62 lines
1.6 KiB
C++
62 lines
1.6 KiB
C++
// Copyright 2018 The Chromium Authors
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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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#ifndef BASE_TASK_SEQUENCE_MANAGER_ENQUEUE_ORDER_H_
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#define BASE_TASK_SEQUENCE_MANAGER_ENQUEUE_ORDER_H_
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#include <stdint.h>
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#include <limits>
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namespace base {
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namespace sequence_manager {
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namespace internal {
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class EnqueueOrderGenerator;
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}
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// 64-bit number which is used to order tasks.
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// SequenceManager assumes this number will never overflow.
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class EnqueueOrder {
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public:
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EnqueueOrder() : value_(kNone) {}
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~EnqueueOrder() = default;
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static EnqueueOrder none() { return EnqueueOrder(kNone); }
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static EnqueueOrder blocking_fence() { return EnqueueOrder(kBlockingFence); }
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// Returns an EnqueueOrder that compares greater than any other EnqueueOrder.
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static EnqueueOrder max() {
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return EnqueueOrder(std::numeric_limits<uint64_t>::max());
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}
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// It's okay to use EnqueueOrder in boolean expressions keeping in mind
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// that some non-zero values have a special meaning.
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operator uint64_t() const { return value_; }
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static EnqueueOrder FromIntForTesting(uint64_t value) {
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return EnqueueOrder(value);
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}
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private:
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// EnqueueOrderGenerator is the only class allowed to create an EnqueueOrder
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// with a non-default constructor.
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friend class internal::EnqueueOrderGenerator;
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explicit EnqueueOrder(uint64_t value) : value_(value) {}
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enum SpecialValues : uint64_t {
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kNone = 0,
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kBlockingFence = 1,
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kFirst = 2,
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};
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uint64_t value_;
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};
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} // namespace sequence_manager
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} // namespace base
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#endif // BASE_TASK_SEQUENCE_MANAGER_ENQUEUE_ORDER_H_
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