org.opendaylight.yangtools.util.ImmutableOffsetMap Maven / Gradle / Ivy
/*
* Copyright (c) 2015 Cisco Systems, Inc. and others. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0 which accompanies this distribution,
* and is available at http://www.eclipse.org/legal/epl-v10.html
*/
package org.opendaylight.yangtools.util;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Verify.verifyNotNull;
import static java.util.Objects.requireNonNull;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.UnmodifiableIterator;
import java.io.Serializable;
import java.util.AbstractMap.SimpleImmutableEntry;
import java.util.AbstractSet;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import org.eclipse.jdt.annotation.NonNull;
import org.eclipse.jdt.annotation.Nullable;
/**
* Implementation of the {@link Map} interface which stores a set of immutable mappings using a key-to-offset map and
* a backing array. This is useful for situations where the same key set is shared across a multitude of maps, as this
* class uses a global cache to share the key-to-offset mapping.
*
*
* In case the set of keys is statically known, you can use {@link ImmutableOffsetMapTemplate} to efficiently create
* {@link ImmutableOffsetMap} instances.
*
* @param the type of keys maintained by this map
* @param the type of mapped values
*/
public abstract sealed class ImmutableOffsetMap implements UnmodifiableMapPhase, Serializable {
static final class Ordered extends ImmutableOffsetMap {
@java.io.Serial
private static final long serialVersionUID = 1L;
Ordered(final ImmutableMap offsets, final V[] objects) {
super(offsets, objects);
}
@Override
public MutableOffsetMap toModifiableMap() {
return MutableOffsetMap.orderedCopyOf(this);
}
@Override
Object writeReplace() {
return new OIOMv1(this);
}
}
static final class Unordered extends ImmutableOffsetMap {
@java.io.Serial
private static final long serialVersionUID = 1L;
Unordered(final ImmutableMap offsets, final V[] objects) {
super(offsets, objects);
}
@Override
public MutableOffsetMap toModifiableMap() {
return MutableOffsetMap.unorderedCopyOf(this);
}
@Override
Object writeReplace() {
return new UIOMv1(this);
}
}
@java.io.Serial
private static final long serialVersionUID = 1L;
private final @NonNull ImmutableMap offsets;
private final @NonNull V[] objects;
private transient int hashCode;
/**
* Construct a new instance backed by specified key-to-offset map and array of objects.
*
* @param offsets Key-to-offset map, may not be null
* @param objects Array of value object, may not be null. The array is stored as is, the caller
* is responsible for ensuring its contents remain unmodified.
*/
private ImmutableOffsetMap(final ImmutableMap offsets, final V[] objects) {
this.offsets = requireNonNull(offsets);
this.objects = requireNonNull(objects);
checkArgument(offsets.size() == objects.length);
}
@Override
public abstract @NonNull MutableOffsetMap toModifiableMap();
/**
* Create an {@link ImmutableOffsetMap} as a copy of an existing map. This is actually not completely true, as this
* method returns an {@link ImmutableMap} for empty and singleton inputs, as those are more memory-efficient. This
* method also recognizes {@link ImmutableOffsetMap} and {@link SharedSingletonMap} on input, and returns it back
* without doing anything else. It also recognizes {@link MutableOffsetMap} (as returned by
* {@link #toModifiableMap()}) and makes an efficient copy of its contents. All other maps are converted to an
* {@link ImmutableOffsetMap} with the same iteration order as input.
*
* @param the type of keys maintained by the map
* @param the type of mapped values
* @param map Input map, may not be null.
* @return An isolated, immutable copy of the input map
* @throws NullPointerException if {@code map} or any of its elements is null.
*/
public static @NonNull Map orderedCopyOf(final @NonNull Map map) {
final Map common = commonCopy(map);
if (common != null) {
return common;
}
final int size = map.size();
if (size == 1) {
// Efficient single-entry implementation
final Entry e = map.entrySet().iterator().next();
return SharedSingletonMap.orderedOf(e.getKey(), e.getValue());
}
final ImmutableMap offsets = OffsetMapCache.orderedOffsets(map.keySet());
return new Ordered<>(offsets, createArray(offsets, map));
}
/**
* Create an {@link ImmutableOffsetMap} as a copy of an existing map. This is actually not completely true, as this
* method returns an {@link ImmutableMap} for empty and singleton inputs, as those are more memory-efficient. This
* method also recognizes {@link ImmutableOffsetMap} and {@link SharedSingletonMap} on input, and returns it back
* without doing anything else. It also recognizes {@link MutableOffsetMap} (as returned by
* {@link #toModifiableMap()}) and makes an efficient copy of its contents. All other maps are converted to an
* {@link ImmutableOffsetMap}. Iterator order is not guaranteed to be retained.
*
* @param the type of keys maintained by the map
* @param the type of mapped values
* @param map Input map, may not be null.
* @return An isolated, immutable copy of the input map
* @throws NullPointerException if {@code map} or any of its elements is null.
*/
public static @NonNull Map unorderedCopyOf(final @NonNull Map map) {
final Map common = commonCopy(map);
if (common != null) {
return common;
}
if (map.size() == 1) {
// Efficient single-entry implementation
final Entry e = map.entrySet().iterator().next();
return SharedSingletonMap.unorderedOf(e.getKey(), e.getValue());
}
final ImmutableMap offsets = OffsetMapCache.unorderedOffsets(map.keySet());
return new Unordered<>(offsets, createArray(offsets, map));
}
private static V[] createArray(final ImmutableMap offsets, final Map map) {
@SuppressWarnings("unchecked")
final V[] array = (V[]) new Object[offsets.size()];
for (Entry e : map.entrySet()) {
array[verifyNotNull(offsets.get(e.getKey()))] = e.getValue();
}
return array;
}
private static @Nullable Map commonCopy(final @NonNull Map map) {
// Prevent a copy. Note that ImmutableMap is not listed here because of its potentially larger keySet overhead.
if (map instanceof ImmutableOffsetMap || map instanceof SharedSingletonMap) {
return map;
}
// Familiar and efficient to copy
if (map instanceof MutableOffsetMap mop) {
return mop.toUnmodifiableMap();
}
if (map.isEmpty()) {
// Shares a single object
return ImmutableMap.of();
}
return null;
}
@Override
public final int size() {
return offsets.size();
}
@Override
public final boolean isEmpty() {
return offsets.isEmpty();
}
@Override
public final int hashCode() {
if (hashCode != 0) {
return hashCode;
}
int result = 0;
for (Entry e : offsets.entrySet()) {
result += e.getKey().hashCode() ^ objects[e.getValue()].hashCode();
}
hashCode = result;
return result;
}
@Override
public final boolean equals(final Object obj) {
if (obj == this) {
return true;
}
if (!(obj instanceof Map other)) {
return false;
}
if (obj instanceof ImmutableOffsetMap om) {
// If the offset match, the arrays have to match, too
if (offsets.equals(om.offsets)) {
return Arrays.deepEquals(objects, om.objects);
}
} else if (obj instanceof MutableOffsetMap) {
// Let MutableOffsetMap do the actual work.
return obj.equals(this);
}
// Size and key sets have to match
if (size() != other.size() || !keySet().equals(other.keySet())) {
return false;
}
try {
// Ensure all objects are present
for (Entry e : offsets.entrySet()) {
if (!objects[e.getValue()].equals(other.get(e.getKey()))) {
return false;
}
}
} catch (ClassCastException e) {
// Can be thrown by other.get() indicating we have incompatible key types
return false;
}
return true;
}
@Override
public final boolean containsKey(final Object key) {
return offsets.containsKey(key);
}
@Override
public final boolean containsValue(final Object value) {
for (Object o : objects) {
if (value.equals(o)) {
return true;
}
}
return false;
}
@Override
public final V get(final Object key) {
Integer offset;
return (offset = offsets.get(key)) == null ? null : objects[offset];
}
@Override
public final V remove(final Object key) {
throw new UnsupportedOperationException();
}
@Override
public final V put(final K key, final V value) {
throw new UnsupportedOperationException();
}
@Override
@SuppressWarnings("checkstyle:parameterName")
public final void putAll(final Map m) {
throw new UnsupportedOperationException();
}
@Override
public final void clear() {
throw new UnsupportedOperationException();
}
@Override
public final Set keySet() {
return offsets.keySet();
}
@Override
public final @NonNull Collection values() {
return new ConstantArrayCollection<>(objects);
}
@Override
public final @NonNull Set> entrySet() {
return new EntrySet();
}
@Override
public final String toString() {
final StringBuilder sb = new StringBuilder("{");
final Iterator it = offsets.keySet().iterator();
int offset = 0;
while (it.hasNext()) {
sb.append(it.next()).append('=').append(objects[offset++]);
if (it.hasNext()) {
sb.append(", ");
}
}
return sb.append('}').toString();
}
final @NonNull ImmutableMap offsets() {
return offsets;
}
final @NonNull V[] objects() {
return objects;
}
private final class EntrySet extends AbstractSet> {
@Override
public @NonNull Iterator> iterator() {
final Iterator> it = offsets.entrySet().iterator();
return new UnmodifiableIterator<>() {
@Override
public boolean hasNext() {
return it.hasNext();
}
@Override
public Entry next() {
final Entry e = it.next();
return new SimpleImmutableEntry<>(e.getKey(), objects[e.getValue()]);
}
};
}
@Override
public int size() {
return offsets.size();
}
}
@java.io.Serial
abstract Object writeReplace();
}