VirtualQuery
The VirtualQuery
function provides information about a range of pages in the virtual address
space of the calling process.
DWORD VirtualQuery(
|
LPCVOID lpAddress, |
// address of
region |
|
PMEMORY_BASIC_INFORMATION lpBuffer, |
// address of
information buffer |
|
DWORD dwLength |
// size of buffer |
|
); |
|
Parameters
lpAddress
Points to the
base address of the region of pages to be queried. This value is rounded down
to the next page boundary. To determine the size of a page on the host
computer, use the GetSystemInfo function.
lpBuffer
Points to a MEMORY_BASIC_INFORMATION structure in which
information about the specified page range is returned.
dwLength
Specifies the
size, in bytes, of the buffer pointed to by the lpBuffer parameter.
Return Values
The return
value is the actual number of bytes returned in the information buffer.
Remarks
VirtualQuery provides information about a region of consecutive
pages beginning at a specified address that share the following attributes:
The state of all pages is the
same with the MEM_COMMIT, MEM_RESERVE, MEM_FREE, MEM_PRIVATE, MEM_MAPPED, or
MEM_IMAGE flag.
If the initial page is not
free, all pages in the region are part of the same initial allocation of pages
reserved by a call to the VirtualAlloc function.
The access of all pages is the
same with the PAGE_READONLY, PAGE_READWRITE, PAGE_NOACCESS, PAGE_WRITECOPY,
PAGE_EXECUTE, PAGE_EXECUTE_READ, PAGE_EXECUTE_READWRITE,
PAGE_EXECUTE_WRITECOPY, PAGE_GUARD, or PAGE_NOCACHE flag.
The function
determines the attributes of the first page in the region and then scans
subsequent pages until it scans the entire range of pages or until it
encounters a page with a nonmatching set of attributes. The function returns
the attributes and the size, in bytes, of the region of pages with matching
attributes. For example, if there is a 40 megabyte (MB) region of free memory,
and VirtualQuery is called on a page that is 10 MB into the region, the
function will obtain a state of MEM_FREE and a size of 30 MB.
This function
reports on a region of pages in the memory of the calling process, and the VirtualQueryEx
function reports on a region of pages in the memory of a specified process.
See Also