How to create a c++struct which is defined in extern c++ lib in MATLAB?

I want to call a c++ method in matlab like:

loadlibrary('ASICamera2');
p = libpointer('string');
gpsData = struct();
x = calllib('ASICamera2','ASIGetDataAfterExpGPS', 0, p, 256*256, gpsData);

In 'ASICamera2.h',method 'ASIGetDataAfterExpGPS' is defined as follow. Obviously, the above matlab code dosen't work because p and gpsData are not correct data type.

int ASIGetDataAfterExpGPS(int iCameraID, unsigned char* pBuffer, long lBuffSize, ASI_GPS_DATA *gpsData);

typedef struct _ASI_GPS_DATA {
	ASI_DATE_TIME Datetime;
	double Latitude;  
	double Longitude; 
	char Unused[64];  
} ASI_GPS_DATA;

typedef struct _ASI_DATE_TIME{
	int Year; 
	char Unused[64]; 
} ASI_DATE_TIME;

Now I have two questions:

1. How to create char* argument in matlab?
2. How to create a struct likes ASI_GPS_DATA * in matlab?

I tried libstruct function in matlab but failed, if anyone can help me?

Answer 1

[Harsh]

Hi,

From what I can gather, you are trying to use a C/C++ function in MATLAB which uses a struct and are facing issues while using the structure.

Follow the following steps to initialize a C/C++ structure and char* in MATLAB:

(sample.c)

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

typedef struct {
    int id;
    char* value;
} sampleStruct;

sampleStruct* initStruct(int id, char* value) {
    sampleStruct* s = (sampleStruct*)malloc(sizeof(sampleStruct));
    s->id = id;
    s->value = strdup(value);
    return s;
}

sampleStruct* useStruct(sampleStruct* s) {
    return s;
}

Compile *.so file of sample.c

gcc -shared -fpic -o sample.so sample.c

Define a sample.h file

typedef struct {
    int id;
    char* value;
} sampleStruct;

sampleStruct* initStruct(int id, char* value);
sampleStruct* useStruct(sampleStruct* s);

Using the loadlibrary function, load sample.h

loadlibrary('sample.so', 'sample.h') 

Call useStruct function which uses a structure from MATLAB using the calllib function in MATLAB.

s_ptr = calllib('sample', 'initStruct', 123, 'sampleStr'); 
val = calllib('sample', 'useStruct', s_ptr); 
disp(val) 

I hope this help, thanks!

[yijia]

Hi Harsh, thank you very much!

Your answer is very specific! Folloing step by step perfectly solves my questions.