Java example source code file (DatagramChannelImpl.c)

This example Java source code file (DatagramChannelImpl.c) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

bool, false, ios_thrown, ios_unavailable, jni_false, jnicall, jniexport, net_getportfromsockaddr, null, socket_error, socketaddress, wsaeconnreset, wsaewouldblock, wsagetlasterror

The DatagramChannelImpl.c Java example source code

/*
 * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

#include "jni.h"
#include "jni_util.h"
#include "jvm.h"
#include "jlong.h"
#include <io.h>
#include "sun_nio_ch_DatagramChannelImpl.h"
#include "nio.h"
#include "nio_util.h"
#include "net_util.h"
#include <winsock2.h>

static jfieldID dci_senderID;   /* sender in sun.nio.ch.DatagramChannelImpl */
static jfieldID dci_senderAddrID; /* sender InetAddress in sun.nio.ch.DatagramChannelImpl */
static jfieldID dci_senderPortID; /* sender port in sun.nio.ch.DatagramChannelImpl */
static jclass isa_class;        /* java.net.InetSocketAddress */
static jmethodID isa_ctorID;    /* java.net.InetSocketAddress(InetAddress, int) */


JNIEXPORT void JNICALL
Java_sun_nio_ch_DatagramChannelImpl_initIDs(JNIEnv *env, jclass clazz)
{
    clazz = (*env)->FindClass(env, "java/net/InetSocketAddress");
    isa_class = (*env)->NewGlobalRef(env, clazz);
    isa_ctorID = (*env)->GetMethodID(env, clazz, "<init>",
                                     "(Ljava/net/InetAddress;I)V");

    clazz = (*env)->FindClass(env, "sun/nio/ch/DatagramChannelImpl");
    dci_senderID = (*env)->GetFieldID(env, clazz, "sender",
                                      "Ljava/net/SocketAddress;");
    dci_senderAddrID = (*env)->GetFieldID(env, clazz,
                                          "cachedSenderInetAddress",
                                          "Ljava/net/InetAddress;");
    dci_senderPortID = (*env)->GetFieldID(env, clazz,
                                          "cachedSenderPort", "I");
}

/*
 * This function "purges" all outstanding ICMP port unreachable packets
 * outstanding on a socket and returns JNI_TRUE if any ICMP messages
 * have been purged. The rational for purging is to emulate normal BSD
 * behaviour whereby receiving a "connection reset" status resets the
 * socket.
 */
jboolean purgeOutstandingICMP(JNIEnv *env, jclass clazz, jint fd)
{
    jboolean got_icmp = JNI_FALSE;
    char buf[1];
    fd_set tbl;
    struct timeval t = { 0, 0 };
    SOCKETADDRESS sa;
    int addrlen = sizeof(sa);

    /*
     * Peek at the queue to see if there is an ICMP port unreachable. If there
     * is then receive it.
     */
    FD_ZERO(&tbl);
    FD_SET((u_int)fd, &tbl);
    while(1) {
        if (select(/*ignored*/fd+1, &tbl, 0, 0, &t) <= 0) {
            break;
        }
        if (recvfrom(fd, buf, 1, MSG_PEEK,
                     (struct sockaddr *)&sa, &addrlen) != SOCKET_ERROR) {
            break;
        }
        if (WSAGetLastError() != WSAECONNRESET) {
            /* some other error - we don't care here */
            break;
        }

        recvfrom(fd, buf, 1, 0,  (struct sockaddr *)&sa, &addrlen);
        got_icmp = JNI_TRUE;
    }

    return got_icmp;
}

JNIEXPORT void JNICALL
Java_sun_nio_ch_DatagramChannelImpl_disconnect0(JNIEnv *env, jobject this,
                                                jobject fdo, jboolean isIPv6)
{
    jint fd = fdval(env, fdo);
    int rv = 0;
    SOCKETADDRESS sa;
    int sa_len = sizeof(sa);

    memset(&sa, 0, sa_len);

    rv = connect((SOCKET)fd, (struct sockaddr *)&sa, sa_len);
    if (rv == SOCKET_ERROR) {
        handleSocketError(env, WSAGetLastError());
    } else {
        /* Disable WSAECONNRESET errors as socket is no longer connected */
        BOOL enable = FALSE;
        DWORD bytesReturned = 0;
        WSAIoctl((SOCKET)fd, SIO_UDP_CONNRESET, &enable, sizeof(enable),
                 NULL, 0, &bytesReturned, NULL, NULL);
    }
}

JNIEXPORT jint JNICALL
Java_sun_nio_ch_DatagramChannelImpl_receive0(JNIEnv *env, jobject this,
                                            jobject fdo, jlong address,
                                            jint len, jboolean connected)
{
    jint fd = fdval(env, fdo);
    void *buf = (void *)jlong_to_ptr(address);
    SOCKETADDRESS sa;
    int sa_len = sizeof(sa);
    BOOL retry = FALSE;
    jint n;
    jobject senderAddr;

    do {
        retry = FALSE;
        n = recvfrom((SOCKET)fd,
                     (char *)buf,
                     len,
                     0,
                     (struct sockaddr *)&sa,
                     &sa_len);

        if (n == SOCKET_ERROR) {
            int theErr = (jint)WSAGetLastError();
            if (theErr == WSAEMSGSIZE) {
                /* Spec says the rest of the data will be discarded... */
                n = len;
            } else if (theErr == WSAECONNRESET) {
                purgeOutstandingICMP(env, this, fd);
                if (connected == JNI_FALSE) {
                    retry = TRUE;
                } else {
                    JNU_ThrowByName(env, JNU_JAVANETPKG "PortUnreachableException", 0);
                    return IOS_THROWN;
                }
            } else if (theErr == WSAEWOULDBLOCK) {
                return IOS_UNAVAILABLE;
            } else return handleSocketError(env, theErr);
        }
    } while (retry);

    /*
     * If the source address and port match the cached address
     * and port in DatagramChannelImpl then we don't need to
     * create InetAddress and InetSocketAddress objects.
     */
    senderAddr = (*env)->GetObjectField(env, this, dci_senderAddrID);
    if (senderAddr != NULL) {
        if (!NET_SockaddrEqualsInetAddress(env, (struct sockaddr *)&sa,
                                           senderAddr)) {
            senderAddr = NULL;
        } else {
            jint port = (*env)->GetIntField(env, this, dci_senderPortID);
            if (port != NET_GetPortFromSockaddr((struct sockaddr *)&sa)) {
                senderAddr = NULL;
            }
        }
    }
    if (senderAddr == NULL) {
        jobject isa = NULL;
        int port;
        jobject ia = NET_SockaddrToInetAddress(env, (struct sockaddr *)&sa,
                                               &port);

        if (ia != NULL) {
            isa = (*env)->NewObject(env, isa_class, isa_ctorID, ia, port);
        }

        if (isa == NULL) {
            JNU_ThrowOutOfMemoryError(env, "heap allocation failed");
            return IOS_THROWN;
        }

        // update cachedSenderInetAddress/cachedSenderPort
        (*env)->SetObjectField(env, this, dci_senderAddrID, ia);
        (*env)->SetIntField(env, this, dci_senderPortID,
                            NET_GetPortFromSockaddr((struct sockaddr *)&sa));
        (*env)->SetObjectField(env, this, dci_senderID, isa);
    }
    return n;
}

JNIEXPORT jint JNICALL
Java_sun_nio_ch_DatagramChannelImpl_send0(JNIEnv *env, jobject this,
                                          jboolean preferIPv6, jobject fdo,
                                          jlong address, jint len,
                                          jobject destAddress, jint destPort)
{
    jint fd = fdval(env, fdo);
    void *buf = (void *)jlong_to_ptr(address);
    SOCKETADDRESS sa;
    int sa_len;
    jint rv = 0;

    if (NET_InetAddressToSockaddr(env, destAddress, destPort,
                                  (struct sockaddr *)&sa,
                                   &sa_len, preferIPv6) != 0) {
      return IOS_THROWN;
    }

    rv = sendto((SOCKET)fd,
               buf,
               len,
               0,
               (struct sockaddr *)&sa,
               sa_len);
    if (rv == SOCKET_ERROR) {
        int theErr = (jint)WSAGetLastError();
        if (theErr == WSAEWOULDBLOCK) {
            return IOS_UNAVAILABLE;
        }
        return handleSocketError(env, (jint)WSAGetLastError());
    }
    return rv;
}