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