How to get the size of a file #50

Here is a function to get the size of a file by using the native Pascal I/O and file management routines. The function returns -1 if the file doesn't exist.

function GetFileSize(FName: string): Int64;
var
  ch: File;
  OldMode: Integer;
begin
  OldMode := FileMode;
  Result := -1;
  if not FileExists(FName) then Exit;
  try
    AssignFile(ch, FName);
    FileMode := 0;
    Reset(ch,1);
    Result := FileSize(ch);
  finally
    CloseFile(ch);
    FileMode := OldMode;
  end;
end;

Author:	Joe Donth
Contributor:	Joe Donth
Added:	2007/08/14
Last updated:	2007/08/14