The Tor Browser: security/sandbox/chromium/base/task

security/sandbox/chromium/base/task_runner.h@141e0f1194b1 (annotated)

security/sandbox/chromium/base/task_runner.h

Wed, 31 Dec 2014 07:16:47 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 07:16:47 +0100
branch: TOR_BUG_9701
changeset 3: 141e0f1194b1
permissions: -rw-r--r--

Revert simplistic fix pending revisit of Mozilla integration attempt.

 // Copyright (c) 2012 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 BASE_TASK_RUNNER_H_
 #define BASE_TASK_RUNNER_H_
 #include "base/base_export.h"
 #include "base/basictypes.h"
 #include "base/callback_forward.h"
 #include "base/memory/ref_counted.h"
 #include "base/time/time.h"
 namespace tracked_objects {
 class Location;
 } // namespace tracked_objects
 namespace base {
 struct TaskRunnerTraits;
 // A TaskRunner is an object that runs posted tasks (in the form of
 // Closure objects).  The TaskRunner interface provides a way of
 // decoupling task posting from the mechanics of how each task will be
 // run.  TaskRunner provides very weak guarantees as to how posted
 // tasks are run (or if they're run at all).  In particular, it only
 // guarantees:
 //
 //   - Posting a task will not run it synchronously.  That is, no
 //     Post*Task method will call task.Run() directly.
 //
 //   - Increasing the delay can only delay when the task gets run.
 //     That is, increasing the delay may not affect when the task gets
 //     run, or it could make it run later than it normally would, but
 //     it won't make it run earlier than it normally would.
 //
 // TaskRunner does not guarantee the order in which posted tasks are
 // run, whether tasks overlap, or whether they're run on a particular
 // thread.  Also it does not guarantee a memory model for shared data
 // between tasks.  (In other words, you should use your own
 // synchronization/locking primitives if you need to share data
 // between tasks.)
 //
 // Implementations of TaskRunner should be thread-safe in that all
 // methods must be safe to call on any thread.  Ownership semantics
 // for TaskRunners are in general not clear, which is why the
 // interface itself is RefCountedThreadSafe.
 //
 // Some theoretical implementations of TaskRunner:
 //
 //   - A TaskRunner that uses a thread pool to run posted tasks.
 //
 //   - A TaskRunner that, for each task, spawns a non-joinable thread
 //     to run that task and immediately quit.
 //
 //   - A TaskRunner that stores the list of posted tasks and has a
 //     method Run() that runs each runnable task in random order.
 class BASE_EXPORT TaskRunner
     : public RefCountedThreadSafe<TaskRunner, TaskRunnerTraits> {
  public:
   // Posts the given task to be run.  Returns true if the task may be
   // run at some point in the future, and false if the task definitely
   // will not be run.
   //
   // Equivalent to PostDelayedTask(from_here, task, 0).
   bool PostTask(const tracked_objects::Location& from_here,
                 const Closure& task);
   // Like PostTask, but tries to run the posted task only after
   // |delay_ms| has passed.
   //
   // It is valid for an implementation to ignore |delay_ms|; that is,
   // to have PostDelayedTask behave the same as PostTask.
   virtual bool PostDelayedTask(const tracked_objects::Location& from_here,
                                const Closure& task,
                                base::TimeDelta delay) = 0;
   // Returns true if the current thread is a thread on which a task
   // may be run, and false if no task will be run on the current
   // thread.
   //
   // It is valid for an implementation to always return true, or in
   // general to use 'true' as a default value.
   virtual bool RunsTasksOnCurrentThread() const = 0;
   // Posts |task| on the current TaskRunner.  On completion, |reply|
   // is posted to the thread that called PostTaskAndReply().  Both
   // |task| and |reply| are guaranteed to be deleted on the thread
   // from which PostTaskAndReply() is invoked.  This allows objects
   // that must be deleted on the originating thread to be bound into
   // the |task| and |reply| Closures.  In particular, it can be useful
   // to use WeakPtr<> in the |reply| Closure so that the reply
   // operation can be canceled. See the following pseudo-code:
   //
   // class DataBuffer : public RefCountedThreadSafe<DataBuffer> {
   //  public:
   //   // Called to add data into a buffer.
   //   void AddData(void* buf, size_t length);
   //   ...
   // };
   //
   //
   // class DataLoader : public SupportsWeakPtr<DataLoader> {
   //  public:
   //    void GetData() {
   //      scoped_refptr<DataBuffer> buffer = new DataBuffer();
   //      target_thread_.message_loop_proxy()->PostTaskAndReply(
   //          FROM_HERE,
   //          base::Bind(&DataBuffer::AddData, buffer),
   //          base::Bind(&DataLoader::OnDataReceived, AsWeakPtr(), buffer));
   //    }
   //
   //  private:
   //    void OnDataReceived(scoped_refptr<DataBuffer> buffer) {
   //      // Do something with buffer.
   //    }
   // };
   //
   //
   // Things to notice:
   //   * Results of |task| are shared with |reply| by binding a shared argument
   //     (a DataBuffer instance).
   //   * The DataLoader object has no special thread safety.
   //   * The DataLoader object can be deleted while |task| is still running,
   //     and the reply will cancel itself safely because it is bound to a
   //     WeakPtr<>.
   bool PostTaskAndReply(const tracked_objects::Location& from_here,
                         const Closure& task,
                         const Closure& reply);
  protected:
   friend struct TaskRunnerTraits;
   // Only the Windows debug build seems to need this: see
   // http://crbug.com/112250.
   friend class RefCountedThreadSafe<TaskRunner, TaskRunnerTraits>;
   TaskRunner();
   virtual ~TaskRunner();
   // Called when this object should be destroyed.  By default simply
   // deletes |this|, but can be overridden to do something else, like
   // delete on a certain thread.
   virtual void OnDestruct() const;
 };
 struct BASE_EXPORT TaskRunnerTraits {
   static void Destruct(const TaskRunner* task_runner);
 };
 }  // namespace base
 #endif  // BASE_TASK_RUNNER_H_

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security/sandbox/chromium/base/task_runner.h@141e0f1194b1 (annotated)

security/sandbox/chromium/base/task_runner.h