{$IFDEF MSWINDOWS}
function DiskFreeEx(const aDir: string): Int64;
var
  Drive: String;
  DChar: AnsiChar;
begin
  Result := 0;
  Drive := System.SysUtils.ExtractFileDrive(aDir).ToUpper;
  if Drive <> '' then
  begin
    DChar := AnsiChar(Drive[Low(Drive)]);
    if DChar in ['A'..'Z'] then
      Result := DiskFree(Ord(DChar) - $40)
  end;
end;
{$ENDIF}

{$IF Defined(POSIX) and not Defined(ANDROID)}
function DiskFreeEx(const aDir: string): Int64;
var
  Bt: TBytes;
  StatBuf: _statvfs;
begin
  Bt := TEncoding.ANSI.GetBytes(aDir);
  Bt := Bt + [0];

  if statvfs(MarshaledAString(Bt), StatBuf) = 0 then
    Result := StatBuf.f_bavail * StatBuf.f_bsize
  else
    raise EInOutError.CreateFmt('Unable to get free size for "%s"', [aDir]);
end;
{$ENDIF}

{$IFDEF ANDROID}
//statvfs do not defined for Android in SysStatvfsAPI.inc
//Therefore we use statfs.
//Check SysStatvfsAPI.inc in future release.
type
  __statfs = record
    f_type,
    f_bsize: LongWord;
    f_blocks,
    f_bfree,
    f_bavail,
    f_files,
    f_ffree,
    f_fsid,
    f_namelen,
    f_frsize,
    f_flags: UInt64;
    f_spare: packed array[0..4-1] of UInt64;
  end;

function _statfs(__file: MarshaledAString; var __buf: __statfs): Integer; cdecl; external libc name _PU + 'statfs';

function DiskFreeEx(aDir: string): Int64;
var
  Bt: TBytes;
  StatBuf: __statfs;
begin
  Bt := TEncoding.ANSI.GetBytes(aDir);
  Bt := Bt + [0];

  if _statfs(MarshaledAString(Bt), StatBuf) = 0 then
    Result := StatBuf.f_bavail * StatBuf.f_bsize
  else
    raise EInOutError.CreateFmt('Unable to get free size for "%s"', [aDir]);
end;
{$ENDIF}