如何使用Valist从C调用Java vararg方法
问题描述:
我有C方法和varargs
I have C method with varargs
void message(int id, ...)
它应该使用vararg调用Java静态方法
And it should call Java static method with vararg
public static void message(String messageName, String ... args)
我该如何使用C valist和JNI API?
How can I do it using C valist and JNI API?
谢谢!
答
将va_list的地址传递给Java的可能性不大.以下是一些片段,显示了如何使用"..."和va_list传递数组.根据需要添加错误/异常/返回检查.
Your not likely to get any use out of passing the address of a va_list up to Java. Here are a few snippets showing how to pass up an array using "..." and va_list. Add error/exception/return checking as necessary.
在Java中:
static private void javaDefineArray(Object ... args) {
for (Object o : args) {
print("javaDefineArray " + o);
}
}
在C中:
// Lookup the method using GetMethodID or GetStaticMethodID
mid = (*env)->GetStaticMethodID(env, class, "javaDefineArray", "([Ljava/lang/Object;)V");
// C function taking variable args ( all String in this example )
static void javaDefineArray(JNIEnv * env, jobject o, ...) {
int i = 0;
int count = 0;
char * msg[100+1] = {0}; // 100 args max
jobjectArray ja;
va_list list;
va_start(list, o);
do {msg[count] = va_arg(list,char *);
} while(msg[count] !=0 && ++count < 100); // end/saftey check
va_end(list);
ja = (*env)->NewObjectArray(env, count, (*env)->FindClass(env, "java/lang/String"), (*env)->NewStringUTF(env, ""));
for(i=0;i!=count;i++) {
(*env)->SetObjectArrayElement(env,ja,i,(*env)->NewStringUTF(env, msg[i]));
}
(*env)->CallVoidMethod(env, o, mid, ja);
}
C用法:
javaDefineArray(env, o, "0", "1", "2", "3", "4", NULL);
Java输出:
javaDefineArray 0
javaDefineArray 1
javaDefineArray 2
javaDefineArray 3
javaDefineArray 4