/*

 * Copyright (c) 2017, 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.

 *

 * 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.

 */

/*

 * Test if a file exists in the file system cache

 */

#include <stdlib.h>

#include <fcntl.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <unistd.h>

#include <sys/mman.h>

#include "jni.h"

/*

 * Throws an exception with the given class name and detail message

 */

static void ThrowException(JNIEnv *env, const char *name, const char *msg) {

    jclass cls = (*env)->FindClass(env, name);

    if (cls != NULL) {

        (*env)->ThrowNew(env, cls, msg);

    }

}

/*

 * Class:     DirectIO

 * Method:    isFileInCache0

 * Signature: (ILjava/lang/String;)Z

 */

JNIEXPORT jboolean Java_DirectIOTest_isFileInCache0(JNIEnv *env,

                                                jclass cls,

                                                jint file_size,

                                                jstring file_path) {

    void *f_mmap;

#ifdef __linux__

    unsigned char *f_seg;

#else

    char *f_seg;

#endif

#ifdef __APPLE__

    size_t mask = MINCORE_INCORE;

#else

    size_t mask = 0x1;

#endif

    size_t page_size = getpagesize();

    size_t index = (file_size + page_size - 1) /page_size;

    jboolean result = JNI_FALSE;

    const char* path = (*env)->GetStringUTFChars(env, file_path, JNI_FALSE);

    int fd = open(path, O_RDWR);

    (*env)->ReleaseStringUTFChars(env, file_path, path);

    f_mmap = mmap(0, file_size, PROT_NONE, MAP_SHARED, fd, 0);

    if (f_mmap == MAP_FAILED) {

        close(fd);

        ThrowException(env, "java/io/IOException",

            "test of whether file exists in cache failed");

    }

    f_seg = malloc(index);

    if (f_seg != NULL) {

        if(mincore(f_mmap, file_size, f_seg) == 0) {

            size_t i;

            for (i = 0; i < index; i++) {

                if (f_seg[i] & mask) {

                    result = JNI_TRUE;

                    break;

                }

            }

        }

        free(f_seg);

    } else {

        ThrowException(env, "java/io/IOException",

            "test of whether file exists in cache failed");

    }

    close(fd);

    munmap(f_mmap, file_size);

    return result;

}