2 * Copyright (c) 2015 Cisco Systems, Inc. and others. All rights reserved.
4 * This program and the accompanying materials are made available under the
5 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
6 * and is available at http://www.eclipse.org/legal/epl-v10.html
8 package org.opendaylight.yangtools.util;
10 import com.google.common.annotations.Beta;
11 import com.google.common.base.Preconditions;
12 import com.google.common.collect.ImmutableMap;
13 import com.google.common.collect.UnmodifiableIterator;
14 import java.io.IOException;
15 import java.io.ObjectInputStream;
16 import java.io.ObjectOutputStream;
17 import java.io.Serializable;
18 import java.lang.reflect.Field;
19 import java.util.AbstractSet;
20 import java.util.ArrayList;
21 import java.util.Arrays;
22 import java.util.Iterator;
23 import java.util.List;
25 import java.util.Objects;
27 import javax.annotation.Nonnull;
30 * Implementation of the {@link Map} interface which stores a set of immutable mappings using a key-to-offset map and
31 * a backing array. This is useful for situations where the same key set is shared across a multitude of maps, as this
32 * class uses a global cache to share the key-to-offset mapping.
34 * This map supports creation of value objects on the fly. To achieve that, subclasses should override {@link #valueToObject(Object)},
35 * {@link #objectToValue(Object, Object)}, {@link #clone()} and {@link #toModifiableMap()} methods.
37 * @param <K> the type of keys maintained by this map
38 * @param <V> the type of mapped values
41 public class ImmutableOffsetMap<K, V> extends AbstractLazyValueMap<K, V> implements UnmodifiableMapPhase<K, V>, Serializable {
42 private static final long serialVersionUID = 1L;
44 private final Map<K, Integer> offsets;
45 private final Object[] objects;
49 * Construct a new instance backed by specified key-to-offset map and array of objects.
51 * @param offsets Key-to-offset map, may not be null
52 * @param objects Array of value object, may not be null. The array is stored as is, the caller
53 * is responsible for ensuring its contents remain unmodified.
55 ImmutableOffsetMap(@Nonnull final Map<K, Integer> offsets, @Nonnull final Object[] objects) {
56 this.offsets = Preconditions.checkNotNull(offsets);
57 this.objects = Preconditions.checkNotNull(objects);
58 Preconditions.checkArgument(offsets.size() == objects.length);
62 * Construct a new instance based on some other instance.
64 * @param m Instance to share data with, may not be null.
66 protected ImmutableOffsetMap(@Nonnull final ImmutableOffsetMap<K, V> m) {
67 this.offsets = m.offsets;
68 this.objects = m.objects;
72 * Create an {@link ImmutableOffsetMap} as a copy of an existing map. This is actually not completely true,
73 * as this method returns an {@link ImmutableMap} for empty and singleton inputs, as those are more memory-efficient.
74 * This method also recognizes {@link ImmutableOffsetMap} on input, and returns it back without doing anything else.
75 * It also recognizes {@link MutableOffsetMap} (as returned by {@link #toModifiableMap()}) and makes an efficient
76 * copy of its contents. All other maps are converted to an {@link ImmutableOffsetMap} with the same iteration
79 * @param m Input map, may not be null.
80 * @return An isolated, immutable copy of the input map
82 @Nonnull public static <K, V> Map<K, V> copyOf(@Nonnull final Map<K, V> m) {
83 // Prevent a copy. Note that ImmutableMap is not listed here because of its potentially larger keySet overhead.
84 if (m instanceof ImmutableOffsetMap || m instanceof SharedSingletonMap) {
88 // Familiar and efficient to copy
89 if (m instanceof MutableOffsetMap) {
90 return ((MutableOffsetMap<K, V>) m).toUnmodifiableMap();
93 final int size = m.size();
95 // Shares a single object
96 return ImmutableMap.of();
99 // Efficient single-entry implementation
100 final Entry<K, V> e = m.entrySet().iterator().next();
101 return SharedSingletonMap.of(e.getKey(), e.getValue());
104 final Map<K, Integer> offsets = OffsetMapCache.offsetsFor(m.keySet());
105 @SuppressWarnings("unchecked")
106 final V[] array = (V[]) new Object[offsets.size()];
107 for (Entry<K, V> e : m.entrySet()) {
108 array[offsets.get(e.getKey())] = e.getValue();
111 return new ImmutableOffsetMap<>(offsets, array);
115 public final int size() {
116 return offsets.size();
120 public final boolean isEmpty() {
121 return offsets.isEmpty();
125 public int hashCode() {
131 for (Entry<K, Integer> e : offsets.entrySet()) {
132 final Object v = objects[e.getValue()];
133 result += e.getKey().hashCode() ^ objectToValue(e.getKey(), v).hashCode();
141 public boolean equals(final Object o) {
149 if (o instanceof ImmutableOffsetMap) {
150 final ImmutableOffsetMap<?, ?> om = (ImmutableOffsetMap<?, ?>) o;
151 if (offsets.equals(om.offsets) && Arrays.deepEquals(objects, om.objects)) {
154 } else if (o instanceof MutableOffsetMap) {
155 // Let MutableOffsetMap do the actual work.
156 return o.equals(this);
157 } else if (o instanceof Map) {
158 final Map<?, ?> om = (Map<?, ?>)o;
160 // Size and key sets have to match
161 if (size() != om.size() || !keySet().equals(om.keySet())) {
166 // Ensure all objects are present
167 for (Entry<K, Integer> e : offsets.entrySet()) {
168 final V v = objectToValue(e.getKey(), objects[e.getValue()]);
169 if (!v.equals(om.get(e.getKey()))) {
173 } catch (ClassCastException e) {
174 // Can be thrown by om.get() and indicate we have incompatible key types
185 public final boolean containsKey(final Object key) {
186 return offsets.containsKey(key);
190 public final boolean containsValue(final Object value) {
191 @SuppressWarnings("unchecked")
192 final Object obj = valueToObject((V)value);
193 for (Object o : objects) {
194 if (Objects.equals(obj, o)) {
201 @SuppressWarnings("unchecked")
203 public final V get(final Object key) {
204 final Integer offset = offsets.get(key);
205 if (offset == null) {
209 return objectToValue((K) key, objects[offset]);
213 public final V remove(final Object key) {
214 throw new UnsupportedOperationException();
218 public final void putAll(final Map<? extends K, ? extends V> m) {
219 throw new UnsupportedOperationException();
223 public final void clear() {
224 throw new UnsupportedOperationException();
228 public final Set<K> keySet() {
229 return offsets.keySet();
233 public final Set<Entry<K, V>> entrySet() {
234 return new EntrySet();
238 public MutableOffsetMap<K, V> toModifiableMap() {
239 return new MutableOffsetMap<>(this);
242 Map<K, Integer> offsets() {
250 private final class EntrySet extends AbstractSet<Entry<K, V>> {
252 public Iterator<Entry<K, V>> iterator() {
253 final Iterator<Entry<K, Integer>> it = offsets.entrySet().iterator();
255 return new UnmodifiableIterator<Entry<K, V>>() {
257 public boolean hasNext() {
262 public Entry<K, V> next() {
263 final Entry<K, Integer> e = it.next();
264 return new SimpleImmutableEntry<>(e.getKey(), objectToValue(e.getKey(), objects[e.getValue()]));
271 return offsets.size();
275 private void writeObject(final ObjectOutputStream out) throws IOException {
276 out.writeInt(offsets.size());
277 for (Entry<K, V> e : entrySet()) {
278 out.writeObject(e.getKey());
279 out.writeObject(e.getValue());
283 private static final Field OFFSETS_FIELD = fieldFor("offsets");
284 private static final Field ARRAY_FIELD = fieldFor("objects");
286 private static Field fieldFor(final String name) {
289 f = ImmutableOffsetMap.class.getDeclaredField(name);
290 } catch (NoSuchFieldException | SecurityException e) {
291 throw new IllegalStateException("Failed to lookup field " + name, e);
294 f.setAccessible(true);
298 private void setField(final Field field, final Object value) throws IOException {
300 field.set(this, value);
301 } catch (IllegalArgumentException | IllegalAccessException e) {
302 throw new IOException("Failed to set field " + field, e);
306 @SuppressWarnings("unchecked")
307 private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
308 final int s = in.readInt();
310 final List<K> keys = new ArrayList<>(s);
311 final V[] values = (V[]) new Object[s];
313 for (int i = 0; i < s; ++i) {
314 keys.add((K)in.readObject());
315 values[i] = (V)in.readObject();
318 setField(OFFSETS_FIELD, OffsetMapCache.offsetsFor(keys));
319 setField(ARRAY_FIELD, values);