/*
 * Copyright (c) 2008, 2016, 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 com.sun.btrace.agent;

import com.sun.btrace.PerfReader;
import java.net.URISyntaxException;
import sun.jvmstat.monitor.IntegerMonitor;
import sun.jvmstat.monitor.LongMonitor;
import sun.jvmstat.monitor.Monitor;
import sun.jvmstat.monitor.MonitoredHost;
import sun.jvmstat.monitor.MonitoredVm;
import sun.jvmstat.monitor.MonitorException;
import sun.jvmstat.monitor.StringMonitor;
import sun.jvmstat.monitor.VmIdentifier;

final class PerfReaderImpl implements PerfReader {
    private volatile MonitoredVm thisVm;

    private synchronized MonitoredVm getThisVm() {
        if (thisVm == null) {
            try {
                MonitoredHost localHost = MonitoredHost.getMonitoredHost("localhost");
                VmIdentifier vmIdent = new VmIdentifier("0");
                thisVm = localHost.getMonitoredVm(vmIdent);
            } catch (MonitorException | URISyntaxException me) {
                throw new IllegalArgumentException("jvmstat perf counters not available: " + me);
            }
        }
        return thisVm;
    }

    private Monitor findByName(String name) {
        try {
            return getThisVm().findByName(name);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    @Override
    public int perfInt(String name) {
        Monitor mon = findByName(name);
        if (mon == null) {
            throw new IllegalArgumentException("no such counter: " + name);
        }
        if (mon instanceof IntegerMonitor) {
            return ((IntegerMonitor)mon).intValue();
        } else if (mon instanceof LongMonitor) {
            return (int) ((LongMonitor)mon).longValue();
        } else {
            throw new IllegalArgumentException(name + " is not an int");
        }
    }

    @Override
    public long perfLong(String name) {
        Monitor mon = findByName(name);
        if (mon == null) {
            throw new IllegalArgumentException("no such counter: " + name);
        }
        if (mon instanceof LongMonitor) {
            return ((LongMonitor)mon).longValue();
        } else {
            throw new IllegalArgumentException(name + " is not a long");
        }
    }

    @Override
    public String perfString(String name) {
        Monitor mon = findByName(name);
        if (mon == null) {
            throw new IllegalArgumentException("no such counter: " + name);
        }
        if (mon instanceof StringMonitor) {
            return ((StringMonitor)mon).stringValue();
        } else {
            throw new IllegalArgumentException(name + " is not a string");
        }
    }
}