我写了个能压缩解压缩字符串的动态链接库，大家帮我看看输入输出参数怎么写才对呢,我一直没有办法解压缩

压缩好像是可以的，就是无法解压缩。
DLL部分代码：用了ZLib单元
function CompressStream (aSource, aTarget: TStream): Single;
var
  comprStream: TCompressionStream;
begin
  comprStream := TCompressionStream.Create(
    clFastest, aTarget);
  try
    comprStream.CopyFrom(aSource, aSource.Size);
    Result := comprStream.CompressionRate;
  finally
    comprStream.Free;
  end;
end;procedure DecompressStream (aSource, aTarget: TStream) ;
var
  decompStream: TDecompressionStream;
  nRead: Integer;
  Buffer: array [0..1023] of Char;
begin
  aSource.Position:=0;
  decompStream := TDecompressionStream.Create(aSource);
  try
    repeat
      nRead := decompStream.Read(Buffer, 1024);
      aTarget.Write (Buffer, nRead);
    until nRead = 0;
  finally
    decompStream.Free;
  end;
end;
//压缩方法：
function CompressStr(FStr:String;out CompressSize:Integer):PChar;stdcall;
var
  StringStrm: TStringStream;
  CompressStrm: TMemoryStream;
  DataStrm: TMemoryStream;
  OldLength:Integer;
begin
    StringStrm:=TStringStream.Create(FStr);
    OldLength:=Length(FStr);
    try
      CompressStrm:=TMemoryStream.Create;
      DataStrm:= TMemoryStream.Create;
      try
        CompressStream(StringStrm,CompressStrm);
        CompressStrm.Position:=0;
        DataStrm.Write(OldLength,SizeOf(OldLength));
        DataStrm.Write(CompressStrm,CompressStrm.Size);
        DataStrm.Position:=0;        StrCopy(Result,DataStrm.Memory);
        CompressSize:=DataStrm.Size;
      finally
        CompressStrm.Free;
      end;
    finally
      StringStrm.Free;
    end;
end;
//解压缩方法：
function DecompressStr(FStr:PChar;CompressSize:Integer):String;stdcall;
var
 StringStrm: TStringStream;
 MemoStrm,DataStrm: TStream;
begin
    StringStrm:=TStringStream.Create('');
    try
      DataStrm:=TMemoryStream.Create;
      MemoStrm:=TMemoryStream.Create;
      try
        DataStrm.WriteBuffer(FStr,CompressSize);
        DataStrm.Position:=SizeOf(Integer);
        MemoStrm.CopyFrom(DataStrm,DataStrm.Size-SizeOf(Integer));
        DecompressStream(MemoStrm,StringStrm);
        Result:=StringStrm.DataString;
      finally
        MemoStrm.Free;
        DataStrm.Free;
      end;
    finally
      StringStrm.Free;
    end;
end;
exports
  CompressStr  name 'CompressStr',
  DecompressStr name 'DecompressStr';程序调用部分：function  CompressStr(FStr:widestring;out CompressSize:Integer):Pchar;stdcall;external 'SZlibDll.dll' name 'CompressStr';
function  DecompressStr(FStr:PChar;CompressSize:Integer):widestring;stdcall;external 'SZlibDll.dll' name 'DecompressStr';procedure TForm1.Button1Click(Sender: TObject);
var comPChar:PChar;
  FSize:Integer;
begin
  memo3.Lines.Clear;
  comPChar:=CompressStr(memo2.Lines.Text,FSize);
  memo3.Lines.Text:=String(comPChar);  memo1.Lines.Clear;
  memo1.Lines.Text:=DecompressStr(comPChar,FSize);
  
end;