Java example source code file (BsdNativeDispatcher.c)

This example Java source code file (BsdNativeDispatcher.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

isreadonly, java_sun_nio_fs_bsdnativedispatcher_endfsstat, java_sun_nio_fs_bsdnativedispatcher_initids, jnicall, jniexport, jnu_newobjectbyname, jnu_throwoutofmemoryerror, mnt_nowait, mnt_rdonly, mnt_wait, null, st_rdonly

The BsdNativeDispatcher.c Java example source code

/*
 * Copyright (c) 2008, 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 <sys/param.h>
#include <sys/mount.h>
#ifdef ST_RDONLY
#define statfs statvfs
#define getfsstat getvfsstat
#define f_flags f_flag
#define ISREADONLY ST_RDONLY
#else
#define ISREADONLY MNT_RDONLY
#endif

#include <stdlib.h>
#include <string.h>

static jfieldID entry_name;
static jfieldID entry_dir;
static jfieldID entry_fstype;
static jfieldID entry_options;

struct fsstat_iter {
    struct statfs *buf;
    int pos;
    int nentries;
};

#include "sun_nio_fs_BsdNativeDispatcher.h"

static void throwUnixException(JNIEnv* env, int errnum) {
    jobject x = JNU_NewObjectByName(env, "sun/nio/fs/UnixException",
        "(I)V", errnum);
    if (x != NULL) {
        (*env)->Throw(env, x);
    }
}

/**
 * Initialize jfieldIDs
 */
JNIEXPORT void JNICALL
Java_sun_nio_fs_BsdNativeDispatcher_initIDs(JNIEnv* env, jclass this)
{
    jclass clazz;

    clazz = (*env)->FindClass(env, "sun/nio/fs/UnixMountEntry");
    if (clazz == NULL) {
        return;
    }
    entry_name = (*env)->GetFieldID(env, clazz, "name", "[B");
    entry_dir = (*env)->GetFieldID(env, clazz, "dir", "[B");
    entry_fstype = (*env)->GetFieldID(env, clazz, "fstype", "[B");
    entry_options = (*env)->GetFieldID(env, clazz, "opts", "[B");
}

JNIEXPORT jlong JNICALL
Java_sun_nio_fs_BsdNativeDispatcher_getfsstat(JNIEnv* env, jclass this)
{
    int nentries;
    size_t bufsize;
    struct fsstat_iter *iter = malloc(sizeof(*iter));

    if (iter == NULL) {
        JNU_ThrowOutOfMemoryError(env, "native heap");
        return 0;
    }

    iter->pos = 0;
    iter->nentries = 0;
    iter->buf = NULL;

    nentries = getfsstat(NULL, 0, MNT_NOWAIT);

    if (nentries <= 0) {
        free(iter);
        throwUnixException(env, errno);
        return 0;
    }

    // It's possible that a new filesystem gets mounted between
    // the first getfsstat and the second so loop until consistant

    while (nentries != iter->nentries) {
        if (iter->buf != NULL)
            free(iter->buf);

        bufsize = nentries * sizeof(struct statfs);
        iter->nentries = nentries;

        iter->buf = malloc(bufsize);
        if (iter->buf == NULL) {
            free(iter);
            JNU_ThrowOutOfMemoryError(env, "native heap");
            return 0;
        }

        nentries = getfsstat(iter->buf, bufsize, MNT_WAIT);
        if (nentries <= 0) {
            free(iter->buf);
            free(iter);
            throwUnixException(env, errno);
            return 0;
        }
    }

    return (jlong)iter;
}

JNIEXPORT jint JNICALL
Java_sun_nio_fs_BsdNativeDispatcher_fsstatEntry(JNIEnv* env, jclass this,
    jlong value, jobject entry)
{
    struct fsstat_iter *iter = jlong_to_ptr(value);
    jsize len;
    jbyteArray bytes;
    char* name;
    char* dir;
    char* fstype;
    char* options;
    dev_t dev;

    if (iter == NULL || iter->pos >= iter->nentries)
       return -1;

    name = iter->buf[iter->pos].f_mntfromname;
    dir = iter->buf[iter->pos].f_mntonname;
    fstype = iter->buf[iter->pos].f_fstypename;
    if (iter->buf[iter->pos].f_flags & ISREADONLY)
        options="ro";
    else
        options="";

    iter->pos++;

    len = strlen(name);
    bytes = (*env)->NewByteArray(env, len);
    if (bytes == NULL)
        return -1;
    (*env)->SetByteArrayRegion(env, bytes, 0, len, (jbyte*)name);
    (*env)->SetObjectField(env, entry, entry_name, bytes);

    len = strlen(dir);
    bytes = (*env)->NewByteArray(env, len);
    if (bytes == NULL)
        return -1;
    (*env)->SetByteArrayRegion(env, bytes, 0, len, (jbyte*)dir);
    (*env)->SetObjectField(env, entry, entry_dir, bytes);

    len = strlen(fstype);
    bytes = (*env)->NewByteArray(env, len);
    if (bytes == NULL)
        return -1;
    (*env)->SetByteArrayRegion(env, bytes, 0, len, (jbyte*)fstype);
    (*env)->SetObjectField(env, entry, entry_fstype, bytes);

    len = strlen(options);
    bytes = (*env)->NewByteArray(env, len);
    if (bytes == NULL)
        return -1;
    (*env)->SetByteArrayRegion(env, bytes, 0, len, (jbyte*)options);
    (*env)->SetObjectField(env, entry, entry_options, bytes);

    return 0;
}

JNIEXPORT void JNICALL
Java_sun_nio_fs_BsdNativeDispatcher_endfsstat(JNIEnv* env, jclass this, jlong value)
{
    struct fsstat_iter *iter = jlong_to_ptr(value);

    if (iter != NULL) {
        free(iter->buf);
        free(iter);
    }
}