/*

 * Copyright (c) 2003, 2006, 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.management.snmp.jvminstr;

// java imports

//

import java.io.Serializable;

import java.util.List;

import java.util.Map;

import java.util.TreeMap;

// jmx imports

//

import com.sun.jmx.snmp.SnmpOid;

import com.sun.jmx.snmp.SnmpStatusException;

// jdmk imports

//

import com.sun.jmx.snmp.agent.SnmpMib;

import com.sun.jmx.snmp.agent.SnmpStandardObjectServer;

import java.lang.management.MemoryManagerMXBean;

import java.lang.management.GarbageCollectorMXBean;

import java.lang.management.ManagementFactory;

import sun.management.snmp.jvmmib.JvmMemGCTableMeta;

import sun.management.snmp.util.SnmpCachedData;

import sun.management.snmp.util.SnmpTableCache;

import sun.management.snmp.util.SnmpTableHandler;

import sun.management.snmp.util.MibLogger;

import sun.management.snmp.util.JvmContextFactory;

/**

 * The class is used for implementing the "JvmMemGCTable" table.

 */

public class JvmMemGCTableMetaImpl extends  JvmMemGCTableMeta {

    /**

     * This class acts as a filter over the SnmpTableHandler

     * used for the JvmMemoryManagerTable. It filters out

     * (skip) all MemoryManagerMXBean that are not instances of

     * GarbageCollectorMXBean so that only Garbage Collectors are

     * seen. This is a better solution than relying on

     * ManagementFactory.getGarbageCollectorMXBeans() because it makes it

     * possible to guarantee the consistency betwen the MemoryManager table

     * and the GCTable since both will be sharing the same cache.

     **/

    protected static class GCTableFilter {

        /**

         * Returns the index that immediately follows the given

         * <var>index</var>. The returned index is strictly greater

         * than the given <var>index</var>, and is contained in the table.

         * <br>If the given <var>index</var> is null, returns the first

         * index in the table.

         * <br>If there are no index after the given <var>index</var>,

         * returns null.

         * This method is an optimization for the case where the

         * SnmpTableHandler is in fact an instance of SnmpCachedData.

         **/

        public SnmpOid getNext(SnmpCachedData datas, SnmpOid index) {

            final boolean dbg = log.isDebugOn();

            // We're going to loop until we find an instance of

            // GarbageCollectorMXBean. First we attempt to find

            // the next element whose OID follows the given index.

            // If `index' is null, the insertion point is -1

            // (the next is 0 = -insertion - 1)

            //

            final int insertion = (index==null)?-1:datas.find(index);

            if (dbg) log.debug("GCTableFilter","oid="+index+

                               " at insertion="+insertion);

            int next;

            if (insertion > -1) next = insertion+1;

            else next = -insertion -1;

            // Now `next' points to the element that imediately

            // follows the given `index'. We're going to loop

            // through the table, starting at `next' (included),

            // and return the first element which is an instance

            // of GarbageCollectorMXBean.

            //

            for (;next<datas.indexes.length;next++) {

                if (dbg) log.debug("GCTableFilter","next="+next);

                final Object value = datas.datas[next];

                if (dbg) log.debug("GCTableFilter","value["+next+"]=" +

                      ((MemoryManagerMXBean)value).getName());

                if (value instanceof GarbageCollectorMXBean) {

                    // That's the next: return it.

                    if (dbg) log.debug("GCTableFilter",

                          ((MemoryManagerMXBean)value).getName() +

                          " is a  GarbageCollectorMXBean.");

                    return datas.indexes[next];

                }

                if (dbg) log.debug("GCTableFilter",

                      ((MemoryManagerMXBean)value).getName() +

                      " is not a  GarbageCollectorMXBean: " +

                      value.getClass().getName());

                // skip to next index...

            }

            return null;

        }

        /**

         * Returns the index that immediately follows the given

         * <var>index</var>. The returned index is strictly greater

         * than the given <var>index</var>, and is contained in the table.

         * <br>If the given <var>index</var> is null, returns the first

         * index in the table.

         * <br>If there are no index after the given <var>index</var>,

         * returns null.

         **/

        public SnmpOid getNext(SnmpTableHandler handler, SnmpOid index) {

            // try to call the optimized method

            if (handler instanceof SnmpCachedData)

                return getNext((SnmpCachedData)handler, index);

            // too bad - revert to non-optimized generic algorithm

            SnmpOid next = index;

            do {

                next = handler.getNext(next);

                final Object value = handler.getData(next);

                if (value instanceof GarbageCollectorMXBean)

                    // That's the next! return it

                    return next;

                // skip to next index...

            } while (next != null);

            return null;

        }

        /**

         * Returns the data associated with the given index.

         * If the given index is not found, null is returned.

         * Note that returning null does not necessarily means that

         * the index was not found.

         **/

        public Object  getData(SnmpTableHandler handler, SnmpOid index) {

            final Object value = handler.getData(index);

            if (value instanceof GarbageCollectorMXBean) return value;

            // Behaves as if there was nothing at this index...

            //

            return null;

        }

        /**

         * Returns true if the given <var>index</var> is present.

         **/

        public boolean contains(SnmpTableHandler handler, SnmpOid index) {

            if (handler.getData(index) instanceof GarbageCollectorMXBean)

                return true;

            // Behaves as if there was nothing at this index...

            //

            return false;

        }

    }

    private transient JvmMemManagerTableMetaImpl managers = null;

    private static GCTableFilter filter = new GCTableFilter();

    /**

     * Constructor for the table. Initialize metadata for "JvmMemGCTableMeta".

     */

    public JvmMemGCTableMetaImpl(SnmpMib myMib,

                                 SnmpStandardObjectServer objserv) {

        super(myMib,objserv);

    }

    // Returns a pointer to the JvmMemManager meta node - we're going

    // to reuse its SnmpTableHandler by filtering out all that is

    // not a GarbageCollectorMXBean.

    private final JvmMemManagerTableMetaImpl getManagers(SnmpMib mib) {

        if (managers == null) {

            managers = (JvmMemManagerTableMetaImpl)

                mib.getRegisteredTableMeta("JvmMemManagerTable");

        }

        return managers;

    }

    /**

     * Returns the JvmMemManagerTable SnmpTableHandler

     **/

    protected SnmpTableHandler getHandler(Object userData) {

        JvmMemManagerTableMetaImpl managerTable= getManagers(theMib);

        return managerTable.getHandler(userData);

    }

    // See com.sun.jmx.snmp.agent.SnmpMibTable

    protected SnmpOid getNextOid(Object userData)

        throws SnmpStatusException {

        // null means get the first OID.

        return getNextOid(null,userData);

    }

    // See com.sun.jmx.snmp.agent.SnmpMibTable

    protected SnmpOid getNextOid(SnmpOid oid, Object userData)

        throws SnmpStatusException {

        final boolean dbg = log.isDebugOn();

        try {

            if (dbg) log.debug("getNextOid", "previous=" + oid);

            // Get the data handler.

            //

            SnmpTableHandler handler = getHandler(userData);

            if (handler == null) {

                // This should never happen.

                // If we get here it's a bug.

                //

                if (dbg) log.debug("getNextOid", "handler is null!");

                throw new

                    SnmpStatusException(SnmpStatusException.noSuchInstance);

            }

            // Get the next oid, using the GC filter.

            //

            final SnmpOid next = filter.getNext(handler,oid);

            if (dbg) log.debug("getNextOid", "next=" + next);

            // if next is null: we reached the end of the table.

            //

            if (next == null)

                throw new

                    SnmpStatusException(SnmpStatusException.noSuchInstance);

            return next;

        } catch (RuntimeException x) {

            // debug. This should never happen.

            //

            if (dbg) log.debug("getNextOid",x);

            throw x;

        }

    }

    // See com.sun.jmx.snmp.agent.SnmpMibTable

    protected boolean contains(SnmpOid oid, Object userData) {

        // Get the handler.

        //

        SnmpTableHandler handler = getHandler(userData);

        // handler should never be null.

        //

        if (handler == null)

            return false;

        return filter.contains(handler,oid);

    }

    // See com.sun.jmx.snmp.agent.SnmpMibTable

    public Object getEntry(SnmpOid oid)

        throws SnmpStatusException {

        if (oid == null)

            throw new SnmpStatusException(SnmpStatusException.noSuchInstance);

        // Get the request contextual cache (userData).

        //

        final Map<Object, Object> m = JvmContextFactory.getUserData();

        // First look in the request contextual cache: maybe we've already

        // created this entry...

        //

        // We know in the case of this table that the index is an integer,

        // it is thus the first OID arc of the index OID.

        //

        final long   index    = oid.getOidArc(0);

        // We're going to use this name to store/retrieve the entry in

        // the request contextual cache.

        //

        // Revisit: Probably better programming to put all these strings

        //          in some interface.

        //

        final String entryTag = ((m==null)?null:("JvmMemGCTable.entry." +

                                                 index));

        // If the entry is in the cache, simply return it.

        //

        if (m != null) {

            final Object entry = m.get(entryTag);

            if (entry != null) return entry;

        }

        // Entry was not in request cache. Make a new one.

        //

        // Get the data hanler.

        //

        SnmpTableHandler handler = getHandler(m);

        // handler should never be null.

        //

        if (handler == null)

            throw new SnmpStatusException(SnmpStatusException.noSuchInstance);

        // Use the filter to retrieve only GarabageCollectorMBean data.

        //

        final Object data = filter.getData(handler,oid);

        // data may be null if the OID we were given is not valid.

        // (e.g. it identifies a MemoryManager which is not a

        // GarbageCollector)

        //

        if (data == null)

            throw new SnmpStatusException(SnmpStatusException.noSuchInstance);

        // Make a new entryy (transient object that will be kept only

        // for the duration of the request.

        //

        final Object entry =

            new JvmMemGCEntryImpl((GarbageCollectorMXBean)data,(int)index);

        // Put the entry in the request cache in case we need it later

        // in the processing of the request. Note that we could have

        // optimized this by making JvmMemGCEntryImpl extend

        // JvmMemManagerEntryImpl, and then make sure that

        // JvmMemManagerTableMetaImpl creates an instance of JvmMemGCEntryImpl

        // instead of JvmMemManagerEntryImpl when the associated data is

        // an instance of GarbageCollectorMXBean. This would have made it

        // possible to share the transient entry object.

        // As it is, we may have two transient objects that points to

        // the same underlying MemoryManagerMXBean (which is definitely

        // not a problem - but is only a small dysatisfaction)

        //

        if (m != null && entry != null) {

            m.put(entryTag,entry);

        }

        return entry;

    }

    static final MibLogger log = new MibLogger(JvmMemGCTableMetaImpl.class);

}