267 lines
10 KiB
Java
267 lines
10 KiB
Java
/*
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* Copyright (c) 2003, 2012, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package sun.management.snmp.util;
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import com.sun.jmx.snmp.SnmpOid;
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import com.sun.jmx.mbeanserver.Util;
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import java.io.Serializable;
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import java.util.Comparator;
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import java.util.Arrays;
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import java.util.Map;
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import java.util.TreeMap;
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import java.util.List;
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import java.util.Iterator;
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import java.lang.ref.WeakReference;
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/**
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* This abstract class implements a weak cache that holds table data, for
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* a table whose data is obtained from a list where a name can be obtained
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* for each item in the list.
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* <p>This object maintains a map between an entry name and its associated
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* SnmpOid index, so that a given entry is always associated to the same
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* index.</p>
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* <p><b>NOTE: This class is not synchronized, subclasses must implement
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* the appropriate synchronization whwn needed.</b></p>
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**/
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public abstract class SnmpNamedListTableCache extends SnmpListTableCache {
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/**
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* This map associate an entry name with the SnmpOid index that's
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* been allocated for it.
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**/
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protected TreeMap<String, SnmpOid> names = new TreeMap<>();
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/**
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* The last allocate index.
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**/
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protected long last = 0;
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/**
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* true if the index has wrapped.
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**/
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boolean wrapped = false;
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/**
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* Returns the key to use as name for the given <var>item</var>.
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* <br>This method is called by {@link #getIndex(Object,List,int,Object)}.
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* The given <var>item</var> is expected to be always associated with
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* the same name.
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* @param context The context passed to
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* {@link #updateCachedDatas(Object,List)}.
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* @param rawDatas Raw table datas passed to
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* {@link #updateCachedDatas(Object,List)}.
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* @param rank Rank of the given <var>item</var> in the
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* <var>rawDatas</var> list iterator.
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* @param item The raw data object for which a key name must be determined.
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**/
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protected abstract String getKey(Object context, List<?> rawDatas,
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int rank, Object item);
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/**
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* Find a new index for the entry corresponding to the
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* given <var>item</var>.
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* <br>This method is called by {@link #getIndex(Object,List,int,Object)}
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* when a new index needs to be allocated for an <var>item</var>. The
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* index returned must not be already in used.
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* @param context The context passed to
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* {@link #updateCachedDatas(Object,List)}.
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* @param rawDatas Raw table datas passed to
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* {@link #updateCachedDatas(Object,List)}.
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* @param rank Rank of the given <var>item</var> in the
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* <var>rawDatas</var> list iterator.
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* @param item The raw data object for which an index must be determined.
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**/
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protected SnmpOid makeIndex(Object context, List<?> rawDatas,
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int rank, Object item) {
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// check we are in the limits of an unsigned32.
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if (++last > 0x00000000FFFFFFFFL) {
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// we just wrapped.
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log.debug("makeIndex", "Index wrapping...");
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last = 0;
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wrapped=true;
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}
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// If we never wrapped, we can safely return last as new index.
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if (!wrapped) return new SnmpOid(last);
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// We wrapped. We must look for an unused index.
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for (int i=1;i < 0x00000000FFFFFFFFL;i++) {
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if (++last > 0x00000000FFFFFFFFL) last = 1;
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final SnmpOid testOid = new SnmpOid(last);
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// Was this index already in use?
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if (names == null) return testOid;
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if (names.containsValue(testOid)) continue;
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// Have we just used it in a previous iteration?
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if (context == null) return testOid;
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if (((Map)context).containsValue(testOid)) continue;
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// Ok, not in use.
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return testOid;
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}
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// all indexes are in use! we're stuck.
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// // throw new IndexOutOfBoundsException("No index available.");
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// better to return null and log an error.
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return null;
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}
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/**
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* Call {@link #getKey(Object,List,int,Object)} in order to get
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* the item name. Then check whether an index was already allocated
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* for the entry by that name. If yes return it. Otherwise, call
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* {@link #makeIndex(Object,List,int,Object)} to compute a new
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* index for that entry.
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* Finally store the association between
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* the name and index in the context TreeMap.
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* @param context The context passed to
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* {@link #updateCachedDatas(Object,List)}.
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* It is expected to
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* be an instance of {@link TreeMap}.
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* @param rawDatas Raw table datas passed to
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* {@link #updateCachedDatas(Object,List)}.
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* @param rank Rank of the given <var>item</var> in the
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* <var>rawDatas</var> list iterator.
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* @param item The raw data object for which an index must be determined.
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**/
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protected SnmpOid getIndex(Object context, List<?> rawDatas,
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int rank, Object item) {
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final String key = getKey(context,rawDatas,rank,item);
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final Object index = (names==null||key==null)?null:names.get(key);
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final SnmpOid result =
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((index != null)?((SnmpOid)index):makeIndex(context,rawDatas,
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rank,item));
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if ((context != null) && (key != null) && (result != null)) {
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Map<Object, Object> map = Util.cast(context);
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map.put(key,result);
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}
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log.debug("getIndex","key="+key+", index="+result);
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return result;
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}
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/**
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* Allocate a new {@link TreeMap} to serve as context, then
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* call {@link SnmpListTableCache#updateCachedDatas(Object,List)}, and
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* finally replace the {@link #names} TreeMap by the new allocated
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* TreeMap.
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* @param rawDatas The table datas from which the cached data will be
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* computed.
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**/
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protected SnmpCachedData updateCachedDatas(Object context, List<?> rawDatas) {
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TreeMap<String,SnmpOid> ctxt = new TreeMap<>();
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final SnmpCachedData result =
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super.updateCachedDatas(context,rawDatas);
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names = ctxt;
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return result;
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}
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/**
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* Load a list of raw data from which to build the cached data.
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* This method is called when nothing is found in the request
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* contextual cache.
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* @param userData The request contextual cache allocated by
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* the {@link JvmContextFactory}.
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*
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**/
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protected abstract List<?> loadRawDatas(Map<Object,Object> userData);
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/**
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*The name under which the raw data is to be found/put in
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* the request contextual cache.
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**/
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protected abstract String getRawDatasKey();
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/**
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* Get a list of raw data from which to build the cached data.
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* Obtains a list of raw data by first looking it up in the
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* request contextual cache <var>userData</var> under the given
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* <var>key</var>. If nothing is found in the cache, calls
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* {@link #loadRawDatas(Map)} to obtain a new rawData list,
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* and cache the result in <var>userData</var> under <var>key</var>.
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* @param userData The request contextual cache allocated by
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* the {@link JvmContextFactory}.
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* @param key The name under which the raw data is to be found/put in
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* the request contextual cache.
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*
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**/
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protected List<?> getRawDatas(Map<Object, Object> userData, String key) {
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List<?> rawDatas = null;
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// Look for memory manager list in request contextual cache.
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if (userData != null)
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rawDatas = (List<?>)userData.get(key);
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if (rawDatas == null) {
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// No list in contextual cache, get it from API
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rawDatas = loadRawDatas(userData);
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// Put list in cache...
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if (rawDatas != null && userData != null)
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userData.put(key, rawDatas);
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}
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return rawDatas;
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}
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/**
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* Update cahed datas.
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* Obtains a {@link List} of raw datas by calling
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* {@link #getRawDatas(Map,String) getRawDatas((Map)context,getRawDatasKey())}.<br>
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* Then allocate a new {@link TreeMap} to serve as temporary map between
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* names and indexes, and call {@link #updateCachedDatas(Object,List)}
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* with that temporary map as context.<br>
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* Finally replaces the {@link #names} TreeMap by the temporary
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* TreeMap.
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* @param context The request contextual cache allocated by the
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* {@link JvmContextFactory}.
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**/
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protected SnmpCachedData updateCachedDatas(Object context) {
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final Map<Object, Object> userData =
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(context instanceof Map)?Util.<Map<Object, Object>>cast(context):null;
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// Look for memory manager list in request contextual cache.
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final List<?> rawDatas = getRawDatas(userData,getRawDatasKey());
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log.debug("updateCachedDatas","rawDatas.size()=" +
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((rawDatas==null)?"<no data>":""+rawDatas.size()));
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TreeMap<String,SnmpOid> ctxt = new TreeMap<>();
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final SnmpCachedData result =
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super.updateCachedDatas(ctxt,rawDatas);
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names = ctxt;
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return result;
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}
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static final MibLogger log = new MibLogger(SnmpNamedListTableCache.class);
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}
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