HeapSize

  • Article

This function returns the size, in bytes, of a memory block allocated from a heap by the HeapAlloc or HeapReAlloc function.

DWORD HeapSize( 
  HANDLE hHeap, 
  DWORD dwFlags, 
  LPCVOID lpMem 
);

Parameters

  • hHeap
    [in] Handle to the heap in which the memory block resides. This handle is returned by the HeapCreate or GetProcessHeap function.

  • dwFlags
    [in] Specifies several controllable aspects of accessing the memory block. Only one flag is currently defined; however, all other flag values are reserved for future use. The following table shows the flag you can specify. Specifying this flag will override the corresponding flag specified in the flOptions parameter when the heap was created using the HeapCreate function.

    Value Description
    HEAP_NO_SERIALIZE Specifies that mutual exclusion will not be used while HeapSize is accessing the heap. This flag should not be specified when accessing the process heap. The system may create additional threads within the application's process that simultaneously access the process heap.

    This flag is ignored.

  • lpMem
    [in] Pointer to the memory block whose size the function will obtain. This is a pointer returned by the HeapAlloc or HeapReAlloc function.

Return Values

The size, in bytes, of the allocated memory block indicates success. 0xFFFFFFFF indicates failure. The function does not call SetLastError. An application cannot call GetLastError for extended error information.

Remarks

Serialization ensures mutual exclusion when two or more threads attempt to simultaneously allocate or free blocks from the same heap. There is a small performance cost to serialization, but it must be used whenever multiple threads allocate and free memory from the same heap. A critical section is always used to serialize access to an individual heap. There is a critical section per heap to protect access to each heap. An attempt to grab a critical section that is not owned is a fast path operation that incurs little overhead. This would be similar to using the HEAP_NO_SERIALIZE flag if only one thread was ever accessing a particular heap. If there is contention for the critical section, and therefore the heap, a new thread request to allocate heap space will serialize.

Requirements

OS Versions: Windows CE 1.0 and later.
Header: Winbase.h.
Link Library: Coredll.lib.

See Also

GetProcessHeap | HeapAlloc | HeapCreate | HeapDestroy | HeapFree | HeapReAlloc | SetLastError

Last updated on Wednesday, April 13, 2005

© 2005 Microsoft Corporation. All rights reserved.