[Android] load file from assets folder

Helper.java

public class Helper {
    private static Context context;
    public static void setContext(Context c) { context = c; }

    public static byte[] loadIntoBytes(String fileName) {
        AssetManager assetManager = context.getAssets();
        try {
            InputStream is = assetManager.open(fileName);
            byte buf[] = new byte[is.available()];
            is.read(buf);
            return buf;
        } catch (IOException e) {
        }
        return null;
    }

helper_android.cpp

const char* boundJavaClass = "common/pinotnoir/Helper";

void *LoadFile(const char *fileName, int* size)
{
	jclass myview = jniEnv->FindClass(boundJavaClass);
	jmethodID method = jniEnv->GetStaticMethodID(myview, "loadIntoBytes", "(Ljava/lang/String;)[B");
	if (method == 0) {
		return nullptr;
	}

	jobject arrayAsJObject = jniEnv->CallStaticObjectMethod(myview, method, jniEnv->NewStringUTF(fileName));
	jbyteArray array = (jbyteArray)arrayAsJObject;

	jbyte* byteArray = jniEnv->GetByteArrayElements(array, NULL);
	jsize arrayLen = jniEnv->GetArrayLength(array);

	void* ptr = calloc(arrayLen + 1, 1);
	memcpy(ptr, byteArray, arrayLen);
	if (size) {
		*size = arrayLen;
	}

	jniEnv->ReleaseByteArrayElements(array, byteArray, 0);

	return ptr;
}