Update RocksDB to 5.8.7

src/rocksdb2/include/rocksdb/persistent_cache.h

@@ -0,0 +1,67 @@
+// Copyright (c) 2013, 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 <stdint.h>
+#include <memory>
+#include <string>
+
+#include "rocksdb/env.h"
+#include "rocksdb/slice.h"
+#include "rocksdb/statistics.h"
+#include "rocksdb/status.h"
+
+namespace rocksdb {
+
+// PersistentCache
+//
+// Persistent cache interface for caching IO pages on a persistent medium. The
+// cache interface is specifically designed for persistent read cache.
+class PersistentCache {
+ public:
+  typedef std::vector<std::map<std::string, double>> StatsType;
+
+  virtual ~PersistentCache() {}
+
+  // Insert to page cache
+  //
+  // page_key   Identifier to identify a page uniquely across restarts
+  // data       Page data
+  // size       Size of the page
+  virtual Status Insert(const Slice& key, const char* data,
+                        const size_t size) = 0;
+
+  // Lookup page cache by page identifier
+  //
+  // page_key   Page identifier
+  // buf        Buffer where the data should be copied
+  // size       Size of the page
+  virtual Status Lookup(const Slice& key, std::unique_ptr<char[]>* data,
+                        size_t* size) = 0;
+
+  // Is cache storing uncompressed data ?
+  //
+  // True if the cache is configured to store uncompressed data else false
+  virtual bool IsCompressed() = 0;
+
+  // Return stats as map of {string, double} per-tier
+  //
+  // Persistent cache can be initialized as a tier of caches. The stats are per
+  // tire top-down
+  virtual StatsType Stats() = 0;
+
+  virtual std::string GetPrintableOptions() const = 0;
+};
+
+// Factor method to create a new persistent cache
+Status NewPersistentCache(Env* const env, const std::string& path,
+                          const uint64_t size,
+                          const std::shared_ptr<Logger>& log,
+                          const bool optimized_for_nvm,
+                          std::shared_ptr<PersistentCache>* cache);
+}  // namespace rocksdb