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/*
* Copyright 2019-present HiveMQ GmbH
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.hivemq.mqtt.topic.tree;
import com.hivemq.extension.sdk.api.annotations.NotNull;
import com.hivemq.extension.sdk.api.annotations.Nullable;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
class TopicTreeNode {
private final @NotNull String topicPart;
/**
* Wildcard and exact subscriptions are stored in separate fields to avoid keeping the distinguishing boolean
* in each subscription and iterating the joint structure if the operation is relevant only to one kind of
* subscriptions.
*
* The fields are NOT private to minimize the number of bypass methods.
* The class is intended to be used only as a part of {@link LocalTopicTree}.
*/
final @NotNull MatchingNodeSubscriptions wildcardSubscriptions;
final @NotNull MatchingNodeSubscriptions exactSubscriptions;
/**
* The child nodes of this node. The children get initialized lazily for memory saving purposes. If a threshold is
* exceeded this is null and the childrenMap contains all the children.
*/
@Nullable TopicTreeNode @Nullable [] children;
/**
* An optional map for quick access to children (only exists if a threshold is exceeded)
*/
@Nullable Map childrenMap;
TopicTreeNode(final @NotNull String topicPart) {
this.topicPart = topicPart;
wildcardSubscriptions = new MatchingNodeSubscriptions();
exactSubscriptions = new MatchingNodeSubscriptions();
}
public @NotNull TopicTreeNode addChildNodeIfAbsent(
final @NotNull String childNodeTopicPart, final int indexMapCreationThreshold) {
if (children != null) {
//Check if we need to create an index for large nodes
if (children.length > indexMapCreationThreshold && childrenMap == null) {
childrenMap = new HashMap<>(children.length + 1);
TopicTreeNode existingNode = null;
//Add all entries to the map
for (final TopicTreeNode child : children) {
if (child != null) {
childrenMap.put(child.getTopicPart(), child);
if (child.getTopicPart().equals(childNodeTopicPart)) {
existingNode = child;
}
}
}
children = null;
if (existingNode != null) {
return existingNode;
}
final TopicTreeNode childNode = new TopicTreeNode(childNodeTopicPart);
childrenMap.put(childNode.getTopicPart(), childNode);
return childNode;
} else {
//check if the node already exists
for (final TopicTreeNode child : children) {
if (child != null) {
if (child.getTopicPart().equals(childNodeTopicPart)) {
return child;
}
}
}
final TopicTreeNode childNode = new TopicTreeNode(childNodeTopicPart);
final int emptySlotIndex = Arrays.asList(children).indexOf(null);
if (emptySlotIndex >= 0) {
children[emptySlotIndex] = childNode;
} else {
final TopicTreeNode[] newChildren = new TopicTreeNode[children.length + 1];
System.arraycopy(children, 0, newChildren, 0, children.length);
newChildren[newChildren.length - 1] = childNode;
children = newChildren;
}
return childNode;
}
} else if (childrenMap != null) {
return childrenMap.computeIfAbsent(childNodeTopicPart, TopicTreeNode::new);
}
final TopicTreeNode childNode = new TopicTreeNode(childNodeTopicPart);
children = new TopicTreeNode[]{childNode};
return childNode;
}
/**
* Checks if the node is empty, that is if:
*
* 1. No Wildcard subscribers are present 2. No Exact subscribers are present 3. No children are present for this
* subnode
*
* @return if the node is empty
*/
public boolean isNodeEmpty() {
final boolean noChildrenPresent = (children == null && childrenMap == null) ||
children != null && isEmptyArray(children) ||
childrenMap != null && childrenMap.isEmpty();
return noChildrenPresent && exactSubscriptions.isEmpty() && wildcardSubscriptions.isEmpty();
}
public @Nullable TopicTreeNode @Nullable [] getChildren() {
return children;
}
public @Nullable Map getChildrenMap() {
return childrenMap;
}
public @NotNull String getTopicPart() {
return topicPart;
}
private static boolean isEmptyArray(final @Nullable TopicTreeNode @Nullable [] array) {
if (array == null) {
return true;
}
for (final TopicTreeNode child : array) {
if (child != null) {
return false;
}
}
return true;
}
@Override
public boolean equals(final @Nullable Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
final TopicTreeNode node = (TopicTreeNode) o;
return topicPart.equals(node.topicPart);
}
@Override
public int hashCode() {
return topicPart.hashCode();
}
@Override
public @NotNull String toString() {
return topicPart;
}
}