unisa_strutture_dati_2013_2014/dictionary/ChainingHashTable.java

package dictionary;

import arraylist.ArrayIndexList;
import arraylist.IndexList;
import exceptions.HashExceptionKey;
import exceptions.InvalidEntryException;
import position.NodePositionList;
import priorityqueue.Entry;

import java.security.InvalidKeyException;
import java.util.Iterator;

/**
 * Created with MONSTER.
 * User: xgiovio
 * Date: 11/05/2014
 * Time: 19:28
 */

//Complete implementation by xgiovio
//Collisions resolved via chaining with LogFile


public class ChainingHashTable<K,V> implements Dictionary<K,V> {

        IndexList<LogFile<K,V>> table = null;
        LogFile<K,V> AVAIBLE = null;
        int avaible_slots = 0;
        int elements = 0;
        int p = 0;
        int scale = 0;
        int shift = 0;

    public ChainingHashTable(int in_p, int in_size){
        table = new ArrayIndexList<LogFile<K, V>>(in_size);
        AVAIBLE = new LogFile<K, V>();
        p = in_p;
        java.util.Random rand = new java.util.Random();
        scale = rand.nextInt(p-1) + 1;
        shift = rand.nextInt(p);

        for (int i= 0 ; i< in_size ;i++){
            table.add(i,AVAIBLE);
            avaible_slots ++;
        }
    }

    public ChainingHashTable(int in_size){
        this(109345121,in_size);
    }

    public ChainingHashTable(){
        this(109345121,100);

    }

    public   float load_factor () throws InvalidKeyException{
        float ret =  (size() / (float)raw_size());
        if ( ret >= 0.9 ) {
            reformat();
            return load_factor();
        }
        return ret;
    }

    public  int raw_size (){
        return table.size();
    }

    @Override
    public int size() {
        return elements;
    }

    @Override
    public boolean isEmpty() {
        return (size() == 0);
    }

    protected int hash ( K key){
        return (int) ((Math.abs(key.hashCode()*scale + shift) % p) % raw_size());
    }


    @Override
    public Entry<K, V> find(K key) throws InvalidKeyException {

            checkKey(key);
            int h = hash(key);
            if (table.get(h) == AVAIBLE)
                return null;
            LogFile<K, V> n = table.get(h);
            return n.find(key);
    }

    @Override
    public Iterable<Entry<K, V>> findAll(K key) throws InvalidKeyException {
        checkKey(key);
        int h = hash(key);
        if (table.get(h) == AVAIBLE)
            return null;
        LogFile<K, V> n = table.get(h);
        return n.entries();
    }

    @Override
    public Entry<K, V> insert(K key, V value) throws InvalidKeyException {
             checkKey(key);
             if (load_factor() >= 0.9 )
                 reformat();
             int h = hash(key);
             if (table.get(h) == AVAIBLE) {
                 LogFile<K, V> n = new LogFile<K, V>();
                 table.set(h,n);
                 avaible_slots--;
                 elements++;
                 return n.insert(key,value);
             } else {
                 LogFile<K, V> n = table.get(h);
                 elements++;
                 return n.insert(key,value);
             }
    }

    protected Entry<K, V> insert_refactor(Entry<K,V> in_e) throws InvalidKeyException {
        // in_e not checked because used internally
        int h = hash(in_e.getKey());
        if (table.get(h) == AVAIBLE) {
            LogFile<K, V> n = new LogFile<K, V>();
            table.set(h,n);
            avaible_slots--;
            elements++;
            return n.insert(in_e);
        } else {
            LogFile<K, V> n = table.get(h);
            elements++;
            return n.insert(in_e);
        }
    }

    @Override
    public Entry<K, V> remove(Entry<K, V> e) throws InvalidEntryException {
        if (e == null)
            throw new InvalidEntryException();
        int h = hash(e.getKey());
        if (table.get(h) == AVAIBLE)
            throw new InvalidEntryException();
        LogFile<K, V> n = table.get(h);
        Entry<K,V> t =  n.remove(e);
        elements--;
        if (n.size() == 0){
            table.set(h,AVAIBLE);
            avaible_slots++;
        }
       return t;
    }

    @Override
    public Iterable<Entry<K, V>> entries() {

        NodePositionList<Entry<K,V>> ret = new NodePositionList<Entry<K, V>>();

        for (int i = 0 ; i< raw_size() ;i++){
            if (table.get(i) != AVAIBLE){
                Iterator<Entry<K,V>> local_it = table.get(i).entries().iterator();
                for (;local_it.hasNext();){
                    ret.addLast(local_it.next());
                }
            }

        }
        return ret;
    }


    protected void checkKey(K key) throws InvalidKeyException {
        if (key == null )
            throw new InvalidKeyException("Invalid key");
    }


    void reformat () throws InvalidKeyException{

        Iterable<Entry<K,V>> ite = entries();
        int new_size = raw_size() * 2;
        IndexList<LogFile<K,V>>  table2 = new ArrayIndexList<LogFile<K, V>>(new_size);
        avaible_slots = 0;
        elements = 0;
        java.util.Random rand = new java.util.Random();
        scale = rand.nextInt(p-1) + 1;    	// new hash scaling factor
        shift = rand.nextInt(p);  //// new hash shifting factor

        for (int i= 0 ; i< (new_size) ;i++){
            table2.add(i,AVAIBLE);
        }
        table = table2;

        for (Entry<K,V> e : ite){
            insert_refactor(e);

        }
    }


    public String toString() {

        Iterator<Entry<K,V>> it = entries().iterator();

        String to_return = "";
        to_return = to_return + "[";

        for (;it.hasNext();){
            Entry<K,V>  t = it.next();

            if (it.hasNext())  {

                to_return+=(t.toString() + " , ");
            }    else {

                to_return+=(t.toString());
            }
        }

        return to_return+= "]";
    }
}