1 // Copyright 2017 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_PUBLIC_CPP_BINDINGS_SYNC_EVENT_WATCHER_H_ 6 #define MOJO_PUBLIC_CPP_BINDINGS_SYNC_EVENT_WATCHER_H_ 7 8 #include <stddef.h> 9 10 #include "base/callback.h" 11 #include "base/macros.h" 12 #include "base/memory/ref_counted.h" 13 #include "base/sequence_checker.h" 14 #include "base/synchronization/waitable_event.h" 15 #include "mojo/public/cpp/bindings/bindings_export.h" 16 #include "mojo/public/cpp/bindings/sync_handle_registry.h" 17 18 namespace mojo { 19 20 // SyncEventWatcher supports waiting on a base::WaitableEvent to signal while 21 // also allowing other SyncEventWatchers and SyncHandleWatchers on the same 22 // sequence to wake up as needed. 23 // 24 // This class is not thread safe. 25 class MOJO_CPP_BINDINGS_EXPORT SyncEventWatcher { 26 public: 27 SyncEventWatcher(base::WaitableEvent* event, const base::Closure& callback); 28 29 ~SyncEventWatcher(); 30 31 // Registers |event_| with SyncHandleRegistry, so that when others perform 32 // sync watching on the same sequence, |event_| will be watched along with 33 // them. 34 void AllowWokenUpBySyncWatchOnSameThread(); 35 36 // Waits on |event_| plus all other events and handles registered with this 37 // sequence's SyncHandleRegistry, running callbacks synchronously for any 38 // ready events and handles. 39 // 40 // |stop_flags| is treated as an array of |const bool*| with |num_stop_flags| 41 // entries. 42 // 43 // This method: 44 // - returns true when any flag in |stop_flags| is set to |true|. 45 // - return false when any error occurs, including this object being 46 // destroyed during a callback. 47 bool SyncWatch(const bool** stop_flags, size_t num_stop_flags); 48 49 private: 50 void IncrementRegisterCount(); 51 void DecrementRegisterCount(); 52 53 base::WaitableEvent* const event_; 54 const base::Closure callback_; 55 56 // Whether |event_| has been registered with SyncHandleRegistry. 57 bool registered_ = false; 58 59 // If non-zero, |event_| should be registered with SyncHandleRegistry. 60 size_t register_request_count_ = 0; 61 62 scoped_refptr<SyncHandleRegistry> registry_; 63 64 scoped_refptr<base::RefCountedData<bool>> destroyed_; 65 66 SEQUENCE_CHECKER(sequence_checker_); 67 68 DISALLOW_COPY_AND_ASSIGN(SyncEventWatcher); 69 }; 70 71 } // namespace mojo 72 73 #endif // MOJO_PUBLIC_CPP_BINDINGS_SYNC_EVENT_WATCHER_H_ 74