henrike@webrtc.org | f048872 | 2014-05-13 18:00:26 +0000 | [diff] [blame] | 1 | /* |
| 2 | * Copyright 2014 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 | |
Mirko Bonadei | 92ea95e | 2017-09-15 06:47:31 +0200 | [diff] [blame] | 11 | #ifndef RTC_BASE_ASYNCINVOKER_H_ |
| 12 | #define RTC_BASE_ASYNCINVOKER_H_ |
henrike@webrtc.org | f048872 | 2014-05-13 18:00:26 +0000 | [diff] [blame] | 13 | |
deadbeef | 3af63b0 | 2017-08-08 17:59:47 -0700 | [diff] [blame] | 14 | #include <atomic> |
Henrik Kjellander | ec78f1c | 2017-06-29 07:52:50 +0200 | [diff] [blame] | 15 | #include <memory> |
| 16 | #include <utility> |
deadbeef | a8bc1a1 | 2017-02-17 18:06:26 -0800 | [diff] [blame] | 17 | |
Mirko Bonadei | 92ea95e | 2017-09-15 06:47:31 +0200 | [diff] [blame] | 18 | #include "rtc_base/asyncinvoker-inl.h" |
| 19 | #include "rtc_base/bind.h" |
| 20 | #include "rtc_base/constructormagic.h" |
| 21 | #include "rtc_base/event.h" |
| 22 | #include "rtc_base/refcountedobject.h" |
| 23 | #include "rtc_base/scoped_ref_ptr.h" |
| 24 | #include "rtc_base/sigslot.h" |
| 25 | #include "rtc_base/thread.h" |
Henrik Kjellander | ec78f1c | 2017-06-29 07:52:50 +0200 | [diff] [blame] | 26 | |
| 27 | namespace rtc { |
| 28 | |
| 29 | // Invokes function objects (aka functors) asynchronously on a Thread, and |
| 30 | // owns the lifetime of calls (ie, when this object is destroyed, calls in |
| 31 | // flight are cancelled). AsyncInvoker can optionally execute a user-specified |
| 32 | // function when the asynchronous call is complete, or operates in |
| 33 | // fire-and-forget mode otherwise. |
| 34 | // |
| 35 | // AsyncInvoker does not own the thread it calls functors on. |
| 36 | // |
| 37 | // A note about async calls and object lifetimes: users should |
| 38 | // be mindful of object lifetimes when calling functions asynchronously and |
| 39 | // ensure objects used by the function _cannot_ be deleted between the |
| 40 | // invocation and execution of the functor. AsyncInvoker is designed to |
| 41 | // help: any calls in flight will be cancelled when the AsyncInvoker used to |
| 42 | // make the call is destructed, and any calls executing will be allowed to |
| 43 | // complete before AsyncInvoker destructs. |
| 44 | // |
| 45 | // The easiest way to ensure lifetimes are handled correctly is to create a |
| 46 | // class that owns the Thread and AsyncInvoker objects, and then call its |
| 47 | // methods asynchronously as needed. |
| 48 | // |
| 49 | // Example: |
| 50 | // class MyClass { |
| 51 | // public: |
| 52 | // void FireAsyncTaskWithResult(Thread* thread, int x) { |
| 53 | // // Specify a callback to get the result upon completion. |
| 54 | // invoker_.AsyncInvoke<int>(RTC_FROM_HERE, |
| 55 | // thread, Bind(&MyClass::AsyncTaskWithResult, this, x), |
| 56 | // &MyClass::OnTaskComplete, this); |
| 57 | // } |
| 58 | // void FireAnotherAsyncTask(Thread* thread) { |
| 59 | // // No callback specified means fire-and-forget. |
| 60 | // invoker_.AsyncInvoke<void>(RTC_FROM_HERE, |
| 61 | // thread, Bind(&MyClass::AnotherAsyncTask, this)); |
| 62 | // |
| 63 | // private: |
| 64 | // int AsyncTaskWithResult(int x) { |
| 65 | // // Some long running process... |
| 66 | // return x * x; |
| 67 | // } |
| 68 | // void AnotherAsyncTask() { |
| 69 | // // Some other long running process... |
| 70 | // } |
| 71 | // void OnTaskComplete(int result) { result_ = result; } |
| 72 | // |
| 73 | // AsyncInvoker invoker_; |
| 74 | // int result_; |
| 75 | // }; |
deadbeef | 3af63b0 | 2017-08-08 17:59:47 -0700 | [diff] [blame] | 76 | // |
| 77 | // More details about threading: |
| 78 | // - It's safe to construct/destruct AsyncInvoker on different threads. |
| 79 | // - It's safe to call AsyncInvoke from different threads. |
| 80 | // - It's safe to call AsyncInvoke recursively from *within* a functor that's |
| 81 | // being AsyncInvoked. |
| 82 | // - However, it's *not* safe to call AsyncInvoke from *outside* a functor |
| 83 | // that's being AsyncInvoked while the AsyncInvoker is being destroyed on |
| 84 | // another thread. This is just inherently unsafe and there's no way to |
| 85 | // prevent that. So, the user of this class should ensure that the start of |
| 86 | // each "chain" of invocations is synchronized somehow with the AsyncInvoker's |
| 87 | // destruction. This can be done by starting each chain of invocations on the |
| 88 | // same thread on which it will be destroyed, or by using some other |
| 89 | // synchronization method. |
Henrik Kjellander | ec78f1c | 2017-06-29 07:52:50 +0200 | [diff] [blame] | 90 | class AsyncInvoker : public MessageHandler { |
| 91 | public: |
| 92 | AsyncInvoker(); |
| 93 | ~AsyncInvoker() override; |
| 94 | |
| 95 | // Call |functor| asynchronously on |thread|, with no callback upon |
| 96 | // completion. Returns immediately. |
| 97 | template <class ReturnT, class FunctorT> |
| 98 | void AsyncInvoke(const Location& posted_from, |
| 99 | Thread* thread, |
| 100 | const FunctorT& functor, |
| 101 | uint32_t id = 0) { |
| 102 | std::unique_ptr<AsyncClosure> closure( |
| 103 | new FireAndForgetAsyncClosure<FunctorT>(this, functor)); |
| 104 | DoInvoke(posted_from, thread, std::move(closure), id); |
| 105 | } |
| 106 | |
| 107 | // Call |functor| asynchronously on |thread| with |delay_ms|, with no callback |
| 108 | // upon completion. Returns immediately. |
| 109 | template <class ReturnT, class FunctorT> |
| 110 | void AsyncInvokeDelayed(const Location& posted_from, |
| 111 | Thread* thread, |
| 112 | const FunctorT& functor, |
| 113 | uint32_t delay_ms, |
| 114 | uint32_t id = 0) { |
| 115 | std::unique_ptr<AsyncClosure> closure( |
| 116 | new FireAndForgetAsyncClosure<FunctorT>(this, functor)); |
| 117 | DoInvokeDelayed(posted_from, thread, std::move(closure), delay_ms, id); |
| 118 | } |
| 119 | |
| 120 | // Synchronously execute on |thread| all outstanding calls we own |
| 121 | // that are pending on |thread|, and wait for calls to complete |
| 122 | // before returning. Optionally filter by message id. |
| 123 | // The destructor will not wait for outstanding calls, so if that |
| 124 | // behavior is desired, call Flush() before destroying this object. |
| 125 | void Flush(Thread* thread, uint32_t id = MQID_ANY); |
| 126 | |
| 127 | private: |
| 128 | void OnMessage(Message* msg) override; |
| 129 | void DoInvoke(const Location& posted_from, |
| 130 | Thread* thread, |
| 131 | std::unique_ptr<AsyncClosure> closure, |
| 132 | uint32_t id); |
| 133 | void DoInvokeDelayed(const Location& posted_from, |
| 134 | Thread* thread, |
| 135 | std::unique_ptr<AsyncClosure> closure, |
| 136 | uint32_t delay_ms, |
| 137 | uint32_t id); |
deadbeef | 3af63b0 | 2017-08-08 17:59:47 -0700 | [diff] [blame] | 138 | |
| 139 | // Used to keep track of how many invocations (AsyncClosures) are still |
| 140 | // alive, so that the destructor can wait for them to finish, as described in |
| 141 | // the class documentation. |
| 142 | // |
| 143 | // TODO(deadbeef): Using a raw std::atomic like this is prone to error and |
| 144 | // difficult to maintain. We should try to wrap this functionality in a |
| 145 | // separate class to reduce the chance of errors being introduced in the |
| 146 | // future. |
| 147 | std::atomic<int> pending_invocations_; |
| 148 | |
| 149 | // Reference counted so that if the AsyncInvoker destructor finishes before |
| 150 | // an AsyncClosure's destructor that's about to call |
| 151 | // "invocation_complete_->Set()", it's not dereferenced after being |
| 152 | // destroyed. |
| 153 | scoped_refptr<RefCountedObject<Event>> invocation_complete_; |
| 154 | |
| 155 | // This flag is used to ensure that if an application AsyncInvokes tasks that |
| 156 | // recursively AsyncInvoke other tasks ad infinitum, the cycle eventually |
| 157 | // terminates. |
| 158 | std::atomic<bool> destroying_; |
| 159 | |
Henrik Kjellander | ec78f1c | 2017-06-29 07:52:50 +0200 | [diff] [blame] | 160 | friend class AsyncClosure; |
| 161 | |
| 162 | RTC_DISALLOW_COPY_AND_ASSIGN(AsyncInvoker); |
| 163 | }; |
| 164 | |
| 165 | // Similar to AsyncInvoker, but guards against the Thread being destroyed while |
| 166 | // there are outstanding dangling pointers to it. It will connect to the current |
| 167 | // thread in the constructor, and will get notified when that thread is |
| 168 | // destroyed. After GuardedAsyncInvoker is constructed, it can be used from |
| 169 | // other threads to post functors to the thread it was constructed on. If that |
| 170 | // thread dies, any further calls to AsyncInvoke() will be safely ignored. |
| 171 | class GuardedAsyncInvoker : public sigslot::has_slots<> { |
| 172 | public: |
| 173 | GuardedAsyncInvoker(); |
| 174 | ~GuardedAsyncInvoker() override; |
| 175 | |
| 176 | // Synchronously execute all outstanding calls we own, and wait for calls to |
| 177 | // complete before returning. Optionally filter by message id. The destructor |
| 178 | // will not wait for outstanding calls, so if that behavior is desired, call |
| 179 | // Flush() first. Returns false if the thread has died. |
| 180 | bool Flush(uint32_t id = MQID_ANY); |
| 181 | |
| 182 | // Call |functor| asynchronously with no callback upon completion. Returns |
| 183 | // immediately. Returns false if the thread has died. |
| 184 | template <class ReturnT, class FunctorT> |
| 185 | bool AsyncInvoke(const Location& posted_from, |
| 186 | const FunctorT& functor, |
| 187 | uint32_t id = 0) { |
deadbeef | 3af63b0 | 2017-08-08 17:59:47 -0700 | [diff] [blame] | 188 | CritScope cs(&crit_); |
Henrik Kjellander | ec78f1c | 2017-06-29 07:52:50 +0200 | [diff] [blame] | 189 | if (thread_ == nullptr) |
| 190 | return false; |
| 191 | invoker_.AsyncInvoke<ReturnT, FunctorT>(posted_from, thread_, functor, id); |
| 192 | return true; |
| 193 | } |
| 194 | |
| 195 | // Call |functor| asynchronously with |delay_ms|, with no callback upon |
| 196 | // completion. Returns immediately. Returns false if the thread has died. |
| 197 | template <class ReturnT, class FunctorT> |
| 198 | bool AsyncInvokeDelayed(const Location& posted_from, |
| 199 | const FunctorT& functor, |
| 200 | uint32_t delay_ms, |
| 201 | uint32_t id = 0) { |
deadbeef | 3af63b0 | 2017-08-08 17:59:47 -0700 | [diff] [blame] | 202 | CritScope cs(&crit_); |
Henrik Kjellander | ec78f1c | 2017-06-29 07:52:50 +0200 | [diff] [blame] | 203 | if (thread_ == nullptr) |
| 204 | return false; |
| 205 | invoker_.AsyncInvokeDelayed<ReturnT, FunctorT>(posted_from, thread_, |
| 206 | functor, delay_ms, id); |
| 207 | return true; |
| 208 | } |
| 209 | |
| 210 | // Call |functor| asynchronously, calling |callback| when done. Returns false |
| 211 | // if the thread has died. |
| 212 | template <class ReturnT, class FunctorT, class HostT> |
| 213 | bool AsyncInvoke(const Location& posted_from, |
| 214 | const Location& callback_posted_from, |
| 215 | const FunctorT& functor, |
| 216 | void (HostT::*callback)(ReturnT), |
| 217 | HostT* callback_host, |
| 218 | uint32_t id = 0) { |
deadbeef | 3af63b0 | 2017-08-08 17:59:47 -0700 | [diff] [blame] | 219 | CritScope cs(&crit_); |
Henrik Kjellander | ec78f1c | 2017-06-29 07:52:50 +0200 | [diff] [blame] | 220 | if (thread_ == nullptr) |
| 221 | return false; |
| 222 | invoker_.AsyncInvoke<ReturnT, FunctorT, HostT>( |
| 223 | posted_from, callback_posted_from, thread_, functor, callback, |
| 224 | callback_host, id); |
| 225 | return true; |
| 226 | } |
| 227 | |
| 228 | // Call |functor| asynchronously calling |callback| when done. Overloaded for |
| 229 | // void return. Returns false if the thread has died. |
| 230 | template <class ReturnT, class FunctorT, class HostT> |
| 231 | bool AsyncInvoke(const Location& posted_from, |
| 232 | const Location& callback_posted_from, |
| 233 | const FunctorT& functor, |
| 234 | void (HostT::*callback)(), |
| 235 | HostT* callback_host, |
| 236 | uint32_t id = 0) { |
deadbeef | 3af63b0 | 2017-08-08 17:59:47 -0700 | [diff] [blame] | 237 | CritScope cs(&crit_); |
Henrik Kjellander | ec78f1c | 2017-06-29 07:52:50 +0200 | [diff] [blame] | 238 | if (thread_ == nullptr) |
| 239 | return false; |
| 240 | invoker_.AsyncInvoke<ReturnT, FunctorT, HostT>( |
| 241 | posted_from, callback_posted_from, thread_, functor, callback, |
| 242 | callback_host, id); |
| 243 | return true; |
| 244 | } |
| 245 | |
| 246 | private: |
| 247 | // Callback when |thread_| is destroyed. |
| 248 | void ThreadDestroyed(); |
| 249 | |
| 250 | CriticalSection crit_; |
danilchap | 3c6abd2 | 2017-09-06 05:46:29 -0700 | [diff] [blame] | 251 | Thread* thread_ RTC_GUARDED_BY(crit_); |
| 252 | AsyncInvoker invoker_ RTC_GUARDED_BY(crit_); |
Henrik Kjellander | ec78f1c | 2017-06-29 07:52:50 +0200 | [diff] [blame] | 253 | }; |
| 254 | |
| 255 | } // namespace rtc |
henrike@webrtc.org | f048872 | 2014-05-13 18:00:26 +0000 | [diff] [blame] | 256 | |
Mirko Bonadei | 92ea95e | 2017-09-15 06:47:31 +0200 | [diff] [blame] | 257 | #endif // RTC_BASE_ASYNCINVOKER_H_ |