src/main/java/com/alibaba/com/caucho/hessian/util/IdentityIntMap.java

/*
 * Copyright (c) 2001-2008 Caucho Technology, Inc.  All rights reserved.
 *
 * The Apache Software License, Version 1.1
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowlegement:
 *       "This product includes software developed by the
 *        Caucho Technology (http://www.caucho.com/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 *
 * 4. The names "Burlap", "Resin", and "Caucho" must not be used to
 *    endorse or promote products derived from this software without prior
 *    written permission. For written permission, please contact
 *    info@caucho.com.
 *
 * 5. Products derived from this software may not be called "Resin"
 *    nor may "Resin" appear in their names without prior written
 *    permission of Caucho Technology.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL CAUCHO TECHNOLOGY OR ITS CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
 * OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
 * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
 * IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * @author Scott Ferguson
 */

package com.alibaba.com.caucho.hessian.util;

/**
 * The IntMap provides a simple hashmap from keys to integers.  The API is
 * an abbreviation of the HashMap collection API.
 *
 * <p>The convenience of IntMap is avoiding all the silly wrapping of
 * integers.
 */
public class IdentityIntMap {
    /**
     * Encoding of a null entry.  Since NULL is equal to Integer.MIN_VALUE,
     * it's impossible to distinguish between the two.
     */
    public final static int NULL = 0xdeadbeef; // Integer.MIN_VALUE + 1;
    public static final int[] PRIMES =
            {
                    1,       /* 1<< 0 = 1 */
                    2,       /* 1<< 1 = 2 */
                    3,       /* 1<< 2 = 4 */
                    7,       /* 1<< 3 = 8 */
                    13,      /* 1<< 4 = 16 */
                    31,      /* 1<< 5 = 32 */
                    61,      /* 1<< 6 = 64 */
                    127,     /* 1<< 7 = 128 */
                    251,     /* 1<< 8 = 256 */
                    509,     /* 1<< 9 = 512 */
                    1021,    /* 1<<10 = 1024 */
                    2039,    /* 1<<11 = 2048 */
                    4093,    /* 1<<12 = 4096 */
                    8191,    /* 1<<13 = 8192 */
                    16381,   /* 1<<14 = 16384 */
                    32749,   /* 1<<15 = 32768 */
                    65521,   /* 1<<16 = 65536 */
                    131071,  /* 1<<17 = 131072 */
                    262139,  /* 1<<18 = 262144 */
                    524287,  /* 1<<19 = 524288 */
                    1048573, /* 1<<20 = 1048576 */
                    2097143, /* 1<<21 = 2097152 */
                    4194301, /* 1<<22 = 4194304 */
                    8388593, /* 1<<23 = 8388608 */
                    16777213, /* 1<<24 = 16777216 */
                    33554393, /* 1<<25 = 33554432 */
                    67108859, /* 1<<26 = 67108864 */
                    134217689, /* 1<<27 = 134217728 */
                    268435399, /* 1<<28 = 268435456 */
            };
    private Object[] _keys;
    private int[] _values;
    private int _size;
    private int _prime;

    /**
     * Create a new IntMap.  Default size is 16.
     */
    public IdentityIntMap(int capacity) {
        _keys = new Object[capacity];
        _values = new int[capacity];

        _prime = getBiggestPrime(_keys.length);
        _size = 0;
    }

    public static int getBiggestPrime(int value) {
        for (int i = PRIMES.length - 1; i >= 0; i--) {
            if (PRIMES[i] <= value)
                return PRIMES[i];
        }

        return 2;
    }

    /**
     * Clear the hashmap.
     */
    public void clear() {
        final Object[] keys = _keys;
        final int[] values = _values;

        for (int i = keys.length - 1; i >= 0; i--) {
            keys[i] = null;
            values[i] = 0;
        }

        _size = 0;
    }

    /**
     * Returns the current number of entries in the map.
     */
    public final int size() {
        return _size;
    }

    /**
     * Puts a new value in the property table with the appropriate flags
     */
    public final int get(Object key) {
        int prime = _prime;
        int hash = System.identityHashCode(key) % prime;
        // int hash = key.hashCode() & mask;

        final Object[] keys = _keys;

        while (true) {
            Object mapKey = keys[hash];

            if (mapKey == null)
                return NULL;
            else if (mapKey == key)
                return _values[hash];

            hash = (hash + 1) % prime;
        }
    }

    /**
     * Puts a new value in the property table with the appropriate flags
     */
    public final int put(Object key, int value, boolean isReplace) {
        int prime = _prime;
        int hash = Math.abs(System.identityHashCode(key) % prime);
        // int hash = key.hashCode() % prime;

        Object[] keys = _keys;

        while (true) {
            Object testKey = keys[hash];

            if (testKey == null) {
                keys[hash] = key;
                _values[hash] = value;

                _size++;

                if (keys.length <= 4 * _size)
                    resize(4 * keys.length);

                return value;
            } else if (key != testKey) {
                hash = (hash + 1) % prime;

                continue;
            } else if (isReplace) {
                int old = _values[hash];

                _values[hash] = value;

                return old;
            } else {
                return _values[hash];
            }
        }
    }

    /**
     * Removes a value in the property table.
     */
    public final void remove(Object key) {
        if (put(key, NULL, true) != NULL) {
            _size--;
        }
    }

    /**
     * Expands the property table
     */
    private void resize(int newSize) {
        Object[] keys = _keys;
        int values[] = _values;

        _keys = new Object[newSize];
        _values = new int[newSize];
        _size = 0;

        _prime = getBiggestPrime(_keys.length);

        for (int i = keys.length - 1; i >= 0; i--) {
            Object key = keys[i];
            int value = values[i];

            if (key != null && value != NULL) {
                put(key, value, true);
            }
        }
    }

    protected int hashCode(Object value) {
        return System.identityHashCode(value);
    }

    public String toString() {
        StringBuffer sbuf = new StringBuffer();

        sbuf.append("IntMap[");
        boolean isFirst = true;

        for (int i = 0; i <= _keys.length; i++) {
            if (_keys[i] != null) {
                if (!isFirst)
                    sbuf.append(", ");

                isFirst = false;
                sbuf.append(_keys[i]);
                sbuf.append(":");
                sbuf.append(_values[i]);
            }
        }
        sbuf.append("]");

        return sbuf.toString();
    }
}