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// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_TASK_SCHEDULER_SCHEDULER_WORKER_STACK_H_
#define BASE_TASK_SCHEDULER_SCHEDULER_WORKER_STACK_H_
#include <stddef.h>
#include <vector>
#include "base/base_export.h"
#include "base/macros.h"
namespace base {
namespace internal {
class SchedulerWorker;
// A stack of SchedulerWorkers which has custom logic to treat the worker on top
// of the stack as being "in-use" (so its time in that position doesn't count
// towards being inactive / reclaimable). Supports removal of arbitrary
// SchedulerWorkers. DCHECKs when a SchedulerWorker is inserted multiple times.
// SchedulerWorkers are not owned by the stack. Push() is amortized O(1). Pop(),
// Peek(), Size() and Empty() are O(1). Contains() and Remove() are O(n). This
// class is NOT thread-safe.
class BASE_EXPORT SchedulerWorkerStack {
public:
SchedulerWorkerStack();
~SchedulerWorkerStack();
// Inserts |worker| at the top of the stack. |worker| must not already be on
// the stack. Flags the SchedulerWorker previously on top of the stack, if
// any, as unused.
void Push(SchedulerWorker* worker);
// Removes the top SchedulerWorker from the stack and returns it. Returns
// nullptr if the stack is empty. Flags the SchedulerWorker now on top of the
// stack, if any, as being in-use.
SchedulerWorker* Pop();
// Returns the top SchedulerWorker from the stack, nullptr if empty.
SchedulerWorker* Peek() const;
// Returns true if |worker| is already on the stack.
bool Contains(const SchedulerWorker* worker) const;
// Removes |worker| from the stack. Must not be invoked for the first worker
// on the stack.
void Remove(const SchedulerWorker* worker);
// Returns the number of SchedulerWorkers on the stack.
size_t Size() const { return stack_.size(); }
// Returns true if the stack is empty.
bool IsEmpty() const { return stack_.empty(); }
private:
std::vector<SchedulerWorker*> stack_;
DISALLOW_COPY_AND_ASSIGN(SchedulerWorkerStack);
};
} // namespace internal
} // namespace base
#endif // BASE_TASK_SCHEDULER_SCHEDULER_WORKER_STACK_H_
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