andresp@webrtc.org | 1dba621 | 2013-05-13 08:06:36 +0000 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (c) 2013 The WebRTC project authors. All Rights Reserved. |
| 3 | * |
| 4 | * Use of this source code is governed by a BSD-style license |
| 5 | * that can be found in the LICENSE file in the root of the source |
| 6 | * tree. An additional intellectual property rights grant can be found |
| 7 | * in the file PATENTS. All contributing project authors may |
| 8 | * be found in the AUTHORS file in the root of the source tree. |
| 9 | */ |
| 10 | |
andrew@webrtc.org | 25613ea | 2013-07-25 18:28:29 +0000 | [diff] [blame] | 11 | #ifndef WEBRTC_COMMON_H_ |
| 12 | #define WEBRTC_COMMON_H_ |
andresp@webrtc.org | 1dba621 | 2013-05-13 08:06:36 +0000 | [diff] [blame] | 13 | |
| 14 | #include <map> |
| 15 | |
| 16 | namespace webrtc { |
| 17 | |
| 18 | // Class Config is designed to ease passing a set of options across webrtc code. |
| 19 | // Options are identified by typename in order to avoid incorrect casts. |
| 20 | // |
| 21 | // Usage: |
| 22 | // * declaring an option: |
| 23 | // struct Algo1_CostFunction { |
| 24 | // virtual float cost(int x) const { return x; } |
| 25 | // virtual ~Algo1_CostFunction() {} |
| 26 | // }; |
| 27 | // |
| 28 | // * accessing an option: |
| 29 | // config.Get<Algo1_CostFunction>().cost(value); |
| 30 | // |
| 31 | // * setting an option: |
| 32 | // struct SqrCost : Algo1_CostFunction { |
| 33 | // virtual float cost(int x) const { return x*x; } |
| 34 | // }; |
| 35 | // config.Set<Algo1_CostFunction>(new SqrCost()); |
| 36 | // |
| 37 | // Note: This class is thread-compatible (like STL containers). |
| 38 | class Config { |
| 39 | public: |
| 40 | // Returns the option if set or a default constructed one. |
andrew@webrtc.org | 25613ea | 2013-07-25 18:28:29 +0000 | [diff] [blame] | 41 | // Callers that access options too often are encouraged to cache the result. |
andresp@webrtc.org | 1dba621 | 2013-05-13 08:06:36 +0000 | [diff] [blame] | 42 | // Returned references are owned by this. |
| 43 | // |
| 44 | // Requires std::is_default_constructible<T> |
| 45 | template<typename T> const T& Get() const; |
| 46 | |
| 47 | // Set the option, deleting any previous instance of the same. |
andrew@webrtc.org | 25613ea | 2013-07-25 18:28:29 +0000 | [diff] [blame] | 48 | // This instance gets ownership of the newly set value. |
andresp@webrtc.org | 1dba621 | 2013-05-13 08:06:36 +0000 | [diff] [blame] | 49 | template<typename T> void Set(T* value); |
| 50 | |
| 51 | Config() {} |
| 52 | ~Config() { |
| 53 | // Note: this method is inline so webrtc public API depends only |
| 54 | // on the headers. |
| 55 | for (OptionMap::iterator it = options_.begin(); |
| 56 | it != options_.end(); ++it) { |
| 57 | delete it->second; |
| 58 | } |
| 59 | } |
| 60 | |
| 61 | private: |
| 62 | typedef void* OptionIdentifier; |
| 63 | |
| 64 | struct BaseOption { |
| 65 | virtual ~BaseOption() {} |
| 66 | }; |
| 67 | |
| 68 | template<typename T> |
| 69 | struct Option : BaseOption { |
| 70 | explicit Option(T* v): value(v) {} |
| 71 | ~Option() { |
| 72 | delete value; |
| 73 | } |
| 74 | T* value; |
| 75 | }; |
| 76 | |
| 77 | // Own implementation of rtti-subset to avoid depending on rtti and its costs. |
| 78 | template<typename T> |
| 79 | static OptionIdentifier identifier() { |
| 80 | static char id_placeholder; |
| 81 | return &id_placeholder; |
| 82 | } |
| 83 | |
| 84 | // Used to instantiate a default constructed object that doesn't needs to be |
| 85 | // owned. This allows Get<T> to be implemented without requiring explicitly |
| 86 | // locks. |
| 87 | template<typename T> |
| 88 | static const T& default_value() { |
| 89 | static const T def; |
| 90 | return def; |
| 91 | } |
| 92 | |
| 93 | typedef std::map<OptionIdentifier, BaseOption*> OptionMap; |
| 94 | OptionMap options_; |
| 95 | |
| 96 | // DISALLOW_COPY_AND_ASSIGN |
| 97 | Config(const Config&); |
| 98 | void operator=(const Config&); |
| 99 | }; |
| 100 | |
| 101 | template<typename T> |
| 102 | const T& Config::Get() const { |
| 103 | OptionMap::const_iterator it = options_.find(identifier<T>()); |
| 104 | if (it != options_.end()) { |
| 105 | const T* t = static_cast<Option<T>*>(it->second)->value; |
| 106 | if (t) { |
| 107 | return *t; |
| 108 | } |
| 109 | } |
| 110 | return default_value<T>(); |
| 111 | } |
| 112 | |
| 113 | template<typename T> |
| 114 | void Config::Set(T* value) { |
| 115 | BaseOption*& it = options_[identifier<T>()]; |
| 116 | delete it; |
| 117 | it = new Option<T>(value); |
| 118 | } |
andrew@webrtc.org | 25613ea | 2013-07-25 18:28:29 +0000 | [diff] [blame] | 119 | |
andresp@webrtc.org | 1dba621 | 2013-05-13 08:06:36 +0000 | [diff] [blame] | 120 | } // namespace webrtc |
andrew@webrtc.org | 25613ea | 2013-07-25 18:28:29 +0000 | [diff] [blame] | 121 | |
| 122 | #endif // WEBRTC_COMMON_H_ |