...set a file's compression state ?

Author: Primoz Gabrijelcic

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{

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).

Ein "compressed" Attribut kann man nicht mit der FileSetAttr Funktion setzen

sondern muss DeviceIoControl Funktion mit dem flag FSCTL_SET_COMPRESSION verwenden:

}

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;