Pass struct from C to Java JNI

Question

I have a struct and I would like to pass its fields from C to Java with JNI.

The struct:

typedef struct {
  short headerCount;
  short lineCount;
  screenLine *headers;
  screenLine *lines;
}ScrollList;

and screenLine is:

typedef char screenLine[ 26 ];

My method in C:

short SrvSelect_GetScrollListSelection( ScrollList *list)
{
...
}

I succeed to pass both shorts to Java, but I struggle to pass the last two fields:

    jshort headerCount = list->headerCount;
    jshort lineCount = list->lineCount;

Thank you

Answer 1

Assuming headerCount and lineCount are the corresponding number of items in headers and lines :

jobjectarray jHeaders = env->NewObjectArray(list->headerCount, "[B", NULL);
for (int h = 0; h < list->headerCount; h++) {
  jbyteArray jHeader = env->NewByteArray(26);
  env->SetByteArrayRegion(jHeader, 0, 26, list->headers[h]);
  env->SetObjectArrayElement(jHeaders, h, jHeader);
  env->DeleteLocalRef(jHeader);
}

Alternatively, if each screenLine fits in Java's "modified UTF-8" (or is just ASCII):

jobjectarray jHeaders = env->NewObjectArray(list->headerCount, "Ljava/lang/String;", NULL);
for (int h = 0; h < list->headerCount; h++) {
  jbyteArray jHeader = env->NewStringUTF(list->headers[h]);
  env->SetObjectArrayElement(jHeaders, h, jHeader);
  env->DeleteLocalRef(jHeader);
}