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110 lines
3.5 KiB
C++
110 lines
3.5 KiB
C++
// Copyright 2016 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "base/task_scheduler/priority_queue.h"
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#include <utility>
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#include "base/logging.h"
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#include "base/memory/ptr_util.h"
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namespace base {
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namespace internal {
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// A class combining a Sequence and the SequenceSortKey that determines its
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// position in a PriorityQueue. Instances are only mutable via take_sequence()
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// which can only be called once and renders its instance invalid after the
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// call.
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class PriorityQueue::SequenceAndSortKey {
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public:
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SequenceAndSortKey(scoped_refptr<Sequence> sequence,
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const SequenceSortKey& sort_key)
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: sequence_(std::move(sequence)), sort_key_(sort_key) {
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DCHECK(sequence_);
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}
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// Note: while |sequence_| should always be non-null post-move (i.e. we
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// shouldn't be moving an invalid SequenceAndSortKey around), there can't be a
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// DCHECK(sequence_) on moves as the Windows STL moves elements on pop instead
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// of overwriting them: resulting in the move of a SequenceAndSortKey with a
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// null |sequence_| in Transaction::Pop()'s implementation.
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SequenceAndSortKey(SequenceAndSortKey&& other) = default;
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SequenceAndSortKey& operator=(SequenceAndSortKey&& other) = default;
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// Extracts |sequence_| from this object. This object is invalid after this
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// call.
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scoped_refptr<Sequence> take_sequence() {
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DCHECK(sequence_);
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return std::move(sequence_);
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}
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// Compares this SequenceAndSortKey to |other| based on their respective
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// |sort_key_|.
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bool operator<(const SequenceAndSortKey& other) const {
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return sort_key_ < other.sort_key_;
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}
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bool operator>(const SequenceAndSortKey& other) const {
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return other < *this;
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}
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const SequenceSortKey& sort_key() const { return sort_key_; }
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private:
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scoped_refptr<Sequence> sequence_;
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SequenceSortKey sort_key_;
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DISALLOW_COPY_AND_ASSIGN(SequenceAndSortKey);
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};
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PriorityQueue::Transaction::Transaction(PriorityQueue* outer_queue)
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: auto_lock_(outer_queue->container_lock_), outer_queue_(outer_queue) {
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}
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PriorityQueue::Transaction::~Transaction() = default;
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void PriorityQueue::Transaction::Push(
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scoped_refptr<Sequence> sequence,
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const SequenceSortKey& sequence_sort_key) {
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outer_queue_->container_.emplace(std::move(sequence), sequence_sort_key);
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}
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const SequenceSortKey& PriorityQueue::Transaction::PeekSortKey() const {
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DCHECK(!IsEmpty());
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return outer_queue_->container_.top().sort_key();
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}
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scoped_refptr<Sequence> PriorityQueue::Transaction::PopSequence() {
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DCHECK(!IsEmpty());
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// The const_cast on top() is okay since the SequenceAndSortKey is
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// transactionally being popped from |container_| right after and taking its
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// Sequence does not alter its sort order (a requirement for the Windows STL's
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// consistency debug-checks for std::priority_queue::top()).
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scoped_refptr<Sequence> sequence =
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const_cast<PriorityQueue::SequenceAndSortKey&>(
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outer_queue_->container_.top())
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.take_sequence();
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outer_queue_->container_.pop();
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return sequence;
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}
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bool PriorityQueue::Transaction::IsEmpty() const {
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return outer_queue_->container_.empty();
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}
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size_t PriorityQueue::Transaction::Size() const {
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return outer_queue_->container_.size();
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}
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PriorityQueue::PriorityQueue() = default;
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PriorityQueue::~PriorityQueue() = default;
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std::unique_ptr<PriorityQueue::Transaction> PriorityQueue::BeginTransaction() {
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return WrapUnique(new Transaction(this));
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}
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} // namespace internal
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} // namespace base
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