console-proxy/src/com/cloud/consoleproxy/AjaxFIFOImageCache.java

// 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 com.cloud.consoleproxy;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import com.cloud.consoleproxy.util.Logger;

public class AjaxFIFOImageCache {
	private static final Logger s_logger = Logger.getLogger(AjaxFIFOImageCache.class);
	
	private List<Integer> fifoQueue;
	private Map<Integer, byte[]> cache;
	private int cacheSize;
	private int nextKey = 1;
	
	public AjaxFIFOImageCache(int cacheSize) {
		this.cacheSize = cacheSize;
		fifoQueue = new ArrayList<Integer>();
		cache = new HashMap<Integer, byte[]>();
	}
	
	public synchronized void clear() {
		fifoQueue.clear();
		cache.clear();
	}
	
	public synchronized int putImage(byte[] image) {
		while(cache.size() >= cacheSize) {
			Integer keyToRemove = fifoQueue.remove(0);
			cache.remove(keyToRemove);
			
			if(s_logger.isTraceEnabled())
				s_logger.trace("Remove image from cache, key: " + keyToRemove);
		}
		
		int key = getNextKey();
		
		if(s_logger.isTraceEnabled())
			s_logger.trace("Add image to cache, key: " + key);
		
		cache.put(key, image);
		fifoQueue.add(key);
		return key;
	}
	
	public synchronized byte[] getImage(int key) {
		if(cache.containsKey(key)) {
			if(s_logger.isTraceEnabled())
				s_logger.trace("Retrieve image from cache, key: " + key);
			
			return cache.get(key);
		}
		
		if(s_logger.isTraceEnabled())
			s_logger.trace("Image is no long in cache, key: " + key);
		return null;
	}
	
	public synchronized int getNextKey() {
		return nextKey++;
	}
}