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

configure, eagain, eintr, ios_eof, ios_interrupted, ios_thrown, ios_unavailable, jni_false, jnicall, jniexport, jnu_throwioexceptionwithlasterror, number, read, write

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 <sys/types.h>
#include <string.h>
#include <sys/resource.h>

#include "jni.h"
#include "jni_util.h"
#include "jvm.h"
#include "jlong.h"
#include "sun_nio_ch_IOUtil.h"
#include "java_lang_Integer.h"
#include "nio.h"
#include "nio_util.h"

static jfieldID fd_fdID;        /* for jint 'fd' in java.io.FileDescriptor */


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");
}

JNIEXPORT jboolean JNICALL
Java_sun_nio_ch_IOUtil_randomBytes(JNIEnv *env, jclass clazz,
                                  jbyteArray randArray)
{
    JNU_ThrowByName(env, "java/lang/UnsupportedOperationException", NULL);
    return JNI_FALSE;
}

JNIEXPORT jint JNICALL
Java_sun_nio_ch_IOUtil_fdVal(JNIEnv *env, jclass clazz, jobject fdo)
{
    return (*env)->GetIntField(env, fdo, fd_fdID);
}

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

static int
configureBlocking(int fd, jboolean blocking)
{
    int flags = fcntl(fd, F_GETFL);
    int newflags = blocking ? (flags & ~O_NONBLOCK) : (flags | O_NONBLOCK);

    return (flags == newflags) ? 0 : fcntl(fd, F_SETFL, newflags);
}

JNIEXPORT void JNICALL
Java_sun_nio_ch_IOUtil_configureBlocking(JNIEnv *env, jclass clazz,
                                         jobject fdo, jboolean blocking)
{
    if (configureBlocking(fdval(env, fdo), blocking) < 0)
        JNU_ThrowIOExceptionWithLastError(env, "Configure blocking failed");
}

JNIEXPORT jlong JNICALL
Java_sun_nio_ch_IOUtil_makePipe(JNIEnv *env, jobject this, jboolean blocking)
{
    int fd[2];

    if (pipe(fd) < 0) {
        JNU_ThrowIOExceptionWithLastError(env, "Pipe failed");
        return 0;
    }
    if (blocking == JNI_FALSE) {
        if ((configureBlocking(fd[0], JNI_FALSE) < 0)
            || (configureBlocking(fd[1], JNI_FALSE) < 0)) {
            JNU_ThrowIOExceptionWithLastError(env, "Configure blocking failed");
            close(fd[0]);
            close(fd[1]);
            return 0;
        }
    }
    return ((jlong) fd[0] << 32) | (jlong) fd[1];
}

JNIEXPORT jboolean JNICALL
Java_sun_nio_ch_IOUtil_drain(JNIEnv *env, jclass cl, jint fd)
{
    char buf[128];
    int tn = 0;

    for (;;) {
        int n = read(fd, buf, sizeof(buf));
        tn += n;
        if ((n < 0) && (errno != EAGAIN))
            JNU_ThrowIOExceptionWithLastError(env, "Drain");
        if (n == (int)sizeof(buf))
            continue;
        return (tn > 0) ? JNI_TRUE : JNI_FALSE;
    }
}

JNIEXPORT jint JNICALL
Java_sun_nio_ch_IOUtil_fdLimit(JNIEnv *env, jclass this)
{
    struct rlimit rlp;
    if (getrlimit(RLIMIT_NOFILE, &rlp) < 0) {
        JNU_ThrowIOExceptionWithLastError(env, "getrlimit failed");
        return -1;
    }
    if (rlp.rlim_max < 0 || rlp.rlim_max > java_lang_Integer_MAX_VALUE) {
        return java_lang_Integer_MAX_VALUE;
    } else {
        return (jint)rlp.rlim_max;
    }
}

JNIEXPORT jint JNICALL
Java_sun_nio_ch_IOUtil_iovMax(JNIEnv *env, jclass this)
{
    jlong iov_max = sysconf(_SC_IOV_MAX);
    if (iov_max == -1)
        iov_max = 16;
    return (jint)iov_max;
}


/* 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;
    }
}

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

jlong
convertLongReturnVal(JNIEnv *env, jlong 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;
    }
}

jint
fdval(JNIEnv *env, jobject fdo)
{
    return (*env)->GetIntField(env, fdo, fd_fdID);
}