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diff --git a/src/rocksdb/util/thread_local.h b/src/rocksdb/util/thread_local.h
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+++ b/src/rocksdb/util/thread_local.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 <functional>
+#include <memory>
+#include <unordered_map>
+#include <vector>
+
+#include "port/port.h"
+#include "util/autovector.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// Cleanup function that will be called for a stored thread local
+// pointer (if not NULL) when one of the following happens:
+// (1) a thread terminates
+// (2) a ThreadLocalPtr is destroyed
+//
+// Warning: this function is called while holding a global mutex. The same mutex
+// is used (at least in some cases) by most methods of ThreadLocalPtr, and it's
+// shared across all instances of ThreadLocalPtr. Thereforere extra care
+// is needed to avoid deadlocks. In particular, the handler shouldn't lock any
+// mutexes and shouldn't call any methods of any ThreadLocalPtr instances,
+// unless you know what you're doing.
+using UnrefHandler = void (*)(void* ptr);
+
+// ThreadLocalPtr stores only values of pointer type.  Different from
+// the usual thread-local-storage, ThreadLocalPtr has the ability to
+// distinguish data coming from different threads and different
+// ThreadLocalPtr instances.  For example, if a regular thread_local
+// variable A is declared in DBImpl, two DBImpl objects would share
+// the same A.  However, a ThreadLocalPtr that is defined under the
+// scope of DBImpl can avoid such confliction.  As a result, its memory
+// usage would be O(# of threads * # of ThreadLocalPtr instances).
+class ThreadLocalPtr {
+ public:
+  explicit ThreadLocalPtr(UnrefHandler handler = nullptr);
+
+  ThreadLocalPtr(const ThreadLocalPtr&) = delete;
+  ThreadLocalPtr& operator=(const ThreadLocalPtr&) = delete;
+
+  ~ThreadLocalPtr();
+
+  // Return the current pointer stored in thread local
+  void* Get() const;
+
+  // Set a new pointer value to the thread local storage.
+  void Reset(void* ptr);
+
+  // Atomically swap the supplied ptr and return the previous value
+  void* Swap(void* ptr);
+
+  // Atomically compare the stored value with expected. Set the new
+  // pointer value to thread local only if the comparison is true.
+  // Otherwise, expected returns the stored value.
+  // Return true on success, false on failure
+  bool CompareAndSwap(void* ptr, void*& expected);
+
+  // Reset all thread local data to replacement, and return non-nullptr
+  // data for all existing threads
+  void Scrape(autovector<void*>* ptrs, void* const replacement);
+
+  using FoldFunc = std::function<void(void*, void*)>;
+  // Update res by applying func on each thread-local value. Holds a lock that
+  // prevents unref handler from running during this call, but clients must
+  // still provide external synchronization since the owning thread can
+  // access the values without internal locking, e.g., via Get() and Reset().
+  void Fold(FoldFunc func, void* res);
+
+  // Add here for testing
+  // Return the next available Id without claiming it
+  static uint32_t TEST_PeekId();
+
+  // Initialize the static singletons of the ThreadLocalPtr.
+  //
+  // If this function is not called, then the singletons will be
+  // automatically initialized when they are used.
+  //
+  // Calling this function twice or after the singletons have been
+  // initialized will be no-op.
+  static void InitSingletons();
+
+  class StaticMeta;
+
+ private:
+  static StaticMeta* Instance();
+
+  const uint32_t id_;
+};
+
+}  // namespace ROCKSDB_NAMESPACE