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.
“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.
Allocates a block of memory of a particular size. If the memory
cannot be allocated (because of an out-of-memory condition), the
process aborts.
| size | - the size of the block to allocate @result the block of memory |
Reallocates a block of memory to a new size.
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, the process aborts.
| ptr | - the block of memory to reallocate |
| size | - the new size @result the reallocated block of memory |
Frees a block of memory. Null is a permissible value, in which case
nothing happens.
| ptr | - the block of memory to free |
Attempts to shrink the heap.
| 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. |
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.
DEPRECATED - Always returns false. See bug 592308.
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.