1 // Copyright (c) 2014 Marshall A. Greenblatt. Portions copyright (c) 2011 2 // Google Inc. All rights reserved. 3 // 4 // Redistribution and use in source and binary forms, with or without 5 // modification, are permitted provided that the following conditions are 6 // met: 7 // 8 // * Redistributions of source code must retain the above copyright 9 // notice, this list of conditions and the following disclaimer. 10 // * Redistributions in binary form must reproduce the above 11 // copyright notice, this list of conditions and the following disclaimer 12 // in the documentation and/or other materials provided with the 13 // distribution. 14 // * Neither the name of Google Inc. nor the name Chromium Embedded 15 // Framework nor the names of its contributors may be used to endorse 16 // or promote products derived from this software without specific prior 17 // written permission. 18 // 19 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 20 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 21 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 22 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 23 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 24 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 25 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 26 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 27 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 28 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 29 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 30 31 #ifndef CEF_INCLUDE_BASE_CEF_ATOMIC_FLAG_H_ 32 #define CEF_INCLUDE_BASE_CEF_ATOMIC_FLAG_H_ 33 #pragma once 34 35 #if defined(USING_CHROMIUM_INCLUDES) 36 // When building CEF include the Chromium header directly. 37 #include "base/synchronization/atomic_flag.h" 38 39 #else // !USING_CHROMIUM_INCLUDES 40 // The following is substantially similar to the Chromium implementation. 41 // If the Chromium implementation diverges the below implementation should be 42 // updated to match. 43 44 #include <stdint.h> 45 46 #include <atomic> 47 48 #include "include/base/cef_thread_checker.h" 49 50 namespace base { 51 52 // A flag that can safely be set from one thread and read from other threads. 53 // 54 // This class IS NOT intended for synchronization between threads. 55 class AtomicFlag { 56 public: 57 AtomicFlag(); 58 59 AtomicFlag(const AtomicFlag&) = delete; 60 AtomicFlag& operator=(const AtomicFlag&) = delete; 61 62 ~AtomicFlag(); 63 64 // Set the flag. Must always be called from the same thread. 65 void Set(); 66 67 // Returns true iff the flag was set. If this returns true, the current thread 68 // is guaranteed to be synchronized with all memory operations on the thread 69 // which invoked Set() up until at least the first call to Set() on it. IsSet()70 bool IsSet() const { 71 // Inline here: this has a measurable performance impact on base::WeakPtr. 72 return flag_.load(std::memory_order_acquire) != 0; 73 } 74 75 // Resets the flag. Be careful when using this: callers might not expect 76 // IsSet() to return false after returning true once. 77 void UnsafeResetForTesting(); 78 79 private: 80 std::atomic<uint_fast8_t> flag_{0}; 81 base::ThreadChecker set_thread_checker_; 82 }; 83 84 } // namespace base 85 86 #endif // !USING_CHROMIUM_INCLUDES 87 88 #endif // CEF_INCLUDE_BASE_CEF_ATOMIC_FLAG_H_ 89