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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "nsISupports.idl"
/**
*
* nsIMemory: interface to allocate and deallocate memory. Also provides
* for notifications in low-memory situations.
*
* The frozen exported symbols moz_xmalloc, moz_xrealloc, and free
* provide a more efficient way to access XPCOM memory allocation. Using
* those symbols is preferred to using the methods on this interface.
*
* A client that wishes to be notified of low memory situations (for
* example, because the client maintains a large memory cache that
* could be released when memory is tight) should register with the
* observer service (see nsIObserverService) using the topic
* "memory-pressure". There are specific types of notications
* that can occur. These types will be passed as the |aData|
* parameter of the of the "memory-pressure" notification:
*
* "low-memory"
* This will be passed as the extra data when the pressure
* observer is being asked to flush for low-memory conditions.
*
* "low-memory-ongoing"
* This will be passed when we continue to be in a low-memory
* condition and we want to flush caches and do other cheap
* forms of memory minimization, but heavy handed approaches like
* a GC are unlikely to succeed.
*
* "-no-forward"
* This is appended to the above two parameters when the resulting
* notification should not be forwarded to the child processes.
*
* "heap-minimize"
* This will be passed as the extra data when the pressure
* observer is being asked to flush because of a heap minimize
* call.
*
* "alloc-failure"
* This will be passed as the extra data when the pressure
* observer has been asked to flush because a malloc() or
* realloc() has failed.
*
* "lowering-priority"
* This will be passed as the extra data when the priority of a child
* process is lowered. The pressure observers could take the chance to
* clear caches that could be easily regenerated. This type of
* notification only appears in child processes.
*/
[scriptable, uuid(1e004834-6d8f-425a-bc9c-a2812ed43bb7)]
interface nsIMemory : nsISupports
{
/**
* Attempts to shrink the heap.
* @param immediate - if true, heap minimization will occur
* immediately if the call was made on the main thread. If
* false, the flush will be scheduled to happen when the app is
* idle.
* @throws NS_ERROR_FAILURE if 'immediate' is set an the call
* was not on the application's main thread.
*/
void heapMinimize(in boolean immediate);
/**
* This predicate can be used to determine if the platform is a "low-memory"
* platform. Callers may use this to dynamically tune their behaviour
* to favour reduced memory usage at the expense of performance. The value
* returned by this function will not change over the lifetime of the process.
*/
boolean isLowMemoryPlatform();
};
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