| /* |
| * Copyright 2015 Google Inc. All Rights Reserved. |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #ifndef COBALT_WEBDRIVER_UTIL_CALL_ON_MESSAGE_LOOP_H_ |
| #define COBALT_WEBDRIVER_UTIL_CALL_ON_MESSAGE_LOOP_H_ |
| |
| #include "base/bind.h" |
| #include "base/callback.h" |
| #include "base/memory/ref_counted.h" |
| #include "base/message_loop.h" |
| #include "base/message_loop_proxy.h" |
| #include "base/synchronization/waitable_event.h" |
| |
| namespace cobalt { |
| namespace webdriver { |
| namespace util { |
| namespace internal { |
| template <class ReturnValue> |
| class CallOnMessageLoopHelper { |
| public: |
| typedef base::Callback<ReturnValue(void)> CallbackType; |
| CallOnMessageLoopHelper( |
| const scoped_refptr<base::MessageLoopProxy>& message_loop_proxy, |
| const CallbackType& callback) |
| : completed_event_(true, false), success_(false) { |
| DCHECK_NE(base::MessageLoopProxy::current(), message_loop_proxy); |
| scoped_ptr<DeletionSignaler> dt(new DeletionSignaler(&completed_event_)); |
| // Note that while MessageLoopProxy::PostTask returns false |
| // after the message loop has gone away, it still can return true |
| // even if tasks are posted during shutdown and will never be run, |
| // so we ignore this return value. |
| message_loop_proxy->PostTask( |
| FROM_HERE, |
| base::Bind(&CallOnMessageLoopHelper::Call, base::Unretained(this), |
| callback, base::Passed(&dt))); |
| } |
| |
| // Waits for result, filling |out| with the return value if successful. |
| // Returns true on success or false if the message loop went away |
| // before the task was executed. |
| bool WaitForResult(ReturnValue* out) { |
| completed_event_.Wait(); |
| if (success_) { |
| *out = result_; |
| } |
| return success_; |
| } |
| |
| ~CallOnMessageLoopHelper() { |
| // We must ensure that we've waited for completion otherwise |
| // DeletionSignaler will have a use-after-free. |
| completed_event_.Wait(); |
| } |
| |
| private: |
| // DeletionSignaler signals an event when the destructor is called. |
| // This allows us to use the base::Passed mechanism to signal our |
| // completed_event_ both when Call() has been invoked and when |
| // the message loop has been deleted. |
| class DeletionSignaler { |
| public: |
| base::WaitableEvent* to_signal_; |
| |
| explicit DeletionSignaler(base::WaitableEvent* to_signal) |
| : to_signal_(to_signal) {} |
| |
| ~DeletionSignaler() { to_signal_->Signal(); } |
| |
| private: |
| DISALLOW_COPY_AND_ASSIGN(DeletionSignaler); |
| }; |
| |
| void Call(const CallbackType& callback, |
| scoped_ptr<DeletionSignaler> dt ALLOW_UNUSED) { |
| result_ = callback.Run(); |
| success_ = true; |
| } |
| |
| base::WaitableEvent completed_event_; |
| ReturnValue result_; |
| bool success_; |
| }; |
| |
| // Used with CallWeakOnMessageLoop. |
| template <typename T, typename ReturnValue> |
| base::optional<ReturnValue> RunWeak(const base::Callback<T*()>& get_weak, |
| const base::Callback<ReturnValue(T*)>& cb) { |
| T* weak_object = get_weak.Run(); |
| if (weak_object) { |
| return cb.Run(weak_object); |
| } else { |
| return base::nullopt; |
| } |
| } |
| } // namespace internal |
| |
| // Call the base::Callback on the specified message loop and wait for it to |
| // complete. Returns true if successful, or false if the underlying |
| // PostTask failed. This can happen if a WebModule shuts down due to a page |
| // navigation. |
| // |
| // On success, |out| is set to the result. |
| template <class ReturnValue> |
| bool TryCallOnMessageLoop( |
| const scoped_refptr<base::MessageLoopProxy>& message_loop_proxy, |
| const base::Callback<ReturnValue(void)>& callback, ReturnValue* out) { |
| internal::CallOnMessageLoopHelper<ReturnValue> call_helper(message_loop_proxy, |
| callback); |
| return call_helper.WaitForResult(out); |
| } |
| |
| // Tries to call |callback| on messageloop |message_loop_proxy|, |
| // retrying a few times if the WebModule thread appears to have gone |
| // away (perhaps because of navigation). If failure persists, |
| // returns a CommandResult of |window_disappeared_code|. |
| template <typename ReturnValue> |
| util::CommandResult<ReturnValue> CallOnMessageLoopWithRetry( |
| const scoped_refptr<base::MessageLoopProxy>& message_loop_proxy, |
| const base::Callback<util::CommandResult<ReturnValue>(void)>& callback, |
| protocol::Response::StatusCode window_disappeared_code) { |
| util::CommandResult<ReturnValue> result; |
| |
| const int kRetryAttempts = 5; |
| bool success = false; |
| for (int i = 0; !success && i < kRetryAttempts; i++) { |
| success = TryCallOnMessageLoop(message_loop_proxy, callback, &result); |
| } |
| |
| if (!success) { |
| result = util::CommandResult<ReturnValue>(window_disappeared_code); |
| } |
| return result; |
| } |
| |
| // Supports a common pattern in the various XXXDriver classes. |
| // On the provided message loop, calls RunWeak which will run the callback |cb| |
| // if |get_weak| returns a non-NULL pointer. RunWeak will return the result of |
| // the callback, or base::nullopt if |get_weak| returned NULL and the callback |
| // wasn't run. |
| // If the return value from RunWeak is valid, return a CommandResult that wraps |
| // the value. Otherwise return |no_such_object_code| to indicate the correct |
| // error. |
| template <typename T, typename ReturnValue> |
| util::CommandResult<ReturnValue> CallWeakOnMessageLoopAndReturnResult( |
| const scoped_refptr<base::MessageLoopProxy>& message_loop, |
| const base::Callback<T*()>& get_weak, |
| const base::Callback<ReturnValue(T*)>& cb, |
| protocol::Response::StatusCode no_such_object_code) { |
| typedef util::CommandResult<ReturnValue> CommandResult; |
| typedef base::optional<ReturnValue> InternalResult; |
| InternalResult result; |
| bool success = util::TryCallOnMessageLoop( |
| message_loop, |
| base::Bind(&internal::RunWeak<T, ReturnValue>, get_weak, cb), &result); |
| if (success && result) { |
| return CommandResult(result.value()); |
| } else { |
| return CommandResult(no_such_object_code); |
| } |
| } |
| |
| } // namespace util |
| } // namespace webdriver |
| } // namespace cobalt |
| |
| #endif // COBALT_WEBDRIVER_UTIL_CALL_ON_MESSAGE_LOOP_H_ |