116 lines
3.9 KiB
C++
116 lines
3.9 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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#ifndef BASE_SEQUENCE_TOKEN_H_
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#define BASE_SEQUENCE_TOKEN_H_
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#include "base/base_export.h"
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#include "base/macros.h"
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namespace base {
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// A token that identifies a series of sequenced tasks (i.e. tasks that run one
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// at a time in posting order).
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class BASE_EXPORT SequenceToken {
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public:
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// Instantiates an invalid SequenceToken.
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SequenceToken() = default;
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// Explicitly allow copy.
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SequenceToken(const SequenceToken& other) = default;
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SequenceToken& operator=(const SequenceToken& other) = default;
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// An invalid SequenceToken is not equal to any other SequenceToken, including
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// other invalid SequenceTokens.
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bool operator==(const SequenceToken& other) const;
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bool operator!=(const SequenceToken& other) const;
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// Returns true if this is a valid SequenceToken.
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bool IsValid() const;
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// Returns the integer uniquely representing this SequenceToken. This method
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// should only be used for tracing and debugging.
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int ToInternalValue() const;
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// Returns a valid SequenceToken which isn't equal to any previously returned
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// SequenceToken.
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static SequenceToken Create();
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// Returns the SequenceToken associated with the task running on the current
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// thread, as determined by the active ScopedSetSequenceTokenForCurrentThread
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// if any.
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static SequenceToken GetForCurrentThread();
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private:
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explicit SequenceToken(int token) : token_(token) {}
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static constexpr int kInvalidSequenceToken = -1;
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int token_ = kInvalidSequenceToken;
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};
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// A token that identifies a task.
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//
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// This is used by ThreadCheckerImpl to determine whether calls to
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// CalledOnValidThread() come from the same task and hence are deterministically
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// single-threaded (vs. calls coming from different sequenced or parallel tasks,
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// which may or may not run on the same thread).
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class BASE_EXPORT TaskToken {
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public:
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// Instantiates an invalid TaskToken.
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TaskToken() = default;
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// Explicitly allow copy.
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TaskToken(const TaskToken& other) = default;
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TaskToken& operator=(const TaskToken& other) = default;
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// An invalid TaskToken is not equal to any other TaskToken, including
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// other invalid TaskTokens.
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bool operator==(const TaskToken& other) const;
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bool operator!=(const TaskToken& other) const;
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// Returns true if this is a valid TaskToken.
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bool IsValid() const;
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// In the scope of a ScopedSetSequenceTokenForCurrentThread, returns a valid
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// TaskToken which isn't equal to any TaskToken returned in the scope of a
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// different ScopedSetSequenceTokenForCurrentThread. Otherwise, returns an
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// invalid TaskToken.
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static TaskToken GetForCurrentThread();
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private:
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friend class ScopedSetSequenceTokenForCurrentThread;
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explicit TaskToken(int token) : token_(token) {}
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// Returns a valid TaskToken which isn't equal to any previously returned
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// TaskToken. This is private as it only meant to be instantiated by
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// ScopedSetSequenceTokenForCurrentThread.
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static TaskToken Create();
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static constexpr int kInvalidTaskToken = -1;
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int token_ = kInvalidTaskToken;
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};
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// Instantiate this in the scope where a single task runs.
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class BASE_EXPORT ScopedSetSequenceTokenForCurrentThread {
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public:
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// Throughout the lifetime of the constructed object,
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// SequenceToken::GetForCurrentThread() will return |sequence_token| and
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// TaskToken::GetForCurrentThread() will return a TaskToken which is not equal
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// to any TaskToken returned in the scope of another
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// ScopedSetSequenceTokenForCurrentThread.
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ScopedSetSequenceTokenForCurrentThread(const SequenceToken& sequence_token);
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~ScopedSetSequenceTokenForCurrentThread();
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private:
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const SequenceToken sequence_token_;
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const TaskToken task_token_;
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DISALLOW_COPY_AND_ASSIGN(ScopedSetSequenceTokenForCurrentThread);
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};
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} // namespace base
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#endif // BASE_SEQUENCE_TOKEN_H_
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