gecko-dev/xpcom/base/nsIMemory.idl

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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
*
* The contents of this file are subject to the Netscape Public
* License Version 1.1 (the "License"); you may not use this file
* except in compliance with the License. You may obtain a copy of
* the License at http://www.mozilla.org/NPL/
*
* Software distributed under the License is distributed on an "AS
* IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
* implied. See the License for the specific language governing
* rights and limitations under the License.
*
* The Original Code is mozilla.org code.
*
* The Initial Developer of the Original Code is Netscape
* Communications Corporation. Portions created by Netscape are
* Copyright (C) 1998 Netscape Communications Corporation. All
* Rights Reserved.
*
* Contributor(s):
*/
/**
* <font color="#FF0000"><b> W A R N I N G
* <p>This API is currently under review in preparation for making it an
* officially supported part of the mozilla platform. Please submit comments
* to porkjockeys@mozilla.org before 6/15/00. Until that time, it is not
* advised to base commercial products on this API because it is subject to
* change. Use at your own risk!
* </b></font>
*
* @status UNDER_REVIEW
*/
#include "nsISupports.idl"
interface nsIMemoryPressureObserver;
/**
* nsIMemory: interface to allocate and deallocate memory. Also provides
* for notifications in low-memory situations.
*/
[scriptable, uuid(59e7e77a-38e4-11d4-8cf5-0060b0fc14a3)]
interface nsIMemory : nsISupports
{
/**
* Allocates a block of memory of a particular size. If the memory
* cannot be allocated (because of an out-of-memory condition), null
* is returned.
*
* @param size - the size of the block to allocate
* @result the block of memory
*/
[noscript, notxpcom] voidPtr alloc(in size_t size);
/**
* Reallocates a block of memory to a new size.
*
* @param ptr - the block of memory to reallocate
* @param size - the new size
* @result the reallocated block of memory
*
* If ptr is null, this function behaves like malloc.
* If s is the size of the block to which ptr points, the first
* min(s, size) bytes of ptr's block are copied to the new block.
* If the allocation succeeds, ptr is freed and a pointer to the
* new block returned. If the allocation fails, ptr is not freed
* and null is returned. The returned value may be the same as ptr.
*/
[noscript, notxpcom] voidPtr realloc(in voidPtr ptr,
in size_t newSize);
/**
* Frees a block of memory. Null is a permissible value, in which case
* nothing happens.
*
* @param ptr - the block of memory to free
*/
[noscript, notxpcom] void free(in voidPtr ptr);
/**
* Attempts to shrink the heap.
*/
void heapMinimize();
/**
* Allows a memory pressure observer to be registered to provide a
* callback for low-memory situations, allowing unnecessary objects to
* be freed (e.g. flushing caches). Observers will be called either
* before alloc or realloc are about to return null, or when
* heapMinimize is called.
* @param obs - the observer to register
*/
void registerObserver(in nsIMemoryPressureObserver obs);
/**
* Allows a memory pressure observer to be unregistered.
* @param obs - the observer to unregister
*/
void unregisterObserver(in nsIMemoryPressureObserver obs);
/**
* This predicate can be used to determine if we're in a low-memory
* situation (what constitutes low-memory is platform dependent). This
* can be used to trigger the memory flushers.
*/
boolean isLowMemory();
};
/**
* nsIMemoryPressureObserver: interface for low-memory notification.
*/
[scriptable, uuid(fe6c8bd4-38e4-11d4-8cf5-0060b0fc14a3)]
interface nsIMemoryPressureObserver : nsISupports
{
const unsigned long REASON_ALLOC_FAILURE = 0;
const unsigned long REASON_HEAP_MINIMIZE = 1;
/**
* Called in response to a low-memory condition.
* @param reason - either REASON_ALLOC_FAILURE when alloc or realloc
* fails, or REASON_HEAP_MINIMIZE when heapMinimize is
* called
* @param requestedAmount - either the size requested by alloc or realloc,
* or 0 if heapMinimize was called
*/
void flushMemory(in unsigned long reason,
in size_t requestedAmount);
};