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

     1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.

     2 // Use of this source code is governed by a BSD-style license that can be

     3 // found in the LICENSE file.

     5 #ifndef BASE_SEQUENCED_TASK_RUNNER_HELPERS_H_

     6 #define BASE_SEQUENCED_TASK_RUNNER_HELPERS_H_

     8 #include "base/basictypes.h"

    10 // TODO(akalin): Investigate whether it's possible to just have

    11 // SequencedTaskRunner use these helpers (instead of MessageLoop).

    12 // Then we can just move these to sequenced_task_runner.h.

    14 namespace tracked_objects {

    15 class Location;

    16 }

    18 namespace base {

    20 namespace subtle {

    21 template <class T, class R> class DeleteHelperInternal;

    22 template <class T, class R> class ReleaseHelperInternal;

    23 }

    25 // Template helpers which use function indirection to erase T from the

    26 // function signature while still remembering it so we can call the

    27 // correct destructor/release function.

    28 //

    29 // We use this trick so we don't need to include bind.h in a header

    30 // file like sequenced_task_runner.h. We also wrap the helpers in a

    31 // templated class to make it easier for users of DeleteSoon to

    32 // declare the helper as a friend.

    33 template <class T>

    34 class DeleteHelper {

    35  private:

    36   template <class T2, class R> friend class subtle::DeleteHelperInternal;

    38   static void DoDelete(const void* object) {

    39     delete reinterpret_cast<const T*>(object);

    40   }

    42   DISALLOW_COPY_AND_ASSIGN(DeleteHelper);

    43 };

    45 template <class T>

    46 class ReleaseHelper {

    47  private:

    48   template <class T2, class R> friend class subtle::ReleaseHelperInternal;

    50   static void DoRelease(const void* object) {

    51     reinterpret_cast<const T*>(object)->Release();

    52   }

    54   DISALLOW_COPY_AND_ASSIGN(ReleaseHelper);

    55 };

    57 namespace subtle {

    59 // An internal SequencedTaskRunner-like class helper for DeleteHelper

    60 // and ReleaseHelper.  We don't want to expose the Do*() functions

    61 // directly directly since the void* argument makes it possible to

    62 // pass/ an object of the wrong type to delete.  Instead, we force

    63 // callers to go through these internal helpers for type

    64 // safety. SequencedTaskRunner-like classes which expose DeleteSoon or

    65 // ReleaseSoon methods should friend the appropriate helper and

    66 // implement a corresponding *Internal method with the following

    67 // signature:

    68 //

    69 // bool(const tracked_objects::Location&,

    70 //      void(*function)(const void*),

    71 //      void* object)

    72 //

    73 // An implementation of this function should simply create a

    74 // base::Closure from (function, object) and return the result of

    75 // posting the task.

    76 template <class T, class ReturnType>

    77 class DeleteHelperInternal {

    78  public:

    79   template <class SequencedTaskRunnerType>

    80   static ReturnType DeleteViaSequencedTaskRunner(

    81       SequencedTaskRunnerType* sequenced_task_runner,

    82       const tracked_objects::Location& from_here,

    83       const T* object) {

    84     return sequenced_task_runner->DeleteSoonInternal(

    85         from_here, &DeleteHelper<T>::DoDelete, object);

    86   }

    88  private:

    89   DISALLOW_COPY_AND_ASSIGN(DeleteHelperInternal);

    90 };

    92 template <class T, class ReturnType>

    93 class ReleaseHelperInternal {

    94  public:

    95   template <class SequencedTaskRunnerType>

    96   static ReturnType ReleaseViaSequencedTaskRunner(

    97       SequencedTaskRunnerType* sequenced_task_runner,

    98       const tracked_objects::Location& from_here,

    99       const T* object) {

   100     return sequenced_task_runner->ReleaseSoonInternal(

   101         from_here, &ReleaseHelper<T>::DoRelease, object);

   102   }

   104  private:

   105   DISALLOW_COPY_AND_ASSIGN(ReleaseHelperInternal);

   106 };

   108 }  // namespace subtle

   110 }  // namespace base

   112 #endif  // BASE_SEQUENCED_TASK_RUNNER_HELPERS_H_

The Tor Browser / file revision