Home | History | Annotate | Download | only in system 
      1 // Copyright 2013 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.
      4 
      5 #ifndef MOJO_SYSTEM_WAITER_H_
      6 #define MOJO_SYSTEM_WAITER_H_
      7 
      8 #include "base/basictypes.h"
      9 #include "base/synchronization/condition_variable.h"
     10 #include "base/synchronization/lock.h"
     11 #include "mojo/public/system/core.h"
     12 #include "mojo/system/system_impl_export.h"
     13 
     14 namespace mojo {
     15 namespace system {
     16 
     17 // IMPORTANT (all-caps gets your attention, right?): |Waiter| methods are called
     18 // under other locks, in particular, |Dispatcher::lock_|s, so |Waiter| methods
     19 // must never call out to other objects (in particular, |Dispatcher|s). This
     20 // class is thread-safe.
     21 class MOJO_SYSTEM_IMPL_EXPORT Waiter {
     22  public:
     23   Waiter();
     24   ~Waiter();
     25 
     26   // A |Waiter| can be used multiple times; |Init()| should be called before
     27   // each time it's used.
     28   void Init();
     29 
     30   // Waits until a suitable |Awake()| is called.
     31   // Returns:
     32   //  - The |wake_result| passed to |Dispatcher::AddWaiter()| if it was woken up
     33   //    by that dispatcher for the reason specified by |flags| (in the call to
     34   //    |AddWaiter()|).
     35   //  - |MOJO_RESULT_CANCELLED| if a handle (on which |MojoWait()| was called)
     36   //    was closed; and
     37   //  - |MOJO_RESULT_FAILED_PRECONDITION| if the reasons for being awoken given
     38   //    by |flags| cannot (or can no longer) be satisfied (e.g., if the other
     39   //    end of a pipe is closed).
     40   MojoResult Wait(MojoDeadline deadline);
     41 
     42   // Wake the waiter up with the given result (or no-op if it's been woken up
     43   // already).
     44   void Awake(MojoResult wait_result);
     45 
     46  private:
     47   base::ConditionVariable cv_;  // Associated to |lock_|.
     48   base::Lock lock_;  // Protects the following members.
     49 #ifndef NDEBUG
     50   bool initialized_;
     51 #endif
     52   bool awoken_;
     53   MojoResult wait_result_;
     54 
     55   DISALLOW_COPY_AND_ASSIGN(Waiter);
     56 };
     57 
     58 }  // namespace system
     59 }  // namespace mojo
     60 
     61 #endif  // MOJO_SYSTEM_WAITER_H_
     62