1 // Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
2 // This source code is licensed under both the GPLv2 (found in the
3 // COPYING file in the root directory) and Apache 2.0 License
4 // (found in the LICENSE.Apache file in the root directory).
5
6 #pragma once
7
8 #include <unordered_map>
9
10 namespace ROCKSDB_NAMESPACE {
11
12 // Helper methods to estimate memroy usage by std containers.
13
14 template <class Key, class Value, class Hash>
ApproximateMemoryUsage(const std::unordered_map<Key,Value,Hash> & umap)15 size_t ApproximateMemoryUsage(
16 const std::unordered_map<Key, Value, Hash>& umap) {
17 typedef std::unordered_map<Key, Value, Hash> Map;
18 return sizeof(umap) +
19 // Size of all items plus a next pointer for each item.
20 (sizeof(typename Map::value_type) + sizeof(void*)) * umap.size() +
21 // Size of hash buckets.
22 umap.bucket_count() * sizeof(void*);
23 }
24
25 } // namespace ROCKSDB_NAMESPACE
26