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uses ..., ZLib;					

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function CompressStream(inpStream: TMemoryStream): TMemoryStream;
var 
  InpBuf, OutBuf: Pointer; 
  InpBytes, OutBytes: Integer; 
  outStream: TMemoryStream;
begin
  InpBuf := nil; 
  OutBuf := nil; 
  outStream:=TMemoryStream.Create;
  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;
  result:=outStream;
end;

function DecompressStream(inpStream: TMemoryStream): TMemoryStream;
var
  InpBuf, OutBuf: Pointer;
  OutBytes, sz: Integer;
  outStream: TMemoryStream;
begin
  InpBuf := nil;
  OutBuf := nil;
  outStream:=TMemoryStream.Create;
  inpStream.Position:=0;
  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;
  Result:=outStream;
end;