ceph/src/rocksdb/util/random.cc

   1 //  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
   2 //  This source code is licensed under the BSD-style license found in the
   3 //  LICENSE file in the root directory of this source tree. An additional grant
   4 //  of patent rights can be found in the PATENTS file in the same directory.
   5 //
   6
   7 #include "util/random.h"
   8
   9 #include <stdint.h>
  10 #include <string.h>
  11 #include <thread>
  12 #include <utility>
  13
  14 #include "port/likely.h"
  15 #include "util/thread_local.h"
  16
  17 #ifdef ROCKSDB_SUPPORT_THREAD_LOCAL
  18 #define STORAGE_DECL static __thread
  19 #else
  20 #define STORAGE_DECL static
  21 #endif
  22
  23 namespace rocksdb {
  24
  25 Random* Random::GetTLSInstance() {
  26   STORAGE_DECL Random* tls_instance;
  27   STORAGE_DECL std::aligned_storage<sizeof(Random)>::type tls_instance_bytes;
  28
  29   auto rv = tls_instance;
  30   if (UNLIKELY(rv == nullptr)) {
  31     size_t seed = std::hash<std::thread::id>()(std::this_thread::get_id());
  32     rv = new (&tls_instance_bytes) Random((uint32_t)seed);
  33     tls_instance = rv;
  34   }
  35   return rv;
  36 }
  37
  38 }  // namespace rocksdb