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QuestDB is High Performance Time Series Database

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 * Copyright (C) 2014-2016 Appsicle
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 * it under the terms of the GNU Affero General Public License, version 3,
 * as published by the Free Software Foundation.
 * 

 * This program 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
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package com.questdb.ql.impl;

import com.questdb.ex.DisconnectedChannelRuntimeException;
import com.questdb.log.Log;
import com.questdb.log.LogFactory;
import com.questdb.misc.Net;
import com.questdb.misc.Numbers;
import com.questdb.ql.CancellationHandler;

public class ChannelCheckCancellationHandler implements CancellationHandler {
    private static final Log LOG = LogFactory.getLog(ChannelCheckCancellationHandler.class);
    private final long fd;
    private final long mask;
    private long loop = 0;

    public ChannelCheckCancellationHandler(long fd, int cyclesBeforeCheck) {
        this.fd = fd;
        this.mask = Numbers.ceilPow2(cyclesBeforeCheck) - 1;
    }

    @Override
    public void check() {
        if (loop > 0 && (loop & mask) == 0) {
            checkChannel();
        }
        loop++;
    }

    public void reset() {
        this.loop = 0;
    }

    private void checkChannel() {
        if (Net.isDead(fd)) {
            LOG.info().$("Socket closed, possibly cancelled request. FD=").$(fd).$();
            throw DisconnectedChannelRuntimeException.INSTANCE;
        }
    }
}