/*
 * Copyright (c) 2017, 2023, 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
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 */
package sun.nio.ch;

import java.io.IOException;
import static sun.nio.ch.KQueue.*;

/**
 * Poller implementation based on the kqueue facility.
 */
class KQueuePoller extends Poller {
    private static final int MAX_EVENTS_TO_POLL = 512;

    private final int kqfd;
    private final int filter;
    private final long address;

    KQueuePoller(boolean read) throws IOException {
        super(read);
        this.kqfd = KQueue.create();
        this.filter = (read) ? EVFILT_READ : EVFILT_WRITE;
        this.address = KQueue.allocatePollArray(MAX_EVENTS_TO_POLL);
    }

    @Override
    int fdVal() {
        return kqfd;
    }

    @Override
    void implRegister(int fdVal) throws IOException {
        int err = KQueue.register(kqfd, fdVal, filter, (EV_ADD|EV_ONESHOT));
        if (err != 0)
            throw new IOException("kevent failed: " + err);
    }

    @Override
    void implDeregister(int fdVal, boolean polled) {
        // event was deleted if already polled
        if (!polled) {
            KQueue.register(kqfd, fdVal, filter, EV_DELETE);
        }
    }

    @Override
    int poll(int timeout) throws IOException {
        int n = KQueue.poll(kqfd, address, MAX_EVENTS_TO_POLL, timeout);
        int i = 0;
        while (i < n) {
            long keventAddress = KQueue.getEvent(address, i);
            int fdVal = KQueue.getDescriptor(keventAddress);
            polled(fdVal);
            i++;
        }
        return n;
    }
}
