Set a file’s compression state in delphi

// Set a file’s compression state

{
To set a file’s compression state, use the DeviceIoControl function with the
FSCTL_SET_COMPRESSION operation.

Call the following function with the name of the file to compress and
boolean parameter ‘forceCompress’. If that one is true, file will be compressed.
If it is false, the file will be compressed only if its parent folder is
compressed (reason for that parameter: if you MoveFile uncompressed file from
uncompressed folder to compressed folder, file will not become automatically
compressed – at least under some NT 4 service packs).
}

const
COMPRESSION_FORMAT_NONE = 0
COMPRESSION_FORMAT_LZNT1 = 2
COMPRESSION_FORMAT_DEFAULT = 1;
FILE_DEVICE_FILE_SYSTEM = 9;
METHOD_BUFFERED = 0;
FILE_READ_DATA = 1;
FILE_WRITE_DATA = 2;
FSCTL_SET_COMPRESSION = (FILE_DEVICE_FILE_SYSTEM shl 16) or
((FILE_READ_DATA or FILE_WRITE_DATA) shl 14) or (16 shl 2) or METHOD_BUFFERED;

function SetCompressedAttribut(FileName: PChar; forceCompress: Boolean): Boolean;
var
hnd: Integer;
Comp: SHORT;
res: DWORD;
begin
if forceCompress or ((GetFileAttributes(PChar(ExtractFilePath(FileName))) and
FILE_ATTRIBUTE_COMPRESSED) <> 0) then
begin
Result := False;
if (GetFileAttributes(FileName) and FILE_ATTRIBUTE_COMPRESSED) = 0 then
begin
hnd := CreateFile(FileName, GENERIC_READ + GENERIC_WRITE, 0, nil, OPEN_EXISTING, 0, 0);
try
Comp := COMPRESSION_FORMAT_DEFAULT;
if not DeviceIoControl(hnd, FSCTL_SET_COMPRESSION, @Comp,
SizeOf(SHORT), nil, 0, res, nil) then Exit;
finally
CloseHandle(hnd);
end;
end;
Result := True;
end
else
Result := True;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
if OpenDialog1.Execute then
begin
SetCompressedAttribut(PChar(OpenDialog1.FileName), True);
end;
end;