// ObjectSpace.java 
// ------------------------
// part of The Kelondro Database
// (C) by Michael Peter Christen; mc@yacy.net
// first published on http://www.anomic.de
// Frankfurt, Germany, 2005
// created: 12.12.2004
//
// $LastChangedDate$
// $LastChangedRevision$
// $LastChangedBy$
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

package net.yacy.kelondro.util;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.NavigableMap;
import java.util.TreeMap;

public class ObjectSpace {

    private static final int minSize = 10;
    private static final int maxSize = 256;
    
    private static Map<Integer, List<byte[]>> objHeap = new HashMap<Integer, List<byte[]>>();
    private static NavigableMap<Integer, Integer> aliveNow = new TreeMap<Integer, Integer>();
    //private static TreeMap aliveMax = new TreeMap();
    
    private static void incAlive(final int size) {
        final Integer s = Integer.valueOf(size);
        synchronized (aliveNow) {
            final Integer x = aliveNow.get(s);
            if (x == null) aliveNow.put(s, Integer.valueOf(1)); else aliveNow.put(s, Integer.valueOf(x.intValue() + 1));
        }
    }
    
    private static void decAlive(final int size) {
        final Integer s = Integer.valueOf(size);
        synchronized (aliveNow) {
            final Integer x = aliveNow.get(s);
            if (x == null) aliveNow.put(s, Integer.valueOf(-1)); else aliveNow.put(s, Integer.valueOf(x.intValue() - 1));
        }
    }
    
    public static byte[] alloc(final int len) {
        if ((len < minSize) || (len > maxSize)) return new byte[len];
        incAlive(len);
        synchronized (objHeap) {
            final List<byte[]> buf = objHeap.get(Integer.valueOf(len));
            if (buf == null || buf.isEmpty()) return new byte[len];
            return buf.remove(buf.size() - 1);
        }
    }
    
    public static void recycle(final byte[] b) {
        if ((b.length < minSize) || (b.length > maxSize)) {
            return;
        }
        decAlive(b.length);
        synchronized (objHeap) {
            final Integer i = Integer.valueOf(b.length);
            List<byte[]> buf = objHeap.get(i);
            if (buf == null) {
                buf = new ArrayList<byte[]>();
                buf.add(b);
                objHeap.put(i, buf);
            } else {
                buf.add(b);
            }
        }
    }
    
    public static NavigableMap<Integer, Integer> statAlive() {
        return aliveNow;
    }
    
    public static TreeMap<Integer, Integer> statHeap() {
        // creates a statistic output of this object space
        // the result is a mapping from Integer (chunk size) to Integer (number of counts)
        // and shows how many Objects are held in this space for usage
        final TreeMap<Integer, Integer> result = new TreeMap<Integer, Integer>();
        synchronized (objHeap) {
            final Iterator<Map.Entry<Integer, List<byte[]>>> i = objHeap.entrySet().iterator();
            Map.Entry<Integer, List<byte[]>> entry;
            while (i.hasNext()) {
                entry = i.next();
                result.put(entry.getKey(), Integer.valueOf(entry.getValue().size()));
            }
        }
        return result;
    }
    
}