我在JNI调用中遇到了奇怪的字符串损坏，这导致了Java端的问题。每隔一段时间，我就会在传递的数组中得到一个损坏的字符串，它有时会包含原始未损坏字符串的现有部分。原始的C ++代码应该将数组的第一个索引设置为地址。第二个版本使用直接缓冲区，因为我试图解决问题。模拟器在与应用程序线程分开的线程中运行，应用程序线程发布要执行的事件。
我之前想过，因为我正在预先分配缓冲区，如果多个线程访问套接字，它可能会被多次使用，导致损坏，所以我将其切换为Mina IoBuffer，它是从一个池，支持ByteBuffer可用。但是，它似乎没有任何区别。
remoteaddress[0]: 10.1.1.2:49153
remoteaddress[0]: 10.1.4.2:49153
remoteaddress[0]: 10.1.6.2:49153
remoteaddress[0]: 10.1.2.2:49153
remoteaddress[0]: 10.1.9.2:49153
remoteaddress[0]: {garbage here}
java.lang.NullPointerException
at kokuks.KKSAddress.<init>(KKSAddress.java:139)
at kokuks.KKSAddress.createAddress(KKSAddress.java:48)
at kokuks.KKSSocket._recvFrom(KKSSocket.java:963)
at kokuks.scheduler.RecvOperation$1.execute(RecvOperation.java:144)
at kokuks.scheduler.RecvOperation$1.execute(RecvOperation.java:1)
at kokuks.KKSEvent.run(KKSEvent.java:58)
at kokuks.KokuKS.handleJNIEventExpiry(KokuKS.java:872)
at kokuks.KokuKS.handleJNIEventExpiry_fjni(KokuKS.java:880)
at kokuks.KokuKS.runSimulator_jni(Native Method)
at kokuks.KokuKS$1.run(KokuKS.java:773)
at java.lang.Thread.run(Thread.java:717)
remoteaddress[0]: 10.1.7.2:49153
空指针异常来自尝试使用损坏的字符串。在C ++中，地址通常会打印到标准输出，但这样做可以降低错误率，我可以看到。
C ++代码：
/*
* Class: kokuks_KKSSocket
* Method: recvFrom2_jni
* Signature: (Ljava/lang/String;Ljava/nio/ByteBuffer;Ljava/nio/ByteBuffer;IIJ)I
*/
JNIEXPORT jint JNICALL Java_kokuks_KKSSocket_recvFrom2_1jni
(JNIEnv *env, jobject obj, jstring sockpath, jobject addrbuf, jobject buf, jint position, jint limit, jlong flags) {
const char* cstr = env->GetStringUTFChars(sockpath, NULL);
std::string spath = std::string(cstr);
env->ReleaseStringUTFChars(sockpath, cstr); // release me!
if (KKS_DEBUG) {
std::cout << "[kks-c~" << spath << "] " << __PRETTY_FUNCTION__ << std::endl;
}
ns3::Ptr<ns3::Object> sockobj = refmap[spath];
ns3::Ptr<ns3::Socket> socket = ns3::DynamicCast<ns3::Socket>(sockobj);
if (!socket) {
std::cout << "[kks-c~" << spath << "] " << __PRETTY_FUNCTION__ << " socket not found for path!!" << std::endl;
return -1; // not found
}
if (!addrbuf) {
std::cout << "[kks-c~" << spath << "] " << __PRETTY_FUNCTION__ << " sender address directbuffer address is null!" << std::endl;
return -1;
}
uint8_t* bufaddr = (uint8_t*)env->GetDirectBufferAddress(buf);
long bufcap = env->GetDirectBufferCapacity(buf);
uint8_t* realbufaddr = bufaddr + position;
uint32_t remaining = limit - position;
uint8_t* addrbufaddr = (uint8_t*)env->GetDirectBufferAddress(addrbuf);
long addrbufcap = env->GetDirectBufferCapacity(buf);
if (KKS_DEBUG) {
std::cout << "[kks-c~" << spath << "] " << __PRETTY_FUNCTION__ << " bufaddr: " << bufaddr << ", cap: " << bufcap << std::endl;
}
ns3::Address aaddr;
uint32_t mflags = flags;
int ret = socket->RecvFrom(realbufaddr, remaining, mflags, aaddr);
if (ret > 0) {
if (KKS_DEBUG) {
std::cout << "[kks-c~" << spath << "] " << __PRETTY_FUNCTION__ << " addr: " << aaddr << std::endl;
}
ns3::InetSocketAddress insa = ns3::InetSocketAddress::ConvertFrom(aaddr);
std::stringstream ss;
insa.GetIpv4().Print(ss);
ss << ":" << insa.GetPort() << std::ends;
if (KKS_DEBUG) {
std::cout << "[kks-c~" << spath << "] " << __PRETTY_FUNCTION__ << " addr: " << ss.str() << std::endl;
}
const char *cstr = ss.str().c_str();
char *dst = (char*)addrbufaddr;
size_t len = strlen(cstr);
strncpy(dst, cstr, len + 1);
if (env->ExceptionOccurred()) {
env->ExceptionDescribe();
}
}
jint jret = ret;
return jret;
}
/*
* Class: kokuks_KKSNode
* Method: node_getID_jni
* Signature: (Ljava/lang/String;)I
*/
JNIEXPORT jint JNICALL Java_kokuks_KKSNode_node_1getID_1jni
(JNIEnv *env, jobject obj, jstring path) {
const char* cstr = env->GetStringUTFChars(path, NULL);
std::string spath = std::string(cstr);
env->ReleaseStringUTFChars(path, cstr); // release me!
if (KKS_DEBUG) {
std::cout << "[kks-c~" << spath << "?] " << __PRETTY_FUNCTION__ << std::endl;
}
ns3::Ptr<ns3::Object> nodeobj = refmap[spath];
ns3::Ptr<ns3::Node> node = ns3::DynamicCast<ns3::Node>(nodeobj);
if (node) {
uint32_t id = node->GetId();
jint j_id = id;
return j_id;
}
return -1;
}
Java代码（如果有帮助）：
/**
*
* @param remoteaddress
* @param bytes
* @param flags
* @return
*/
protected int _core_recvFrom(final KKSAddress[] remoteaddress, final ByteBuffer bytes, final long flags) throws IOException {
if (!kks.isRealtime() || kks.isSimulationThread()) {
return _core_recvFrom_st(remoteaddress, bytes, flags);
}
boolean usejnibb = !bytes.isDirect();
final IoBuffer iob;
final ByteBuffer mybuf;
if (usejnibb) {
if (USE_IOB) {
iob = IoBuffer.allocate(bytes.remaining(), true);
mybuf = iob.buf();
} else {
mybuf = jnibb;
}
mybuf.clear();
mybuf.limit(bytes.remaining());
} else {
mybuf = bytes;
iob = null;
}
try {
KKSEvent<Integer> kev = new KKSSocketEvent<Integer>(this) {
@Override
protected Integer execute(long timeMS) throws IOException {
return _core_recvFrom_st(remoteaddress, mybuf, flags);
}
/* (non-Javadoc)
* @see kokuks.KKSEvent#getType()
*/
public String getType() {
return "_core_recvFrom()";
}
};
try {
int ret = kks.scheduleEventRTWait(kev);
if (ret > 0 && usejnibb) {
mybuf.flip();
bytes.put(mybuf);
}
return ret;
} catch (InterruptedException e) {
throw new InterruptedIOException();
} catch (EventExecException e) {
if (e.getCause() instanceof IOException) {
throw (IOException)e.getCause();
}
throw new IOException(e.getCause());
} catch (Exception e) {
throw new IOException(e);
}
} finally {
if (usejnibb) {
if (USE_IOB) {
iob.free();
}
}
}
}
/**
* Pass an array of size 1 into remote address, and this will be set with
* the sender of the packet (hax). This emulates C++ references.
*
* @param remoteaddress
* @param buf
* @param flags
* @return
*/
protected int _core_recvFrom_st(final KKSAddress[] remoteaddress, ByteBuffer buf, long flags) throws IOException {
try {
_syncJNI();
boolean recvfrom = remoteaddress != null;
errNo = SocketErrno.ERROR_NOTERROR;
ByteBuffer mybuf = buf;
if (!buf.isDirect()) {
errNo = SocketErrno.ERROR_BUFFERNOTDIRECT;
throw new IllegalArgumentException("Buffer not direct!");
}
final IoBuffer iob;
ByteBuffer bb = null;
if (recvfrom) {
if (USE_IOB) {
iob = IoBuffer.allocate(128, true);
bb = iob.buf();
} else {
bb = addrbb;
}
bb.clear();
} else {
iob = null;
}
try {
//IoBuffer pre = IoBuffer.wrap(mybuf.duplicate());
//printMessage("sockrecv (pre) // rxavailable: " + getRxAvailable());
// use new mechanism
int ret = recvfrom ?
recvFrom2_jni(
path.toPortableString(),
bb,
mybuf,
mybuf.position(),
mybuf.limit(),
flags
) : recv_jni(
path.toPortableString(),
mybuf,
mybuf.position(),
mybuf.limit(),
flags
);
_syncJNI();
if (ret >= 0) {
rxTotal += ret;
/*
printMessage("local addr: " + LOCAL_ADDR + ", real local addr: " + getRemoteAddress().toNormalAddress());
printMessage("remote addr: " + REMOTE_ADDR + ", real remote addr: " + getApp().getNode().getIPV4Address());
if (
getType() == SOCKET_TYPE_TCP &&
getRemoteAddress().toNormalAddress().equals(LOCAL_ADDR) &&
getApp().getNode().getIPV4Address().equals(REMOTE_ADDR)
) {
mrTest_testRecvd(mybuf, ret);
}
*/
//printMessage("sockrecv // mybuf: " + mybuf + ", ret: " + ret + " rxavailable: " + getRxAvailable() + ", data: " + BufUtils.asText(mybuf, ret));
buf.position(buf.position() + ret);
if (recvfrom) {
String st;
try {
st = IoBuffer.wrap(bb).getString(CDE);
remoteaddress[0] = KKSAddress.createAddress(st);
if (remoteaddress[0] == null) {
System.out.println("warning; remote address is null!! original: " + st);
}
} catch (CharacterCodingException e) {
e.printStackTrace();
}
}
return ret;
//pre.limit(pre.position() + ret);
//printMessage("_core_recvFrom_st recvd from " + ((!recvfrom || remoteaddress[0] == null || remoteaddress == null) ? getRemoteAddress() : remoteaddress[0]) + ": " + pre.getHexDump());
}
throw new IOException("I/O exception, retval: " + ret + ", errNo: " + errNo);
} finally {
if (recvfrom) {
if (USE_IOB) {
iob.free();
}
}
}
} finally {
errNo = _getErrNo();
}
}
编辑：我还发现数据包数据已损坏。此外，问题发生在我的工作PC上，而不是我的家用电脑。我的PC运行Windows XP，有4GB内存并有Q6600，我的家用PC有超频的Q6600,4GB内存，并运行Windows 7 64位，虽然它是32位Java。
答案 0 :(得分：0)
我没有测试过您的代码，但我认为这是一个字符编码问题。尝试使用std::wstring代替std::string或类似的东西。对不起，此刻此刻无济于事，但我想这应该给你一个起点。
答案 1 :(得分：0)
不能是线程安全问题吗？尝试同步对本机方法的访问。