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7c673cae | 1 | // Copyright (c) 2016-present, Facebook, Inc. All rights reserved. |
11fdf7f2 TL |
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). | |
7c673cae FG |
5 | |
6 | #pragma once | |
7 | ||
8 | #ifndef ROCKSDB_LITE | |
9 | ||
10 | #include <functional> | |
11 | #include <memory> | |
12 | #include <regex> | |
13 | #include <string> | |
14 | #include <vector> | |
15 | ||
16 | #include "rocksdb/env.h" | |
17 | ||
18 | namespace rocksdb { | |
19 | ||
20 | // Creates a new T using the factory function that was registered with a pattern | |
21 | // that matches the provided "target" string according to std::regex_match. | |
22 | // | |
23 | // If no registered functions match, returns nullptr. If multiple functions | |
24 | // match, the factory function used is unspecified. | |
25 | // | |
26 | // Populates res_guard with result pointer if caller is granted ownership. | |
27 | template <typename T> | |
28 | T* NewCustomObject(const std::string& target, std::unique_ptr<T>* res_guard); | |
29 | ||
30 | // Returns a new T when called with a string. Populates the unique_ptr argument | |
31 | // if granting ownership to caller. | |
32 | template <typename T> | |
33 | using FactoryFunc = std::function<T*(const std::string&, std::unique_ptr<T>*)>; | |
34 | ||
35 | // To register a factory function for a type T, initialize a Registrar<T> object | |
36 | // with static storage duration. For example: | |
37 | // | |
38 | // static Registrar<Env> hdfs_reg("hdfs://.*", &CreateHdfsEnv); | |
39 | // | |
40 | // Then, calling NewCustomObject<Env>("hdfs://some_path", ...) will match the | |
41 | // regex provided above, so it returns the result of invoking CreateHdfsEnv. | |
42 | template <typename T> | |
43 | class Registrar { | |
44 | public: | |
45 | explicit Registrar(std::string pattern, FactoryFunc<T> factory); | |
46 | }; | |
47 | ||
48 | // Implementation details follow. | |
49 | ||
50 | namespace internal { | |
51 | ||
52 | template <typename T> | |
53 | struct RegistryEntry { | |
54 | std::regex pattern; | |
55 | FactoryFunc<T> factory; | |
56 | }; | |
57 | ||
58 | template <typename T> | |
59 | struct Registry { | |
60 | static Registry* Get() { | |
61 | static Registry<T> instance; | |
62 | return &instance; | |
63 | } | |
64 | std::vector<RegistryEntry<T>> entries; | |
65 | ||
66 | private: | |
67 | Registry() = default; | |
68 | }; | |
69 | ||
70 | } // namespace internal | |
71 | ||
72 | template <typename T> | |
73 | T* NewCustomObject(const std::string& target, std::unique_ptr<T>* res_guard) { | |
74 | res_guard->reset(); | |
75 | for (const auto& entry : internal::Registry<T>::Get()->entries) { | |
76 | if (std::regex_match(target, entry.pattern)) { | |
77 | return entry.factory(target, res_guard); | |
78 | } | |
79 | } | |
80 | return nullptr; | |
81 | } | |
82 | ||
83 | template <typename T> | |
84 | Registrar<T>::Registrar(std::string pattern, FactoryFunc<T> factory) { | |
85 | internal::Registry<T>::Get()->entries.emplace_back(internal::RegistryEntry<T>{ | |
86 | std::regex(std::move(pattern)), std::move(factory)}); | |
87 | } | |
88 | ||
89 | } // namespace rocksdb | |
90 | #endif // ROCKSDB_LITE |