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// Copyright (c) 2011 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.
// WARNING: You should probably be using Thread (thread.h) instead. Thread is
// Chrome's message-loop based Thread abstraction, and if you are a
// thread running in the browser, there will likely be assumptions
// that your thread will have an associated message loop.
// This is a simple thread interface that backs to a native operating system
// thread. You should use this only when you want a thread that does not have
// an associated MessageLoop. Unittesting is the best example of this.
// The simplest interface to use is DelegateSimpleThread, which will create
// a new thread, and execute the Delegate's virtual Run() in this new thread
// until it has completed, exiting the thread.
// NOTE: You *MUST* call Join on the thread to clean up the underlying thread
// resources. You are also responsible for destructing the SimpleThread object.
// It is invalid to destroy a SimpleThread while it is running, or without
// Start() having been called (and a thread never created). The Delegate
// object should live as long as a DelegateSimpleThread.
// Thread Safety: A SimpleThread is not completely thread safe. It is safe to
// access it from the creating thread or from the newly created thread. This
// implies that the creator thread should be the thread that calls Join.
// Example:
// class MyThreadRunner : public DelegateSimpleThread::Delegate { ... };
// MyThreadRunner runner;
// DelegateSimpleThread thread(&runner, "good_name_here");
// thread.Start();
// // Start will return after the Thread has been successfully started and
// // initialized. The newly created thread will invoke runner->Run(), and
// // run until it returns.
// thread.Join(); // Wait until the thread has exited. You *MUST* Join!
// // The SimpleThread object is still valid, however you may not call Join
// // or Start again.
#include <string>
#include <queue>
#include <vector>
#include "base/base_export.h"
#include "base/basictypes.h"
#include "base/compiler_specific.h"
#include "base/threading/platform_thread.h"
#include "base/synchronization/lock.h"
#include "base/synchronization/waitable_event.h"
namespace base {
// This is the base SimpleThread. You can derive from it and implement the
// virtual Run method, or you can use the DelegateSimpleThread interface.
class BASE_EXPORT SimpleThread : public PlatformThread::Delegate {
class BASE_EXPORT Options {
Options() : stack_size_(0), priority_(kThreadPriority_Default),
affinity_(kNoThreadAffinity) { }
Options(size_t stack_size, ThreadPriority priority)
: stack_size_(stack_size), priority_(priority),
affinity_(kNoThreadAffinity) { }
Options(size_t stack_size, ThreadPriority priority, ThreadAffinity affinity)
: stack_size_(stack_size), priority_(priority), affinity_(affinity) { }
~Options() { }
// We use the standard compiler-supplied copy constructor.
// A custom stack size, or 0 for the system default.
void set_stack_size(size_t size) { stack_size_ = size; }
size_t stack_size() const { return stack_size_; }
// Thread priority
void set_priority(ThreadPriority priority) { priority_ = priority; }
ThreadPriority priority() const { return priority_; }
// Core affinity
void set_affinity(ThreadAffinity affinity) { affinity_ = affinity; }
ThreadAffinity affinity() const { return affinity_; }
size_t stack_size_;
ThreadPriority priority_;
ThreadAffinity affinity_;
// Create a SimpleThread. |options| should be used to manage any specific
// configuration involving the thread creation and management.
// Every thread has a name, in the form of |name_prefix|/TID, for example
// "my_thread/321". The thread will not be created until Start() is called.
explicit SimpleThread(const std::string& name_prefix);
SimpleThread(const std::string& name_prefix, const Options& options);
virtual ~SimpleThread();
virtual void Start();
virtual void Join();
// Subclasses should override the Run method.
virtual void Run() = 0;
// Return the thread name prefix, or "unnamed" if none was supplied.
std::string name_prefix() { return name_prefix_; }
// Return the completed name including TID, only valid after Start().
std::string name() { return name_; }
// The native thread handle.
PlatformThreadHandle thread_handle() { return thread_; }
// Return the thread id, only valid after Start().
PlatformThreadId tid() { return tid_; }
// Return True if Start() has ever been called.
bool HasBeenStarted();
// Return True if Join() has evern been called.
bool HasBeenJoined() { return joined_; }
// Overridden from PlatformThread::Delegate:
virtual void ThreadMain() override;
// Only set priorities with a careful understanding of the consequences.
// This is meant for very limited use cases.
void SetThreadPriority(ThreadPriority priority) {
PlatformThread::SetThreadPriority(thread_, priority);
const std::string name_prefix_;
std::string name_;
const Options options_;
PlatformThreadHandle thread_; // PlatformThread handle, invalid after Join!
WaitableEvent event_; // Signaled if Start() was ever called.
PlatformThreadId tid_; // The backing thread's id.
bool joined_; // True if Join has been called.
class BASE_EXPORT DelegateSimpleThread : public SimpleThread {
class BASE_EXPORT Delegate {
Delegate() { }
virtual ~Delegate() { }
virtual void Run() = 0;
DelegateSimpleThread(Delegate* delegate,
const std::string& name_prefix);
DelegateSimpleThread(Delegate* delegate,
const std::string& name_prefix,
const Options& options);
virtual ~DelegateSimpleThread();
virtual void Run() override;
Delegate* delegate_;
// DelegateSimpleThreadPool allows you to start up a fixed number of threads,
// and then add jobs which will be dispatched to the threads. This is
// convenient when you have a lot of small work that you want done
// multi-threaded, but don't want to spawn a thread for each small bit of work.
// You just call AddWork() to add a delegate to the list of work to be done.
// JoinAll() will make sure that all outstanding work is processed, and wait
// for everything to finish. You can reuse a pool, so you can call Start()
// again after you've called JoinAll().
class BASE_EXPORT DelegateSimpleThreadPool
: public DelegateSimpleThread::Delegate {
typedef DelegateSimpleThread::Delegate Delegate;
DelegateSimpleThreadPool(const std::string& name_prefix, int num_threads);
virtual ~DelegateSimpleThreadPool();
// Start up all of the underlying threads, and start processing work if we
// have any.
void Start();
// Make sure all outstanding work is finished, and wait for and destroy all
// of the underlying threads in the pool.
void JoinAll();
// It is safe to AddWork() any time, before or after Start().
// Delegate* should always be a valid pointer, NULL is reserved internally.
void AddWork(Delegate* work, int repeat_count);
void AddWork(Delegate* work) {
AddWork(work, 1);
// We implement the Delegate interface, for running our internal threads.
virtual void Run() override;
const std::string name_prefix_;
int num_threads_;
std::vector<DelegateSimpleThread*> threads_;
std::queue<Delegate*> delegates_;
base::Lock lock_; // Locks delegates_
WaitableEvent dry_; // Not signaled when there is no work to do.
} // namespace base