nsIMemory in Firefox 3.6a1pre

Implemented by


 nsIMemory: interface to allocate and deallocate memory. Also provides
 for notifications in low-memory situations.

 The frozen exported symbols NS_Alloc, NS_Realloc, and NS_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 three 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.

 "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.

 @status FROZEN

[scriptable, uuid(59e7e77a-38e4-11d4-8cf5-0060b0fc14a3)]

Methods

 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)

 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.
 @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.
 @return 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 we're in a low-memory
 situation (what constitutes low-memory is platform dependent). This
 can be used to trigger the memory pressure observers.

boolean isLowMemory()

 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)