Message broker

Table of Contents

• Defining API for messages
  • Defining the size of the message
  • Defining the message constructor
  • Defining the message destructor
  • Defining a vtable
  • Complete API
• Publish and subscribe
  • Initializing a broker
  • Creating a subscriber
  • Subscribing to a topic
  • Publishing to a topic
  • Receiving a message
  • Complete example

This is an example usage of the message broker.

Defining API for messages

Defining the size of the message

static size_t size(void)
{
        return sizeof(char[8]);
}

Defining the message constructor

static void init(StLoad* load, va_list vlist)
{
        const char* format = va_arg(vlist, char*);
 
        vsnprintf(load, 8, format, vlist);
}

Defining the message destructor

static void deinit(StLoad* load)
{
        (void)load;
}

Defining a vtable

const struct StLoadVt SAMPLE_LOAD_API[] = {
        {.size = size, .ctor = init, .dtor = deinit}};

Complete API

static size_t size(void)
{
        return sizeof(char[8]);
}
 
static void init(StLoad* load, va_list vlist)
{
        const char* format = va_arg(vlist, char*);
 
        vsnprintf(load, 8, format, vlist);
}
 
static void deinit(StLoad* load)
{
        (void)load;
}
 
const struct StLoadVt SAMPLE_LOAD_API[] = {
        {.size = size, .ctor = init, .dtor = deinit}};

Publish and subscribe

Initializing a broker

StBroker* broker = broker_create(SAMPLE_LOAD_API);

Note

‍[!NOTE] The API passed here is the previously defined vtable.

Creating a subscriber

StSubscriber* sber = subscriber_create(broker);

Subscribing to a topic

subscribe(sber, "test");

Publishing to a topic

publish(broker_search(broker, "test"), "%X", 0xF00D);

Note

‍[!NOTE] The behaviour of the publish procedure is controlled with the message constructor.

Receiving a message

load = subscriber_await(sber);

Complete example

TEST(subscriber, should_receive_enqueued_message)
{
        StBroker* broker = broker_create(SAMPLE_LOAD_API);
        StSubscriber* sber = subscriber_create(broker);
        StLoad* load = NULL;
 
        subscribe(sber, "test");
        publish(broker_search(broker, "test"), "%X", 0xF00D);
        TEST_ASSERT_NULL(channel_gettopic(load_getchan(load)));
        load = subscriber_await(sber);
        TEST_ASSERT_EQUAL_STRING("F00D", load);
        TEST_ASSERT_NULL("test", channel_gettopic(load_getchan(load)));
        broker_destroy(broker);
}