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 // MemoryPressure provides static APIs for handling memory pressure on 6 // platforms that have such signals, such as Android. 7 // The app will try to discard buffers that aren't deemed essential (individual 8 // modules will implement their own policy). 9 // 10 // Refer to memory_pressure_level_list.h for information about what sorts of 11 // signals can be sent under what conditions. 12 13 #ifndef BASE_MEMORY_PRESSURE_LISTENER_H_ 14 #define BASE_MEMORY_PRESSURE_LISTENER_H_ 15 16 #include "base/base_export.h" 17 #include "base/basictypes.h" 18 #include "base/callback.h" 19 20 namespace base { 21 22 // To start listening, create a new instance, passing a callback to a 23 // function that takes a MemoryPressureLevel parameter. To stop listening, 24 // simply delete the listener object. The implementation guarantees 25 // that the callback will always be called on the thread that created 26 // the listener. 27 // Note that even on the same thread, the callback is not guaranteed to be 28 // called synchronously within the system memory pressure broadcast. 29 // Please see notes on memory_pressure_level_list.h: some levels are absolutely 30 // critical, and if not enough memory is returned to the system, it'll 31 // potentially kill the app, and then later the app will have to be 32 // cold-started. 33 // 34 // 35 // Example: 36 // 37 // void OnMemoryPressure(MemoryPressureLevel memory_pressure_level) { 38 // ... 39 // } 40 // 41 // // Start listening. 42 // MemoryPressureListener* my_listener = 43 // new MemoryPressureListener(base::Bind(&OnMemoryPressure)); 44 // 45 // ... 46 // 47 // // Stop listening. 48 // delete my_listener; 49 // 50 class BASE_EXPORT MemoryPressureListener { 51 public: 52 enum MemoryPressureLevel { 53 #define DEFINE_MEMORY_PRESSURE_LEVEL(name, value) name = value, 54 #include "base/memory/memory_pressure_level_list.h" 55 #undef DEFINE_MEMORY_PRESSURE_LEVEL 56 }; 57 58 typedef base::Callback<void(MemoryPressureLevel)> MemoryPressureCallback; 59 60 explicit MemoryPressureListener( 61 const MemoryPressureCallback& memory_pressure_callback); 62 ~MemoryPressureListener(); 63 64 // Intended for use by the platform specific implementation. 65 static void NotifyMemoryPressure(MemoryPressureLevel memory_pressure_level); 66 67 private: 68 void Notify(MemoryPressureLevel memory_pressure_level); 69 70 MemoryPressureCallback callback_; 71 72 DISALLOW_COPY_AND_ASSIGN(MemoryPressureListener); 73 }; 74 75 } // namespace base 76 77 #endif // BASE_MEMORY_PRESSURE_LISTENER_H_ 78
