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function SplitFile(FileName : TFileName; SizeofFiles : Integer) : integer;
var
  i : Word;
  fs, sStream: TFileStream;
  SplitFileName: String;
begin

  fs := TFileStream.Create(FileName, fmOpenRead or fmShareDenyWrite);
  try
    for i := 1 to Trunc(fs.Size / SizeofFiles) + 1 do
    begin
      SplitFileName := ChangeFileExt(FileName, '.'+ FormatFloat('000', i));
      sStream := TFileStream.Create(SplitFileName, fmCreate or fmShareExclusive);
      try
        if fs.Size - fs.Position < SizeofFiles then
          SizeofFiles := fs.Size - fs.Position;
        sStream.CopyFrom(fs, SizeofFiles);
      finally
        sStream.Free;
      end;
      Result := i;
    end;
  finally
    fs.Free;
  end;

end;

function CombineFiles(FileName, CombinedFileName : TFileName) : Boolean;
var
  i: integer;
  fs, sStream: TFileStream;
  filenameOrg: String;
begin
  i := 1;
  fs := TFileStream.Create(CombinedFileName, fmCreate or fmShareExclusive);
  try
    while FileExists(FileName) do
    begin
      sStream := TFileStream.Create(FileName, fmOpenRead or fmShareDenyWrite);
      try
        fs.CopyFrom(sStream, 0);
      finally
        sStream.Free;
      end;
      Inc(i);
      FileName := ChangeFileExt(FileName, '.'+ FormatFloat('000', i));
    end;
  finally
    fs.Free;
  end;
end;					

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SplitFileName := ChangeFileExt(FileName, '.'+ FormatFloat('000', i));					

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Format('%0.3d', [i])