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116 lines
4.3 KiB
Plaintext
116 lines
4.3 KiB
Plaintext
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "nsISupports.idl"
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/**
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*
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* nsIMemory: interface to allocate and deallocate memory. Also provides
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* for notifications in low-memory situations.
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*
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* The frozen exported symbols NS_Alloc, NS_Realloc, and NS_Free
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* provide a more efficient way to access XPCOM memory allocation. Using
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* those symbols is preferred to using the methods on this interface.
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*
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* A client that wishes to be notified of low memory situations (for
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* example, because the client maintains a large memory cache that
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* could be released when memory is tight) should register with the
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* observer service (see nsIObserverService) using the topic
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* "memory-pressure". There are three specific types of notications
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* that can occur. These types will be passed as the |aData|
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* parameter of the of the "memory-pressure" notification:
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*
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* "low-memory"
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* This will be passed as the extra data when the pressure
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* observer is being asked to flush for low-memory conditions.
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*
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* "low-memory-ongoing"
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* This will be passed when we continue to be in a low-memory
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* condition and we want to flush caches and do other cheap
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* forms of memory minimization, but heavy handed approaches like
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* a GC are unlikely to succeed.
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*
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* "-no-forward"
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* This is appended to the above two parameters when the resulting
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* notification should not be forwarded to the child processes.
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*
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* "heap-minimize"
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* This will be passed as the extra data when the pressure
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* observer is being asked to flush because of a heap minimize
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* call.
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*
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* "alloc-failure"
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* This will be passed as the extra data when the pressure
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* observer has been asked to flush because a malloc() or
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* realloc() has failed.
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*/
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[scriptable, uuid(6aef11c4-8615-44a6-9711-98f43805693d)]
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interface nsIMemory : nsISupports
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{
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/**
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* Allocates a block of memory of a particular size. If the memory
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* cannot be allocated (because of an out-of-memory condition), the
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* process aborts.
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*
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* @param size - the size of the block to allocate
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* @result the block of memory
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*/
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[noscript, notxpcom] voidPtr alloc(in size_t size);
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/**
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* Reallocates a block of memory to a new size.
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*
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* @param ptr - the block of memory to reallocate
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* @param size - the new size
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* @result the reallocated block of memory
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*
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* If ptr is null, this function behaves like malloc.
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* If s is the size of the block to which ptr points, the first
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* min(s, size) bytes of ptr's block are copied to the new block.
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* If the allocation succeeds, ptr is freed and a pointer to the
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* new block returned. If the allocation fails, the process aborts.
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*/
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[noscript, notxpcom] voidPtr realloc(in voidPtr ptr,
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in size_t newSize);
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/**
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* Frees a block of memory. Null is a permissible value, in which case
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* nothing happens.
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*
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* @param ptr - the block of memory to free
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*/
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[noscript, notxpcom] void free(in voidPtr ptr);
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/**
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* Attempts to shrink the heap.
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* @param immediate - if true, heap minimization will occur
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* immediately if the call was made on the main thread. If
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* false, the flush will be scheduled to happen when the app is
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* idle.
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* @throws NS_ERROR_FAILURE if 'immediate' is set an the call
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* was not on the application's main thread.
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*/
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void heapMinimize(in boolean immediate);
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/**
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* This predicate can be used to determine if we're in a low-memory
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* situation (what constitutes low-memory is platform dependent). This
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* can be used to trigger the memory pressure observers.
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*
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* DEPRECATED - Always returns false. See bug 592308.
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*/
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boolean isLowMemory();
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/**
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* This predicate can be used to determine if the platform is a "low-memory"
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* platform. Callers may use this to dynamically tune their behaviour
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* to favour reduced memory usage at the expense of performance. The value
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* returned by this function will not change over the lifetime of the process.
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*/
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boolean isLowMemoryPlatform();
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};
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