Como salvar 1 istream e ler?

Cambalinho · 19 de julho de 2016

na minha classe image estou a fazer o overloading dos << >> operadores:

friend std::ostream& operator << (std::ostream& lhs, const image& rhs)
    {

        //Create an empty IStream:
        IStream* pIStream = nullptr;
        if(CreateStreamOnHGlobal(NULL, TRUE, (LPSTREAM*)&pIStream)!=S_OK)
            DebugText("error on creating an empty IStream");

        //choose image format for save it on IStream:
        // Get encoder class id for jpg compression
        // for other compressions use
        //    image/bmp
        //    image/jpeg
        //    image/gif
        //    image/tiff
        //    image/png
        CLSID pngClsid;
        GetEncoderClsid(L"image/gif", &pngClsid);

        // Setup encoder parameters
        EncoderParameters encoderParameters;
        encoderParameters.Count = 1;
        encoderParameters.Parameter[0].Guid = EncoderQuality;
        encoderParameters.Parameter[0].Type = EncoderParameterValueTypeLong;
        encoderParameters.Parameter[0].NumberOfValues = 1;

        // setup compression level
        ULONG quality = 50;
        encoderParameters.Parameter[0].Value = &quality;

        //  Save the image to the stream

        if(rhs.img->Save(pIStream, &pngClsid, &encoderParameters) != Ok)
        {
            pIStream->Release();
            DebugText("error on saving to IStream");
        }

        //getting the stream size:

        STATSTG sts;
        pIStream->Stat(&sts, STATFLAG_DEFAULT);
        ULARGE_INTEGER uli = sts.cbSize;
        LARGE_INTEGER zero;
        zero.QuadPart = 0;
        ULONG size = (ULONG)uli.QuadPart;
        char* bits = new char[size];
        ULONG written;
        pIStream->Seek(zero, STREAM_SEEK_SET, NULL);
        pIStream->Read(bits, size, &written);

        //write the stream size on file
        lhs.write(reinterpret_cast<char*>(&size),sizeof(size));

        //write pBuff data on file
        lhs.write(reinterpret_cast<char*>(&bits),size);

        //clean resources
        delete[] bits;
        pIStream->Release();

        return lhs;
    }

    friend std::istream& operator >> (std::istream& lhs, image& rhs)
    {
        //getting IStream size:
        int streamsize;
        lhs.read(reinterpret_cast<char*>(&streamsize), sizeof(streamsize));

        // getting IStream data:
        IStream* pIStream = nullptr;
        HGLOBAL hg= ::GlobalAlloc(GMEM_MOVEABLE,streamsize);
        void* p =GlobalLock(hg);
        lhs.read(reinterpret_cast<char*>(p),streamsize);
        GlobalUnlock(hg);

        if(CreateStreamOnHGlobal(hg, TRUE, (LPSTREAM*)&pIStream)!=S_OK)
            DebugText("error on creating an empty IStream");


        LARGE_INTEGER zero;
        zero.QuadPart = 0;
        pIStream->Seek(zero, STREAM_SEEK_SET, NULL);
        //reading IStream to Image class:
        rhs.img=Image::FromStream(pIStream);
        Status stat = rhs.img->GetLastStatus();
        if(stat!=S_OK)
            DebugText("error reading stream to Image: "  + to_string(stat));
        else
        {
            DebugText("reading stream to Image sucessfull");
        }


        //realease resources:
        pIStream->Release();
        return lhs;
    }