C++ /内存文件使用例程

/// c++ 内存文件使用例程
class   MemoryBuffer : public std::strstreambuf
{
public:
    using Base      =   std::basic_streambuf<char>;
    using char_type =   typename Base::char_type;

    MemoryBuffer(char* buf,size_t len) 
        :std::strstreambuf(buf,len)
    {
    }
};

class   IStream :public std::istream
{
public:
    MemoryBuffer*   _buffer;
public:
    IStream(MemoryBuffer * buf)
        :std::istream(buf)
    {
        _buffer =   buf;
    }
    ~IStream()
    {
        delete  _buffer;
    }
};

std::istream*   pStream =   new IStream(new MemoryBuffer((char*)buf,len));