byte 데이터형 값 주고 받기
숫자를 전달하면 2의 보수를 반환하는 예제를 작성해 보자.
$ vi PassAndReturnByte.cpp
#include <jni.h>
jbyte complement2
(
JNIEnv *env,
jobject thiz,
jbyte value
)
{
return (~value) + 1;
}
JNIEXPORT jint JNICALL JNI_OnLoad
(
JavaVM *vm,
void *reserved
)
{
JNIEnv *env;
if(vm->GetEnv(reinterpret_cast<void**>(&env), JNI_VERSION_1_6)) {
return -1;
}
JNINativeMethod nm {
const_cast<char*>("complement2"),
const_cast<char*>("(B)B"),
reinterpret_cast<void*>(complement2)
};
jclass cls = env->FindClass("Client");
env->RegisterNatives(cls, &nm, 1);
return JNI_VERSION_1_6;
}
컴파일하고 라이브러리로 만든다.
$ g++ "-I/System/Library/Java/JavaVirtualMachines/Current/" -std=c++11 -c PassAndReturnByte.cpp
$ g++ -dynamiclib -o libparbyte.jnilib passandreturnbyte.o
자바 코드에서 라이브러리를 사용해 보자.
$ vi Client.java
public class Client {
public native byte complement2(byte value);
public static void main(String[] args) {
Client client = new Client();
System.out.println("The two's complement of 2 is " + client.complement2((byte)2));
System.out.println("The two's complement of 3 is " + client.complement2((byte)3));
System.out.println("The two's complement of -1 is " + client.complement2((byte)-1));
}
static {
System.loadLibrary("parbyte");
}
}
컴파일하고 실행해 본다.
$ javac Client.java
$ java Client
The two's complement of 2 is -2
The two's complement of 3 is -3
The two's complement of -1 is 1
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