//memory allocated
    cfx = xmalloc_clear (sizeof *cfx);
    cfx->release = release_context;
    cfx->algo = cd->algorithm;
    // cdx can be copied in a cd->buf field
    push_compress_filter(cd->buf,cfx,cd->algorithm);
    if( callback )
	rc = callback(cd->buf, passthru );
    else
      rc = proc_packets (ctrl,procctx, cd->buf);
    //cd->buf goes out of scope
    cd->buf = NULL;
    //patch should be xfree(cfx);
    return rc;