Rename ChromeThread to BrowserThread Part3:

chrome/browser/browser_thread.h

+// Copyright (c) 2009 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.
+
+#ifndef CHROME_BROWSER_BROWSER_THREAD_H_
+#define CHROME_BROWSER_BROWSER_THREAD_H_
+#pragma once
+
+#include "base/lock.h"
+#include "base/task.h"
+#include "base/thread.h"
+
+namespace base {
+class MessageLoopProxy;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// ChromeThread
+//
+// This class represents a thread that is known by a browser-wide name.  For
+// example, there is one IO thread for the entire browser process, and various
+// pieces of code find it useful to retrieve a pointer to the IO thread's
+// Invoke a task by thread ID:
+//
+//   ChromeThread::PostTask(ChromeThread::IO, FROM_HERE, task);
+//
+// The return value is false if the task couldn't be posted because the target
+// thread doesn't exist.  If this could lead to data loss, you need to check the
+// result and restructure the code to ensure it doesn't occur.
+//
+// This class automatically handles the lifetime of different threads.
+// It's always safe to call PostTask on any thread.  If it's not yet created,
+// the task is deleted.  There are no race conditions.  If the thread that the
+// task is posted to is guaranteed to outlive the current thread, then no locks
+// are used.  You should never need to cache pointers to MessageLoops, since
+// they're not thread safe.
+class ChromeThread : public base::Thread {
+ public:
+  // An enumeration of the well-known threads.
+  // NOTE: threads must be listed in the order of their life-time, with each
+  // thread outliving every other thread below it.
+  enum ID {
+    // The main thread in the browser.
+    UI,
+
+    // This is the thread that interacts with the database.
+    DB,
+
+    // This is the "main" thread for WebKit within the browser process when
+    // NOT in --single-process mode.
+    WEBKIT,
+
+    // This is the thread that interacts with the file system.
+    FILE,
+
+    // Used to launch and terminate processes.
+    PROCESS_LAUNCHER,
+
+    // This is the thread to handle slow HTTP cache operations.
+    CACHE,
+
+    // This is the thread that processes IPC and network messages.
+    IO,
+
+#if defined(USE_X11)
+    // This thread has a second connection to the X server and is used to
+    // process UI requests when routing the request to the UI thread would risk
+    // deadlock.
+    BACKGROUND_X11,
+#endif
+
+    // This identifier does not represent a thread.  Instead it counts the
+    // number of well-known threads.  Insert new well-known threads before this
+    // identifier.
+    ID_COUNT
+  };
+
+  // Construct a ChromeThread with the supplied identifier.  It is an error
+  // to construct a ChromeThread that already exists.
+  explicit ChromeThread(ID identifier);
+
+  // Special constructor for the main (UI) thread and unittests. We use a dummy
+  // thread here since the main thread already exists.
+  ChromeThread(ID identifier, MessageLoop* message_loop);
+
+  virtual ~ChromeThread();
+
+  // These are the same methods in message_loop.h, but are guaranteed to either
+  // get posted to the MessageLoop if it's still alive, or be deleted otherwise.
+  // They return true iff the thread existed and the task was posted.  Note that
+  // even if the task is posted, there's no guarantee that it will run, since
+  // the target thread may already have a Quit message in its queue.
+  static bool PostTask(ID identifier,
+                       const tracked_objects::Location& from_here,
+                       Task* task);
+  static bool PostDelayedTask(ID identifier,
+                              const tracked_objects::Location& from_here,
+                              Task* task,
+                              int64 delay_ms);
+  static bool PostNonNestableTask(ID identifier,
+                                  const tracked_objects::Location& from_here,
+                                  Task* task);
+  static bool PostNonNestableDelayedTask(
+      ID identifier,
+      const tracked_objects::Location& from_here,
+      Task* task,
+      int64 delay_ms);
+
+  template <class T>
+  static bool DeleteSoon(ID identifier,
+                         const tracked_objects::Location& from_here,
+                         T* object) {
+    return PostNonNestableTask(
+        identifier, from_here, new DeleteTask<T>(object));
+  }
+
+  template <class T>
+  static bool ReleaseSoon(ID identifier,
+                          const tracked_objects::Location& from_here,
+                          T* object) {
+    return PostNonNestableTask(
+        identifier, from_here, new ReleaseTask<T>(object));
+  }
+
+  // Callable on any thread.  Returns whether the given ID corresponds to a well
+  // known thread.
+  static bool IsWellKnownThread(ID identifier);
+
+  // Callable on any thread.  Returns whether you're currently on a particular
+  // thread.
+  static bool CurrentlyOn(ID identifier);
+
+  // Callable on any thread.  Returns whether the threads message loop is valid.
+  // If this returns false it means the thread is in the process of shutting
+  // down.
+  static bool IsMessageLoopValid(ID identifier);
+
+  // If the current message loop is one of the known threads, returns true and
+  // sets identifier to its ID.  Otherwise returns false.
+  static bool GetCurrentThreadIdentifier(ID* identifier);
+
+  // Callers can hold on to a refcounted MessageLoopProxy beyond the lifetime
+  // of the thread.
+  static scoped_refptr<base::MessageLoopProxy> GetMessageLoopProxyForThread(
+      ID identifier);
+
+  // Use these templates in conjuction with RefCountedThreadSafe when you want
+  // to ensure that an object is deleted on a specific thread.  This is needed
+  // when an object can hop between threads (i.e. IO -> FILE -> IO), and thread
+  // switching delays can mean that the final IO tasks executes before the FILE
+  // task's stack unwinds.  This would lead to the object destructing on the
+  // FILE thread, which often is not what you want (i.e. to unregister from
+  // NotificationService, to notify other objects on the creating thread etc).
+  template<ID thread>
+  struct DeleteOnThread {
+    template<typename T>
+    static void Destruct(T* x) {
+      if (CurrentlyOn(thread)) {
+        delete x;
+      } else {
+        DeleteSoon(thread, FROM_HERE, x);
+      }
+    }
+  };
+
+  // Sample usage:
+  // class Foo
+  //     : public base::RefCountedThreadSafe<
+  //           Foo, ChromeThread::DeleteOnIOThread> {
+  //
+  // ...
+  //  private:
+  //   friend struct ChromeThread::DeleteOnThread<ChromeThread::IO>;
+  //   friend class DeleteTask<Foo>;
+  //
+  //   ~Foo();
+  struct DeleteOnUIThread : public DeleteOnThread<UI> { };
+  struct DeleteOnIOThread : public DeleteOnThread<IO> { };
+  struct DeleteOnFileThread : public DeleteOnThread<FILE> { };
+  struct DeleteOnDBThread : public DeleteOnThread<DB> { };
+  struct DeleteOnWebKitThread : public DeleteOnThread<WEBKIT> { };
+
+ private:
+  // Common initialization code for the constructors.
+  void Initialize();
+
+  static bool PostTaskHelper(
+      ID identifier,
+      const tracked_objects::Location& from_here,
+      Task* task,
+      int64 delay_ms,
+      bool nestable);
+
+  // The identifier of this thread.  Only one thread can exist with a given
+  // identifier at a given time.
+  ID identifier_;
+
+  // This lock protects |chrome_threads_|.  Do not read or modify that array
+  // without holding this lock.  Do not block while holding this lock.
+  static Lock lock_;
+
+  // An array of the ChromeThread objects.  This array is protected by |lock_|.
+  // The threads are not owned by this array.  Typically, the threads are owned
+  // on the UI thread by the g_browser_process object.  ChromeThreads remove
+  // themselves from this array upon destruction.
+  static ChromeThread* chrome_threads_[ID_COUNT];
+};
+
+typedef ChromeThread BrowserThread;
+
+#endif  // CHROME_BROWSER_CHROME_THREAD_H_