// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// MemoryPressure provides static APIs for handling memory pressure on
// platforms that have such signals, such as Android.
// The app will try to discard buffers that aren't deemed essential (individual
// modules will implement their own policy).
//
// Refer to memory_pressure_level_list.h for information about what sorts of
// signals can be sent under what conditions.
#ifndef BASE_MEMORY_PRESSURE_LISTENER_H_
#define BASE_MEMORY_PRESSURE_LISTENER_H_
#include "base/base_export.h"
#include "base/basictypes.h"
#include "base/callback.h"
namespace base {
// To start listening, create a new instance, passing a callback to a
// function that takes a MemoryPressureLevel parameter. To stop listening,
// simply delete the listener object. The implementation guarantees
// that the callback will always be called on the thread that created
// the listener.
// Note that even on the same thread, the callback is not guaranteed to be
// called synchronously within the system memory pressure broadcast.
// Please see notes on memory_pressure_level_list.h: some levels are absolutely
// critical, and if not enough memory is returned to the system, it'll
// potentially kill the app, and then later the app will have to be
// cold-started.
//
//
// Example:
//
// void OnMemoryPressure(MemoryPressureLevel memory_pressure_level) {
// ...
// }
//
// // Start listening.
// MemoryPressureListener* my_listener =
// new MemoryPressureListener(base::Bind(&OnMemoryPressure));
//
// ...
//
// // Stop listening.
// delete my_listener;
//
class BASE_EXPORT MemoryPressureListener {
public:
enum MemoryPressureLevel {
#define DEFINE_MEMORY_PRESSURE_LEVEL(name, value) name = value,
#include "base/memory/memory_pressure_level_list.h"
#undef DEFINE_MEMORY_PRESSURE_LEVEL
};
typedef base::Callback<void(MemoryPressureLevel)> MemoryPressureCallback;
explicit MemoryPressureListener(
const MemoryPressureCallback& memory_pressure_callback);
~MemoryPressureListener();
// Intended for use by the platform specific implementation.
static void NotifyMemoryPressure(MemoryPressureLevel memory_pressure_level);
private:
void Notify(MemoryPressureLevel memory_pressure_level);
MemoryPressureCallback callback_;
DISALLOW_COPY_AND_ASSIGN(MemoryPressureListener);
};
} // namespace base
#endif // BASE_MEMORY_PRESSURE_LISTENER_H_