1 /*
2 * Copyright (c) 2003, 2014, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25 package sun.management.snmp.util;
26
27 import com.sun.jmx.snmp.SnmpOid;
28 import com.sun.jmx.mbeanserver.Util;
29
30 import java.io.Serializable;
31
32 import java.util.Comparator;
33 import java.util.Arrays;
34 import java.util.Map;
35 import java.util.TreeMap;
36 import java.util.List;
37 import java.util.Iterator;
38
39 import java.lang.ref.WeakReference;
40
41
42 /**
43 * This abstract class implements a weak cache that holds table data, for
44 * a table whose data is obtained from a list where a name can be obtained
45 * for each item in the list.
46 * <p>This object maintains a map between an entry name and its associated
47 * SnmpOid index, so that a given entry is always associated to the same
48 * index.</p>
49 * <p><b>NOTE: This class is not synchronized, subclasses must implement
50 * the appropriate synchronization whwn needed.</b></p>
51 **/
52 @SuppressWarnings("serial") // JDK implementation class
53 public abstract class SnmpNamedListTableCache extends SnmpListTableCache {
54
55 /**
56 * This map associate an entry name with the SnmpOid index that's
57 * been allocated for it.
58 **/
59 protected TreeMap<String, SnmpOid> names = new TreeMap<>();
60
61 /**
62 * The last allocate index.
63 **/
64 protected long last = 0;
65
66 /**
67 * true if the index has wrapped.
68 **/
69 boolean wrapped = false;
70
71 /**
72 * Returns the key to use as name for the given <var>item</var>.
73 * <br>This method is called by {@link #getIndex(Object,List,int,Object)}.
74 * The given <var>item</var> is expected to be always associated with
75 * the same name.
76 * @param context The context passed to
77 * {@link #updateCachedDatas(Object,List)}.
78 * @param rawDatas Raw table datas passed to
79 * {@link #updateCachedDatas(Object,List)}.
80 * @param rank Rank of the given <var>item</var> in the
81 * <var>rawDatas</var> list iterator.
82 * @param item The raw data object for which a key name must be determined.
83 **/
84 protected abstract String getKey(Object context, List<?> rawDatas,
85 int rank, Object item);
86
87 /**
88 * Find a new index for the entry corresponding to the
89 * given <var>item</var>.
90 * <br>This method is called by {@link #getIndex(Object,List,int,Object)}
91 * when a new index needs to be allocated for an <var>item</var>. The
92 * index returned must not be already in used.
93 * @param context The context passed to
94 * {@link #updateCachedDatas(Object,List)}.
95 * @param rawDatas Raw table datas passed to
96 * {@link #updateCachedDatas(Object,List)}.
97 * @param rank Rank of the given <var>item</var> in the
98 * <var>rawDatas</var> list iterator.
99 * @param item The raw data object for which an index must be determined.
100 **/
101 protected SnmpOid makeIndex(Object context, List<?> rawDatas,
102 int rank, Object item) {
103
104 // check we are in the limits of an unsigned32.
105 if (++last > 0x00000000FFFFFFFFL) {
106 // we just wrapped.
107 log.debug("makeIndex", "Index wrapping...");
108 last = 0;
109 wrapped=true;
110 }
111
112 // If we never wrapped, we can safely return last as new index.
113 if (!wrapped) return new SnmpOid(last);
114
115 // We wrapped. We must look for an unused index.
116 for (int i=1;i < 0x00000000FFFFFFFFL;i++) {
117 if (++last > 0x00000000FFFFFFFFL) last = 1;
118 final SnmpOid testOid = new SnmpOid(last);
119
120 // Was this index already in use?
121 if (names == null) return testOid;
122 if (names.containsValue(testOid)) continue;
123
124 // Have we just used it in a previous iteration?
125 if (context == null) return testOid;
126 if (((Map)context).containsValue(testOid)) continue;
127
128 // Ok, not in use.
129 return testOid;
130 }
131 // all indexes are in use! we're stuck.
132 // // throw new IndexOutOfBoundsException("No index available.");
133 // better to return null and log an error.
134 return null;
135 }
136
137 /**
138 * Call {@link #getKey(Object,List,int,Object)} in order to get
139 * the item name. Then check whether an index was already allocated
140 * for the entry by that name. If yes return it. Otherwise, call
141 * {@link #makeIndex(Object,List,int,Object)} to compute a new
142 * index for that entry.
143 * Finally store the association between
144 * the name and index in the context TreeMap.
145 * @param context The context passed to
146 * {@link #updateCachedDatas(Object,List)}.
147 * It is expected to
148 * be an instance of {@link TreeMap}.
149 * @param rawDatas Raw table datas passed to
150 * {@link #updateCachedDatas(Object,List)}.
151 * @param rank Rank of the given <var>item</var> in the
152 * <var>rawDatas</var> list iterator.
153 * @param item The raw data object for which an index must be determined.
154 **/
155 protected SnmpOid getIndex(Object context, List<?> rawDatas,
156 int rank, Object item) {
157 final String key = getKey(context,rawDatas,rank,item);
158 final Object index = (names==null||key==null)?null:names.get(key);
159 final SnmpOid result =
160 ((index != null)?((SnmpOid)index):makeIndex(context,rawDatas,
161 rank,item));
162 if ((context != null) && (key != null) && (result != null)) {
163 Map<Object, Object> map = Util.cast(context);
164 map.put(key,result);
165 }
166 log.debug("getIndex","key="+key+", index="+result);
167 return result;
168 }
169
170 /**
171 * Allocate a new {@link TreeMap} to serve as context, then
172 * call {@link SnmpListTableCache#updateCachedDatas(Object,List)}, and
173 * finally replace the {@link #names} TreeMap by the new allocated
174 * TreeMap.
175 * @param rawDatas The table datas from which the cached data will be
176 * computed.
177 **/
178 protected SnmpCachedData updateCachedDatas(Object context, List<?> rawDatas) {
179 TreeMap<String,SnmpOid> ctxt = new TreeMap<>();
180 final SnmpCachedData result =
181 super.updateCachedDatas(context,rawDatas);
182 names = ctxt;
183 return result;
184 }
185
186
187 /**
188 * Load a list of raw data from which to build the cached data.
189 * This method is called when nothing is found in the request
190 * contextual cache.
191 * @param userData The request contextual cache allocated by
192 * the {@link JvmContextFactory}.
193 *
194 **/
195 protected abstract List<?> loadRawDatas(Map<Object,Object> userData);
196
197 /**
198 *The name under which the raw data is to be found/put in
199 * the request contextual cache.
200 **/
201 protected abstract String getRawDatasKey();
202
203 /**
204 * Get a list of raw data from which to build the cached data.
205 * Obtains a list of raw data by first looking it up in the
206 * request contextual cache <var>userData</var> under the given
207 * <var>key</var>. If nothing is found in the cache, calls
208 * {@link #loadRawDatas(Map)} to obtain a new rawData list,
209 * and cache the result in <var>userData</var> under <var>key</var>.
210 * @param userData The request contextual cache allocated by
211 * the {@link JvmContextFactory}.
212 * @param key The name under which the raw data is to be found/put in
213 * the request contextual cache.
214 *
215 **/
216 protected List<?> getRawDatas(Map<Object, Object> userData, String key) {
217 List<?> rawDatas = null;
218
219 // Look for memory manager list in request contextual cache.
220 if (userData != null)
221 rawDatas = (List<?>)userData.get(key);
222
223 if (rawDatas == null) {
224 // No list in contextual cache, get it from API
225 rawDatas = loadRawDatas(userData);
226
227
228 // Put list in cache...
229 if (rawDatas != null && userData != null)
230 userData.put(key, rawDatas);
231 }
232
233 return rawDatas;
234 }
235
236 /**
237 * Update cahed datas.
238 * Obtains a {@link List} of raw datas by calling
239 * {@link #getRawDatas(Map,String) getRawDatas((Map)context,getRawDatasKey())}.<br>
240 * Then allocate a new {@link TreeMap} to serve as temporary map between
241 * names and indexes, and call {@link #updateCachedDatas(Object,List)}
242 * with that temporary map as context.<br>
243 * Finally replaces the {@link #names} TreeMap by the temporary
244 * TreeMap.
245 * @param context The request contextual cache allocated by the
246 * {@link JvmContextFactory}.
247 **/
248 protected SnmpCachedData updateCachedDatas(Object context) {
249
250 final Map<Object, Object> userData =
251 (context instanceof Map)?Util.<Map<Object, Object>>cast(context):null;
252
253 // Look for memory manager list in request contextual cache.
254 final List<?> rawDatas = getRawDatas(userData,getRawDatasKey());
255
256 log.debug("updateCachedDatas","rawDatas.size()=" +
257 ((rawDatas==null)?"<no data>":""+rawDatas.size()));
258
259 TreeMap<String,SnmpOid> ctxt = new TreeMap<>();
260 final SnmpCachedData result =
261 super.updateCachedDatas(ctxt,rawDatas);
262 names = ctxt;
263 return result;
264 }
265
266 static final MibLogger log = new MibLogger(SnmpNamedListTableCache.class);
267 }