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(
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LPCTSTR lpFileName, |
// pointer to name of file |
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LPDWORD lpFileSizeHigh |
// pointer to DWORD to receive high-order doubleword of file size |
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); |
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.
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.
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