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+// Copyright (c) 2010 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.
+
+#ifndef BASE_THREADING_SIMPLE_THREAD_H_
+#define BASE_THREADING_SIMPLE_THREAD_H_
+#pragma once
+
+#include <string>
+#include <queue>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/lock.h"
+#include "base/waitable_event.h"
+#include "base/platform_thread.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 SimpleThread : public PlatformThread::Delegate {
+ public:
+  class Options {
+   public:
+    Options() : stack_size_(0) { }
+    ~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_; }
+   private:
+    size_t stack_size_;
+  };
+
+  // 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();
+
+  // We follow the PlatformThread Delegate interface.
+  virtual void ThreadMain();
+
+  // 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_; }
+
+  // Return the thread id, only valid after Start().
+  PlatformThreadId tid() { return tid_; }
+
+  // Return True if Start() has ever been called.
+  bool HasBeenStarted() { return event_.IsSignaled(); }
+
+  // Return True if Join() has evern been called.
+  bool HasBeenJoined() { return joined_; }
+
+ private:
+  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 DelegateSimpleThread : public SimpleThread {
+ public:
+  class Delegate {
+   public:
+    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();
+ private:
+  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 DelegateSimpleThreadPool : public DelegateSimpleThread::Delegate {
+ public:
+  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();
+
+ private:
+  const std::string name_prefix_;
+  int num_threads_;
+  std::vector<DelegateSimpleThread*> threads_;
+  std::queue<Delegate*> delegates_;
+  Lock lock_;            // Locks delegates_
+  WaitableEvent dry_;    // Not signaled when there is no work to do.
+};
+
+}  // namespace base
+
+#endif  // BASE_THREADING_SIMPLE_THREAD_H_