JNI Android - Converting char* to byte array and return it to java

Question

I initially used a function to return a char* to java as UTF-8 string, but since I kept getting errors, I wrote the following function to return a char* as a Java byte[], so that I could try to convert the array into a String in java side:

jbyteArray Java_com_vektor_amapper_util_InputDeviceManager_getDevNameBytes(JNIEnv* env, jobject thiz, jint index) {
    if(pDevs[index].device_name == NULL) return NULL;
    int n=0;
    while(pDevs[index].device_name){
        n++;
    } if (n==0) return NULL;
    jbyteArray arr = (*env)->NewByteArray(env, n);
    (*env)->SetByteArrayRegion(env,arr,0,n, (jbyte*)pDevs[index].device_name);
    return arr;
}

But when I call it my application crashes. Am I missing something?

Update: The condition was missing a ++ and this caused an infinite loop. But now with the following code:

jbyteArray Java_com_vektor_amapper_util_InputDeviceManager_getDevNameBytes(JNIEnv* env, jobject thiz, jint index) {
    int n=0;
    if(pDevs[index].device_name == NULL) return NULL;
    while(pDevs[index].device_name++){
        n++;
    } if(n==0) return NULL;
        jbyteArray arr = (*env)->NewByteArray(env, n);
        (*env)->SetByteArrayRegion(env,arr,0,n, (jbyte*)pDevs[index].device_name);
        return arr;
}

I get this weird JNI warning:

06-15 22:40:02.303: W/dalvikvm(7616): JNI WARNING: negative jsize (NewByteArray)

How can it be since I am only increasing the value of n?

Update 2: the following code works:

jbyteArray Java_com_vektor_amapper_util_InputDeviceManager_getDevNameBytes(
        JNIEnv* env, jobject thiz, jint index) {

    if(pDevs[index].device_name == NULL) return NULL;
    int n=0;
    char* p = pDevs[index].device_name;
    while(*p++){
        n++;
    } if(n<=0) return NULL;
    jbyteArray arr = (*env)->NewByteArray(env, n);
    (*env)->SetByteArrayRegion(env,arr,0,n, (jbyte*)pDevs[index].device_name);

    return arr;
}

Answer 1

Shouldn't be this ?

char* p = pDevs[index].device_name;
while( *p++) {
...
}