org.apache.yoko.rmi.util.DynamicHashMap Maven / Gradle / Ivy

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/**
*
* Licensed to the Apache Software Foundation (ASF) under one or more
*  contributor license agreements.  See the NOTICE file distributed with
*  this work for additional information regarding copyright ownership.
*  The ASF licenses this file to You 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.
*/ 

package org.apache.yoko.rmi.util;

import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;

/**
 * Class DynamicHashMap is a generic dynamic hash map.
 */
public class DynamicHashMap extends GenericMap implements Map {
    class Entry extends GenericMap.Entry {
        Entry next;

        int hash;

        Object key;

        Object value;

        Entry(int hash, Object key, Object value, Entry next) {
            this.hash = hash;
            this.key = key;
            this.value = value;
            this.next = next;
        }

        public Object getKey() {
            return key;
        }

        public Object getValue() {
            return value;
        }

        public Object setValue(Object value) {
            Object result = this.value;
            this.value = value;
            return result;
        }

        boolean sameKey(int hash, Object key) {
            return this.hash == hash && keyEquals(this.key, key);
        }
    }

    /** the hash index */
    private Entry[] table;

    /** the current range for table. */
    private int range;

    private float ratio;

    /** translate hash code bucket to index */
    private int index(int hash) {
        return (hash & 0x7ffffff) % range;
    }

    /** the default and only constructor */
    public DynamicHashMap() {
        clear();
    }

    public void clear() {
        range = 3;
        size = 0;
        ratio = 0.75F;
        table = new Entry[range];
    }

    /** return the element with the given key */
    public Object get(Object key) {
        int hash = keyHash(key);
        return get(hash, key);
    }

    public Object get(int hash, Object key) {
        int idx = index(hash);

        for (Entry ent = table[idx]; ent != null; ent = ent.next) {
            if (ent.sameKey(hash, key))
                return ent.value;
        }

        return null;
    }

    /** return the element with the given key */
    public boolean containsKey(Object key) {
        int hash = keyHash(key);
        return containsKey(hash, key);
    }

    public boolean containsKey(int hash, Object key) {
        int idx = index(hash);

        for (Entry ent = table[idx]; ent != null; ent = ent.next) {
            if (ent.sameKey(hash, key))
                return true;
        }

        return false;
    }

    public Object put(Object key, Object value) {
        int hash = keyHash(key);
        return put(hash, key, value);
    }

    public Object put(int hash, Object key, Object value) {
        int idx = index(hash);

        for (Entry ent = table[idx]; ent != null; ent = ent.next) {
            if (ent.sameKey(hash, key)) {
                return ent.setValue(value);
            }
        }

        if (1.0F * size / range > ratio) {
            grow();
            idx = index(hash);
        }

        table[idx] = new Entry(hash, key, value, table[idx]);

        size += 1;

        return null;
    }

    public Object remove(Object key) {
        int hash = keyHash(key);
        return remove(hash, key);
    }

    public Object remove(int hash, Object key) {
        int idx = index(hash);

        Entry entry = table[idx];
        if (entry != null) {

            if (entry.sameKey(hash, key)) {
                table[idx] = entry.next;
                size -= 1;
                return entry.getValue();

            } else {
                Entry ahead = entry.next;

                while (ahead != null) {
                    if (ahead.sameKey(hash, key)) {
                        entry.next = ahead.next;
                        size -= 1;
                        return ahead.getValue();
                    }

                    entry = ahead;
                    ahead = ahead.next;
                }
            }
        }

        // it was not found at all!
        return null;
    }

    private void grow() {
        int old_range = range;
        Entry[] old_table = table;

        range = old_range * 2 + 1;
        table = new Entry[range];

        for (int i = 0; i < old_range; i++) {
            Entry entry = old_table[i];

            while (entry != null) {
                Entry ahead = entry.next;
                int idx = index(entry.hash);
                entry.next = table[idx];
                table[idx] = entry;
                entry = ahead;
            }
        }
    }

    final class EntryIterator implements Iterator {
        int idx;

        Entry entry;

        EntryIterator() {
            idx = 0;
            entry = table[0];
            locateNext();
        }

        private void locateNext() {
            // we reached the end of a list
            while (entry == null) {
                // goto next bucket
                idx += 1;
                if (idx == range) {
                    // we reached the end
                    return;
                }

                // entry is the first element of this bucket
                entry = table[idx];
            }
        }

        public boolean hasNext() {
            return (entry != null);
        }

        public Object next() {
            Object result = entry;

            if (result == null) {
                throw new NoSuchElementException();
            } else {
                entry = entry.next;
                locateNext();
                return result;
            }
        }

        public void remove() {
            Entry remove = entry;

            entry = entry.next;
            locateNext();

            DynamicHashMap.this.remove(remove.key);
        }
    }

    protected Iterator entryIterator() {
        return new EntryIterator();
    }

}