[fpc-pascal] Get empty memory quickly or... an empty file

[Reinier Olislagers]

I'm working on implementing zip64 support and trying to test things by
compressing large files or streams using FPC's zip code.

Currently using this to get a huge memorystream filled with the same
data - so it should compress very well:
...
  ContentStream:=TMemoryStream.Create();
  ContentStream.SetSize(1+$FFFFFFFF); //4 bytes+1
  ContentStream.Position:=0;
  Buffer:='A'; //pchar
  for i:=0 to ContentStream.Size-1 do
  begin
    ContentStream.Write(Buffer,1);
  end;
  ContentStream.Position:=0;
  writeln('Buffer created');
  try
    Zipper.Entries.AddFileEntry(ContentStream, ArchiveFile);
    writeln('entry added');
    Zipper.ZipAllFiles;
  finally
    ContentStream.Free;
...

However, I'm sure there must be quicker ways (e.g. less newbie code;
using OS functions to quickly create empty memor, or alternatively
create a sparse file and zip the file instead of the stream).

Suggestions?

Thanks,
Reinier