How to obtain Hashtable element (array) base type?

Question

Hi,
     I have read the thread
          http://forum.java.sun.com/thread.jspa?forumID=52&threadID=531561
     on determining the base type of an object array.
     I tried applying the technique to my Hashtable where the element are arrays, this is how I am setting up my Hashtable to pass on to my native method
Hashtable ht = new Hashtable();
Float Kd[] = new Float[1];
Kd[0] = 0.1f;
Float from[] = new Float[3];
from[0] = -4.0f;
from[1] = 2.0f;
from[2] = 1.0f;
Integer indices[] = new Integer[4];
indices[0] = 217;
indices[1] = 17;
indices[2] = 769;
indices[3] = 23;
     myNativeMethod("dbname",ht);
     In my native method, I have the following which is able to determine the array size so I think it is kind of working/correct but when I tried to determine the base type of the array, I keep getting Bus error.
     Here is my native code (as part of my SWIG code)
     Should I be handling arrays obtained from Hashtable differently, can someone point out to me what the correct approach is?
Regards
8<------8<------8<------8<------8<------8<------8<------8<------
if ($input != 0) {
std::cout << "SWIG ...parameterlist..." << std::endl;
// Generated typemap code
const jclass hashtable = jenv->FindClass("java/util/Hashtable");
if (hashtable != 0) {
const jclass enumeration = jenv->FindClass("java/util/Enumeration");
const jmethodID keys =
     jenv->GetMethodID(hashtable, "keys",
               "()Ljava/util/Enumeration;");
const jmethodID get =
     jenv->GetMethodID(hashtable, "get",
               "(Ljava/lang/Object;)Ljava/lang/Object;");
if (enumeration != 0) {
     const jmethodID hasMoreElements =
     jenv->GetMethodID(enumeration,
               "hasMoreElements", "()Z");
     const jmethodID nextElement =
     jenv->GetMethodID(enumeration,
               "nextElement", "()Ljava/lang/Object;");
     for (jobject keyset = jenv->CallObjectMethod($input, keys);
     jenv->CallBooleanMethod(keyset, hasMoreElements) == JNI_TRUE;) {
     jstring key = (jstring)jenv->CallObjectMethod(keyset, nextElement);
     jarray value = (jarray)jenv->CallObjectMethod($input, get, key);
     jclass valueClass = jenv->GetObjectClass(value);
     jclass valueClassClass = jenv->GetObjectClass(valueClass);
     const jmethodID getName =
     jenv->GetMethodID(valueClass,
               "getName", "()Ljava/lang/String;");
     jstring valueClassClassName =
     (jstring)jenv->CallObjectMethod(value, getName);
     const char *vccptr = jenv->GetStringUTFChars(valueClassClassName,
                              0);
     std::cout << "vccptr is " << vccptr << std::endl;
     jenv->ReleaseStringUTFChars(valueClassClassName, vccptr);
     const char *keyptr = jenv->GetStringUTFChars(key, 0);
     std::cout << "key is " << keyptr << std::endl;
     int numElements = jenv->GetArrayLength(value);
     std::cout << "value array size is " << numElements << std::endl;
     // const char *valptr = jenv->GetStringUTFChars(value, 0);
     // $1 = CSLAddNameValue($1, keyptr, valptr);
     jenv->ReleaseStringUTFChars(key, keyptr);
     // jenv->ReleaseStringUTFChars(value, valptr);
8<------8<------8<------8<------8<------8<------8<------8<------
Regards
Message was edited by:
nicholas_yue

Answer 1

You've asked the same thing before. Assuming that you've defined the function prototype correctly when you built the DLL from the VI, you should be able to call it and get the results from it. You do not need to change the return type when you build the DLL. Read the information at http://zone.ni.com/devzone/conceptd.nsf/webmain/7D6A20FE02EDBF318625690700704CF3. Even though it was written for LabVIEW 6, the section on Accessing LabVIEW 6x Arrays from Microsoft Visual C++ is still valid.