IotMqtt_GetConnectPacketSize

Calculate the size and "Remaining length" of a CONNECT packet generated from the given parameters.

IotMqttError_t IotMqtt_GetConnectPacketSize( const IotMqttConnectInfo_t * pConnectInfo,
                                             size_t * pRemainingLength,
                                             size_t * pPacketSize );

Parameters

[in]	pConnectInfo	User-provided CONNECT information struct.
[out]	pRemainingLength	Output for calculated "Remaining length" field.
[out]	pPacketSize	Output for calculated total packet size.

Returns

IOT_MQTT_SUCCESS if the packet is within the length allowed by MQTT 3.1.1 spec; IOT_MQTT_BAD_PARAMETER otherwise. If this function returns IOT_MQTT_BAD_PARAMETER, the output parameters should be ignored.

Note

This call is part of serializer API used for implementing light-weight MQTT client.

Example

// Example code below shows how IotMqtt_GetConnectPacketSize() should be used to calculate
// the size of connect request.

IotMqttConnectInfo_t xConnectInfo;
size_t xRemainingLength = 0;
size_t xPacketSize = 0;
IotMqttError_t xResult;

// start with everything set to zero
memset( ( void * ) &xConnectInfo, 0x00, sizeof( xConnectInfo ) );

// Initialize connection info, details are out of scope for this example.
_initializeConnectInfo( &xConnectInfo );
// Get size requirement for the connect packet
xResult = IotMqtt_GetConnectPacketSize( &xConnectInfo, &xRemainingLength, &xPacketSize );
IotMqtt_Assert( xResult == IOT_MQTT_SUCCESS );

 // Application should allocate buffer with size == xPacketSize or use static buffer
 // with size >= xPacketSize to serialize connect request.