/*

 * 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.

 */

package sun.nio.ch;

import java.io.IOException;

import sun.misc.Unsafe;

/**

 * Provides access to the Linux epoll facility.

 */

class EPoll {

    private EPoll() { }

    private static final Unsafe unsafe = Unsafe.getUnsafe();

    /**

     * typedef union epoll_data {

     *     void *ptr;

     *     int fd;

     *     __uint32_t u32;

     *     __uint64_t u64;

     *  } epoll_data_t;

     *

     * struct epoll_event {

     *     __uint32_t events;

     *     epoll_data_t data;

     * }

     */

    private static final int SIZEOF_EPOLLEVENT   = eventSize();

    private static final int OFFSETOF_EVENTS     = eventsOffset();

    private static final int OFFSETOF_FD         = dataOffset();

    // opcodes

    static final int EPOLL_CTL_ADD  = 1;

    static final int EPOLL_CTL_DEL  = 2;

    static final int EPOLL_CTL_MOD  = 3;

    // flags

    static final int EPOLLONESHOT   = (1 << 30);

    /**

     * Allocates a poll array to handle up to {@code count} events.

     */

    static long allocatePollArray(int count) {

        return unsafe.allocateMemory(count * SIZEOF_EPOLLEVENT);

    }

    /**

     * Free a poll array

     */

    static void freePollArray(long address) {

        unsafe.freeMemory(address);

    }

    /**

     * Returns event[i];

     */

    static long getEvent(long address, int i) {

        return address + (SIZEOF_EPOLLEVENT*i);

    }

    /**

     * Returns event->data.fd

     */

    static int getDescriptor(long eventAddress) {

        return unsafe.getInt(eventAddress + OFFSETOF_FD);

    }

    /**

     * Returns event->events

     */

    static int getEvents(long eventAddress) {

        return unsafe.getInt(eventAddress + OFFSETOF_EVENTS);

    }

    // -- Native methods --

    private static native int eventSize();

    private static native int eventsOffset();

    private static native int dataOffset();

    static native int epollCreate() throws IOException;

    static native int epollCtl(int epfd, int opcode, int fd, int events);

    static native int epollWait(int epfd, long pollAddress, int numfds)

        throws IOException;

    static {

        Util.load();

    }

}