JNI: converting unsigned int to jint

java c++ java-native-interface unsigned-integer
Pedro picture Pedro · Nov 4, 2011 · Viewed 33.8k times · Source

How do I convert an unsigned int to jint? Do I have to convert it at all, or can I just return it without any special treatment? This is basically my code right now, but I can't test it, as I haven't setup JNI locally. 

JNIEXPORT jint JNICALL
Java_test_test(JNIEnv* env, jobject obj, jlong ptr)
{
    MyObject* m = (MyObject*) ptr; 
    unsigned int i = m->get(); 
    return i; 
}

Answer

Jonathan Grynspan picture Jonathan Grynspan · Nov 4, 2011

In the general case, jint is equivalent to int, and so can hold about half the values of unsigned int. Conversion will work silently, but if a jint value is negative or if an unsigned int value is larger than the maximum value a jint can hold, the result will not be what you are expecting.

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