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Java example source code file (IOUtil.c)

This example Java source code file (IOUtil.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

eof, handle, ios_eof, java_sun_security_provider_nativeseedgenerator_nativegenerateseed, jni_false, jni_true, jnicall, jniexport, jnu_throwioexceptionwithlasterror, null, number, read\/write, set_blocking, set_nonblocking

The IOUtil.c Java example source code

/*
 * Copyright (c) 2000, 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 <windows.h>
#include <winsock2.h>
#include <io.h>
#include "jni.h"
#include "jni_util.h"
#include "jvm.h"
#include "jlong.h"

#include "nio.h"
#include "nio_util.h"
#include "sun_nio_ch_IOUtil.h"

/* field id for jlong 'handle' in java.io.FileDescriptor used for file fds */
static jfieldID handle_fdID;

/* field id for jint 'fd' in java.io.FileDescriptor used for socket fds */
static jfieldID fd_fdID;

JNIEXPORT jboolean JNICALL
Java_sun_security_provider_NativeSeedGenerator_nativeGenerateSeed
(JNIEnv *env, jclass clazz, jbyteArray randArray);

/**************************************************************
 * static method to store field IDs in initializers
 */

JNIEXPORT void JNICALL
Java_sun_nio_ch_IOUtil_initIDs(JNIEnv *env, jclass clazz)
{
    clazz = (*env)->FindClass(env, "java/io/FileDescriptor");
    fd_fdID = (*env)->GetFieldID(env, clazz, "fd", "I");
    handle_fdID = (*env)->GetFieldID(env, clazz, "handle", "J");
}

/**************************************************************
 * IOUtil.c
 */
JNIEXPORT jboolean JNICALL
Java_sun_nio_ch_IOUtil_randomBytes(JNIEnv *env, jclass clazz,
                                  jbyteArray randArray)
{
    return
        Java_sun_security_provider_NativeSeedGenerator_nativeGenerateSeed(env,
                                                                    clazz,
                                                                    randArray);
}

JNIEXPORT jint JNICALL
Java_sun_nio_ch_IOUtil_iovMax(JNIEnv *env, jclass this)
{
    return 16;
}


jint
convertReturnVal(JNIEnv *env, jint n, jboolean reading)
{
    if (n > 0) /* Number of bytes written */
        return n;
    if (n == 0) {
        if (reading) {
            return IOS_EOF; /* EOF is -1 in javaland */
        } else {
            return 0;
        }
    }
    JNU_ThrowIOExceptionWithLastError(env, "Read/write failed");
    return IOS_THROWN;
}

jlong
convertLongReturnVal(JNIEnv *env, jlong n, jboolean reading)
{
    if (n > 0) /* Number of bytes written */
        return n;
    if (n == 0) {
        if (reading) {
            return IOS_EOF; /* EOF is -1 in javaland */
        } else {
            return 0;
        }
    }
    JNU_ThrowIOExceptionWithLastError(env, "Read/write failed");
    return IOS_THROWN;
}

JNIEXPORT jint JNICALL
Java_sun_nio_ch_IOUtil_fdVal(JNIEnv *env, jclass clazz, jobject fdo)
{
    return fdval(env, fdo);
}

JNIEXPORT void JNICALL
Java_sun_nio_ch_IOUtil_setfdVal(JNIEnv *env, jclass clazz, jobject fdo, jint val)
{
    (*env)->SetIntField(env, fdo, fd_fdID, val);
}


#define SET_BLOCKING 0
#define SET_NONBLOCKING 1

JNIEXPORT void JNICALL
Java_sun_nio_ch_IOUtil_configureBlocking(JNIEnv *env, jclass clazz,
                                        jobject fdo, jboolean blocking)
{
    u_long argp;
    int result = 0;
    jint fd = fdval(env, fdo);

    if (blocking == JNI_FALSE) {
        argp = SET_NONBLOCKING;
    } else {
        argp = SET_BLOCKING;
        /* Blocking fd cannot be registered with EventSelect */
        WSAEventSelect(fd, NULL, 0);
    }
    result = ioctlsocket(fd, FIONBIO, &argp);
    if (result == SOCKET_ERROR) {
        int error = WSAGetLastError();
        handleSocketError(env, (jint)error);
    }
}

/* Note: Drain uses the int fd value. It is currently not called
   on windows.
*/
JNIEXPORT jboolean JNICALL
Java_sun_nio_ch_IOUtil_drain(JNIEnv *env, jclass cl, jint fd)
{
    DWORD read = 0;
    int totalRead = 0;
    BOOL result = 0;
    HANDLE h = (HANDLE)_get_osfhandle(fd);
    char buf[128];

    if (h == INVALID_HANDLE_VALUE) {
        JNU_ThrowIOExceptionWithLastError(env, "Read failed");
        return JNI_FALSE;
    }

    for (;;) {
        result = ReadFile(h,          /* File handle to read */
                          (LPVOID)&buf,    /* address to put data */
                          128,        /* number of bytes to read */
                          &read,      /* number of bytes read */
                          NULL);      /* no overlapped struct */

        if (result == 0) {
            int error = GetLastError();
            if (error == ERROR_NO_DATA) {
                return (totalRead > 0) ? JNI_TRUE : JNI_FALSE;
            }
            JNU_ThrowIOExceptionWithLastError(env, "Drain");
            return JNI_FALSE;
        }
        if (read > 0) {
            totalRead += read;
        } else {
            break;
        }
    }
    return (totalRead > 0) ? JNI_TRUE : JNI_FALSE;
}

/* Note: This function returns the int fd value from file descriptor.
   It is mostly used for sockets which should use the int fd value.
*/
jint
fdval(JNIEnv *env, jobject fdo)
{
    return (*env)->GetIntField(env, fdo, fd_fdID);
}

jlong
handleval(JNIEnv *env, jobject fdo)
{
    return (*env)->GetLongField(env, fdo, handle_fdID);
}

Other Java examples (source code examples)

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