Getting Started Status

Language: C++ Java Python

Basic:	Intro/Trade	Quote	Category	Status	Symbol	Options
Detailed:	Trade	Quote

Introduction to Statuses

Status messages indicate general information about the tape has changed. pNxCoreSys contains details of the status message. pNxCoreSys is also populated for non-status messages as well. For this example we will be printing a timestamp every minute and printing the API version on initialization. Both NxCORESTATUS_WAITFORCOREACCESS and NxCORESTATUS_ERROR will not occur for demo.XU.nx2, but they are generally good checks to have while processing.

Code

#include "stdio.h"
#include "NxCoreAPI_Wrapper_C++.h"
NxCoreClass NxCore;

int OnNxCoreCallback(const NxCoreSystem* pNxCoreSys, const NxCoreMessage* pNxCoreMsg) {
    if(pNxCoreMsg->MessageType == NxMSG_STATUS) {
        if (pNxCoreSys->ClockUpdateInterval >= NxCLOCK_MINUTE) {
            int year = pNxCoreSys->nxDate.Year;
            int month = pNxCoreSys->nxDate.Month;
            int day = pNxCoreSys->nxDate.Day;
            int hour = pNxCoreSys->nxTime.Hour;
            int minute = pNxCoreSys->nxTime.Minute;
            printf("%02d/%02d/%04d %02d:%02d\n", month, day, year, hour, minute);
        }

        if (pNxCoreSys->Status == NxCORESTATUS_WAITFORCOREACCESS)
            printf("Waiting on NxCore Access\n");

        if (pNxCoreSys->Status == NxCORESTATUS_ERROR)
            printf("tape error:%d\n", pNxCoreSys->StatusData);

        if (pNxCoreSys->Status == NxCORESTATUS_INITIALIZING) {
            int major = NxCore.GetMajorVersion(pNxCoreSys->DLLVersion);
            int minor = NxCore.GetMinorVersion(pNxCoreSys->DLLVersion);
            int build = NxCore.GetBuildVersion(pNxCoreSys->DLLVersion);
            printf("Initialized with decoder version %d.%d.%d\n", major, minor, build);
        }
    }
    return NxCALLBACKRETURN_CONTINUE;
}

int main(int argc, char* argv[]) {
    if (argc < 3)
        return 1;

    if (NxCore.LoadNxCore(argv[1])){
        int returnValue = NxCore.ProcessTape(argv[2], 0, 0, 0, OnNxCoreCallback);
        NxCore.ProcessReturnValue(returnValue);
    }
    else
        printf("loading library failed\n");

    return 0;
}

Callback Function

Since we only want to process status messages we check that MessageType equals NxMSG_STATUS.

@Override
int OnNxCoreCallback(
    const NxCoreSystem* pNxCoreSys, const NxCoreMessage* pNxCoreMsg) {
    if(pNxCoreMsg->MessageType == NxMSG_STATUS) {
        ...
    }
    return defines.NxCALLBACKRETURN_CONTINUE;
}

On Interval

During status messages ClockUpdateInterval indicates if the timestamp has changed and whether it is a new hour, minute, or second. In this example we want to do something every minute, so we will check if ClockUpdateInterval is greater or equal to NxCLOCK_MINUTE, which is equivalent to 3. Checking greater than ensures we also perform the action on a new hour, since NxCLOCK_HOUR is equivalent to 4.
The fields nxDate and nxTime reflect the date and time of the server processing the data.

if (pNxCoreSys->ClockUpdateInterval >= NxCLOCK_MINUTE) {
    int year = pNxCoreSys->nxDate.Year;
    int month = pNxCoreSys->nxDate.Month;
    int day = pNxCoreSys->nxDate.Day;
    int hour = pNxCoreSys->nxTime.Hour;
    int minute = pNxCoreSys->nxTime.Minute;
    ...
}

Incomplete File

The Status field of NxCore message is the current state of the tape. Most of the time Status will be NxCORESTATUS_RUNNING. If the API is unable process the next message after a period of time, either because the file is incomplete or real-time stream is paused, Status will be set to NxCORESTATUS_WAITFORCOREACCESS.

if (pNxCoreSys->Status == NxCORESTATUS_WAITFORCOREACCESS)
    printf("Waiting on NxCore Access\n");

Errors

If there is a problem while processing the tape, Status is set to NxCORESTATUS_ERROR. StatusData contains details of the Status. In this case it corresponds to the Error Codes Table.

if (pNxCoreSys->Status == NxCORESTATUS_ERROR)
    printf("tape error:%d\n", pNxCoreSys->StatusData);

Initialization

The first Status when beginning at the start of the file is NxCORESTATUS_INITIALIZING. If loading midday using states then the first status will instead be NxCORESTATUS_LOADED_STATE.
During the first message we will print the version of the API being used to process the tape. GetMajorVersion, GetMinorVersion, and GetBuildVersion can be used to get a more readable version from the int DLLVersion.

if (pNxCoreSys->Status == NxCORESTATUS_INITIALIZING) {
    int major = NxCore.GetMajorVersion(pNxCoreSys->DLLVersion);
    int minor = NxCore.GetMinorVersion(pNxCoreSys->DLLVersion);
    int build = NxCore.GetBuildVersion(pNxCoreSys->DLLVersion);
    printf("Initialized with decoder version %d.%d.%d\n", major, minor, build);
}

Next:
Symbol

API Documentation