Java example source code file (WindowsSelectorImpl.c)

This example Java source code file (WindowsSelectorImpl.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

dword, fd_set, fd_setsize, fionread, java_sun_nio_ch_windowsselectorimpl_00024subselector_poll0, java_sun_nio_ch_windowsselectorimpl_discardurgentdata, java_sun_nio_ch_windowsselectorimpl_resetwakeupsocket0, java_sun_nio_ch_windowsselectorimpl_setwakeupsocket0, jni_false, jnicall, jniexport, null, socket_error, wakeup_socket_buf_size

The WindowsSelectorImpl.c Java example source code

/*
 * Copyright (c) 2002, 2010, 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.
 */

/*
 */

/* Maximum number of sockets per select() */
/* This number should be equal to WindowsSelectorImpl.MAX_SELECTABLE_FDS */
/* This definition MUST precede the inclusion of winsock2.h */

#define FD_SETSIZE 1024

#include <stdlib.h>
#include "jvm.h"
#include "jni.h"
#include "jni_util.h"
#include "sun_nio_ch_WindowsSelectorImpl.h"
#include "sun_nio_ch_PollArrayWrapper.h"
#include "winsock2.h"


typedef struct {
    jint fd;
    jshort events;
} pollfd;

#define WAKEUP_SOCKET_BUF_SIZE 16


JNIEXPORT jint JNICALL
Java_sun_nio_ch_WindowsSelectorImpl_00024SubSelector_poll0(JNIEnv *env, jobject this,
                                   jlong pollAddress, jint numfds,
                                   jintArray returnReadFds, jintArray returnWriteFds,
                                   jintArray returnExceptFds, jlong timeout)
{
    DWORD result = 0;
    pollfd *fds = (pollfd *) pollAddress;
    int i;
    FD_SET readfds, writefds, exceptfds;
    struct timeval timevalue, *tv;
    static struct timeval zerotime = {0, 0};
    int read_count = 0, write_count = 0, except_count = 0;

#ifdef _WIN64
    int resultbuf[FD_SETSIZE + 1];
#endif

    if (timeout == 0) {
        tv = &zerotime;
    } else if (timeout < 0) {
        tv = NULL;
    } else {
        tv = &timevalue;
        tv->tv_sec =  (long)(timeout / 1000);
        tv->tv_usec = (long)((timeout % 1000) * 1000);
    }

    /* Set FD_SET structures required for select */
    for (i = 0; i < numfds; i++) {
        if (fds[i].events & sun_nio_ch_PollArrayWrapper_POLLIN) {
           readfds.fd_array[read_count] = fds[i].fd;
           read_count++;
        }
        if (fds[i].events & (sun_nio_ch_PollArrayWrapper_POLLOUT |
                             sun_nio_ch_PollArrayWrapper_POLLCONN))
        {
           writefds.fd_array[write_count] = fds[i].fd;
           write_count++;
        }
        exceptfds.fd_array[except_count] = fds[i].fd;
        except_count++;
    }

    readfds.fd_count = read_count;
    writefds.fd_count = write_count;
    exceptfds.fd_count = except_count;

    /* Call select */
    if ((result = select(0 , &readfds, &writefds, &exceptfds, tv))
                                                             == SOCKET_ERROR) {
        /* Bad error - this should not happen frequently */
        /* Iterate over sockets and call select() on each separately */
        FD_SET errreadfds, errwritefds, errexceptfds;
        readfds.fd_count = 0;
        writefds.fd_count = 0;
        exceptfds.fd_count = 0;
        for (i = 0; i < numfds; i++) {
            /* prepare select structures for the i-th socket */
            errreadfds.fd_count = 0;
            errwritefds.fd_count = 0;
            if (fds[i].events & sun_nio_ch_PollArrayWrapper_POLLIN) {
               errreadfds.fd_array[0] = fds[i].fd;
               errreadfds.fd_count = 1;
            }
            if (fds[i].events & (sun_nio_ch_PollArrayWrapper_POLLOUT |
                                 sun_nio_ch_PollArrayWrapper_POLLCONN))
            {
                errwritefds.fd_array[0] = fds[i].fd;
                errwritefds.fd_count = 1;
            }
            errexceptfds.fd_array[0] = fds[i].fd;
            errexceptfds.fd_count = 1;

            /* call select on the i-th socket */
            if (select(0, &errreadfds, &errwritefds, &errexceptfds, &zerotime)
                                                             == SOCKET_ERROR) {
                /* This socket causes an error. Add it to exceptfds set */
                exceptfds.fd_array[exceptfds.fd_count] = fds[i].fd;
                exceptfds.fd_count++;
            } else {
                /* This socket does not cause an error. Process result */
                if (errreadfds.fd_count == 1) {
                    readfds.fd_array[readfds.fd_count] = fds[i].fd;
                    readfds.fd_count++;
                }
                if (errwritefds.fd_count == 1) {
                    writefds.fd_array[writefds.fd_count] = fds[i].fd;
                    writefds.fd_count++;
                }
                if (errexceptfds.fd_count == 1) {
                    exceptfds.fd_array[exceptfds.fd_count] = fds[i].fd;
                    exceptfds.fd_count++;
                }
            }
        }
    }

    /* Return selected sockets. */
    /* Each Java array consists of sockets count followed by sockets list */

#ifdef _WIN64
    resultbuf[0] = readfds.fd_count;
    for (i = 0; i < (int)readfds.fd_count; i++) {
        resultbuf[i + 1] = (int)readfds.fd_array[i];
    }
    (*env)->SetIntArrayRegion(env, returnReadFds, 0,
                              readfds.fd_count + 1, resultbuf);

    resultbuf[0] = writefds.fd_count;
    for (i = 0; i < (int)writefds.fd_count; i++) {
        resultbuf[i + 1] = (int)writefds.fd_array[i];
    }
    (*env)->SetIntArrayRegion(env, returnWriteFds, 0,
                              writefds.fd_count + 1, resultbuf);

    resultbuf[0] = exceptfds.fd_count;
    for (i = 0; i < (int)exceptfds.fd_count; i++) {
        resultbuf[i + 1] = (int)exceptfds.fd_array[i];
    }
    (*env)->SetIntArrayRegion(env, returnExceptFds, 0,
                              exceptfds.fd_count + 1, resultbuf);
#else
    (*env)->SetIntArrayRegion(env, returnReadFds, 0,
                              readfds.fd_count + 1, (jint *)&readfds);

    (*env)->SetIntArrayRegion(env, returnWriteFds, 0,
                              writefds.fd_count + 1, (jint *)&writefds);
    (*env)->SetIntArrayRegion(env, returnExceptFds, 0,
                              exceptfds.fd_count + 1, (jint *)&exceptfds);
#endif
    return 0;
}

JNIEXPORT void JNICALL
Java_sun_nio_ch_WindowsSelectorImpl_setWakeupSocket0(JNIEnv *env, jclass this,
                                                jint scoutFd)
{
    /* Write one byte into the pipe */
    const char byte = 1;
    send(scoutFd, &byte, 1, 0);
}

JNIEXPORT void JNICALL
Java_sun_nio_ch_WindowsSelectorImpl_resetWakeupSocket0(JNIEnv *env, jclass this,
                                                jint scinFd)
{
    char bytes[WAKEUP_SOCKET_BUF_SIZE];
    long bytesToRead;

    /* Drain socket */
    /* Find out how many bytes available for read */
    ioctlsocket (scinFd, FIONREAD, &bytesToRead);
    if (bytesToRead == 0) {
        return;
    }
    /* Prepare corresponding buffer if needed, and then read */
    if (bytesToRead > WAKEUP_SOCKET_BUF_SIZE) {
        char* buf = (char*)malloc(bytesToRead);
        recv(scinFd, buf, bytesToRead, 0);
        free(buf);
    } else {
        recv(scinFd, bytes, WAKEUP_SOCKET_BUF_SIZE, 0);
    }
}

JNIEXPORT jboolean JNICALL
Java_sun_nio_ch_WindowsSelectorImpl_discardUrgentData(JNIEnv* env, jobject this,
                                                      jint s)
{
    char data[8];
    jboolean discarded = JNI_FALSE;
    int n;
    do {
        n = recv(s, (char*)&data, sizeof(data), MSG_OOB);
        if (n > 0) {
            discarded = JNI_TRUE;
        }
    } while (n > 0);
    return discarded;
}