GetCompressedFileSizeW function (fileapi.h)

Article
06/01/2023

Retrieves 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.

To perform this operation as a transacted operation, use the GetCompressedFileSizeTransacted function.

Syntax

DWORD GetCompressedFileSizeW(
  [in]            LPCWSTR lpFileName,
  [out, optional] LPDWORD lpFileSizeHigh
);

Parameters

[in] lpFileName

The name of the file.

Do not specify the name of a file on a nonseeking device, such as a pipe or a communications device, as its file size has no meaning.

This parameter may include the path.

By default, the name is limited to MAX_PATH characters. To extend this limit to 32,767 wide characters, prepend "\\?\" to the path. For more information, see Naming Files, Paths, and Namespaces.

Tip

Starting with Windows 10, Version 1607, you can opt-in to remove the MAX_PATH limitation without prepending "\\?\". See the "Maximum Path Length Limitation" section of Naming Files, Paths, and Namespaces for details.

[out, optional] lpFileSizeHigh

The high-order DWORD of the compressed file size. The function's return value is the low-order DWORD of the compressed file size.

This parameter can be NULL if the high-order DWORD of the compressed file size is not needed. Files less than 4 gigabytes in size do not need the high-order DWORD.

Return value

If the function succeeds, the return value is the low-order DWORD 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 DWORD 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 INVALID_FILE_SIZE. To get extended error information, call GetLastError.

If the return value is INVALID_FILE_SIZE and lpFileSizeHigh is non-NULL, an application must call GetLastError to determine whether the function has succeeded (value is NO_ERROR) or failed (value is other than NO_ERROR).

Remarks

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.

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.

Symbolic link behavior—If the path points to a symbolic link, the function returns the file size of the target.

In Windows 8 and Windows Server 2012, this function is supported by the following technologies.

Technology	Supported
Server Message Block (SMB) 3.0 protocol	Yes
SMB 3.0 Transparent Failover (TFO)	Yes
SMB 3.0 with Scale-out File Shares (SO)	Yes
Cluster Shared Volume File System (CsvFS)	Yes
Resilient File System (ReFS)	Yes

Note

The fileapi.h header defines GetCompressedFileSize as an alias which automatically selects the ANSI or Unicode version of this function based on the definition of the UNICODE preprocessor constant. Mixing usage of the encoding-neutral alias with code that not encoding-neutral can lead to mismatches that result in compilation or runtime errors. For more information, see Conventions for Function Prototypes.

Requirements

Requirement	Value
Minimum supported client	Windows XP [desktop apps only]
Minimum supported server	Windows Server 2003 [desktop apps only]
Target Platform	Windows
Header	fileapi.h (include Windows.h, WinBase.h, Fileapi.h, Windows.h, WinBase.h, Fileapi.h)
Library	Kernel32.lib
DLL	Kernel32.dll