PvaClientChannelPtr PvaClient::channel(
        std::string const & channelName,
        std::string const & providerName,
        double timeOut)
{
    PvaClientChannelPtr pvaClientChannel = 
        pvaClientChannelCache->getChannel(channelName,providerName);
    if(pvaClientChannel) return pvaClientChannel;
    pvaClientChannel = createChannel(channelName,providerName);
    pvaClientChannel->connect(timeOut);
    pvaClientChannelCache->addChannel(pvaClientChannel);
    return pvaClientChannel;
}
static void exampleCADoubleArray(PvaClientPtr const &pva)
{
    cout << "__exampleCADoubleArray__\n";
    shared_vector<const double> value;
    try {
        cout << "short way\n";
        value =  pva->channel("DBRdoubleArray","ca",5.0)->get()->getData()->getDoubleArray();
        cout << "as doubleArray " << value << endl;
    } catch (std::runtime_error e) {
        cout << "exception " << e.what() << endl;
    }
    try {
        cout << "long way\n";
        PvaClientChannelPtr pvaChannel = pva->createChannel("DBRdoubleArray","ca");
        pvaChannel->connect(2.0);
        PvaClientGetPtr pvaGet = pvaChannel->createGet();
        PvaClientGetDataPtr pvaData = pvaGet->getData();
        value = pvaData->getDoubleArray();
        cout << "as doubleArray " << value << endl;
    } catch (std::runtime_error e) {
        cout << "exception " << e.what() << endl;
    }
}
static void exampleDouble(PvaClientPtr const &pvaClient)
{
    testDiag("== exampleDouble ==");

    PvaClientChannelPtr pvaChannel;
    try {
        pvaChannel = pvaClient->createChannel("PVRdouble");
        pvaChannel->connect(2.0);
        testDiag("channel connected");
    } catch (std::runtime_error e) {
        testAbort("channel connection exception '%s'", e.what());
    }

    PvaClientPutPtr put;
    PvaClientPutDataPtr putData;
    try {
        put = pvaChannel->createPut();
        putData = put->getData();
        testDiag("put connected");
        if (!putData)
            testAbort("NULL data pointer from putGet");
    } catch (std::runtime_error e) {
        testAbort("put connection exception '%s'", e.what());
    }

    PvaClientGetPtr get;
    PvaClientGetDataPtr getData;
    try {
        get = pvaChannel->createGet();
        getData = get->getData();
        testDiag("get connected");
        if (!getData)
            testAbort("NULL data pointer from putGet");
    } catch (std::runtime_error e) {
        testAbort("get connection exception '%s'", e.what());
    }

    PvaClientMonitorRequesterPtr requester(new MyMonitor());
    PvaClientMonitorPtr monitor;
    expected.set(0);        // structure definition
    try {
        monitor = pvaChannel->monitor(requester);
        testDiag("monitor connected");
    } catch (std::runtime_error e) {
        testAbort("monitor connection exception '%s'", e.what());
    }
    epicsThreadSleep(0.1);  // Allow connection monitor event to fire

    expected.clear();       // FIXME: Magic numbers here...
    expected.set(1);        // value
    expected.set(6);        // timestamp

    try {
        for (int i=0; i<5; ++i) {
            testDiag("= put %d =", i);

            double out = i;
            putData->putDouble(out);
            put->put();

            get->get();
            double in = getData->getDouble();
            testOk(in == out, "get value matches put");
        }

        PvaClientProcessPtr process = pvaChannel->createProcess();
        process->connect();

        testDiag("= process =");
        expected.clear(1);  // no value change
        process->process();
    } catch (std::runtime_error e) {
        testAbort("exception '%s'", e.what());
    }
}