GetCompressedFileSize
The GetCompressedFileSize
function obtains the compressed size, in bytes, of a specified file.
The GetCompressedFileSize
function obtains the actual number of bytes of disk storage used to store a
specified file. If the file is located on a volume that supports compression,
and the file is compressed, the value obtained is the compressed size of the
specified file. If the file is not located on a volume that supports
compression, or if the file is not compressed, the value obtained is the actual
file size, the same as the value returned by a call to GetFileSize.
DWORD GetCompressedFileSize(
|
LPCTSTR lpFileName, |
// pointer to name
of file |
|
LPDWORD lpFileSizeHigh |
// pointer to DWORD
to receive high-order doubleword of file size |
|
); |
|
Parameters
lpFileName
Pointer to a
null-terminated string that specifies the name of the file.
lpFileSizeHigh
Pointer to a DWORD
variable that the function sets to the high-order doubleword of the compressed
file size. The function s return value is the low-order doubleword of the compressed
file size.
This parameter can be NULL if the high-order doubleword of the
compressed file size is not needed. Files less than 4 gigabytes in size do not
need the high-order doubleword.
Return Values
If the
function succeeds, the return value is the low-order doubleword of the actual
number of bytes of disk storage used to store the specified file, and if lpFileSizeHigh
is non-NULL, the function puts the high-order doubleword of that actual value
into the DWORD pointed to by that parameter. This is the compressed file
size for compressed files, the actual file size for noncompressed files.
If the
function fails, and lpFileSizeHigh is NULL, the return value is
0xFFFFFFFF. To get extended error information, call GetLastError.
If the function
fails, and lpFileSizeHigh is non-NULL, the return value is 0xFFFFFFFF,
and GetLastError returns a value other than NO_ERROR.
Remarks
Calling the GetCompressedFileSize
function with the name of a nonseeking device, such as a pipe or a
communications device, has no meaning.
Note that if
the return value is 0xFFFFFFFF and lpFileSizeHigh is non-NULL, an
application must call GetLastError to determine whether the function has
succeeded or failed.
An
application can determine whether a volume is compressed by calling GetVolumeInformation,
then checking the status of the FS_VOL_IS_COMPRESSED flag in the DWORD pointed
to by that function s lpFileSystemFlags parameter.
An
application can determine whether a file is compressed by implementing the
following pseudocode:
call GetVolumeInformation on the file's
volume
if the file's volume is compressed
call GetCompressedFileSize
on the file
call GetFileSize
on the file
if the
sizes don't match
the
file is compressed
See Also