Remove unnecessary -1 predicate because write will not return -1 unless NioChannel is CLOSED_NIO_CHANNEL

[tianshuang]

The following are the low-level implementations of the Solaris platform, other platforms are similar:

Java_sun_nio_ch_DatagramDispatcher_write0:

JNIEXPORT jint JNICALL
Java_sun_nio_ch_DatagramDispatcher_write0(JNIEnv *env, jclass clazz,
                              jobject fdo, jlong address, jint len)
{
    jint fd = fdval(env, fdo);
    void *buf = (void *)jlong_to_ptr(address);
    int result = send(fd, buf, len, 0);
    if (result < 0 && errno == ECONNREFUSED) {
        JNU_ThrowByName(env, JNU_JAVANETPKG "PortUnreachableException", 0);
        return -2;
    }
    return convertReturnVal(env, result, JNI_FALSE);
}

Java_sun_nio_ch_FileDispatcherImpl_write0:

JNIEXPORT jint JNICALL
Java_sun_nio_ch_FileDispatcherImpl_write0(JNIEnv *env, jclass clazz,
                              jobject fdo, jlong address, jint len)
{
    jint fd = fdval(env, fdo);
    void *buf = (void *)jlong_to_ptr(address);

    return convertReturnVal(env, write(fd, buf, len), JNI_FALSE);
}

convertReturnVal:

/* Declared in nio_util.h for use elsewhere in NIO */

jint
convertReturnVal(JNIEnv *env, jint n, jboolean reading)
{
    if (n > 0) /* Number of bytes written */
        return n;
    else if (n == 0) {
        if (reading) {
            return IOS_EOF; /* EOF is -1 in javaland */
        } else {
            return 0;
        }
    }
    else if (errno == EAGAIN)
        return IOS_UNAVAILABLE;
    else if (errno == EINTR)
        return IOS_INTERRUPTED;
    else {
        const char *msg = reading ? "Read failed" : "Write failed";
        JNU_ThrowIOExceptionWithLastError(env, msg);
        return IOS_THROWN;
    }
}

In fact, it is only possible to return -1 when read is called, indicating that the end of the channel stream has been reached.

[markt-asf]

Thanks for the PR. I applied to it manually so I could use a slightly different fix and add a change log entry.