cachetable.java

java1.6众多例子参考

/*
 * @(#)CacheTable.java	1.17 05/11/17
 * 
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package com.sun.corba.se.impl.orbutil;
import org.omg.CORBA.INTERNAL;
import org.omg.CORBA.CompletionStatus;

import com.sun.corba.se.spi.logging.CORBALogDomains;
import com.sun.corba.se.spi.orb.ORB;

import com.sun.corba.se.impl.logging.ORBUtilSystemException;

public class CacheTable {
    class Entry {
        java.lang.Object key;
        int val;
        Entry next;  // this chains the collision list of table "map"
        Entry rnext; // this chains the collision list of table "rmap" 
        public Entry(java.lang.Object k, int v) {
            key = k;
            val = v;
            next = null;
	    rnext = null;
        } 
    }
    private boolean noReverseMap;
    // size must be power of 2
    static final int INITIAL_SIZE = 16;
    static final int MAX_SIZE = 1 << 30;
    int size;
    int entryCount;
    private Entry [] map;
    private Entry [] rmap;
      
    private ORB orb;
    private ORBUtilSystemException wrapper;

    private CacheTable() {}
    public  CacheTable(ORB orb, boolean u) {
	//System.out.println("using new cache table");
        this.orb = orb;
        wrapper = ORBUtilSystemException.get(orb, 
            CORBALogDomains.RPC_ENCODING);
	noReverseMap = u;
        size = INITIAL_SIZE;
	entryCount = 0;
	initTables();
    }
    private void initTables() {
	map = new Entry[size];
	rmap = noReverseMap ? null : new Entry[size];
    }
    private void grow() {
	if (size == MAX_SIZE)
		return;	
	Entry [] oldMap = map;
        int oldSize = size;
	size <<= 1;
	initTables();
	// now rehash the entries into the new table
	for (int i = 0; i < oldSize; i++) {
	    for (Entry e = oldMap[i]; e != null; e = e.next)
	        put_table(e.key, e.val);
	}
    }
    private int moduloTableSize(int h) {
	// these are the "supplemental hash function" copied from
        // java.util.HashMap, supposed to be "critical"
        h += ~(h << 9);
        h ^=  (h >>> 14);
        h +=  (h << 4);
        h ^=  (h >>> 10);
	return h & (size - 1);
    }
    private int hash(java.lang.Object key) {
	return moduloTableSize(System.identityHashCode(key));
    }
    private int hash(int val) {
	return moduloTableSize(val);
    }
    public final void put(java.lang.Object key, int val) {
	if (put_table(key, val)) {
	    entryCount++;
	    if (entryCount > size * 3 / 4)
		grow();
	}
    }
    private boolean put_table(java.lang.Object key, int val) {
	int index = hash(key);
	for (Entry e = map[index]; e != null; e = e.next) {
	    if (e.key == key) {
	        if (e.val != val) {
                    throw wrapper.duplicateIndirectionOffset();
		}	
		// if we get here we are trying to put in the same key/val pair
		// this is a no-op, so we just return
		return false;
	    }
        }
	// this means the key is not present in our table
	// then it shouldnt be present in our reverse table either
	Entry newEntry = new Entry(key, val);
	newEntry.next = map[index];
	map[index] = newEntry;
	if (!noReverseMap) {
	    int rindex = hash(val);
	    newEntry.rnext = rmap[rindex];
	    rmap[rindex] = newEntry;
        }
	return true;
    }
    public final boolean containsKey(java.lang.Object key) {
	return (getVal(key) != -1);
    }
    public final int getVal(java.lang.Object key) {
	int index = hash(key);
        for (Entry e = map[index]; e != null; e = e.next) {
            if (e.key == key) 
                return e.val;
        }
        return -1;
    }
    public final boolean containsVal(int val) {
	return (getKey(val) != null); 
    }
    public final boolean containsOrderedVal(int val) {
	return containsVal(val);
    }
    public final java.lang.Object getKey(int val) {
	int index = hash(val);
        for (Entry e = rmap[index]; e != null; e = e.rnext) {
            if (e.val == val)
                return e.key;
        }
        return null;
    }
    public void done() {
	map = null;
        rmap = null;
    }
}