GetCompressedFileSizeW
lazarus / 21-General

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HomeBoy38 · 2023-11-22 18:02

Hi,

I want to retrieve the file size of a NTFS compressed file, using
GetCompressedFileSizeW:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i CompSizeL,
CompSizeH: DWORD;CompSizeL :=
GetCompressedFileSizeW(PWideChar(MyFilePathLong), @CompSizeH); 
This is correctly working for small files (less than 4 GB).
As far as the file is bigger, the size is wrong.

Either I have not understood what really is in CompSizeH, either it is
because I have no idea of how to put both sizes into another variable
(which kind I should use?).

I have tried a bunch of ways to get the correct size, everything
failed.
I have an idea on how to have my code working, but I want to share my
questionning to have a chance to learn something and maybe help
someone else.

Thanks

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Fibonacci · 2023-11-22 18:06

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i uses
Windows; var  l, h: dword;  li: LARGE_INTEGER; begin  l :=
GetCompressedFileSizeW('...', @h);   li.LowPart := l;  li.HighPart :=
h;   writeln('size = ', li.QuadPart);  readln;end.

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HomeBoy38 · 2023-11-22 18:34

Wow, you were fast!

I found that somewhere, but I did not understood it and was not able
to reproduce it correctly.
With your answer, I totally understood that and was able to correct my
code.

Thanks a lot!

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KodeZwerg · 2023-11-22 19:31

Here's a two-in-one method that, if succeed, gives back filesize for
both situations, compressed and uncompressed:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i function
GetFileSizeEx(hFile: THandle; lpFileSize: PULARGE_INTEGER): BOOL;
stdcall; external 'kernel32.dll' name 'GetFileSizeEx';function
GetFileSize(const AFileName: UnicodeString; out AValue: UInt64):
Boolean;var  FileSizeHigh,  FileSizeLow: DWORD;  hFile: THandle; 
LargeFileSize: ULARGE_INTEGER;begin  hFile :=
CreateFileW(PWideChar(AFileName), GENERIC_READ, FILE_SHARE_READ, nil,
OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);  if (hFile =
INVALID_HANDLE_VALUE) then    Exit(False);  try    FileSizeLow :=
GetCompressedFileSizeW(PWideChar(AFileName), @FileSizeHigh);    if
(not FileSizeLow = INVALID_FILE_SIZE) then      begin        AValue :=
UInt64(FileSizeHigh) shl 32 or FileSizeLow;        Result := True;   
 end    else      begin        if (not GetFileSizeEx(hFile,
@LargeFileSize)) then          Exit(False);        AValue :=
LargeFileSize.QuadPart;        Result := True;      end;  finally   
CloseHandle(hFile);  end;end;

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Remy Lebeau · 2023-11-23 20:40

Quote from: KodeZwerg on November 22, 2023, 08:31:04 pmCode: Pascal
 [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i FileSizeLow
:= GetCompressedFileSizeW(PWideChar(AFileName), @FileSizeHigh);if (not
FileSizeLow = INVALID_FILE_SIZE) then
That is not the correct way to check for success when the 2nd
parameter is not nil.  For files >= 4GB, the returned FileSizeLow can
be $FFFFFFFF (ie, INVALID_FILE_SIZE) for valid file sizes, so you MUST
check GetLastError() to differentiate success from failure.  This is
documented behavior:

https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-
fileapi-getcompressedfilesizew

QuoteIf 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).
So, use this instead:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i if
(FileSizeLow <> INVALID_FILE_SIZE) or (GetLastError() = 0) then

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HomeBoy38 · 2023-11-24 07:07

I did not experienced this when I tested Fibonacci's suggestion, my
file was correctly processed instead of showing an error in the log.
In my test case, the 6 GB file reported 2 GB in filesizelow.

But you are right, Microsoft's documentation says that, but I think it
is in rare case exceptions.
I am not really concerned for my tool (not a big deal if I am in that
case) but it may help other people experiencing such issue

Thanks

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Remy Lebeau · 2023-11-26 20:13

Quote from: HomeBoy38 on November 24, 2023, 08:07:43 amIn my test
case, the 6 GB file reported 2 GB in filesizelow.

Correct.  6GB is 6442450944 (hex $180000000), which has its lower 32
bits as 2147483648 (hex $80000000), which is 2GB.

Quote from: HomeBoy38 on November 24, 2023, 08:07:43 amBut you are
right, Microsoft's documentation says that, but I think it is in rare
case exceptions.

Any file size that is an even multiple of 4GB (minus 1) will have its
low 32bits set as $FFFFFFFF, eg:

$0FFFFFFFF = 4294967295 (4GB - 1)
$1FFFFFFFF = 8589934591  (8GB - 1)
$2FFFFFFFF = 12884901887 (12GB - 1)
$3FFFFFFFF = 17179869183 (16GB - 1)
etc...

So, your code would fail on such files if you don't check the error
code as Microsoft describes.

6GB is obviously not an even multiple of 4GB.