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Java example source code file (io_util_md.c)

This example Java source code file (io_util_md.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

cfrelease, end_platform_string, jnu_throwioexceptionwithlasterror, jnu_throwoutofmemoryerror, null, restartable, s_ischr, seek_cur, seek_end, set_fd, stderr_fileno, stdin_fileno, with_platform_string

The io_util_md.c Java example source code

/*
 * Copyright (c) 2001, 2013, 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 "io_util.h"
#include "io_util_md.h"
#include <string.h>
#include <unistd.h>

#ifdef __solaris__
#include <sys/filio.h>
#endif

#if defined(__linux__) || defined(_ALLBSD_SOURCE)
#include <sys/ioctl.h>
#endif

#ifdef MACOSX

#include <CoreFoundation/CoreFoundation.h>

__private_extern__
jstring newStringPlatform(JNIEnv *env, const char* str)
{
    jstring rv = NULL;
    CFMutableStringRef csref = CFStringCreateMutable(NULL, 0);
    if (csref == NULL) {
        JNU_ThrowOutOfMemoryError(env, "native heap");
    } else {
        CFStringAppendCString(csref, str, kCFStringEncodingUTF8);
        CFStringNormalize(csref, kCFStringNormalizationFormC);
        int clen = CFStringGetLength(csref);
        int ulen = (clen + 1) * 2;        // utf16 + zero padding
        char* chars = malloc(ulen);
        if (chars == NULL) {
            CFRelease(csref);
            JNU_ThrowOutOfMemoryError(env, "native heap");
        } else {
            if (CFStringGetCString(csref, chars, ulen, kCFStringEncodingUTF16)) {
                rv = (*env)->NewString(env, (jchar*)chars, clen);
            }
            free(chars);
            CFRelease(csref);
        }
    }
    return rv;
}
#endif

FD
handleOpen(const char *path, int oflag, int mode) {
    FD fd;
    RESTARTABLE(open64(path, oflag, mode), fd);
    if (fd != -1) {
        struct stat64 buf64;
        int result;
        RESTARTABLE(fstat64(fd, &buf64), result);
        if (result != -1) {
            if (S_ISDIR(buf64.st_mode)) {
                close(fd);
                errno = EISDIR;
                fd = -1;
            }
        } else {
            close(fd);
            fd = -1;
        }
    }
    return fd;
}

void
fileOpen(JNIEnv *env, jobject this, jstring path, jfieldID fid, int flags)
{
    WITH_PLATFORM_STRING(env, path, ps) {
        FD fd;

#if defined(__linux__) || defined(_ALLBSD_SOURCE)
        /* Remove trailing slashes, since the kernel won't */
        char *p = (char *)ps + strlen(ps) - 1;
        while ((p > ps) && (*p == '/'))
            *p-- = '\0';
#endif
        fd = handleOpen(ps, flags, 0666);
        if (fd != -1) {
            SET_FD(this, fd, fid);
        } else {
            throwFileNotFoundException(env, path);
        }
    } END_PLATFORM_STRING(env, ps);
}

void
fileClose(JNIEnv *env, jobject this, jfieldID fid)
{
    FD fd = GET_FD(this, fid);
    if (fd == -1) {
        return;
    }

    /* Set the fd to -1 before closing it so that the timing window
     * of other threads using the wrong fd (closed but recycled fd,
     * that gets re-opened with some other filename) is reduced.
     * Practically the chance of its occurance is low, however, we are
     * taking extra precaution over here.
     */
    SET_FD(this, -1, fid);

    /*
     * Don't close file descriptors 0, 1, or 2. If we close these stream
     * then a subsequent file open or socket will use them. Instead we
     * just redirect these file descriptors to /dev/null.
     */
    if (fd >= STDIN_FILENO && fd <= STDERR_FILENO) {
        int devnull = open("/dev/null", O_WRONLY);
        if (devnull < 0) {
            SET_FD(this, fd, fid); // restore fd
            JNU_ThrowIOExceptionWithLastError(env, "open /dev/null failed");
        } else {
            dup2(devnull, fd);
            close(devnull);
        }
    } else if (close(fd) == -1) {
        JNU_ThrowIOExceptionWithLastError(env, "close failed");
    }
}

ssize_t
handleRead(FD fd, void *buf, jint len)
{
    ssize_t result;
    RESTARTABLE(read(fd, buf, len), result);
    return result;
}

ssize_t
handleWrite(FD fd, const void *buf, jint len)
{
    ssize_t result;
    RESTARTABLE(write(fd, buf, len), result);
    return result;
}

jint
handleAvailable(FD fd, jlong *pbytes)
{
    int mode;
    struct stat64 buf64;
    jlong size = -1, current = -1;

    int result;
    RESTARTABLE(fstat64(fd, &buf64), result);
    if (result != -1) {
        mode = buf64.st_mode;
        if (S_ISCHR(mode) || S_ISFIFO(mode) || S_ISSOCK(mode)) {
            int n;
            int result;
            RESTARTABLE(ioctl(fd, FIONREAD, &n), result);
            if (result >= 0) {
                *pbytes = n;
                return 1;
            }
        } else if (S_ISREG(mode)) {
            size = buf64.st_size;
        }
    }

    if ((current = lseek64(fd, 0, SEEK_CUR)) == -1) {
        return 0;
    }

    if (size < current) {
        if ((size = lseek64(fd, 0, SEEK_END)) == -1)
            return 0;
        else if (lseek64(fd, current, SEEK_SET) == -1)
            return 0;
    }

    *pbytes = size - current;
    return 1;
}

jint
handleSetLength(FD fd, jlong length)
{
    int result;
    RESTARTABLE(ftruncate64(fd, length), result);
    return result;
}

size_t
getLastErrorString(char *buf, size_t len)
{
    if (errno == 0 || len < 1) return 0;

    const char *err = strerror(errno);
    size_t n = strlen(err);
    if (n >= len)
        n = len - 1;

    strncpy(buf, err, n);
    buf[n] = '\0';
    return n;
}

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