/*

 * Copyright (c) 2012, 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.

 */

package sun.nio.ch;

import java.io.IOException;

/**

 * Provides access to the BSD kqueue facility.

 */

class KQueue {

    private KQueue() { }

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

    /**

     * struct kevent {

     *        uintptr_t       ident;          // identifier for this event, usually the fd

     *        int16_t         filter;         // filter for event

     *        uint16_t        flags;          // general flags

     *        uint32_t        fflags;         // filter-specific flags

     *        intptr_t        data;           // filter-specific data

     *        void            *udata;         // opaque user data identifier

     * };

     */

    private static final int SIZEOF_KQUEUEEVENT    = keventSize();

    private static final int OFFSET_IDENT          = identOffset();

    private static final int OFFSET_FILTER         = filterOffset();

    private static final int OFFSET_FLAGS          = flagsOffset();

    // filters

    static final int EVFILT_READ  = -1;

    static final int EVFILT_WRITE = -2;

    // flags

    static final int EV_ADD     = 0x0001;

    static final int EV_ONESHOT = 0x0010;

    static final int EV_CLEAR   = 0x0020;

    /**

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

     */

    static long allocatePollArray(int count) {

        return unsafe.allocateMemory(count * SIZEOF_KQUEUEEVENT);

    }

    /**

     * Free a poll array

     */

    static void freePollArray(long address) {

        unsafe.freeMemory(address);

    }

    /**

     * Returns kevent[i].

     */

    static long getEvent(long address, int i) {

        return address + (SIZEOF_KQUEUEEVENT*i);

    }

    /**

     * Returns the file descriptor from a kevent (assuming to be in ident field)

     */

    static int getDescriptor(long address) {

        return unsafe.getInt(address + OFFSET_IDENT);

    }

    static int getFilter(long address) {

        return unsafe.getShort(address + OFFSET_FILTER);

    }

    static int getFlags(long address) {

        return unsafe.getShort(address + OFFSET_FLAGS);

    }

    // -- Native methods --

    private static native int keventSize();

    private static native int identOffset();

    private static native int filterOffset();

    private static native int flagsOffset();

    static native int kqueue() throws IOException;

    static native int keventRegister(int kqpfd, int fd, int filter, int flags);

    static native int keventPoll(int kqpfd, long pollAddress, int nevents)

        throws IOException;

    static {

        IOUtil.load();

    }

}