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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
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package org.graalvm.compiler.graph;

import java.util.AbstractList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.RandomAccess;

import org.graalvm.compiler.core.common.PermanentBailoutException;
import org.graalvm.compiler.graph.iterators.NodeIterable;

public abstract class NodeList<T extends Node> extends AbstractList<T> implements NodeIterable<T>, RandomAccess {

    
This constant limits the maximum number of entries in a node list. The reason for the limitations is the constraints of the code iterating over a node's inputs and successors. It uses a bit data structure where only 16 bits are available for the current index into the list. See the methods NodeClass.getSuccessorIterable(Node) and NodeClass.getInputIterable(Node). /**
     * This constant limits the maximum number of entries in a node list. The reason for the
     * limitations is the constraints of the code iterating over a node's inputs and successors. It
     * uses a bit data structure where only 16 bits are available for the current index into the
     * list. See the methods {@link NodeClass#getSuccessorIterable(Node)} and
     * {@link NodeClass#getInputIterable(Node)}.
     */
    private static final int MAX_ENTRIES = 65536;

    protected static final Node[] EMPTY_NODE_ARRAY = new Node[0];

    protected final Node self;
    protected Node[] nodes;
    private int size;
    protected final int initialSize;

    protected NodeList(Node self) {
        this.self = self;
        this.nodes = EMPTY_NODE_ARRAY;
        this.initialSize = 0;
    }

    protected NodeList(Node self, int initialSize) {
        this.self = self;
        checkMaxSize(initialSize);
        this.size = initialSize;
        this.initialSize = initialSize;
        this.nodes = new Node[initialSize];
    }

    protected NodeList(Node self, T[] elements) {
        this.self = self;
        if (elements == null || elements.length == 0) {
            this.size = 0;
            this.nodes = EMPTY_NODE_ARRAY;
            this.initialSize = 0;
        } else {
            checkMaxSize(elements.length);
            this.size = elements.length;
            this.initialSize = this.size;
            this.nodes = new Node[elements.length];
            for (int i = 0; i < elements.length; i++) {
                this.nodes[i] = elements[i];
                assert this.nodes[i] == null || !this.nodes[i].isDeleted() : "Initializing nodelist with deleted element : " + nodes[i];
            }
        }
    }

    protected NodeList(Node self, List<? extends T> elements) {
        this.self = self;
        if (elements == null || elements.isEmpty()) {
            this.size = 0;
            this.nodes = EMPTY_NODE_ARRAY;
            this.initialSize = 0;
        } else {
            int newSize = elements.size();
            checkMaxSize(newSize);
            this.size = newSize;
            this.initialSize = newSize;
            this.nodes = new Node[elements.size()];
            for (int i = 0; i < elements.size(); i++) {
                this.nodes[i] = elements.get(i);
                assert this.nodes[i] == null || !this.nodes[i].isDeleted();
            }
        }
    }

    private static void checkMaxSize(int value) {
        if (value > MAX_ENTRIES) {
            throw new PermanentBailoutException("Number of elements in a node list too high: %d", value);
        }
    }

    protected NodeList(Node self, Collection<? extends NodeInterface> elements) {
        this.self = self;
        if (elements == null || elements.isEmpty()) {
            this.size = 0;
            this.nodes = EMPTY_NODE_ARRAY;
            this.initialSize = 0;
        } else {
            int newSize = elements.size();
            checkMaxSize(newSize);
            this.size = newSize;
            this.initialSize = newSize;
            this.nodes = new Node[elements.size()];
            int i = 0;
            for (NodeInterface n : elements) {
                this.nodes[i] = n.asNode();
                assert this.nodes[i] == null || !this.nodes[i].isDeleted();
                i++;
            }
        }
    }

    
Removes null values from the list. /**
     * Removes {@code null} values from the list.
     */
    public void trim() {
        int newSize = 0;
        for (int i = 0; i < nodes.length; ++i) {
            if (nodes[i] != null) {
                nodes[newSize] = nodes[i];
                newSize++;
            }
        }
        size = newSize;
    }

    protected abstract void update(T oldNode, T newNode);

    public abstract Edges.Type getEdgesType();

    @Override
    public final int size() {
        return size;
    }

    @Override
    public final boolean isEmpty() {
        return size == 0;
    }

    @Override
    public boolean isNotEmpty() {
        return size > 0;
    }

    @Override
    public int count() {
        return size;
    }

    protected final void incModCount() {
        modCount++;
    }

    
Adds a new node to the list. The total number of nodes in the list must not exceed NodeList<T>.MAX_ENTRIES, otherwise a PermanentBailoutException is thrown. /**
     * Adds a new node to the list. The total number of nodes in the list must not exceed
     * {@link #MAX_ENTRIES}, otherwise a {@link PermanentBailoutException} is thrown.
     */
    @SuppressWarnings("unchecked")
    @Override
    public boolean add(Node node) {
        assert node == null || !node.isDeleted() : node;
        checkMaxSize(size + 1);
        self.incModCount();
        incModCount();
        int length = nodes.length;
        if (length == 0) {
            nodes = new Node[2];
        } else if (size == length) {
            Node[] newNodes = new Node[nodes.length * 2 + 1];
            System.arraycopy(nodes, 0, newNodes, 0, length);
            nodes = newNodes;
        }
        nodes[size++] = node;
        update(null, (T) node);
        return true;
    }

    
Get a node from the list given an index. /**
     * Get a node from the list given an {@code index}.
     */
    @Override
    @SuppressWarnings("unchecked")
    public T get(int index) {
        assert assertInRange(index);
        return (T) nodes[index];
    }

    private boolean assertInRange(int index) {
        assert index >= 0 && index < size() : index + " < " + size();
        return true;
    }

    public T last() {
        return get(size() - 1);
    }

    
Set the node of the list at the given index to a new value. /**
     * Set the node of the list at the given {@code index} to a new value.
     */
    @Override
    @SuppressWarnings("unchecked")
    public T set(int index, Node node) {
        incModCount();
        T oldValue = (T) nodes[index];
        assert assertInRange(index);
        update((T) nodes[index], (T) node);
        nodes[index] = node;
        return oldValue;
    }

    public void initialize(int index, Node node) {
        incModCount();
        assert index < size();
        nodes[index] = node;
    }

    void copy(NodeList<? extends Node> other) {
        self.incModCount();
        incModCount();
        Node[] newNodes = new Node[other.size];
        System.arraycopy(other.nodes, 0, newNodes, 0, newNodes.length);
        nodes = newNodes;
        size = other.size;
    }

    @Override
    public boolean equals(Object other) {
        if (other == this) {
            return true;
        }
        if (other instanceof List<?>) {
            List<?> otherList = (List<?>) other;
            if (size != otherList.size()) {
                return false;
            }
            for (int i = 0; i < size; i++) {
                if (nodes[i] != otherList.get(i)) {
                    return false;
                }
            }
            return true;
        }
        return false;
    }

    @SuppressWarnings("unchecked")
    @Override
    public void clear() {
        self.incModCount();
        incModCount();
        for (int i = 0; i < size; i++) {
            update((T) nodes[i], null);
        }
        clearWithoutUpdate();
    }

    void clearWithoutUpdate() {
        nodes = EMPTY_NODE_ARRAY;
        size = 0;
    }

    @Override
    @SuppressWarnings("unchecked")
    public boolean remove(Object node) {
        self.incModCount();
        int i = 0;
        incModCount();
        while (i < size && nodes[i] != node) {
            i++;
        }
        if (i < size) {
            T oldValue = (T) nodes[i];
            i++;
            while (i < size) {
                nodes[i - 1] = nodes[i];
                i++;
            }
            nodes[--size] = null;
            update(oldValue, null);
            return true;
        } else {
            return false;
        }
    }

    @Override
    @SuppressWarnings("unchecked")
    public T remove(int index) {
        self.incModCount();
        T oldValue = (T) nodes[index];
        int i = index + 1;
        incModCount();
        while (i < size) {
            nodes[i - 1] = nodes[i];
            i++;
        }
        nodes[--size] = null;
        update(oldValue, null);
        return oldValue;
    }

    boolean replaceFirst(Node node, Node other) {
        for (int i = 0; i < size; i++) {
            if (nodes[i] == node) {
                nodes[i] = other;
                return true;
            }
        }
        return false;
    }

    @Override
    public Iterator<T> iterator() {
        return new NodeListIterator<>(this, 0);
    }

    @Override
    public boolean contains(T other) {
        for (int i = 0; i < size; i++) {
            if (nodes[i] == other) {
                return true;
            }
        }
        return false;
    }

    @SuppressWarnings("unchecked")
    @Override
    public List<T> snapshot() {
        return (List<T>) Arrays.asList(Arrays.copyOf(this.nodes, this.size));
    }

    @Override
    public void snapshotTo(Collection<? super T> to) {
        for (int i = 0; i < size; i++) {
            to.add(get(i));
        }
    }

    @SuppressWarnings("unchecked")
    public void setAll(NodeList<T> values) {
        self.incModCount();
        incModCount();
        for (int i = 0; i < size(); i++) {
            update((T) nodes[i], null);
        }
        nodes = Arrays.copyOf(values.nodes, values.size());
        size = values.size();

        for (int i = 0; i < size(); i++) {
            update(null, (T) nodes[i]);
        }
    }

    @Override
    @SuppressWarnings("unchecked")
    public <A> A[] toArray(A[] a) {
        if (a.length >= size) {
            System.arraycopy(nodes, 0, a, 0, size);
            return a;
        }
        return (A[]) Arrays.copyOf(nodes, size, a.getClass());
    }

    @Override
    public Object[] toArray() {
        return Arrays.copyOf(nodes, size);
    }

    protected void replace(T node, T other) {
        incModCount();
        for (int i = 0; i < size(); i++) {
            if (nodes[i] == node) {
                nodes[i] = other;
                update(node, other);
            }
        }
    }

    @Override
    public int indexOf(Object node) {
        for (int i = 0; i < size; i++) {
            if (nodes[i] == node) {
                return i;
            }
        }
        return -1;
    }

    @Override
    public boolean contains(Object o) {
        return indexOf(o) != -1;
    }

    @Override
    public boolean containsAll(Collection<?> c) {
        throw new UnsupportedOperationException("not implemented");
    }

    @Override
    public boolean addAll(Collection<? extends T> c) {
        for (T e : c) {
            add(e);
        }
        return true;
    }

    public boolean addAll(T[] c) {
        for (T e : c) {
            add(e);
        }
        return true;
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append('[');
        for (int i = 0; i < size; i++) {
            if (i != 0) {
                sb.append(", ");
            }
            sb.append(nodes[i]);
        }
        sb.append(']');
        return sb.toString();
    }

    @Override
    public T first() {
        if (size() > 0) {
            return get(0);
        }
        return null;
    }

    public SubList<T> subList(int startIndex) {
        assert assertInRange(startIndex);
        return new SubList<>(this, startIndex);
    }

    public static final class SubList<R extends Node> extends AbstractList<R> implements NodeIterable<R>, RandomAccess {
        private final NodeList<R> list;
        private final int offset;

        private SubList(NodeList<R> list, int offset) {
            this.list = list;
            this.offset = offset;
        }

        @Override
        public R get(int index) {
            assert index >= 0 : index;
            return list.get(offset + index);
        }

        @Override
        public int size() {
            return list.size() - offset;
        }

        public SubList<R> subList(int startIndex) {
            assert startIndex >= 0 && startIndex < size() : startIndex;
            return new SubList<>(this.list, startIndex + offset);
        }

        @Override
        public Iterator<R> iterator() {
            return new NodeListIterator<>(list, offset);
        }
    }

    private static final class NodeListIterator<R extends Node> implements Iterator<R> {
        private final NodeList<R> list;
        private final int expectedModCount;
        private int index;

        private NodeListIterator(NodeList<R> list, int startIndex) {
            this.list = list;
            this.expectedModCount = list.modCount;
            this.index = startIndex;
        }

        @Override
        public boolean hasNext() {
            assert expectedModCount == list.modCount;
            return index < list.size;
        }

        @SuppressWarnings("unchecked")
        @Override
        public R next() {
            assert expectedModCount == list.modCount;
            return (R) list.nodes[index++];
        }

        @Override
        public void remove() {
            throw new UnsupportedOperationException();
        }
    }
}