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// Copyright 2016 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_TASK_THREAD_POOL_WORKER_THREAD_SET_H_
#define BASE_TASK_THREAD_POOL_WORKER_THREAD_SET_H_
#include <stddef.h>
#include <set>
#include "base/base_export.h"
#include "base/memory/raw_ptr.h"
namespace base {
namespace internal {
class WorkerThread;
// An ordered set of WorkerThreads which has custom logic to treat the worker at
// the front of the set as being "in-use" (so its time in that position doesn't
// count towards being inactive / reclaimable). Supports removal of arbitrary
// WorkerThreads. DCHECKs when a WorkerThread is inserted multiple times.
// WorkerThreads are not owned by the set. All operations are amortized
// O(log(n)). This class is NOT thread-safe.
class BASE_EXPORT WorkerThreadSet {
struct Compare {
bool operator()(const WorkerThread* a, const WorkerThread* b) const;
};
public:
WorkerThreadSet();
WorkerThreadSet(const WorkerThreadSet&) = delete;
WorkerThreadSet& operator=(const WorkerThreadSet&) = delete;
~WorkerThreadSet();
// Inserts |worker| in the set. |worker| must not already be on the set. Flags
// the WorkerThread previously at the front of the set, if it
// changed, or |worker| as unused.
void Insert(WorkerThread* worker);
// Removes the front WorkerThread from the set and returns it. Returns nullptr
// if the set is empty. Flags the WorkerThread now at the front of the set, if
// any, as being in-use.
WorkerThread* Take();
// Returns the front WorkerThread from the set, nullptr if empty.
WorkerThread* Peek() const;
// Returns true if |worker| is already in the set.
bool Contains(const WorkerThread* worker) const;
// Removes |worker| from the set. Must not be invoked for the first worker
// on the set.
void Remove(const WorkerThread* worker);
// Returns the number of WorkerThreads on the set.
size_t Size() const { return set_.size(); }
// Returns true if the set is empty.
bool IsEmpty() const { return set_.empty(); }
private:
std::set<raw_ptr<WorkerThread, SetExperimental>, Compare> set_;
};
} // namespace internal
} // namespace base
#endif // BASE_TASK_THREAD_POOL_WORKER_THREAD_SET_H_
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