Begin = prev->Begin; 
-                pos.Iter = Chain.Erase(prev); 
-            } 
-        } 
-        if (rope) { // insert remains 
-            Chain.Splice(pos.Iter, rope.Chain, rope.Chain.begin(), rope.Chain.end()); 
-        } 
-        Y_VERIFY_DEBUG(!rope); 
-        InvalidateIterators(); 
-    } 
- 
-    void EraseFront(size_t len) { 
-        Y_VERIFY_DEBUG(Size >= len); 
-        Size -= len; 
- 
-        while (len) { 
-            Y_VERIFY_DEBUG(Chain); 
-            TChunk& item = Chain.GetFirstChunk(); 
-            const size_t itemSize = item.GetSize(); 
-            if (len >= itemSize) { 
-                Chain.EraseFront(); 
-                len -= itemSize; 
-            } else { 
-                item.Begin += len; 
-                break; 
-            } 
-        } 
- 
-        InvalidateIterators(); 
-    } 
- 
-    void EraseBack(size_t len) { 
-        Y_VERIFY_DEBUG(Size >= len); 
-        Size -= len; 
- 
-        while (len) { 
-            Y_VERIFY_DEBUG(Chain); 
-            TChunk& item = Chain.GetLastChunk(); 
-            const size_t itemSize = item.GetSize(); 
-            if (len >= itemSize) { 
-                Chain.EraseBack(); 
-                len -= itemSize; 
-            } else { 
-                item.End -= len; 
-                break; 
-            } 
-        } 
- 
-        InvalidateIterators(); 
-    } 
- 
-    bool ExtractFrontPlain(void *buffer, size_t len) { 
-        // check if we have enough data in the rope 
-        if (Size < len) { 
-            return false; 
-        } 
-        Size -= len; 
-        while (len) { 
-            auto& chunk = Chain.GetFirstChunk(); 
-            const size_t num = Min(len, chunk.GetSize()); 
-            memcpy(buffer, chunk.Begin, num); 
-            buffer = static_cast<char*>(buffer) + num; 
-            len -= num; 
-            chunk.Begin += num; 
-            if (chunk.Begin == chunk.End) { 
-                Chain.Erase(Chain.begin()); 
-            } 
-        } 
-        InvalidateIterators(); 
-        return true; 
-    } 
- 
-    bool FetchFrontPlain(char **ptr, size_t *remain) { 
-        const size_t num = Min(*remain, Size); 
-        ExtractFrontPlain(*ptr, num); 
-        *ptr += num; 
-        *remain -= num; 
-        return !*remain; 
-    } 
- 
-    static int Compare(const TRope& x, const TRope& y) { 
-        TConstIterator xIter = x.Begin(), yIter = y.Begin(); 
-        while (xIter.Valid() && yIter.Valid()) { 
-            const size_t step = std::min(xIter.ContiguousSize(), yIter.ContiguousSize()); 
-            if (int res = memcmp(xIter.ContiguousData(), yIter.ContiguousData(), step)) { 
-                return res; 
-            } 
-            xIter += step; 
-            yIter += step; 
-        } 
-        return xIter.Valid() - yIter.Valid(); 
-    } 
- 
-    // Use this method carefully -- it may significantly reduce performance when misused. 
-    TString ConvertToString() const { 
-        TString res = TString::Uninitialized(GetSize()); 
-        Begin().ExtractPlainDataAndAdvance(res.Detach(), res.size()); 
-        return res; 
-    } 
- 
-    TString DebugString() const { 
-        TStringStream s; 
-        s << "{Size# " << Size; 
-        for (const auto& chunk : Chain) { 
-            const char *data; 
-            std::tie(data, std::ignore) = chunk.Backend.GetData(); 
-            s << " [" << chunk.Begin - data << ", " << chunk.End - data << ")@" << chunk.Backend.UniqueId(); 
-        } 
-        s << "}"; 
-        return s.Str(); 
-    } 
- 
-    friend bool operator==(const TRope& x, const TRope& y) { return Compare(x, y) == 0; } 
-    friend bool operator!=(const TRope& x, const TRope& y) { return Compare(x, y) != 0; } 
-    friend bool operator< (const TRope& x, const TRope& y) { return Compare(x, y) <  0; } 
-    friend bool operator<=(const TRope& x, const TRope& y) { return Compare(x, y) <= 0; } 
-    friend bool operator> (const TRope& x, const TRope& y) { return Compare(x, y) >  0; } 
-    friend bool operator>=(const TRope& x, const TRope& y) { return Compare(x, y) >= 0; } 
- 
-private: 
-    void Cut(TIterator begin, TIterator end, TRope *target) { 
-        // ensure all iterators are belong to us 
-        Y_VERIFY_DEBUG(this == begin.Rope && this == end.Rope); 
- 
-        // if begin and end are equal, we do nothing -- checking this case allows us to find out that begin does not 
-        // point to End(), for example 
-        if (begin == end) { 
-            return; 
-        } 
- 
-        auto addBlock = [&](const TChunk& from, const char *begin, const char *end) { 
-            if (target) { 
-                target->Chain.PutToEnd(TChunk::Slice, begin, end, from); 
-                target->Size += end - begin; 
-            } 
-            Size -= end - begin; 
-        }; 
- 
-        // consider special case -- when begin and end point to the same block; in this case we have to split up this 
-        // block into two parts 
-        if (begin.Iter == end.Iter) { 
-            addBlock(begin.GetChunk(), begin.Ptr, end.Ptr); 
-            const char *firstChunkBegin = begin.PointsToChunkMiddle() ? begin->Begin : nullptr; 
-            begin->Begin = end.Ptr; // this affects both begin and end iterator pointed values 
-            if (firstChunkBegin) { 
-                Chain.InsertBefore(begin.Iter, TChunk::Slice, firstChunkBegin, begin.Ptr, begin.GetChunk()); 
-            } 
-        } else { 
-            // check the first iterator -- if it starts not from the begin of the block, we have to adjust end of the 
-            // first block to match begin iterator and switch to next block 
-            if (begin.PointsToChunkMiddle()) { 
-                addBlock(begin.GetChunk(), begin.Ptr, begin->End); 
-                begin->End = begin.Ptr; 
-                begin.AdvanceToNextContiguousBlock(); 
-            } 
- 
-            // now drop full blocks 
-            size_t rangeSize = 0; 
-            for (auto it = begin.Iter; it != end.Iter; ++it) { 
-                Y_VERIFY_DEBUG(it->GetSize()); 
-                rangeSize += it->GetSize(); 
-            } 
-            if (rangeSize) { 
-                if (target) { 
-                    end.Iter = target->Chain.Splice(target->Chain.end(), Chain, begin.Iter, end.Iter); 
-                    target->Size += rangeSize; 
-                } else { 
-                    end.Iter = Chain.Erase(begin.Iter, end.Iter); 
-                } 
-                Size -= rangeSize; 
-            } 
- 
-            // and cut the last block if necessary 
-            if (end.PointsToChunkMiddle()) { 
-                addBlock(end.GetChunk(), end->Begin, end.Ptr); 
-                end->Begin = end.Ptr; 
-            } 
-        } 
- 
-        InvalidateIterators(); 
-    } 
-}; 
- 
-class TRopeArena { 
-    using TAllocateCallback = std::function<TIntrusivePtr<IRopeChunkBackend>()>; 
- 
-    TAllocateCallback Allocator; 
-    TRope Arena; 
-    size_t Size = 0; 
-    THashSet<const void*> AccountedBuffers; 
- 
-public: 
-    TRopeArena(TAllocateCallback&& allocator) 
-        : Allocator(std::move(allocator)) 
-    {} 
- 
-    TRope CreateRope(const void *buffer, size_t len) { 
-        TRope res; 
- 
-        while (len) { 
-            if (Arena) { 
-                auto iter = Arena.Begin(); 
-                Y_VERIFY_DEBUG(iter.Valid()); 
-                char *dest = const_cast<char*>(iter.ContiguousData()); 
-                const size_t bytesToCopy = std::min(len, iter.ContiguousSize()); 
-                memcpy(dest, buffer, bytesToCopy); 
-                buffer = static_cast<const char*>(buffer) + bytesToCopy; 
-                len -= bytesToCopy; 
-                res.Insert(res.End(), Arena.Extract(Arena.Begin(), Arena.Position(bytesToCopy))); 
-            } else { 
-                Arena.Insert(Arena.End(), TRope(Allocator())); 
-            } 
-        } 
- 
-        // align arena on 8-byte boundary 
-        const size_t align = 8; 
-        if (const size_t padding = Arena.GetSize() % align) { 
-            Arena.EraseFront(padding); 
-        } 
- 
-        return res; 
-    } 
- 
-    size_t GetSize() const { 
-        return Size; 
-    } 
- 
-    void AccountChunk(const TRope::TChunk& chunk) { 
-        if (AccountedBuffers.insert(chunk.Backend.UniqueId()).second) { 
-            Size += chunk.GetCapacity(); 
-        } 
-    } 
-}; 
- 
+            Chain.PutToEnd(std::move(s));
+        }
+    }
+
+    TRope(IRopeChunkBackend::TPtr item) {
+        std::tie(std::ignore, Size) = item->GetData();
+        Chain.PutToEnd(std::move(item));
+    }
+
+    TRope(TConstIterator begin, TConstIterator end) {
+        Y_VERIFY_DEBUG(begin.Rope == end.Rope);
+        if (begin.Rope == this) {
+            TRope temp(begin, end);
+            *this = std::move(temp);
+            return;
+        }
+
+        while (begin.Iter != end.Iter) {
+            const size_t size = begin.ContiguousSize();
+            Chain.PutToEnd(TChunk::Slice, begin.ContiguousData(), size, begin.GetChunk());
+            begin.AdvanceToNextContiguousBlock();
+            Size += size;
+        }
+
+        if (begin != end && end.PointsToChunkMiddle()) {
+            Chain.PutToEnd(TChunk::Slice, begin.Ptr, end.Ptr, begin.GetChunk());
+            Size += end.Ptr - begin.Ptr;
+        }
+    }
+
+    ~TRope() {
+    }
+
+    // creates a copy of rope with chunks with inefficient storage ratio being copied with arena allocator
+    static TRope CopySpaceOptimized(TRope&& origin, size_t worstRatioPer1k, TRopeArena& arena);
+
+    TRope& operator=(const TRope& other) {
+        Chain = other.Chain;
+        Size = other.Size;
+        return *this;
+    }
+
+    TRope& operator=(TRope&& other) {
+        Chain = std::move(other.Chain);
+        Size = std::exchange(other.Size, 0);
+        InvalidateIterators();
+        other.InvalidateIterators();
+        return *this;
+    }
+
+    size_t GetSize() const {
+        return Size;
+    }
+
+    bool IsEmpty() const {
+        return !Size;
+    }
+
+    operator bool() const {
+        return Chain;
+    }
+
+    TIterator Begin() {
+        return *this ? TIterator(this, Chain.begin(), Chain.GetFirstChunk().Begin) : End();
+    }
+
+    TIterator End() {
+        return TIterator(this, Chain.end());
+    }
+
+    TIterator Iterator(TChunkList::iterator it) {
+        return TIterator(this, it, it != Chain.end() ? it->Begin : nullptr);
+    }
+
+    TIterator Position(size_t index) {
+        return Begin() + index;
+    }
+
+    TConstIterator Begin() const {
+        return *this ? TConstIterator(this, Chain.begin(), Chain.GetFirstChunk().Begin) : End();
+    }
+
+    TConstIterator End() const {
+        return TConstIterator(this, Chain.end());
+    }
+
+    TConstIterator Position(size_t index) const {
+        return Begin() + index;
+    }
+
+    TConstIterator begin() const { return Begin(); }
+    TConstIterator end() const { return End(); }
+
+    void Erase(TIterator begin, TIterator end) {
+        Cut(begin, end, nullptr);
+    }
+
+    TRope Extract(TIterator begin, TIterator end) {
+        TRope res;
+        Cut(begin, end, &res);
+        return res;
+    }
+
+    void ExtractFront(size_t num, TRope *dest) {
+        Y_VERIFY(Size >= num);
+        if (num == Size && !*dest) {
+            *dest = std::move(*this);
+            return;
+        }
+        Size -= num;
+        dest->Size += num;
+        TChunkList::iterator it, first = Chain.begin();
+        for (it = first; num && num >= it->GetSize(); ++it) {
+            num -= it->GetSize();
+        }
+        if (it != first) {
+            if (dest->Chain) {
+                auto& last = dest->Chain.GetLastChunk();
+                if (last.Backend == first->Backend && last.End == first->Begin) {
+                    last.End = first->End;
+                    first = Chain.Erase(first); // TODO(alexvru): "it" gets invalidated here on some containers
+                }
+            }
+            dest->Chain.Splice(dest->Chain.end(), Chain, first, it);
+        }
+        if (num) {
+            auto it = Chain.begin();
+            if (dest->Chain) {
+                auto& last = dest->Chain.GetLastChunk();
+                if (last.Backend == first->Backend && last.End == first->Begin) {
+                    first->Begin += num;
+                    last.End = first->Begin;
+                    return;
+                }
+            }
+            dest->Chain.PutToEnd(TChunk::Slice, it->Begin, it->Begin + num, *it);
+            it->Begin += num;
+        }
+    }
+
+    void Insert(TIterator pos, TRope&& rope) {
+        Y_VERIFY_DEBUG(this == pos.Rope);
+        Y_VERIFY_DEBUG(this != &rope);
+
+        if (!rope) {
+            return; // do nothing for empty rope
+        }
+
+        // adjust size
+        Size += std::exchange(rope.Size, 0);
+
+        // check if we have to split the block
+        if (pos.PointsToChunkMiddle()) {
+            pos.Iter = Chain.InsertBefore(pos.Iter, TChunk::Slice, pos->Begin, pos.Ptr, pos.GetChunk());
+            ++pos.Iter;
+            pos->Begin = pos.Ptr;
+        }
+
+        // perform glueing if possible
+        TChunk *ropeLeft = &rope.Chain.GetFirstChunk();
+        TChunk *ropeRight = &rope.Chain.GetLastChunk();
+        bool gluedLeft = false, gluedRight = false;
+        if (pos.Iter != Chain.begin()) { // glue left part whenever possible
+            // obtain iterator to previous chunk
+            auto prev(pos.Iter);
+            --prev;
+            if (prev->End == ropeLeft->Begin && prev->Backend == ropeLeft->Backend) { // it is glueable
+                prev->End = ropeLeft->End;
+                gluedLeft = true;
+            }
+        }
+        if (pos.Iter != Chain.end() && ropeRight->End == pos->Begin && ropeRight->Backend == pos->Backend) {
+            pos->Begin = ropeRight->Begin;
+            gluedRight = true;
+        }
+        if (gluedLeft) {
+            rope.Chain.EraseFront();
+        }
+        if (gluedRight) {
+            if (rope) {
+                rope.Chain.EraseBack();
+            } else { // it looks like double-glueing for the same chunk, we have to drop previous one
+                auto prev(pos.Iter);
+                --prev;
+                pos->Begin = prev->Begin;
+                pos.Iter = Chain.Erase(prev);
+            }
+        }
+        if (rope) { // insert remains
+            Chain.Splice(pos.Iter, rope.Chain, rope.Chain.begin(), rope.Chain.end());
+        }
+        Y_VERIFY_DEBUG(!rope);
+        InvalidateIterators();
+    }
+
+    void EraseFront(size_t len) {
+        Y_VERIFY_DEBUG(Size >= len);
+        Size -= len;
+
+        while (len) {
+            Y_VERIFY_DEBUG(Chain);
+            TChunk& item = Chain.GetFirstChunk();
+            const size_t itemSize = item.GetSize();
+            if (len >= itemSize) {
+                Chain.EraseFront();
+                len -= itemSize;
+            } else {
+                item.Begin += len;
+                break;
+            }
+        }
+
+        InvalidateIterators();
+    }
+
+    void EraseBack(size_t len) {
+        Y_VERIFY_DEBUG(Size >= len);
+        Size -= len;
+
+        while (len) {
+            Y_VERIFY_DEBUG(Chain);
+            TChunk& item = Chain.GetLastChunk();
+            const size_t itemSize = item.GetSize();
+            if (len >= itemSize) {
+                Chain.EraseBack();
+                len -= itemSize;
+            } else {
+                item.End -= len;
+                break;
+            }
+        }
+
+        InvalidateIterators();
+    }
+
+    bool ExtractFrontPlain(void *buffer, size_t len) {
+        // check if we have enough data in the rope
+        if (Size < len) {
+            return false;
+        }
+        Size -= len;
+        while (len) {
+            auto& chunk = Chain.GetFirstChunk();
+            const size_t num = Min(len, chunk.GetSize());
+            memcpy(buffer, chunk.Begin, num);
+            buffer = static_cast<char*>(buffer) + num;
+            len -= num;
+            chunk.Begin += num;
+            if (chunk.Begin == chunk.End) {
+                Chain.Erase(Chain.begin());
+            }
+        }
+        InvalidateIterators();
+        return true;
+    }
+
+    bool FetchFrontPlain(char **ptr, size_t *remain) {
+        const size_t num = Min(*remain, Size);
+        ExtractFrontPlain(*ptr, num);
+        *ptr += num;
+        *remain -= num;
+        return !*remain;
+    }
+
+    static int Compare(const TRope& x, const TRope& y) {
+        TConstIterator xIter = x.Begin(), yIter = y.Begin();
+        while (xIter.Valid() && yIter.Valid()) {
+            const size_t step = std::min(xIter.ContiguousSize(), yIter.ContiguousSize());
+            if (int res = memcmp(xIter.ContiguousData(), yIter.ContiguousData(), step)) {
+                return res;
+            }
+            xIter += step;
+            yIter += step;
+        }
+        return xIter.Valid() - yIter.Valid();
+    }
+
+    // Use this method carefully -- it may significantly reduce performance when misused.
+    TString ConvertToString() const {
+        TString res = TString::Uninitialized(GetSize());
+        Begin().ExtractPlainDataAndAdvance(res.Detach(), res.size());
+        return res;
+    }
+
+    TString DebugString() const {
+        TStringStream s;
+        s << "{Size# " << Size;
+        for (const auto& chunk : Chain) {
+            const char *data;
+            std::tie(data, std::ignore) = chunk.Backend.GetData();
+            s << " [" << chunk.Begin - data << ", " << chunk.End - data << ")@" << chunk.Backend.UniqueId();
+        }
+        s << "}";
+        return s.Str();
+    }
+
+    friend bool operator==(const TRope& x, const TRope& y) { return Compare(x, y) == 0; }
+    friend bool operator!=(const TRope& x, const TRope& y) { return Compare(x, y) != 0; }
+    friend bool operator< (const TRope& x, const TRope& y) { return Compare(x, y) <  0; }
+    friend bool operator<=(const TRope& x, const TRope& y) { return Compare(x, y) <= 0; }
+    friend bool operator> (const TRope& x, const TRope& y) { return Compare(x, y) >  0; }
+    friend bool operator>=(const TRope& x, const TRope& y) { return Compare(x, y) >= 0; }
+
+private:
+    void Cut(TIterator begin, TIterator end, TRope *target) {
+        // ensure all iterators are belong to us
+        Y_VERIFY_DEBUG(this == begin.Rope && this == end.Rope);
+
+        // if begin and end are equal, we do nothing -- checking this case allows us to find out that begin does not
+        // point to End(), for example
+        if (begin == end) {
+            return;
+        }
+
+        auto addBlock = [&](const TChunk& from, const char *begin, const char *end) {
+            if (target) {
+                target->Chain.PutToEnd(TChunk::Slice, begin, end, from);
+                target->Size += end - begin;
+            }
+            Size -= end - begin;
+        };
+
+        // consider special case -- when begin and end point to the same block; in this case we have to split up this
+        // block into two parts
+        if (begin.Iter == end.Iter) {
+            addBlock(begin.GetChunk(), begin.Ptr, end.Ptr);
+            const char *firstChunkBegin = begin.PointsToChunkMiddle() ? begin->Begin : nullptr;
+            begin->Begin = end.Ptr; // this affects both begin and end iterator pointed values
+            if (firstChunkBegin) {
+                Chain.InsertBefore(begin.Iter, TChunk::Slice, firstChunkBegin, begin.Ptr, begin.GetChunk());
+            }
+        } else {
+            // check the first iterator -- if it starts not from the begin of the block, we have to adjust end of the
+            // first block to match begin iterator and switch to next block
+            if (begin.PointsToChunkMiddle()) {
+                addBlock(begin.GetChunk(), begin.Ptr, begin->End);
+                begin->End = begin.Ptr;
+                begin.AdvanceToNextContiguousBlock();
+            }
+
+            // now drop full blocks
+            size_t rangeSize = 0;
+            for (auto it = begin.Iter; it != end.Iter; ++it) {
+                Y_VERIFY_DEBUG(it->GetSize());
+                rangeSize += it->GetSize();
+            }
+            if (rangeSize) {
+                if (target) {
+                    end.Iter = target->Chain.Splice(target->Chain.end(), Chain, begin.Iter, end.Iter);
+                    target->Size += rangeSize;
+                } else {
+                    end.Iter = Chain.Erase(begin.Iter, end.Iter);
+                }
+                Size -= rangeSize;
+            }
+
+            // and cut the last block if necessary
+            if (end.PointsToChunkMiddle()) {
+                addBlock(end.GetChunk(), end->Begin, end.Ptr);
+                end->Begin = end.Ptr;
+            }
+        }
+
+        InvalidateIterators();
+    }
+};
+
+class TRopeArena {
+    using TAllocateCallback = std::function<TIntrusivePtr<IRopeChunkBackend>()>;
+
+    TAllocateCallback Allocator;
+    TRope Arena;
+    size_t Size = 0;
+    THashSet<const void*> AccountedBuffers;
+
+public:
+    TRopeArena(TAllocateCallback&& allocator)
+        : Allocator(std::move(allocator))
+    {}
+
+    TRope CreateRope(const void *buffer, size_t len) {
+        TRope res;
+
+        while (len) {
+            if (Arena) {
+                auto iter = Arena.Begin();
+                Y_VERIFY_DEBUG(iter.Valid());
+                char *dest = const_cast<char*>(iter.ContiguousData());
+                const size_t bytesToCopy = std::min(len, iter.ContiguousSize());
+                memcpy(dest, buffer, bytesToCopy);
+                buffer = static_cast<const char*>(buffer) + bytesToCopy;
+                len -= bytesToCopy;
+                res.Insert(res.End(), Arena.Extract(Arena.Begin(), Arena.Position(bytesToCopy)));
+            } else {
+                Arena.Insert(Arena.End(), TRope(Allocator()));
+            }
+        }
+
+        // align arena on 8-byte boundary
+        const size_t align = 8;
+        if (const size_t padding = Arena.GetSize() % align) {
+            Arena.EraseFront(padding);
+        }
+
+        return res;
+    }
+
+    size_t GetSize() const {
+        return Size;
+    }
+
+    void AccountChunk(const TRope::TChunk& chunk) {
+        if (AccountedBuffers.insert(chunk.Backend.UniqueId()).second) {
+            Size += chunk.GetCapacity();
+        }
+    }
+};
+
 struct TRopeUtils {
     static void Memset(TRope::TConstIterator dst, char c, size_t size) {
         while (size) {
@@ -1117,24 +1117,24 @@ public:
     }
 };
 
-inline TRope TRope::CopySpaceOptimized(TRope&& origin, size_t worstRatioPer1k, TRopeArena& arena) { 
-    TRope res; 
-    for (TChunk& chunk : origin.Chain) { 
-        size_t ratio = chunk.GetSize() * 1024 / chunk.GetCapacity(); 
-        if (ratio < 1024 - worstRatioPer1k) { 
-            res.Insert(res.End(), arena.CreateRope(chunk.Begin, chunk.GetSize())); 
-        } else { 
-            res.Chain.PutToEnd(std::move(chunk)); 
-        } 
-    } 
-    res.Size = origin.Size; 
-    origin = TRope(); 
-    for (const TChunk& chunk : res.Chain) { 
-        arena.AccountChunk(chunk); 
-    } 
-    return res; 
-} 
- 
+inline TRope TRope::CopySpaceOptimized(TRope&& origin, size_t worstRatioPer1k, TRopeArena& arena) {
+    TRope res;
+    for (TChunk& chunk : origin.Chain) {
+        size_t ratio = chunk.GetSize() * 1024 / chunk.GetCapacity();
+        if (ratio < 1024 - worstRatioPer1k) {
+            res.Insert(res.End(), arena.CreateRope(chunk.Begin, chunk.GetSize()));
+        } else {
+            res.Chain.PutToEnd(std::move(chunk));
+        }
+    }
+    res.Size = origin.Size;
+    origin = TRope();
+    for (const TChunk& chunk : res.Chain) {
+        arena.AccountChunk(chunk);
+    }
+    return res;
+}
+
 
 #if defined(WITH_VALGRIND) || defined(_msan_enabled_)