// required, this must send a single CAN message with the given arbitration
// ID (i.e. the CAN message ID) and data. The size will never be more than 8
// bytes.
bool send_can(const uint32_t arbitration_id, const uint8_t* data,
        const uint8_t size) {
    ...
}

// optional, provide to receive debugging log messages
void debug(const char* format, ...) {
    ...
}


// not used in the current version
void set_timer(uint16_t time_ms, void (*callback)) {
    ...
}

DiagnosticShims shims = diagnostic_init_shims(debug, send_can, set_timer);

// Optional: This is your callback that will be called the response to your
// diagnostic request is received.
void response_received_handler(const DiagnosticResponse* response) {
    // You received a response! Do something with it.
}

DiagnosticRequestHandle handle = diagnostic_request_pid(&shims,
        DIAGNOSTIC_STANDARD_PID, // this is a standard PID request, not an extended or enhanced one
        OBD2_FUNCTIONAL_BROADCAST_ID, // the request is going out to the broadcast arbitration ID
        0x2, // we want PID 0x2
        response_received_handler); // our callback (optional, use NULL if you don't have one)

if(handle.completed) {
    if(!handle.success) {
        // something happened and it already failed - possibly we aren't
        // able to send CAN messages
        return;
    } else {
        // this should never occur right away - you need to receive a fresh
        // CAN message first
    }
} else {
    while(true) {
        // Continue to read from CAN, passing off each message to the handle.
        // This will return a 'completed' DiagnosticResponse when the when
        // the request is completely sent and the response is received
        // (which may take more than 1 CAN frames)
        DiagnosticResponse response = diagnostic_receive_can_frame(&shims,
            &handle, can_message_id, can_data, sizeof(can_data));

        if(response.completed && handle.completed) {
            if(handle.success) {
              if(response.success) {
                  // The request was sent successfully, the response was
                  // received successfully, and it was a positive response - we
                  // got back some data!
              } else {
                  // The request was sent successfully, the response was
                  // received successfully, BUT it was a negative response
                  // from the other node.
                  printf("This is the error code: %d", response.negative_response_code);
              }
            } else {
                // Some other fatal error ocurred - we weren't able to send
                // the request or receive the response. The CAN connection
                // may be down.
            }
        }
    }
}

DiagnosticRequest request = {
    arbitration_id: OBD2_FUNCTIONAL_BROADCAST_ID,
    mode: OBD2_MODE_EMISSIONS_DTC_REQUEST
};
DiagnosticRequestHandle handle = diagnostic_request(&SHIMS, &request, NULL);

if(handle.completed) {
    if(!handle.success) {
        // something happened and it already failed - possibly we aren't
        // able to send CAN messages
        return;
    } else {
        // this should never occur right away - you need to receive a fresh
        // CAN message first
    }
} else {
    while(true) {
        // Continue to read from CAN, passing off each message to the handle.
        // This will return a 'completed' DiagnosticResponse when the when
        // the request is completely sent and the response is received
        // (which may take more than 1 CAN frames)
        DiagnosticResponse response = diagnostic_receive_can_frame(&shims,
            &handle, can_message_id, can_data, sizeof(can_data));

        if(response.completed && handle.completed) {
            if(handle.success) {
              if(response.success) {
                  // The request was sent successfully, the response was
                  // received successfully, and it was a positive response - we
                  // got back some data!
                  printf("The DTCs are: ");
                  for(int i = 0; i < response.payload_length; i++) {
                    printf("0x%x ", response.payload[i]);
                  }
              } else {
                  // The request was sent successfully, the response was
                  // received successfully, BUT it was a negative response
                  // from the other node.
                  printf("This is the error code: %d", response.negative_response_code);
              }
            } else {
                // Some other fatal error ocurred - we weren't able to send
                // the request or receive the response. The CAN connection
                // may be down.
            }
        }
    }
}

$ make test

$ BROWSER=google-chrome-stable make coverage