Issues With FileSize Function - delphi

Question

I am trying to use the system.filesize function to get the size of a file in delphi, it works ok for files < 4GB but fails for files > 4GB.
so i implemented my own that opens the required file as a filestream and gets the streamsize which works perfectly.
Here is a Snippet
function GiveMeSize(PathtoFile : string): int64;
var
stream : TFileStream;
size : int64;
begin
try
stream := TFileStream.Create(PathtoFile, fmOpenReadWrite or fmShareDenyNone);
size := stream.size;
except
showmessage('Unable to get FileSize');
end
finally
stream.free;
end;
but the problem with my above function is that it opens the file which incurs some overhead when processing a large number of files.
is there any function that can get filesize of files > 4GB without opening the file first?
I have tried some functions online but they tend to report wrong file size for files greater than 4GB.
Delphi Version : XE5
Thanks.

Answer 1

System.FileSize is a Pascal I/O function that operates on Pascal File variables. If you want to get the size of a file specified by path, then System.FileSize is simply wrong function to use.
What's more, you quite likely don't want to open the file just to obtain its size. I obtain the file size like this:
function FileSize(const FileName: string): Int64;
var
AttributeData: TWin32FileAttributeData;
begin
if GetFileAttributesEx(PChar(FileName), GetFileExInfoStandard, #AttributeData) then
begin
Int64Rec(Result).Lo := AttributeData.nFileSizeLow;
Int64Rec(Result).Hi := AttributeData.nFileSizeHigh;
end
else
Result := -1;
end;

Answer 2

Googling for the keywords "delphi get file size int64" gives you plenty of examples
I use this:
function GetSizeOfFile(const Filename: string): Int64;
var
sr : TSearchRec;
begin
if FindFirst(fileName, faAnyFile, sr ) <> 0 then
Exit(-1);
try
result := Int64(sr.FindData.nFileSizeHigh) shl Int64(32) + Int64(sr.FindData.nFileSizeLow);
finally
System.SysUtils.FindClose(sr) ;
end;
end;

Answer 3

You can avoid bit-shifting by assigning into a variant record which I think makes the code below more efficient.
function GetSizeOfFile(const Filename: string): Int64;
type
TSizeType = (stDWORD, stInt64);
var
sizerec: packed record
case TSizeType of
stDWORD: (SizeLow: LongWord; SizeHigh: LongWord);
stInt64: (Size: Int64);
end;
sr : TSearchRec;
begin
if FindFirst(fileName, faAnyFile, sr ) <> 0 then
begin
Result := -1;
Exit;
end;
try
sizerec.SizeLow := sr.FindData.nFileSizeLow;
sizerec.SizeHigh := sr.FindData.nFileSizeHigh;
Result := sizerec.Size;
finally
SysUtils.FindClose(sr) ;
end;
end;
I could've just used "case Boolean of" but like to use the power of Pascal to make the code more descriptive.