Question

SWIG converts the below unsigned char array (“id”) to short[]. On the C side, the id attribute of the sender_id_t_ struct is a pointer to an array that contains alphanumeric data like “TEST123-E”. I suppose you could loop over short[] (sender_id_t_.getId()) and cast each element to a char and concatenate to build a Java String. I’m wondering if their is a better and simpler way of handling this situation?

C Header File:

#define SAMPLE_ID_SIZE_V1 32
#define SAMPLE_ID_SIZE SAMPLE_ID_SIZE_V1

typedef unsigned char sample_id_v1_t[SAMPLE_ID_SIZE];
typedef sample_id_v1_t sample_id_t;

struct sample_sender_id_t_ {
    sample_id_t           id;
    uint32_t              idx;
};
typedef struct sample_sender_id_t_ sample_sender_id_t;

SWIG.i:

%rename (Sample) sender_id_t_;
struct sender_id_t_ {
    unsigned char id_v1_t[32]      id;
    uint32_t   phy_idx;
};

Exception:

 [exec] test_wrap.c: In function `TestJNI_Sample_1id_1set':
 [exec] test_wrap.c:826: error: cast specifies array type
 [exec] test_wrap.c:829: error: incompatible types in assignment
 [exec] test_wrap.c:832: error: `jarr2' undeclared (first use in this function)

Answer 1

It gets treated as an array of short because of the unsigned of the type, which makes the largest value too large to fit in a (signed) byte or char. If you want to force it to be treated a String you can use %apply to use the normal String typemaps, something like:

%module test

%rename (Sample) sender_id_t_;
%apply char * { unsigned char id[32] };

struct sender_id_t_ {
    unsigned char id[32];
    uint32_t   phy_idx;
};

(I had to fix some syntax in your struct, that was a bit odd).