blob: f6b71d7b2070e92e1d1dea1cd04c5902ca6ea367 [file] [log] [blame]
// 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 "base/base_export.h"
#include "base/callback_helpers.h"
#include "base/compiler_specific.h"
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/single_thread_task_runner.h"
namespace base {
// ThreadTaskRunnerHandle stores a reference to a thread's TaskRunner
// in thread-local storage. Callers can then retrieve the TaskRunner
// for the current thread by calling ThreadTaskRunnerHandle::Get().
// At most one TaskRunner may be bound to each thread at a time.
// Prefer SequencedTaskRunnerHandle to this unless thread affinity is required.
class BASE_EXPORT ThreadTaskRunnerHandle {
// Gets the SingleThreadTaskRunner for the current thread.
static scoped_refptr<SingleThreadTaskRunner> Get();
// Returns true if the SingleThreadTaskRunner is already created for
// the current thread.
static bool IsSet();
// Overrides ThreadTaskRunnerHandle::Get()'s |task_runner_| to point at
// |overriding_task_runner| until the returned ScopedClosureRunner goes out of
// scope (instantiates a ThreadTaskRunnerHandle for that scope if |!IsSet()|).
// Nested overrides are allowed but callers must ensure the
// ScopedClosureRunners expire in LIFO (stack) order. Note: nesting
// ThreadTaskRunnerHandles isn't generally desired but it's useful in unit
// tests where multiple task runners can share the main thread for simplicity
// and determinism.
static ScopedClosureRunner OverrideForTesting(
scoped_refptr<SingleThreadTaskRunner> overriding_task_runner)
// Binds |task_runner| to the current thread. |task_runner| must belong
// to the current thread for this to succeed.
explicit ThreadTaskRunnerHandle(
scoped_refptr<SingleThreadTaskRunner> task_runner);
scoped_refptr<SingleThreadTaskRunner> task_runner_;
} // namespace base