Correct format of parameters in extern function

Question

I am creating a c# app for reading rxp data using the RiVLIB library (http://riegl.com/index.php?id=224). I don't know how to properly define the attributes of the external function.

I can already call some functions like scanifc_get_library_version and scanifc_point3dstream_open but I can't figure out the correct format of the parameters for the scanifc_point3dstream_read function.

after calling scanifc_point3dstream_read (with h3ds acquired from the scanifc_point3dstream_open) I get System.AccessViolationException.

the call looks like:

IntPtr h3ds = IntPtr.Zero;
int sync_to_pps = 0;
//this works ok -> h3ds gets assigned
int opened = scanifc_point3dstream_open_with_logging("190910_092831.rxp", ref sync_to_pps, "log.txt", ref h3ds);

uint PointCount = 0;
int EndOfFrame = 1;
const uint BLOCK_SIZE = 10;
scanifc_xyz32[] BufferXYZ = new scanifc_xyz32[BLOCK_SIZE];
scanifc_attributes[] BufferMISC = new scanifc_attributes[BLOCK_SIZE];
ulong[] BufferTIME = new ulong[BLOCK_SIZE];
//throws AccessViolationException
int read = scanifc_point3dstream_read(
    h3ds, BLOCK_SIZE,
    ref BufferXYZ, ref BufferMISC, ref BufferTIME,
    ref PointCount, ref EndOfFrame);

[DllImport("scanifc-mt.dll")]
static extern int scanifc_point3dstream_read(
    IntPtr h3ds,
    uint want,
    [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 1)] ref scanifc_xyz32[] pxyz32,
    [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 1)] ref scanifc_attributes[] pattributes,
    [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 1)] ref ulong[] ptime,
    ref uint got,
    ref int end_of_frame);

used structs:

[StructLayout(LayoutKind.Sequential)]
struct scanifc_xyz32
{
    float x;
    float y;
    float z;
}

[StructLayout(LayoutKind.Sequential)]
struct scanifc_attributes
{
    float amplitude;
    float reflectance;
    ushort deviation;
    ushort flags;
    float background_radiation;
}

Here is the library function header:

SCANIFC_API int
scanifc_point3dstream_read(point3dstream_handle, scanifc_uint32_t,
 scanifc_xyz32 *, scanifc_attributes *,
 scanifc_time_ns *, scanifc_uint32_t *,
 scanifc_bool *);

and typedefs:

typedef IMPLEMENTATION_DEFINED scanifc_uint8_t; // unsigned 8 bit integer
typedef IMPLEMENTATION_DEFINED scanifc_int8_t; // signed 8 bit integer
typedef IMPLEMENTATION_DEFINED scanifc_uint16_t; // unsigned 16 bit integer
typedef IMPLEMENTATION_DEFINED scanifc_int16_t; // signed 16 bit integer
typedef IMPLEMENTATION_DEFINED scanifc_uint32_t; // unsigned 32 bit integer
typedef IMPLEMENTATION_DEFINED scanifc_int32_t; // signed 32 bit integer
typedef IMPLEMENTATION_DEFINED scanifc_uint64_t; // unsigned 64 bit integer
typedef IMPLEMENTATION_DEFINED scanifc_int64_t; // signed 64 bit integer
typedef IMPLEMENTATION_DEFINED scanifc_uintmax_t; // unsigned largest available bitsize integer
typedef IMPLEMENTATION_DEFINED scanifc_intmax_t; // signed largest available bitsize integer
typedef IMPLEMENTATION_DEFINED scanifc_float32_t; // 32 bit floating point
typedef IMPLEMENTATION_DEFINED scanifc_float64_t; // 64 bit floating point
typedef char* scanifc_sz;
typedef const char* scanifc_csz; // pointer to zero delimited string
typedef scanifc_int32_t scanifc_bool; // pointer to constant zero delimited string 

typedef struct scanifc_xyz32_t scanifc_xyz32; // a point in cartesian coordinates
typedef struct scanifc_attributes_t scanifc_attributes; // per point attributes
typedef scanifc_uint64_t scanifc_time_ns;

struct scanifc_xyz32_t {
 // public data members
 scanifc_float32_t x; // x coordinates
 scanifc_float32_t y; // y coordinates
 scanifc_float32_t z; // z coordinates
};

struct scanifc_attributes_t {
 // public data members
 scanifc_float32_t amplitude; // relative amplitude in [dB]
 scanifc_float32_t reflectance; // relative reflectance in [dB]
 scanifc_uint16_t deviation; // a measure of pulse shape distortion.
 scanifc_uint16_t flags; // some bit-mapped attribute values
 scanifc_float32_t background_radiation; // background radiation.
};

Answer 1

so after several hours, I found the solution...I am posting it if somebody would find it helpful. I found my answer in this post: Referencing an object array in C# PInvoke

int read = scanifc_point3dstream_read(
    h3ds, BLOCK_SIZE,
    BufferXYZ, BufferMISC, BufferTIME,
    ref PointCount, ref EndOfFrame);

[DllImport("scanifc-mt.dll")]
static extern int scanifc_point3dstream_read(
    IntPtr h3ds,
    uint want,
    [Out] scanifc_xyz32[] pxyz32,
    [Out] scanifc_attributes[] pattributes,
    [Out] ulong[] ptime,
    ref uint got,
    ref int end_of_frame);