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diff --git a/src/rocksdb/file/file_prefetch_buffer.h b/src/rocksdb/file/file_prefetch_buffer.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 <atomic>
+#include <sstream>
+#include <string>
+#include "file/random_access_file_reader.h"
+#include "port/port.h"
+#include "rocksdb/env.h"
+#include "util/aligned_buffer.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// FilePrefetchBuffer is a smart buffer to store and read data from a file.
+class FilePrefetchBuffer {
+ public:
+  // Constructor.
+  //
+  // All arguments are optional.
+  // file_reader        : the file reader to use. Can be a nullptr.
+  // readahead_size     : the initial readahead size.
+  // max_readahead_size : the maximum readahead size.
+  //   If max_readahead_size > readahead_size, the readahead size will be
+  //   doubled on every IO until max_readahead_size is hit.
+  //   Typically this is set as a multiple of readahead_size.
+  //   max_readahead_size should be greater than equal to readahead_size.
+  // enable : controls whether reading from the buffer is enabled.
+  //   If false, TryReadFromCache() always return false, and we only take stats
+  //   for the minimum offset if track_min_offset = true.
+  // track_min_offset : Track the minimum offset ever read and collect stats on
+  //   it. Used for adaptable readahead of the file footer/metadata.
+  //
+  // Automatic readhead is enabled for a file if file_reader, readahead_size,
+  // and max_readahead_size are passed in.
+  // If file_reader is a nullptr, setting readadhead_size and max_readahead_size
+  // does not make any sense. So it does nothing.
+  // A user can construct a FilePrefetchBuffer without any arguments, but use
+  // `Prefetch` to load data into the buffer.
+  FilePrefetchBuffer(RandomAccessFileReader* file_reader = nullptr,
+                     size_t readadhead_size = 0, size_t max_readahead_size = 0,
+                     bool enable = true, bool track_min_offset = false)
+      : buffer_offset_(0),
+        file_reader_(file_reader),
+        readahead_size_(readadhead_size),
+        max_readahead_size_(max_readahead_size),
+        min_offset_read_(port::kMaxSizet),
+        enable_(enable),
+        track_min_offset_(track_min_offset) {}
+
+  // Load data into the buffer from a file.
+  // reader : the file reader.
+  // offset : the file offset to start reading from.
+  // n      : the number of bytes to read.
+  // for_compaction : if prefetch is done for compaction read.
+  Status Prefetch(RandomAccessFileReader* reader, uint64_t offset, size_t n,
+                  bool for_compaction = false);
+
+  // Tries returning the data for a file raed from this buffer, if that data is
+  // in the buffer.
+  // It handles tracking the minimum read offset if track_min_offset = true.
+  // It also does the exponential readahead when readadhead_size is set as part
+  // of the constructor.
+  //
+  // offset : the file offset.
+  // n      : the number of bytes.
+  // result : output buffer to put the data into.
+  // for_compaction : if cache read is done for compaction read.
+  bool TryReadFromCache(uint64_t offset, size_t n, Slice* result,
+                        bool for_compaction = false);
+
+  // The minimum `offset` ever passed to TryReadFromCache(). This will nly be
+  // tracked if track_min_offset = true.
+  size_t min_offset_read() const { return min_offset_read_; }
+
+ private:
+  AlignedBuffer buffer_;
+  uint64_t buffer_offset_;
+  RandomAccessFileReader* file_reader_;
+  size_t readahead_size_;
+  size_t max_readahead_size_;
+  // The minimum `offset` ever passed to TryReadFromCache().
+  size_t min_offset_read_;
+  // if false, TryReadFromCache() always return false, and we only take stats
+  // for track_min_offset_ if track_min_offset_ = true
+  bool enable_;
+  // If true, track minimum `offset` ever passed to TryReadFromCache(), which
+  // can be fetched from min_offset_read().
+  bool track_min_offset_;
+};
+}  // namespace ROCKSDB_NAMESPACE