org.eclipse.jdt.internal.compiler.util.SimpleSet.java Source code

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Here is the source code for org.eclipse.jdt.internal.compiler.util.SimpleSet.java

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/*******************************************************************************
 * Copyright (c) 2000, 2009 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jdt.internal.compiler.util;

/**
 * A simple lookup table is a non-synchronized Hashtable, whose keys
 * and values are Objects. It also uses linear probing to resolve collisions
 * rather than a linked list of hash table entries.
 */
public final class SimpleSet implements Cloneable {

    // to avoid using Enumerations, walk the individual values skipping nulls
    public Object[] values;
    public int elementSize; // number of elements in the table
    public int threshold;

    public SimpleSet() {
        this(13);
    }

    public SimpleSet(int size) {
        if (size < 3)
            size = 3;
        this.elementSize = 0;
        this.threshold = size + 1; // size is the expected number of elements
        this.values = new Object[2 * size + 1];
    }

    public Object add(Object object) {
        int length = this.values.length;
        int index = (object.hashCode() & 0x7FFFFFFF) % length;
        Object current;
        while ((current = this.values[index]) != null) {
            if (current.equals(object))
                return this.values[index] = object;
            if (++index == length)
                index = 0;
        }
        this.values[index] = object;

        // assumes the threshold is never equal to the size of the table
        if (++this.elementSize > this.threshold)
            rehash();
        return object;
    }

    public Object addIfNotIncluded(Object object) {
        int length = this.values.length;
        int index = (object.hashCode() & 0x7FFFFFFF) % length;
        Object current;
        while ((current = this.values[index]) != null) {
            if (current.equals(object))
                return null; // already existed
            if (++index == length)
                index = 0;
        }
        this.values[index] = object;

        // assumes the threshold is never equal to the size of the table
        if (++this.elementSize > this.threshold)
            rehash();
        return object;
    }

    public void asArray(Object[] copy) {
        if (this.elementSize != copy.length)
            throw new IllegalArgumentException();
        int index = this.elementSize;
        for (int i = 0, l = this.values.length; i < l && index > 0; i++)
            if (this.values[i] != null)
                copy[--index] = this.values[i];
    }

    public void clear() {
        for (int i = this.values.length; --i >= 0;)
            this.values[i] = null;
        this.elementSize = 0;
    }

    @Override
    public Object clone() throws CloneNotSupportedException {
        SimpleSet result = (SimpleSet) super.clone();
        result.elementSize = this.elementSize;
        result.threshold = this.threshold;

        int length = this.values.length;
        result.values = new Object[length];
        System.arraycopy(this.values, 0, result.values, 0, length);
        return result;
    }

    public boolean includes(Object object) {
        int length = this.values.length;
        int index = (object.hashCode() & 0x7FFFFFFF) % length;
        Object current;
        while ((current = this.values[index]) != null) {
            if (current.equals(object))
                return true;
            if (++index == length)
                index = 0;
        }
        return false;
    }

    public Object remove(Object object) {
        int length = this.values.length;
        int index = (object.hashCode() & 0x7FFFFFFF) % length;
        Object current;
        while ((current = this.values[index]) != null) {
            if (current.equals(object)) {
                this.elementSize--;
                Object oldValue = this.values[index];
                this.values[index] = null;
                if (this.values[index + 1 == length ? 0 : index + 1] != null)
                    rehash(); // only needed if a possible collision existed
                return oldValue;
            }
            if (++index == length)
                index = 0;
        }
        return null;
    }

    private void rehash() {
        SimpleSet newSet = new SimpleSet(this.elementSize * 2); // double the number of expected elements
        Object current;
        for (int i = this.values.length; --i >= 0;)
            if ((current = this.values[i]) != null)
                newSet.add(current);

        this.values = newSet.values;
        this.elementSize = newSet.elementSize;
        this.threshold = newSet.threshold;
    }

    @Override
    public String toString() {
        String s = ""; //$NON-NLS-1$
        Object object;
        for (int i = 0, l = this.values.length; i < l; i++)
            if ((object = this.values[i]) != null)
                s += object.toString() + "\n"; //$NON-NLS-1$
        return s;
    }
}