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diff --git a/src/rocksdb/table/block_based/index_reader_common.h b/src/rocksdb/table/block_based/index_reader_common.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 "table/block_based/block_based_table_reader.h"
+#include "table/block_based/reader_common.h"
+
+namespace ROCKSDB_NAMESPACE {
+// Encapsulates common functionality for the various index reader
+// implementations. Provides access to the index block regardless of whether
+// it is owned by the reader or stored in the cache, or whether it is pinned
+// in the cache or not.
+class BlockBasedTable::IndexReaderCommon : public BlockBasedTable::IndexReader {
+ public:
+  IndexReaderCommon(const BlockBasedTable* t,
+                    CachableEntry<Block>&& index_block)
+      : table_(t), index_block_(std::move(index_block)) {
+    assert(table_ != nullptr);
+  }
+
+ protected:
+  static Status ReadIndexBlock(const BlockBasedTable* table,
+                               FilePrefetchBuffer* prefetch_buffer,
+                               const ReadOptions& read_options, bool use_cache,
+                               GetContext* get_context,
+                               BlockCacheLookupContext* lookup_context,
+                               CachableEntry<Block>* index_block);
+
+  const BlockBasedTable* table() const { return table_; }
+
+  const InternalKeyComparator* internal_comparator() const {
+    assert(table_ != nullptr);
+    assert(table_->get_rep() != nullptr);
+
+    return &table_->get_rep()->internal_comparator;
+  }
+
+  bool index_has_first_key() const {
+    assert(table_ != nullptr);
+    assert(table_->get_rep() != nullptr);
+    return table_->get_rep()->index_has_first_key;
+  }
+
+  bool index_key_includes_seq() const {
+    assert(table_ != nullptr);
+    assert(table_->get_rep() != nullptr);
+    return table_->get_rep()->index_key_includes_seq;
+  }
+
+  bool index_value_is_full() const {
+    assert(table_ != nullptr);
+    assert(table_->get_rep() != nullptr);
+    return table_->get_rep()->index_value_is_full;
+  }
+
+  bool cache_index_blocks() const {
+    assert(table_ != nullptr);
+    assert(table_->get_rep() != nullptr);
+    return table_->get_rep()->table_options.cache_index_and_filter_blocks;
+  }
+
+  Status GetOrReadIndexBlock(bool no_io, Env::IOPriority rate_limiter_priority,
+                             GetContext* get_context,
+                             BlockCacheLookupContext* lookup_context,
+                             CachableEntry<Block>* index_block) const;
+
+  size_t ApproximateIndexBlockMemoryUsage() const {
+    assert(!index_block_.GetOwnValue() || index_block_.GetValue() != nullptr);
+    return index_block_.GetOwnValue()
+               ? index_block_.GetValue()->ApproximateMemoryUsage()
+               : 0;
+  }
+
+ private:
+  const BlockBasedTable* table_;
+  CachableEntry<Block> index_block_;
+};
+
+}  // namespace ROCKSDB_NAMESPACE