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Thread: Java Native Access and arrays

  1. #1
    Junior Member
    Join Date
    Sep 2011
    Thanked 1 Time in 1 Post

    Default Java Native Access and arrays

    I plan to write an interface for a spectrometer in JAVA. The manufacturer provides a c-dll to access the spectrometer. Therefore I have written a JNA-wrapper.

    I could connect to the spectrometer and access simple methods of the dll. But I have problems to write appropriate functions, if the c-functions accept pointer-to-type arguments to return arrays.

    For example:

    c-header to access calibration data, from rcu1a.h:

    USHORT WINAPI RC_ReadCalibrationValue(
    	HANDLE DeviceHandle,
    	double *DataArray

    according function in rcu1a.java:

    short RC_ReadCalibrationValue(Pointer DeviceHandle, DoubleByReference DataArray);

    and the code snipplet from Spectrometer.java, the class to access the spectrometer data:

    private rcu1a lib = (rcu1a) Native.loadLibrary("rcu1a", rcu1a.class);
    private DoubleByReference  calibData = new DoubleByReference();
     public double [] calibrationData()
           lib.RC_ReadCalibrationValue(DeviceHandle, calibData);
            return calibData.getPointer().getDoubleArray(0,6);

    The function should return an array with 6 calibration parameters. Like this I get and array out of bounds exception:

    java.lang.IndexOutOfBoundsException: Bounds exceeds available space : size=8, offset=48
    if I change to calibData.getValue(); I get the value that should be in the first field of the array.

    Am I doing something substantially wrong in handling arrays?

    Thx Richard

  2. The Following User Says Thank You to p0llux For This Useful Post:

    morphtechnologies34a (September 25th, 2012)

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