Delphi 5 提供了 Zlib 單元可以讓你在程式中內建壓縮資料的功能。
使用時需 Uses Zlib。

範例一：CompressBuf 及 DecompressBuf

procedure TForm1.Button1Click(Sender: TObject);
var
  i: integer;
  RawBuf: Pointer;
  ZipBuf: Pointer;
  RawBytes, ZipBytes: integer;
  s: string;
  p: PBYTE;
begin
  RawBytes := 100;
  GetMem(RawBuf, RawBytes);
  GetMem(ZipBuf, RawBytes * 2);
  // 準備測試資料
  p := RawBuf;
  for i := 0 to RawBytes-1 do
  begin
    p^ := (i div 8) mod 255;
    Inc(p);
  end;

  // 壓縮
  CompressBuf(RawBuf, RawBytes, ZipBuf, ZipBytes);

  // 解壓縮
  DecompressBuf(ZipBuf, ZipBytes, 100, RawBuf, RawBytes);

  // 把解壓縮後的資料以 Memo 元件顯示
  s := '';
  p := RawBuf;
  for i := 0 to RawBytes-1 do
  begin
    s := s + IntToStr(p^);
    Inc(p);
  end;
  Memo1.Lines.Add(s);

  FreeMem(RawBuf);
  FreeMem(ZipBuf);
end;


範例二：以串流的方式壓縮/解壓縮工具函式

// Compress inpStream into outStream.
procedure CompressStream(inpStream, outStream: TStream);
var
  InpBuf,OutBuf: Pointer;
  InpBytes,OutBytes: integer;
begin
  InpBuf := nil;
  OutBuf := nil;
  try
    GetMem(InpBuf, inpStream.Size);
    inpStream.Position := 0;
    InpBytes := inpStream.Read(InpBuf^, inpStream.Size);

    CompressBuf(InpBuf, InpBytes, OutBuf, OutBytes);

    outStream.Write(OutBuf^, OutBytes);
  finally
    if InpBuf <> nil then
      FreeMem(InpBuf);
    if OutBuf <> nil then
      FreeMem(OutBuf);
  end;
end;

(*--------------------------------------------------------
  Decompress inpStream from it's current position
  If you want to decompress the whole inpStream, remember
  set inpStream.Position to 0 beforehand.
--------------------------------------------------------*)
procedure DecompressStream(inpStream, outStream: TStream);
var
  InpBuf, OutBuf: Pointer;
  OutBytes, sz: integer;
begin
  InpBuf := nil;
  OutBuf := nil;
  sz := inpStream.Size - inpStream.Position;
  if sz > 0 then
  try
    GetMem(InpBuf, sz);
    inpStream.Read(InpBuf^, sz);
    DecompressBuf(InpBuf, sz, 0, OutBuf, OutBytes);
    outStream.Write(OutBuf^, OutBytes);
  finally
    if InpBuf <> nil then
      FreeMem(InpBuf);
    if OutBuf <> nil then
      FreeMem(OutBuf);
  end;
  outStream.Position := 0;
end;