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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.
#include <stddef.h>
#include <vector>
#include "base/base_export.h"
#include "base/macros.h"
namespace base {
namespace internal {
class SchedulerWorker;
// A stack of SchedulerWorkers. 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 {
// Inserts |worker| at the top of the stack. |worker| must not already be on
// the stack.
void Push(SchedulerWorker* worker);
// Removes the top SchedulerWorker from the stack and returns it.
// Returns nullptr if the stack is empty.
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.
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(); }
std::vector<SchedulerWorker*> stack_;
} // namespace internal
} // namespace base