org.javimmutable.collections.tree.BranchNode Maven / Gradle / Ivy
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package org.javimmutable.collections.tree;
import org.javimmutable.collections.Cursor;
import org.javimmutable.collections.Func1;
import org.javimmutable.collections.Holder;
import org.javimmutable.collections.Holders;
import org.javimmutable.collections.JImmutableMap;
import org.javimmutable.collections.SplitableIterator;
import org.javimmutable.collections.Tuple2;
import org.javimmutable.collections.common.ArrayHelper;
import org.javimmutable.collections.cursors.LazyMultiCursor;
import org.javimmutable.collections.indexed.IndexedArray;
import org.javimmutable.collections.iterators.LazyMultiIterator;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import javax.annotation.concurrent.Immutable;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Objects;
@Immutable
public class BranchNode
implements Node,
ArrayHelper.Allocator>
{
private final Node[] children;
private final K baseKey;
private final int childCount;
public BranchNode(@Nonnull Node child1,
@Nonnull Node child2)
{
children = allocate(2);
children[0] = child1;
children[1] = child2;
baseKey = child1.baseKey();
childCount = 2;
}
private BranchNode(@Nonnull Node[] children)
{
this.children = children;
this.baseKey = children[0].baseKey();
this.childCount = children.length;
}
@Nullable
@Override
public K baseKey()
{
return baseKey;
}
@Override
public int childCount()
{
return childCount;
}
@Override
public int valueCount()
{
int answer = 0;
for (Node child : children) {
answer += child.valueCount();
}
return answer;
}
@Override
public V getValueOr(@Nonnull Comparator comparator,
@Nonnull K key,
V defaultValue)
{
final Node[] children = this.children;
final int index = findChildIndex(comparator, key, children, -1);
return (index >= 0) ? children[index].getValueOr(comparator, key, defaultValue) : defaultValue;
}
@Nonnull
@Override
public Holder find(@Nonnull Comparator comparator,
@Nonnull K key)
{
final Node[] children = this.children;
final int index = findChildIndex(comparator, key, children, -1);
return (index >= 0) ? children[index].find(comparator, key) : Holders.of();
}
@Nonnull
@Override
public Holder> findEntry(@Nonnull Comparator comparator,
@Nonnull K key)
{
final Node[] children = this.children;
final int index = findChildIndex(comparator, key, children, -1);
return (index >= 0) ? children[index].findEntry(comparator, key) : Holders.of();
}
@Nonnull
@Override
public UpdateResult assign(@Nonnull Comparator comparator,
@Nonnull K key,
V value)
{
final Node[] children = this.children;
final int index = findChildIndex(comparator, key, children, 0);
final UpdateResult childResult = children[index].assign(comparator, key, value);
return resultForAssign(children, index, childResult);
}
@Nonnull
@Override
public UpdateResult update(@Nonnull Comparator comparator,
@Nonnull K key,
@Nonnull Func1, V> generator)
{
final Node[] children = this.children;
final int index = findChildIndex(comparator, key, children, 0);
final UpdateResult childResult = children[index].update(comparator, key, generator);
return resultForAssign(children, index, childResult);
}
@Nonnull
@Override
public Node delete(@Nonnull Comparator comparator,
@Nonnull K key)
{
final Node[] children = this.children;
final int index = findChildIndex(comparator, key, children, -1);
if (index < 0) {
return this;
}
final Node child = children[index];
final Node newChild = child.delete(comparator, key);
if (newChild == child) {
return this;
}
final int thisChildCount = this.childCount;
final int newChildCount = newChild.childCount();
if (newChildCount >= MIN_CHILDREN) {
return new BranchNode<>(ArrayHelper.assign(children, index, newChild));
} else if (newChildCount == 0) {
if (thisChildCount == 1) {
return EmptyNode.of();
} else {
return new BranchNode<>(ArrayHelper.delete(this, children, index));
}
} else if (thisChildCount == 1) {
// special case for the root
return new BranchNode<>(ArrayHelper.assign(children, index, newChild));
} else {
Node mergeChild;
Node nextChild;
int mergeIndex;
if (index == (thisChildCount - 1)) {
// can't merge at the end of the array
mergeIndex = index - 1;
mergeChild = children[mergeIndex];
nextChild = newChild;
} else {
mergeIndex = index;
mergeChild = newChild;
nextChild = children[index + 1];
}
if ((mergeChild.childCount() + nextChild.childCount()) <= MAX_CHILDREN) {
final Node newMergeChild = mergeChild.mergeChildren(nextChild);
return new BranchNode<>(ArrayHelper.assignDelete(this, children, mergeIndex, newMergeChild));
} else {
final Tuple2, Node> distributed = mergeChild.distributeChildren(nextChild);
return new BranchNode<>(ArrayHelper.assignTwo(children, mergeIndex, distributed.getFirst(), distributed.getSecond()));
}
}
}
@Nonnull
@Override
public Node mergeChildren(@Nonnull Node sibling)
{
final BranchNode branch = (BranchNode)sibling;
return new BranchNode<>(ArrayHelper.concat(this, children, branch.children));
}
@Nonnull
@Override
public Tuple2, Node> distributeChildren(@Nonnull Node sibling)
{
final BranchNode branch = (BranchNode)sibling;
return Tuple2.of(new BranchNode<>(ArrayHelper.subArray(this, children, branch.children, 0, MIN_CHILDREN)),
new BranchNode<>(ArrayHelper.subArray(this, children, branch.children, MIN_CHILDREN, childCount + branch.childCount)));
}
@Nonnull
@Override
public Node compress()
{
return children.length == 1 ? children[0].compress() : this;
}
@Override
public int depth()
{
return 1 + children[0].depth();
}
@Nonnull
@Override
public Cursor> cursor()
{
return LazyMultiCursor.cursor(IndexedArray.retained(children));
}
@Nonnull
@Override
public SplitableIterator> iterator()
{
return LazyMultiIterator.iterator(IndexedArray.retained(children));
}
@Override
public void checkInvariants(@Nonnull Comparator comparator)
{
if (childCount != children.length) {
throw new IllegalStateException();
}
if (childCount > MAX_CHILDREN) {
throw new IllegalStateException();
}
final int depth = children[0].depth();
for (int i = 0; i < childCount; ++i) {
final Node child = children[i];
if (child.depth() != depth) {
throw new IllegalStateException();
}
if (i > 0 && comparator.compare(children[i - 1].baseKey(), children[i].baseKey()) >= 0) {
throw new IllegalStateException();
}
child.checkInvariants(comparator);
}
}
@Nonnull
@Override
@SuppressWarnings("unchecked")
public Node[] allocate(int size)
{
return new Node[size];
}
@Override
public boolean equals(Object o)
{
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
BranchNode that = (BranchNode)o;
return childCount == that.childCount &&
Arrays.equals(children, that.children) &&
Objects.equals(baseKey, that.baseKey);
}
@Override
public int hashCode()
{
return Objects.hash(children, baseKey, childCount);
}
@Nonnull
private UpdateResult resultForAssign(Node[] children,
int index,
UpdateResult childResult)
{
switch (childResult.type) {
case UNCHANGED:
return childResult;
case INPLACE: {
final Node[] newChildren = ArrayHelper.assign(children, index, childResult.newNode);
return UpdateResult.createInPlace(new BranchNode<>(newChildren), childResult.sizeDelta);
}
case SPLIT: {
final Node[] newChildren = ArrayHelper.assignInsert(this, children, index, childResult.newNode, childResult.extraNode);
final int newChildCount = newChildren.length;
if (newChildCount <= MAX_CHILDREN) {
return UpdateResult.createInPlace(new BranchNode<>(newChildren), childResult.sizeDelta);
} else {
final Node newChild1 = new BranchNode<>(ArrayHelper.subArray(this, newChildren, 0, MIN_CHILDREN));
final Node newChild2 = new BranchNode<>(ArrayHelper.subArray(this, newChildren, MIN_CHILDREN, newChildCount));
return UpdateResult.createSplit(newChild1, newChild2, childResult.sizeDelta);
}
}
default:
throw new IllegalStateException("unknown UpdateResult.Type value");
}
}
static int findChildIndex(@Nonnull Comparator comparator,
@Nonnull K key,
@Nonnull Node[] children,
int beforeFirstChildIndex)
{
int first = 0;
int last = children.length - 1;
while (first <= last) {
final int middle = (first + last) >>> 1;
final K value = children[middle].baseKey();
final int diff = comparator.compare(key, value);
if (diff < 0) {
last = middle - 1;
} else if (diff > 0) {
first = middle + 1;
} else {
return middle;
}
}
return first > 0 ? first - 1 : beforeFirstChildIndex;
}
}
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