1 // Copyright 2016 The Chromium Authors 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef BASE_TASK_THREAD_POOL_WORKER_THREAD_SET_H_ 6 #define BASE_TASK_THREAD_POOL_WORKER_THREAD_SET_H_ 7 8 #include <stddef.h> 9 10 #include <set> 11 12 #include "base/base_export.h" 13 #include "base/memory/raw_ptr.h" 14 15 namespace base { 16 namespace internal { 17 18 class WorkerThreadWaitableEvent; 19 20 // An ordered set of WorkerThreads which has custom logic to treat the worker at 21 // the front of the set as being "in-use" (so its time in that position doesn't 22 // count towards being inactive / reclaimable). Supports removal of arbitrary 23 // WorkerThreads. DCHECKs when a WorkerThread is inserted multiple times. 24 // WorkerThreads are not owned by the set. All operations are amortized 25 // O(log(n)). This class is NOT thread-safe. 26 class BASE_EXPORT WorkerThreadSet { 27 struct Compare { 28 bool operator()(const WorkerThreadWaitableEvent* a, 29 const WorkerThreadWaitableEvent* b) const; 30 }; 31 32 public: 33 WorkerThreadSet(); 34 WorkerThreadSet(const WorkerThreadSet&) = delete; 35 WorkerThreadSet& operator=(const WorkerThreadSet&) = delete; 36 ~WorkerThreadSet(); 37 38 // Inserts |worker| in the set. |worker| must not already be on the set. Flags 39 // the WorkerThreadWaitableEvent previously at the front of the set, if it 40 // changed, or |worker| as unused. 41 void Insert(WorkerThreadWaitableEvent* worker); 42 43 // Removes the front WorkerThread from the set and returns it. Returns nullptr 44 // if the set is empty. Flags the WorkerThread now at the front of the set, if 45 // any, as being in-use. 46 WorkerThreadWaitableEvent* Take(); 47 48 // Returns the front WorkerThread from the set, nullptr if empty. 49 WorkerThreadWaitableEvent* Peek() const; 50 51 // Returns true if |worker| is already in the set. 52 bool Contains(const WorkerThreadWaitableEvent* worker) const; 53 54 // Removes |worker| from the set. Must not be invoked for the first worker 55 // on the set. 56 void Remove(const WorkerThreadWaitableEvent* worker); 57 58 // Returns the number of WorkerThreads on the set. Size()59 size_t Size() const { return set_.size(); } 60 61 // Returns true if the set is empty. IsEmpty()62 bool IsEmpty() const { return set_.empty(); } 63 64 private: 65 std::set<raw_ptr<WorkerThreadWaitableEvent, SetExperimental>, Compare> set_; 66 }; 67 68 } // namespace internal 69 } // namespace base 70 71 #endif // BASE_TASK_THREAD_POOL_WORKER_THREAD_SET_H_ 72