GetCompressedFileSize

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 located on a volume that supports sparse files, and the file is a sparse file, the value obtained is the sparse size of the specified file.

If the file is not located on a volume that supports compression or sparse files, or if the file is not compressed or a sparse file, 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 value 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 
 

QuickInfo

  Windows NT: Requires version 3.1 or later.
  Windows: Unsupported.
  Windows CE: Unsupported.
  Header: Declared in winbase.h.
  Import Library: Use kernel32.lib.
  Unicode: Implemented as Unicode and ANSI versions on Windows NT.

See Also

File Systems Overview, File System Functions, GetFileSize, GetVolumeInformation