/***** BEGIN LICENSE BLOCK *****
 * Version: CPL 1.0/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Common Public
 * License Version 1.0 (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.eclipse.org/legal/cpl-v10.html
 *
 * 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.
 *
 * Copyright (C) 2007 Ye Zheng <dreamhead.cn@gmail.com>
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either of the GNU General Public License Version 2 or later (the "GPL"),
 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
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package org.jruby.util;

import java.lang.ref.Reference;
import java.lang.ref.WeakReference;
import org.jruby.RubyClass;
import org.jruby.RubyModule;
import org.jruby.internal.runtime.methods.DynamicMethod;

public class MethodCache {
    private static final Reference NULL_REFERENCE = new WeakReference(null);
    private static int CACHE_SIZE = 0x800;
    private static int CACHE_MASK = 0x7ff;
    
    private boolean initialized;
    
    private CacheEntry[] cache;
    
    public MethodCache() {
        initialized = false;
        
        cache = new CacheEntry[CACHE_SIZE];
        clearAllEntries();
    }
    
    public void initialized() {
        initialized = true;
    }
    
    public void clearCache() {
        if (!initialized) {
            return;
        }
        
        clearAllEntries();
    }

    private void clearAllEntries() {
        for (int i = 0; i < CACHE_SIZE; i++) {
            cache[i] = new CacheEntry();
            cache[i].klass = NULL_REFERENCE;
            cache[i].mid = null;
            cache[i].method = NULL_REFERENCE;
        }
    }
    
    private int cacheIndex(RubyModule c, String id) {        
        return (((c.hashCode() >> 3) ^ (id.hashCode())) & CACHE_MASK);
    }
    
    public CacheEntry getMethod(RubyModule c, String id) {       
        int index = cacheIndex(c, id);
        return cache[index];
    }
    
    public void putMethod(RubyModule c, String id, DynamicMethod m) {
        int index = cacheIndex(c, id);
        
        cache[index].klass = new WeakReference(c);
        cache[index].mid = id;
        cache[index].method = new WeakReference(m);
    }
    
    public void removeMethod(RubyClass c, String id) { 
        if (!initialized) {
            return;
        }
        
        for (int i = 0; i < CACHE_SIZE; i++) {
            CacheEntry entry = cache[i];
            if (id.equals(entry.mid) && entry.klass.get() == c) {
                entry.mid = null;
            }
        }
    }
    
    public void removeMethod(String id) { 
        if (!initialized) {
            return;
        }
        
        for (int i = 0; i < CACHE_SIZE; i++) {
            CacheEntry entry = cache[i];
            if (id.equals(entry.mid)) {
                entry.mid = null;
            }
        }
    }
    
    public void removeClass(RubyClass c) {  
        if (!initialized) {
            return;
        }
        
        for (int i = 0; i < CACHE_SIZE; i++) {
            CacheEntry entry = cache[i]; 
            if (entry.klass.get() == c) {
                entry.mid = null;
            }
        }
    }
    
    public static class CacheEntry {
        public Reference klass = NULL_REFERENCE;
        public String mid;
        public Reference method = NULL_REFERENCE;
    }
}