uintmap.java

java中比较著名的js引擎当属mozilla开源的rhino

/* -*- Mode: java; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (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.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Rhino code, released
 * May 6, 1999.
 *
 * The Initial Developer of the Original Code is
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 1997-2000
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Igor Bukanov
 *
 * Alternatively, the contents of this file may be used under the terms of
 * the GNU General Public License Version 2 or later (the "GPL"), in which
 * case the provisions of the GPL are applicable instead of those above. If
 * you wish to allow use of your version of this file only under the terms of
 * the GPL and not to allow others to use your version of this file under the
 * MPL, indicate your decision by deleting the provisions above and replacing
 * them with the notice and other provisions required by the GPL. If you do
 * not delete the provisions above, a recipient may use your version of this
 * file under either the MPL or the GPL.
 *
 * ***** END LICENSE BLOCK ***** */

package org.mozilla.javascript;

import java.io.Serializable;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;

/**
 * Map to associate non-negative integers to objects or integers.
 * The map does not synchronize any of its operation, so either use
 * it from a single thread or do own synchronization or perform all mutation
 * operations on one thread before passing the map to others.
 *
 * @author Igor Bukanov
 *
 */

public class UintMap implements Serializable
{
    static final long serialVersionUID = 4242698212885848444L;

// Map implementation via hashtable,
// follows "The Art of Computer Programming" by Donald E. Knuth

    public UintMap() {
        this(4);
    }

    public UintMap(int initialCapacity) {
        if (initialCapacity < 0) Kit.codeBug();
        // Table grow when number of stored keys >= 3/4 of max capacity
        int minimalCapacity = initialCapacity * 4 / 3;
        int i;
        for (i = 2; (1 << i) < minimalCapacity; ++i) { }
        power = i;
        if (check && power < 2) Kit.codeBug();
    }

    public boolean isEmpty() {
        return keyCount == 0;
    }

    public int size() {
        return keyCount;
    }

    public boolean has(int key) {
        if (key < 0) Kit.codeBug();
        return 0 <= findIndex(key);
    }

    /**
     * Get object value assigned with key.
     * @return key object value or null if key is absent
     */
    public Object getObject(int key) {
        if (key < 0) Kit.codeBug();
        if (values != null) {
            int index = findIndex(key);
            if (0 <= index) {
                return values[index];
            }
        }
        return null;
    }

    /**
     * Get integer value assigned with key.
     * @return key integer value or defaultValue if key is absent
     */
    public int getInt(int key, int defaultValue) {
        if (key < 0) Kit.codeBug();
        int index = findIndex(key);
        if (0 <= index) {
            if (ivaluesShift != 0) {
                return keys[ivaluesShift + index];
            }
            return 0;
        }
        return defaultValue;
    }

    /**
     * Get integer value assigned with key.
     * @return key integer value or defaultValue if key does not exist or does
     * not have int value
     * @throws RuntimeException if key does not exist
     */
    public int getExistingInt(int key) {
        if (key < 0) Kit.codeBug();
        int index = findIndex(key);
        if (0 <= index) {
            if (ivaluesShift != 0) {
                return keys[ivaluesShift + index];
            }
            return 0;
        }
        // Key must exist
        Kit.codeBug();
        return 0;
    }

    /**
     * Set object value of the key.
     * If key does not exist, also set its int value to 0.
     */
    public void put(int key, Object value) {
        if (key < 0) Kit.codeBug();
        int index = ensureIndex(key, false);
        if (values == null) {
            values = new Object[1 << power];
        }
        values[index] = value;
    }

    /**
     * Set int value of the key.
     * If key does not exist, also set its object value to null.
     */
    public void put(int key, int value) {
        if (key < 0) Kit.codeBug();
        int index = ensureIndex(key, true);
        if (ivaluesShift == 0) {
            int N = 1 << power;
            // keys.length can be N * 2 after clear which set ivaluesShift to 0
            if (keys.length != N * 2) {
                int[] tmp = new int[N * 2];
                System.arraycopy(keys, 0, tmp, 0, N);
                keys = tmp;
            }
            ivaluesShift = N;
        }
        keys[ivaluesShift + index] = value;
    }

    public void remove(int key) {
        if (key < 0) Kit.codeBug();
        int index = findIndex(key);
        if (0 <= index) {
            keys[index] = DELETED;
            --keyCount;
            // Allow to GC value and make sure that new key with the deleted
            // slot shall get proper default values
            if (values != null) { values[index] = null; }
            if (ivaluesShift != 0) { keys[ivaluesShift + index] = 0; }
        }
    }

    public void clear() {
        int N = 1 << power;
        if (keys != null) {
            for (int i = 0; i != N; ++i) {
                keys[i] = EMPTY;
            }
            if (values != null) {
                for (int i = 0; i != N; ++i) {
                    values[i] = null;
                }
            }
        }
        ivaluesShift = 0;
        keyCount = 0;
        occupiedCount = 0;
    }

    /** Return array of present keys */
    public int[] getKeys() {
        int[] keys = this.keys;
        int n = keyCount;
        int[] result = new int[n];
        for (int i = 0; n != 0; ++i) {
            int entry = keys[i];
            if (entry != EMPTY && entry != DELETED) {
                result[--n] = entry;
            }
        }
        return result;
    }

    private static int tableLookupStep(int fraction, int mask, int power) {
        int shift = 32 - 2 * power;
        if (shift >= 0) {
            return ((fraction >>> shift) & mask) | 1;
        }
        else {
            return (fraction & (mask >>> -shift)) | 1;
        }
    }

    private int findIndex(int key) {
        int[] keys = this.keys;
        if (keys != null) {
            int fraction = key * A;
            int index = fraction >>> (32 - power);
            int entry = keys[index];
            if (entry == key) { return index; }
            if (entry != EMPTY) {
                // Search in table after first failed attempt
                int mask = (1 << power) - 1;
                int step = tableLookupStep(fraction, mask, power);
                int n = 0;
                do {
                    if (check) {
                        if (n >= occupiedCount) Kit.codeBug();
                        ++n;
                    }
                    index = (index + step) & mask;
                    entry = keys[index];
                    if (entry == key) { return index; }
                } while (entry != EMPTY);
            }
        }
        return -1;
    }

// Insert key that is not present to table without deleted entries
// and enough free space
    private int insertNewKey(int key) {
        if (check && occupiedCount != keyCount) Kit.codeBug();
        if (check && keyCount == 1 << power) Kit.codeBug();
        int[] keys = this.keys;
        int fraction = key * A;
        int index = fraction >>> (32 - power);
        if (keys[index] != EMPTY) {
            int mask = (1 << power) - 1;
            int step = tableLookupStep(fraction, mask, power);
            int firstIndex = index;
            do {
                if (check && keys[index] == DELETED) Kit.codeBug();
                index = (index + step) & mask;
                if (check && firstIndex == index) Kit.codeBug();
            } while (keys[index] != EMPTY);
        }
        keys[index] = key;
        ++occupiedCount;
        ++keyCount;
        return index;
    }

    private void rehashTable(boolean ensureIntSpace) {
        if (keys != null) {
            // Check if removing deleted entries would free enough space
            if (keyCount * 2 >= occupiedCount) {
                // Need to grow: less then half of deleted entries
                ++power;
            }
        }
        int N = 1 << power;
        int[] old = keys;
        int oldShift = ivaluesShift;
        if (oldShift == 0 && !ensureIntSpace) {
            keys = new int[N];
        }
        else {
            ivaluesShift = N; keys = new int[N * 2];
        }
        for (int i = 0; i != N; ++i) { keys[i] = EMPTY; }

        Object[] oldValues = values;
        if (oldValues != null) { values = new Object[N]; }

        int oldCount = keyCount;
        occupiedCount = 0;
        if (oldCount != 0) {
            keyCount = 0;
            for (int i = 0, remaining = oldCount; remaining != 0; ++i) {
                int key = old[i];
                if (key != EMPTY && key != DELETED) {
                    int index = insertNewKey(key);
                    if (oldValues != null) {
                        values[index] = oldValues[i];
                    }
                    if (oldShift != 0) {
                        keys[ivaluesShift + index] = old[oldShift + i];
                    }
                    --remaining;
                }
            }
        }
    }

// Ensure key index creating one if necessary
    private int ensureIndex(int key, boolean intType) {
        int index = -1;
        int firstDeleted = -1;
        int[] keys = this.keys;
        if (keys != null) {
            int fraction = key * A;
            index = fraction >>> (32 - power);
            int entry = keys[index];
            if (entry == key) { return index; }
            if (entry != EMPTY) {