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/*
* Java Genetic Algorithm Library (jenetics-8.1.0).
* Copyright (c) 2007-2024 Franz Wilhelmstötter
*
* 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.
*
* Author:
* Franz Wilhelmstötter ([email protected])
*/
package io.jenetics.ext.util;
import static java.util.Objects.requireNonNull;
import static io.jenetics.internal.util.SerialIO.readIntArray;
import static io.jenetics.internal.util.SerialIO.readObjectArray;
import static io.jenetics.internal.util.SerialIO.writeIntArray;
import static io.jenetics.internal.util.SerialIO.writeObjectArray;
import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.ObjectInput;
import java.io.ObjectInputStream;
import java.io.ObjectOutput;
import java.io.Serial;
import java.io.Serializable;
import java.lang.reflect.Array;
import java.util.Arrays;
import java.util.Iterator;
import java.util.Optional;
import java.util.function.BiFunction;
import java.util.function.Function;
import java.util.stream.IntStream;
import java.util.stream.Stream;
import io.jenetics.util.ISeq;
/**
* Default implementation of the {@link FlatTree} interface. Beside the
* flattened and dense layout it is also an immutable implementation of
* the {@link Tree} interface. It can only be created from an existing tree.
*
* {@snippet lang="java":
* final Tree immutable = FlatTreeNode.ofTree(TreeNode.parse(null)); // @replace substring='null' replacement="..."
* }
*
* @implNote
* This class is immutable and thread-safe.
*
* @author Franz Wilhelmstötter
* @version 7.1
* @since 3.9
*/
public final class FlatTreeNode
implements
FlatTree>,
Serializable
{
/**
* The flattened tree nodes.
*/
private record Nodes(Object[] values, int[] childOffsets, int[] childCounts) {
Nodes(final int size) {
this(new Object[size], new int[size], new int[size]);
}
}
@Serial
private static final long serialVersionUID = 3L;
private static final int NULL_INDEX = -1;
private final Nodes _nodes;
private final int _index;
private FlatTreeNode(final Nodes nodes, final int index) {
_nodes = requireNonNull(nodes);
_index = index;
}
private FlatTreeNode(final Nodes nodes) {
this(nodes, 0);
}
/**
* Returns the root of the tree that contains this node. The root is the
* ancestor with no parent. This implementation has a runtime complexity
* of O(1).
*
* @return the root of the tree that contains this node
*/
@Override
public FlatTreeNode root() {
return nodeAt(0);
}
@Override
public boolean isRoot() {
return _index == 0;
}
private FlatTreeNode nodeAt(final int index) {
return new FlatTreeNode<>(_nodes, index);
}
@SuppressWarnings("unchecked")
@Override
public V value() {
return (V)_nodes.values[_index];
}
@Override
public Optional> parent() {
int index = NULL_INDEX;
for (int i = _index; --i >= 0 && index == NULL_INDEX;) {
if (isParent(i)) {
index = i;
}
}
return index != NULL_INDEX
? Optional.of(nodeAt(index))
: Optional.empty();
}
private boolean isParent(final int index) {
return _nodes.childCounts[index] > 0 &&
_nodes.childOffsets[index] <= _index &&
_nodes.childOffsets[index] + _nodes.childCounts[index] > _index;
}
@Override
public FlatTreeNode childAt(final int index) {
if (index < 0 || index >= childCount()) {
throw new IndexOutOfBoundsException(Integer.toString(index));
}
return nodeAt(childOffset() + index);
}
@Override
public int childCount() {
return _nodes.childCounts[_index];
}
/**
* Return the index of the first child node in the underlying node array.
* {@code -1} is returned if {@code this} node is a leaf.
*
* @return Return the index of the first child node in the underlying node
* array, or {@code -1} if {@code this} node is a leaf
*/
@Override
public int childOffset() {
return _nodes.childOffsets[_index];
}
@Override
public ISeq> flattenedNodes() {
return stream().collect(ISeq.toISeq());
}
@Override
public Iterator> breadthFirstIterator() {
return isRoot()
? new IntFunctionIterator<>(this::nodeAt, _nodes.values.length)
: FlatTree.super.breadthFirstIterator();
}
@Override
public Stream> breadthFirstStream() {
return isRoot()
? IntStream.range(0, _nodes.values.length).mapToObj(this::nodeAt)
: FlatTree.super.breadthFirstStream();
}
/**
* Return a sequence of all mapped nodes of the whole underlying
* tree. This is a convenient method for
* {@snippet lang="java":
* final ISeq seq = stream()
* .map(mapper)
* .collect(ISeq.toISeq());
* }
*
* @param mapper the mapper function
* @param the mapped type
* @return a sequence of all mapped nodes
*/
public ISeq
map(final Function, ? extends B> mapper) {
return stream()
.map(mapper)
.collect(ISeq.toISeq());
}
@Override
public boolean identical(final Tree other) {
return other == this ||
other instanceof FlatTreeNode node &&
node._index == _index &&
node._nodes == _nodes;
}
@Override
public U reduce(
final U[] neutral,
final BiFunction reducer
) {
requireNonNull(neutral);
requireNonNull(reducer);
@SuppressWarnings("unchecked")
final class Reducing {
private U reduce(final int index) {
return _nodes.childCounts[index] == 0
? reducer.apply((V)_nodes.values[index], neutral)
: reducer.apply((V)_nodes.values[index], children(index));
}
private U[] children(final int index) {
final U[] values = (U[])Array.newInstance(
neutral.getClass().getComponentType(),
_nodes.childCounts[index]
);
for (int i = 0; i < _nodes.childCounts[index]; ++i) {
values[i] = reduce(_nodes.childOffsets[index] + i);
}
return values;
}
}
return isEmpty() ? null : new Reducing().reduce(_index);
}
@Override
public int hashCode() {
return Tree.hashCode(this);
}
@Override
public boolean equals(final Object obj) {
return obj == this ||
(obj instanceof FlatTreeNode ftn && equals(ftn)) ||
(obj instanceof Tree tree && Tree.equals(tree, this));
}
private boolean equals(final FlatTreeNode tree) {
return tree._index == _index &&
Arrays.equals(tree._nodes.values, _nodes.values) &&
Arrays.equals(tree._nodes.childCounts, _nodes.childCounts) &&
Arrays.equals(tree._nodes.childOffsets, _nodes.childOffsets);
}
@Override
public String toString() {
return toParenthesesString();
}
@Override
public int size() {
return isRoot()
? _nodes.values.length
: countChildren(_index) + 1;
}
private int countChildren(final int index) {
int count = _nodes.childCounts[index];
for (int i = 0; i < _nodes.childCounts[index]; ++i) {
count += countChildren(_nodes.childOffsets[index] + i);
}
return count;
}
/* *************************************************************************
* Static factories
* ************************************************************************/
/**
* Create a new, immutable {@code FlatTreeNode} from the given {@code tree}.
*
* @param tree the source tree
* @param the tree value types
* @return a {@code FlatTreeNode} from the given {@code tree}
* @throws NullPointerException if the given {@code tree} is {@code null}
*/
public static FlatTreeNode ofTree(final Tree tree) {
requireNonNull(tree);
if (tree instanceof FlatTreeNode ft && ft.isRoot()) {
@SuppressWarnings("unchecked")
final var result = (FlatTreeNode)ft;
return result;
}
final int size = tree.size();
assert size >= 1;
final var nodes = new Nodes(size);
int childOffset = 1;
int index = 0;
for (var node : tree) {
nodes.values[index] = node.value();
nodes.childCounts[index] = node.childCount();
nodes.childOffsets[index] = node.isLeaf() ? NULL_INDEX : childOffset;
childOffset += node.childCount();
++index;
}
assert index == size;
return new FlatTreeNode<>(nodes);
}
/**
* Parses a (parentheses) tree string, created with
* {@link Tree#toParenthesesString()}. The tree string might look like this:
*
* mul(div(cos(1.0),cos(π)),sin(mul(1.0,z)))
*
*
* @see Tree#toParenthesesString(Function)
* @see Tree#toParenthesesString()
* @see TreeNode#parse(String)
*
* @since 5.0
*
* @param tree the parentheses tree string
* @return the parsed tree
* @throws NullPointerException if the given {@code tree} string is
* {@code null}
* @throws IllegalArgumentException if the given tree string could not be
* parsed
*/
public static FlatTreeNode parse(final String tree) {
return ofTree(ParenthesesTreeParser.parse(tree, Function.identity()));
}
/**
* Parses a (parentheses) tree string, created with
* {@link Tree#toParenthesesString()}. The tree string might look like this
*
* 0(1(4,5),2(6),3(7(10,11),8,9))
*
* and can be parsed to an integer tree with the following code:
* {@snippet lang="java":
* final Tree tree = FlatTreeNode.parse(
* "0(1(4,5),2(6),3(7(10,11),8,9))",
* Integer::parseInt
* );
* }
*
* @see Tree#toParenthesesString(Function)
* @see Tree#toParenthesesString()
* @see TreeNode#parse(String, Function)
*
* @since 5.0
*
* @param the tree node value type
* @param tree the parentheses tree string
* @param mapper the mapper which converts the serialized string value to
* the desired type
* @return the parsed tree object
* @throws NullPointerException if one of the arguments is {@code null}
* @throws IllegalArgumentException if the given parentheses tree string
* doesn't represent a valid tree
*/
public static FlatTreeNode parse(
final String tree,
final Function mapper
) {
return ofTree(ParenthesesTreeParser.parse(tree, mapper));
}
/* *************************************************************************
* Java object serialization
* ************************************************************************/
@Serial
private Object writeReplace() {
return new SerialProxy(SerialProxy.FLAT_TREE_NODE, this);
}
@Serial
private void readObject(final ObjectInputStream stream)
throws InvalidObjectException
{
throw new InvalidObjectException("Serialization proxy required.");
}
void write(final ObjectOutput out) throws IOException {
final FlatTreeNode node = isRoot()
? this
: FlatTreeNode.ofTree(this);
writeObjectArray(node._nodes.values, out);
writeIntArray(node._nodes.childOffsets, out);
writeIntArray(node._nodes.childCounts, out);
}
@SuppressWarnings("rawtypes")
static FlatTreeNode read(final ObjectInput in)
throws IOException, ClassNotFoundException
{
return new FlatTreeNode(new Nodes(
readObjectArray(in),
readIntArray(in),
readIntArray(in)
));
}
}