int aws_mqtt_packet_connect_decode()

in source/packets.c [286:382]

• 66 lines of code
• 20 McCabe index (conditional complexity)

int aws_mqtt_packet_connect_decode(struct aws_byte_cursor *cur, struct aws_mqtt_packet_connect *packet) {

    AWS_PRECONDITION(cur);
    AWS_PRECONDITION(packet);

    /*************************************************************************/
    /* Fixed Header                                                          */

    if (aws_mqtt_fixed_header_decode(cur, &packet->fixed_header)) {
        return AWS_OP_ERR;
    }

    /*************************************************************************/
    /* Variable Header                                                       */

    /* Check protocol name */
    struct aws_byte_cursor protocol_name = {
        .ptr = NULL,
        .len = 0,
    };
    if (s_decode_buffer(cur, &protocol_name)) {
        return aws_raise_error(AWS_ERROR_SHORT_BUFFER);
    }
    AWS_ASSERT(protocol_name.ptr && protocol_name.len);
    if (protocol_name.len != s_protocol_name.len) {
        return aws_raise_error(AWS_ERROR_MQTT_UNSUPPORTED_PROTOCOL_NAME);
    }
    if (memcmp(protocol_name.ptr, s_protocol_name.ptr, s_protocol_name.len) != 0) {
        return aws_raise_error(AWS_ERROR_MQTT_UNSUPPORTED_PROTOCOL_NAME);
    }

    /* Check protocol level */
    struct aws_byte_cursor protocol_level = aws_byte_cursor_advance(cur, 1);
    if (protocol_level.len == 0) {
        return aws_raise_error(AWS_ERROR_SHORT_BUFFER);
    }
    if (*protocol_level.ptr != S_PROTOCOL_LEVEL) {
        return aws_raise_error(AWS_ERROR_MQTT_UNSUPPORTED_PROTOCOL_LEVEL);
    }

    /* Read connect flags [MQTT-3.1.2.3] */
    uint8_t connect_flags = 0;
    if (!aws_byte_cursor_read_u8(cur, &connect_flags)) {
        return aws_raise_error(AWS_ERROR_SHORT_BUFFER);
    }
    packet->clean_session = (connect_flags >> 1) & 0x1;
    packet->has_will = (connect_flags >> 2) & 0x1;
    packet->will_qos = (connect_flags >> 3) & 0x3;
    packet->will_retain = (connect_flags >> 5) & 0x1;
    packet->has_password = (connect_flags >> 6) & 0x1;
    packet->has_username = (connect_flags >> 7) & 0x1;

    /* Read keep alive */
    if (!aws_byte_cursor_read_be16(cur, &packet->keep_alive_timeout)) {
        return aws_raise_error(AWS_ERROR_SHORT_BUFFER);
    }

    /*************************************************************************/
    /* Payload                                                               */

    /* Client identifier is required, Read it */
    if (s_decode_buffer(cur, &packet->client_identifier)) {
        return AWS_OP_ERR;
    }

    /* Read will */
    if (packet->has_will) {
        if (s_decode_buffer(cur, &packet->will_topic)) {
            return AWS_OP_ERR;
        }
        if (s_decode_buffer(cur, &packet->will_message)) {
            return AWS_OP_ERR;
        }
    }

    /* Read username */
    if (packet->has_username) {
        if (s_decode_buffer(cur, &packet->username)) {
            return AWS_OP_ERR;
        }
    }

    /* Read password */
    if (packet->has_password) {
        if (s_decode_buffer(cur, &packet->password)) {
            return AWS_OP_ERR;
        }
    }

    /* Do validation */
    if (packet->has_password && !packet->has_username) {

        return aws_raise_error(AWS_ERROR_MQTT_INVALID_CREDENTIALS);
    }

    return AWS_OP_SUCCESS;
}