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comparison: media/webrtc/signaling/src/common/Wrapper.h
media/webrtc/signaling/src/common/Wrapper.h
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| 1 /* This Source Code Form is subject to the terms of the Mozilla Public | |
| 2 * License, v. 2.0. If a copy of the MPL was not distributed with this | |
| 3 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ | |
| 4 | |
| 5 #pragma once | |
| 6 | |
| 7 /* | |
| 8 * Wrapper - Helper class for wrapper objects. | |
| 9 * | |
| 10 * This helps to construct a shared_ptr object which wraps access to an underlying handle. | |
| 11 * (The handle could be a pointer to some low-level type, a conventional C handle, an int ID, a GUID, etc.) | |
| 12 * | |
| 13 * Usage: | |
| 14 * To obtain a FooPtr from a foo_handle_t, call FooPtr Foo::wrap(foo_handle_t); | |
| 15 * | |
| 16 * To implement Foo using Wrapper, Foo needs to include this macro in its class definition: | |
| 17 * CSF_DECLARE_WRAP(Foo, foo_handle_t); | |
| 18 * It also needs to include this in the cpp file, to provide the wrap() implementation and define the static Wrapper. | |
| 19 * CSF_IMPLEMENT_WRAP(Foo, foo_handle_t); | |
| 20 * These are all declared in common/Wrapper.h - Foo.h needs to include this too. | |
| 21 * The client needs to declare Foo(foo_handle_t) as private, and provide a suitable implementation, as well as | |
| 22 * implementing wrappers for any other functions to be exposed. | |
| 23 * The client needs to implement ~Foo() to perform any cleanup as usual. | |
| 24 * | |
| 25 * wrap() will always return the same FooPtr for a given foo_handle_t, it will not construct additional objects | |
| 26 * if a suitable one already exists. | |
| 27 * changeHandle() is used in rare cases where the underlying handle is changed, but the wrapper object is intended | |
| 28 * to remain. This is the case for the "fake" CC_DPCall generated on CC_DPLine::CreateCall(), where | |
| 29 * the correct IDPCall* is provided later. | |
| 30 * reset() is a cleanup step to wipe the handle map and allow memory to be reclaimed. | |
| 31 * | |
| 32 * Future enhancements: | |
| 33 * - For now, objects remain in the map forever. Better would be to add a releaseHandle() function which would | |
| 34 * allow the map to be emptied as underlying handles expired. While we can't force the client to give up its | |
| 35 * shared_ptr<Foo> objects, we can remove our own copy, for instance on a call ended event. | |
| 36 */ | |
| 37 | |
| 38 #include <map> | |
| 39 #include "prlock.h" | |
| 40 #include "mozilla/Assertions.h" | |
| 41 | |
| 42 /* | |
| 43 * Wrapper has its own autolock class because the instances are declared | |
| 44 * statically and mozilla::Mutex will not work properly when instantiated | |
| 45 * in a static constructor. | |
| 46 */ | |
| 47 | |
| 48 class LockNSPR { | |
| 49 public: | |
| 50 LockNSPR() : lock_(nullptr) { | |
| 51 lock_ = PR_NewLock(); | |
| 52 MOZ_ASSERT(lock_); | |
| 53 } | |
| 54 ~LockNSPR() { | |
| 55 PR_DestroyLock(lock_); | |
| 56 } | |
| 57 | |
| 58 void Acquire() { | |
| 59 PR_Lock(lock_); | |
| 60 } | |
| 61 | |
| 62 void Release() { | |
| 63 PR_Unlock(lock_); | |
| 64 } | |
| 65 | |
| 66 private: | |
| 67 PRLock *lock_; | |
| 68 }; | |
| 69 | |
| 70 class AutoLockNSPR { | |
| 71 public: | |
| 72 AutoLockNSPR(LockNSPR& lock) : lock_(lock) { | |
| 73 lock_.Acquire(); | |
| 74 } | |
| 75 ~AutoLockNSPR() { | |
| 76 lock_.Release(); | |
| 77 } | |
| 78 | |
| 79 private: | |
| 80 LockNSPR& lock_; | |
| 81 }; | |
| 82 | |
| 83 template <class T> | |
| 84 class Wrapper | |
| 85 { | |
| 86 private: | |
| 87 typedef std::map<typename T::Handle, typename T::Ptr> HandleMapType; | |
| 88 HandleMapType handleMap; | |
| 89 LockNSPR handleMapMutex; | |
| 90 | |
| 91 public: | |
| 92 Wrapper() {} | |
| 93 | |
| 94 typename T::Ptr wrap(typename T::Handle handle) | |
| 95 { | |
| 96 AutoLockNSPR lock(handleMapMutex); | |
| 97 typename HandleMapType::iterator it = handleMap.find(handle); | |
| 98 if(it != handleMap.end()) | |
| 99 { | |
| 100 return it->second; | |
| 101 } | |
| 102 else | |
| 103 { | |
| 104 typename T::Ptr p(new T(handle)); | |
| 105 handleMap[handle] = p; | |
| 106 return p; | |
| 107 } | |
| 108 } | |
| 109 | |
| 110 bool changeHandle(typename T::Handle oldHandle, typename T::Handle newHandle) | |
| 111 { | |
| 112 AutoLockNSPR lock(handleMapMutex); | |
| 113 typename HandleMapType::iterator it = handleMap.find(oldHandle); | |
| 114 if(it != handleMap.end()) | |
| 115 { | |
| 116 typename T::Ptr p = it->second; | |
| 117 handleMap.erase(it); | |
| 118 handleMap[newHandle] = p; | |
| 119 return true; | |
| 120 } | |
| 121 else | |
| 122 { | |
| 123 return false; | |
| 124 } | |
| 125 } | |
| 126 | |
| 127 bool release(typename T::Handle handle) | |
| 128 { | |
| 129 AutoLockNSPR lock(handleMapMutex); | |
| 130 typename HandleMapType::iterator it = handleMap.find(handle); | |
| 131 if(it != handleMap.end()) | |
| 132 { | |
| 133 handleMap.erase(it); | |
| 134 return true; | |
| 135 } | |
| 136 else | |
| 137 { | |
| 138 return false; | |
| 139 } | |
| 140 } | |
| 141 | |
| 142 void reset() | |
| 143 { | |
| 144 AutoLockNSPR lock(handleMapMutex); | |
| 145 handleMap.clear(); | |
| 146 } | |
| 147 }; | |
| 148 | |
| 149 #define CSF_DECLARE_WRAP(classname, handletype) \ | |
| 150 public: \ | |
| 151 static classname ## Ptr wrap(handletype handle); \ | |
| 152 static void reset(); \ | |
| 153 static void release(handletype handle); \ | |
| 154 private: \ | |
| 155 friend class Wrapper<classname>; \ | |
| 156 typedef classname ## Ptr Ptr; \ | |
| 157 typedef handletype Handle; \ | |
| 158 static Wrapper<classname>& getWrapper() { \ | |
| 159 static Wrapper<classname> wrapper; \ | |
| 160 return wrapper; \ | |
| 161 } | |
| 162 | |
| 163 #define CSF_IMPLEMENT_WRAP(classname, handletype) \ | |
| 164 classname ## Ptr classname::wrap(handletype handle) \ | |
| 165 { \ | |
| 166 return getWrapper().wrap(handle); \ | |
| 167 } \ | |
| 168 void classname::reset() \ | |
| 169 { \ | |
| 170 getWrapper().reset(); \ | |
| 171 } \ | |
| 172 void classname::release(handletype handle) \ | |
| 173 { \ | |
| 174 getWrapper().release(handle); \ | |
| 175 } |
