流的压缩与解压缩

uses Zlib; 
//压缩 
procedure DoCompress(var CompressedStream: TMemoryStream); 
var 
  SourceStream: TCompressionStream; 
  DestStream: TMemoryStream; 
  Count: int64; 
Begin 
  CompressedStream.Position := 0; 
  Count := CompressedStream.Size; 
  if Count=0 then     //错误 
    Exit; 
  DestStream := TMemoryStream.Create; 
  SourceStream:=TCompressionStream.Create(clMax, DestStream); 
  Try 
    CompressedStream.SaveToStream(SourceStream); 
    SourceStream.Free; 
    CompressedStream.Clear; 
    CompressedStream.WriteBuffer(Count, SizeOf(Count)); 
    CompressedStream.CopyFrom(DestStream, 0); 
  finally 
    DestStream.Free; 
  end; 
  CompressedStream.Position := 0; 
end; 

//解压缩 
procedure DoUncompress(var UnCompressedStream: TMemoryStream); 
var 
  Count: int64; 
  SourceStream: TDecompressionStream; 
  Buffer: pchar; 
begin 
  UnCompressedStream.Position:=0; 
  UnCompressedStream.ReadBuffer(Count, sizeof(Count)); 
  if count<0 then 
  begin 
    UnCompressedStream.Position:=0; 
    exit; 
  end; 
  SourceStream := TDecompressionStream.Create(UnCompressedStream); 
  Getmem(Buffer, Count); 
  SourceStream.Read(Buffer^, Count); 
  freeandnil(SourceStream); 
  UnCompressedStream.Clear; 
  UnCompressedStream.WriteBuffer(Buffer^,Count); 
  UnCompressedStream.Position:=0; 
  freemem(Buffer); 
end;