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diff --git a/src/rocksdb/table/plain/plain_table_reader.h b/src/rocksdb/table/plain/plain_table_reader.h
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+// Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+// 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
+
+#ifndef ROCKSDB_LITE
+#include <stdint.h>
+
+#include <memory>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+#include "file/random_access_file_reader.h"
+#include "memory/arena.h"
+#include "rocksdb/env.h"
+#include "rocksdb/iterator.h"
+#include "rocksdb/slice_transform.h"
+#include "rocksdb/table.h"
+#include "rocksdb/table_properties.h"
+#include "table/plain/plain_table_bloom.h"
+#include "table/plain/plain_table_factory.h"
+#include "table/plain/plain_table_index.h"
+#include "table/table_reader.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+class Block;
+struct BlockContents;
+class BlockHandle;
+class Footer;
+struct Options;
+class RandomAccessFile;
+struct ReadOptions;
+class TableCache;
+class TableReader;
+class InternalKeyComparator;
+class PlainTableKeyDecoder;
+class GetContext;
+
+extern const uint32_t kPlainTableVariableLength;
+
+struct PlainTableReaderFileInfo {
+  bool is_mmap_mode;
+  Slice file_data;
+  uint32_t data_end_offset;
+  std::unique_ptr<RandomAccessFileReader> file;
+
+  PlainTableReaderFileInfo(std::unique_ptr<RandomAccessFileReader>&& _file,
+                           const EnvOptions& storage_options,
+                           uint32_t _data_size_offset)
+      : is_mmap_mode(storage_options.use_mmap_reads),
+        data_end_offset(_data_size_offset),
+        file(std::move(_file)) {}
+};
+
+// The reader class of PlainTable. For description of PlainTable format
+// See comments of class PlainTableFactory, where instances of
+// PlainTableReader are created.
+class PlainTableReader : public TableReader {
+ public:
+  // Based on following output file format shown in plain_table_factory.h
+  // When opening the output file, PlainTableReader creates a hash table
+  // from key prefixes to offset of the output file. PlainTable will decide
+  // whether it points to the data offset of the first key with the key prefix
+  // or the offset of it. If there are too many keys share this prefix, it will
+  // create a binary search-able index from the suffix to offset on disk.
+  static Status Open(const ImmutableOptions& ioptions,
+                     const EnvOptions& env_options,
+                     const InternalKeyComparator& internal_comparator,
+                     std::unique_ptr<RandomAccessFileReader>&& file,
+                     uint64_t file_size, std::unique_ptr<TableReader>* table,
+                     const int bloom_bits_per_key, double hash_table_ratio,
+                     size_t index_sparseness, size_t huge_page_tlb_size,
+                     bool full_scan_mode, const bool immortal_table = false,
+                     const SliceTransform* prefix_extractor = nullptr);
+
+  // Returns new iterator over table contents
+  // compaction_readahead_size: its value will only be used if for_compaction =
+  // true
+  InternalIterator* NewIterator(const ReadOptions&,
+                                const SliceTransform* prefix_extractor,
+                                Arena* arena, bool skip_filters,
+                                TableReaderCaller caller,
+                                size_t compaction_readahead_size = 0,
+                                bool allow_unprepared_value = false) override;
+
+  void Prepare(const Slice& target) override;
+
+  Status Get(const ReadOptions& readOptions, const Slice& key,
+             GetContext* get_context, const SliceTransform* prefix_extractor,
+             bool skip_filters = false) override;
+
+  uint64_t ApproximateOffsetOf(const Slice& key,
+                               TableReaderCaller caller) override;
+
+  uint64_t ApproximateSize(const Slice& start, const Slice& end,
+                           TableReaderCaller caller) override;
+
+  uint32_t GetIndexSize() const { return index_.GetIndexSize(); }
+  void SetupForCompaction() override;
+
+  std::shared_ptr<const TableProperties> GetTableProperties() const override {
+    return table_properties_;
+  }
+
+  virtual size_t ApproximateMemoryUsage() const override {
+    return arena_.MemoryAllocatedBytes();
+  }
+
+  PlainTableReader(const ImmutableOptions& ioptions,
+                   std::unique_ptr<RandomAccessFileReader>&& file,
+                   const EnvOptions& env_options,
+                   const InternalKeyComparator& internal_comparator,
+                   EncodingType encoding_type, uint64_t file_size,
+                   const TableProperties* table_properties,
+                   const SliceTransform* prefix_extractor);
+  virtual ~PlainTableReader();
+
+ protected:
+  // Check bloom filter to see whether it might contain this prefix.
+  // The hash of the prefix is given, since it can be reused for index lookup
+  // too.
+  virtual bool MatchBloom(uint32_t hash) const;
+
+  // PopulateIndex() builds index of keys. It must be called before any query
+  // to the table.
+  //
+  // props: the table properties object that need to be stored. Ownership of
+  //        the object will be passed.
+  //
+
+  Status PopulateIndex(TableProperties* props, int bloom_bits_per_key,
+                       double hash_table_ratio, size_t index_sparseness,
+                       size_t huge_page_tlb_size);
+
+  Status MmapDataIfNeeded();
+
+ private:
+  const InternalKeyComparator internal_comparator_;
+  EncodingType encoding_type_;
+  // represents plain table's current status.
+  Status status_;
+
+  PlainTableIndex index_;
+  bool full_scan_mode_;
+
+  // data_start_offset_ and data_end_offset_ defines the range of the
+  // sst file that stores data.
+  const uint32_t data_start_offset_ = 0;
+  const uint32_t user_key_len_;
+  const SliceTransform* prefix_extractor_;
+
+  static const size_t kNumInternalBytes = 8;
+
+  // Bloom filter is used to rule out non-existent key
+  bool enable_bloom_;
+  PlainTableBloomV1 bloom_;
+  PlainTableReaderFileInfo file_info_;
+  Arena arena_;
+  CacheAllocationPtr index_block_alloc_;
+  CacheAllocationPtr bloom_block_alloc_;
+
+  const ImmutableOptions& ioptions_;
+  std::unique_ptr<Cleanable> dummy_cleanable_;
+  uint64_t file_size_;
+
+ protected:  // for testing
+  std::shared_ptr<const TableProperties> table_properties_;
+
+ private:
+  bool IsFixedLength() const {
+    return user_key_len_ != kPlainTableVariableLength;
+  }
+
+  size_t GetFixedInternalKeyLength() const {
+    return user_key_len_ + kNumInternalBytes;
+  }
+
+  Slice GetPrefix(const Slice& target) const {
+    assert(target.size() >= 8);  // target is internal key
+    return GetPrefixFromUserKey(ExtractUserKey(target));
+  }
+
+  Slice GetPrefix(const ParsedInternalKey& target) const {
+    return GetPrefixFromUserKey(target.user_key);
+  }
+
+  Slice GetPrefixFromUserKey(const Slice& user_key) const {
+    if (!IsTotalOrderMode()) {
+      return prefix_extractor_->Transform(user_key);
+    } else {
+      // Use empty slice as prefix if prefix_extractor is not set.
+      // In that case,
+      // it falls back to pure binary search and
+      // total iterator seek is supported.
+      return Slice();
+    }
+  }
+
+  friend class TableCache;
+  friend class PlainTableIterator;
+
+  // Internal helper function to generate an IndexRecordList object from all
+  // the rows, which contains index records as a list.
+  // If bloom_ is not null, all the keys' full-key hash will be added to the
+  // bloom filter.
+  Status PopulateIndexRecordList(PlainTableIndexBuilder* index_builder,
+                                 std::vector<uint32_t>* prefix_hashes);
+
+  // Internal helper function to allocate memory for bloom filter
+  void AllocateBloom(int bloom_bits_per_key, int num_prefixes,
+                     size_t huge_page_tlb_size);
+
+  void FillBloom(const std::vector<uint32_t>& prefix_hashes);
+
+  // Read the key and value at `offset` to parameters for keys, the and
+  // `seekable`.
+  // On success, `offset` will be updated as the offset for the next key.
+  // `parsed_key` will be key in parsed format.
+  // if `internal_key` is not empty, it will be filled with key with slice
+  // format.
+  // if `seekable` is not null, it will return whether we can directly read
+  // data using this offset.
+  Status Next(PlainTableKeyDecoder* decoder, uint32_t* offset,
+              ParsedInternalKey* parsed_key, Slice* internal_key, Slice* value,
+              bool* seekable = nullptr) const;
+  // Get file offset for key target.
+  // return value prefix_matched is set to true if the offset is confirmed
+  // for a key with the same prefix as target.
+  Status GetOffset(PlainTableKeyDecoder* decoder, const Slice& target,
+                   const Slice& prefix, uint32_t prefix_hash,
+                   bool& prefix_matched, uint32_t* offset) const;
+
+  bool IsTotalOrderMode() const { return (prefix_extractor_ == nullptr); }
+
+  // No copying allowed
+  explicit PlainTableReader(const TableReader&) = delete;
+  void operator=(const TableReader&) = delete;
+};
+}  // namespace ROCKSDB_NAMESPACE
+#endif  // ROCKSDB_LITE