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diff --git a/src/rocksdb/table/iterator_wrapper.h b/src/rocksdb/table/iterator_wrapper.h
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+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#pragma once
+
+#include <set>
+
+#include "table/internal_iterator.h"
+#include "test_util/sync_point.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// A internal wrapper class with an interface similar to Iterator that caches
+// the valid() and key() results for an underlying iterator.
+// This can help avoid virtual function calls and also gives better
+// cache locality.
+template <class TValue = Slice>
+class IteratorWrapperBase {
+ public:
+  IteratorWrapperBase() : iter_(nullptr), valid_(false) {}
+  explicit IteratorWrapperBase(InternalIteratorBase<TValue>* _iter)
+      : iter_(nullptr) {
+    Set(_iter);
+  }
+  ~IteratorWrapperBase() {}
+  InternalIteratorBase<TValue>* iter() const { return iter_; }
+
+  // Set the underlying Iterator to _iter and return
+  // previous underlying Iterator.
+  InternalIteratorBase<TValue>* Set(InternalIteratorBase<TValue>* _iter) {
+    InternalIteratorBase<TValue>* old_iter = iter_;
+
+    iter_ = _iter;
+    if (iter_ == nullptr) {
+      valid_ = false;
+    } else {
+      Update();
+    }
+    return old_iter;
+  }
+
+  void DeleteIter(bool is_arena_mode) {
+    if (iter_) {
+      if (!is_arena_mode) {
+        delete iter_;
+      } else {
+        iter_->~InternalIteratorBase<TValue>();
+      }
+    }
+  }
+
+  // Iterator interface methods
+  bool Valid() const { return valid_; }
+  Slice key() const {
+    assert(Valid());
+    return result_.key;
+  }
+  TValue value() const {
+    assert(Valid());
+    return iter_->value();
+  }
+  // Methods below require iter() != nullptr
+  Status status() const {
+    assert(iter_);
+    return iter_->status();
+  }
+  void Next() {
+    assert(iter_);
+    valid_ = iter_->NextAndGetResult(&result_);
+    assert(!valid_ || iter_->status().ok());
+  }
+  void Prev() {
+    assert(iter_);
+    iter_->Prev();
+    Update();
+  }
+  void Seek(const Slice& k) {
+    assert(iter_);
+    iter_->Seek(k);
+    Update();
+  }
+  void SeekForPrev(const Slice& k) {
+    assert(iter_);
+    iter_->SeekForPrev(k);
+    Update();
+  }
+  void SeekToFirst() {
+    assert(iter_);
+    iter_->SeekToFirst();
+    Update();
+  }
+  void SeekToLast() {
+    assert(iter_);
+    iter_->SeekToLast();
+    Update();
+  }
+
+  bool MayBeOutOfLowerBound() {
+    assert(Valid());
+    return iter_->MayBeOutOfLowerBound();
+  }
+
+  bool MayBeOutOfUpperBound() {
+    assert(Valid());
+    return result_.may_be_out_of_upper_bound;
+  }
+
+  void SetPinnedItersMgr(PinnedIteratorsManager* pinned_iters_mgr) {
+    assert(iter_);
+    iter_->SetPinnedItersMgr(pinned_iters_mgr);
+  }
+  bool IsKeyPinned() const {
+    assert(Valid());
+    return iter_->IsKeyPinned();
+  }
+  bool IsValuePinned() const {
+    assert(Valid());
+    return iter_->IsValuePinned();
+  }
+
+ private:
+  void Update() {
+    valid_ = iter_->Valid();
+    if (valid_) {
+      assert(iter_->status().ok());
+      result_.key = iter_->key();
+      result_.may_be_out_of_upper_bound = true;
+    }
+  }
+
+  InternalIteratorBase<TValue>* iter_;
+  IterateResult result_;
+  bool valid_;
+};
+
+using IteratorWrapper = IteratorWrapperBase<Slice>;
+
+class Arena;
+// Return an empty iterator (yields nothing) allocated from arena.
+template <class TValue = Slice>
+extern InternalIteratorBase<TValue>* NewEmptyInternalIterator(Arena* arena);
+
+}  // namespace ROCKSDB_NAMESPACE