IWMSBufferAllocator::AllocateBuffer

The AllocateBuffer method initializes an INSSBuffer object.

HRESULT AllocateBuffer(
  DWORD  dwMaxBufferSize,
  INSSBuffer**  ppBuffer
);

Arguments

dwMaxBufferSize	[in] DWORD containing the maximum size of the buffer in bytes. This must be less than 16 MB (16,777,216 bytes).
ppBuffer	[out] Pointer to a pointer to an INSSBufferINSSBuffer Interface.

Return Value

If the method succeeds, it returns S_OK. If it fails, it returns an HRESULT error code.

Return code	Number	Description
E_INVALIDARG	0x80070057	One or both parameters are not valid.
E_OUTOFMEMORY	0x8007000E	The method failed to allocate memory.

Remarks

This method is used internally mainly by media parser, data sink, and data source plug-ins. Custom plug-in applications include, but are not limited to, data source and cache proxy plug-ins.

Example

The following example uses the IWMSBufferAllocator object to allocate a buffer to hold the written playlist file.

HRESULT STDMETHODCALLTYPE 
CSDKSamplePlaylistParser::WritePlaylist( 
                        IXMLDOMDocument *pPlayList,
                        IWMSPlaylistParserCallback *pCallback,
                        QWORD qwContext)
{
    IXMLDOMNode           *pAttrNode, *pNode;
    IXMLDOMNodeList       *pNodeList;
    IXMLDOMNamedNodeMap   *pNodeAttr;
    IWMSBufferAllocator   *pBufAllocator;
    INSSBuffer            *pBuffer;
    CComBSTR               bstrAttrName, bstrAttrValue, bstrTemp;
    CComVariant            varValue;
    int                    i, j;
    long                   lLength, lLength2;
    HRESULT                hr;

    bstrTemp = "media";
    hr = pPlayList->getElementsByTagName(bstrTemp, &pNodeList);
    if (FAILED(hr)) goto EXIT;

    hr = pNodeList->get_length(&lLength);
    if (FAILED(hr)) goto EXIT;

    bstrTemp = "";
    for (i=0; i < lLength; i++)
    {
        hr = pNodeList->get_item((long)i, &pNode);
        if (FAILED(hr)) goto EXIT;

        hr = pNode->get_attributes(&pNodeAttr);
        if (FAILED(hr)) goto EXIT;

        hr = pNodeAttr->get_length(&lLength2);
        if (FAILED(hr)) goto EXIT;

        for (j=0; j < lLength2; j++)
        {
            hr = pNodeAttr->get_item((long)j, &pAttrNode);
            if (FAILED(hr)) goto EXIT;
            hr = pAttrNode->get_nodeName(&bstrAttrName);
            if (FAILED(hr)) goto EXIT;

            if( bstrAttrName == "src" )
            {
                hr = pAttrNode->get_nodeValue(&varValue);
                if (FAILED(hr)) goto EXIT;

                bstrTemp.Append(varValue.bstrVal);
                bstrTemp.Append("\r\n");
                break;
            }
        }
    }

    if( bstrTemp.ByteLength() > 0 )
    {
        m_spClassFactory.QueryInterface(&pBufAllocator);
        pBufAllocator->AllocateBuffer(bstrTemp.ByteLength(), &pBuffer);

        BYTE *pBuf;
        pBuffer->SetLength(bstrTemp.ByteLength());
        pBuffer->GetBuffer(&pBuf);
        memcpy(pBuf, (char *)bstrTemp.m_str, bstrTemp.ByteLength());

        hr = S_OK;
        pCallback->OnWritePlaylist(hr, pBuffer, qwContext);
        return( hr );
    }

EXIT:
    // TODO: Release temporary COM objects.
    return( hr );
}

Requirements

Header: wmsbuffer.h.

Library: WMSServerTypeLib.dll.

Platform: Windows Server 2003, Enterprise Edition; Windows Server 2003, Datacenter Edition; Windows Server 2008.

See Also

Concepts

INSSBuffer Interface

IWMSBufferAllocator Interface