Memory Management Functions (Windows)

Memory Management Functions

This topic describes the memory management functions:

General Memory Functions
Data Execution Prevention Functions
File Mapping Functions
AWE Functions
Heap Functions
Virtual Memory Functions
Global and Local Functions
Obsolete Functions

General Memory Functions

The following functions are used in memory management.

Function	Description
AddSecureMemoryCacheCallback	Registers a callback function to be called when a secured memory range is freed or its protections are changed.
CopyMemory	Copies a block of memory from one location to another.
CreateMemoryResourceNotification	Creates a memory resource notification object.
FillMemory	Fills a block of memory with a specified value.
GetLargePageMinimum	Retrieves the minimum size of a large page.
GetPhysicallyInstalledSystemMemory	Retrieves the amount of RAM that is physically installed on the computer.
GetSystemFileCacheSize	Retrieves the current size limits for the working set of the system cache.
GetWriteWatch	Retrieves the addresses of the pages that have been written to in a region of virtual memory.
GlobalMemoryStatusEx	Obtains information about the system's current usage of both physical and virtual memory.
MoveMemory	Moves a block of memory from one location to another.
QueryMemoryResourceNotification	Retrieves the state of the specified memory resource object.
RemoveSecureMemoryCacheCallback	Unregisters a callback function that was previously registered with the AddSecureMemoryCacheCallback function.
ResetWriteWatch	Resets the write-tracking state for a region of virtual memory.
SecureMemoryCacheCallback	An application-defined function that is called when a secured memory range is freed or its protections are changed.
SecureZeroMemory	Fills a block of memory with zeros.
SetSystemFileCacheSize	Limits the size of the working set for the file system cache.
ZeroMemory	Fills a block of memory with zeros.

Data Execution Prevention Functions

The following functions are used with Data Execution Prevention (DEP).

Function	Description
GetProcessDEPPolicy	Retrieves DEP settings for a process.
GetSystemDEPPolicy	Retrieves DEP settings for the system.
SetProcessDEPPolicy	Changes DEP settings for a process.

File Mapping Functions

The following functions are used in file mapping.

Function	Description
CreateFileMapping	Creates or opens a named or unnamed file mapping object for a specified file.
CreateFileMappingNuma	Creates or opens a named or unnamed file mapping object for a specified file, and specifies the NUMA node for the physical memory.
FlushViewOfFile	Writes to the disk a byte range within a mapped view of a file.
GetMappedFileName	Checks whether the specified address is within a memory-mapped file in the address space of the specified process. If so, the function returns the name of the memory-mapped file.
MapViewOfFile	Maps a view of a file mapping into the address space of a calling process.
MapViewOfFileEx	Maps a view of a file mapping into the address space of a calling process. A caller can optionally specify a suggested memory address for the view.
MapViewOfFileExNuma	Maps a view of a file mapping into the address space of a calling process, and specifies the NUMA node for the physical memory.
OpenFileMapping	Opens a named file mapping object.
UnmapViewOfFile	Unmaps a mapped view of a file from the calling process's address space.

AWE Functions

The following are the AWE functions.

Function	Description
AllocateUserPhysicalPages	Allocates physical memory pages to be mapped and unmapped within any AWE region of the process.
FreeUserPhysicalPages	Frees physical memory pages previously allocated with AllocateUserPhysicalPages.
MapUserPhysicalPages	Maps previously allocated physical memory pages at the specified address within an AWE region.
MapUserPhysicalPagesScatter	Maps previously allocated physical memory pages at the specified address within an AWE region.

Heap Functions

The following are the heap functions.

Function	Description
GetProcessHeap	Obtains a handle to the heap of the calling process.
GetProcessHeaps	Obtains handles to all of the heaps that are valid for the calling process.
HeapAlloc	Allocates a block of memory from a heap.
HeapCompact	Coalesces adjacent free blocks of memory on a heap.
HeapCreate	Creates a heap object.
HeapDestroy	Destroys the specified heap object.
HeapFree	Frees a memory block allocated from a heap.
HeapLock	Attempts to acquire the lock associated with a specified heap.
HeapQueryInformation	Retrieves information about the specified heap.
HeapReAlloc	Reallocates a block of memory from a heap.
HeapSetInformation	Sets heap information for the specified heap.
HeapSize	Retrieves the size of a memory block allocated from a heap.
HeapUnlock	Releases ownership of the lock associated with a specified heap.
HeapValidate	Attempts to validate a specified heap.
HeapWalk	Enumerates the memory blocks in a specified heap.

Virtual Memory Functions

The following are the virtual memory functions.

Function	Description
VirtualAlloc	Reserves or commits a region of pages in the virtual address space of the calling process.
VirtualAllocEx	Reserves or commits a region of pages in the virtual address space of the specified process.
VirtualAllocExNuma	Reserves or commits a region of memory within the virtual address space of the specified process, and specifies the NUMA node for the physical memory.
VirtualFree	Releases or decommits a region of pages within the virtual address space of the calling process.
VirtualFreeEx	Releases or decommits a region of memory within the virtual address space of a specified process.
VirtualLock	Locks the specified region of the process's virtual address space into physical memory.
VirtualProtect	Changes the access protection on a region of committed pages in the virtual address space of the calling process.
VirtualProtectEx	Changes the access protection on a region of committed pages in the virtual address space of the calling process.
VirtualQuery	Provides information about a range of pages in the virtual address space of the calling process.
VirtualQueryEx	Provides information about a range of pages in the virtual address space of the calling process.
VirtualUnlock	Unlocks a specified range of pages in the virtual address space of a process.

Global and Local Functions

The following are the global and local functions. These functions are provided for compatibility with 16-bit Windows and are used with Dynamic Data Exchange (DDE), the clipboard functions, and OLE data objects. Unless documentation specifically states that a global or local function should be used, new applications should use the corresponding heap function with the handle returned by GetProcessHeap. For equivalent functionality to the global or local function, set the heap function's dwFlags parameter to 0.

Function	Description	Corresponding heap function
GlobalAlloc, LocalAlloc	Allocates the specified number of bytes from the heap.	HeapAlloc
GlobalDiscard, LocalDiscard	Discards the specified global memory block.	Not applicable.
GlobalFlags, LocalFlags	Returns information about the specified global memory object.	Not applicable. Use HeapValidate to validate the heap.
GlobalFree, LocalFree	Frees the specified global memory object.	HeapFree
GlobalHandle, LocalHandle	Retrieves the handle associated with the specified pointer to a global memory block. This function should be used only with OLE and clipboard functions that require it.	Not applicable.
GlobalLock, LocalLock	Locks a global memory object and returns a pointer to the first byte of the object's memory block.	Not applicable.
GlobalReAlloc, LocalReAlloc	Changes the size or attributes of a specified global memory object.	HeapReAlloc
GlobalSize, LocalSize	Retrieves the current size of the specified global memory object.	HeapSize
GlobalUnlock, LocalUnlock	Decrements the lock count associated with a memory object. This function should be used only with OLE and clipboard functions that require it.	Not applicable.

Obsolete Functions

The following functions are provided only for compatibility with 16-bit versions of Windows:

The following function can return incorrect information and should not be used. Use the GlobalMemoryStatusEx function instead:

GlobalMemoryStatus

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Build date: 11/19/2009