tphashtable.java

分布式数据库原形代码 可以支持个用户同时登陆到数据库中查询需要的资源

package lockmgr;

import java.util.Vector;
import java.util.Enumeration;

/*
    HashTable class for the Lock Manager.
*/

public class TPHashTable
{
    private static final int HASH_DEPTH = 8;
    
    private Vector vect;
    private int iSize;    // size of the hash table
    
    TPHashTable(int iSize)
    {
        this.iSize = iSize;
        
        vect = new Vector(iSize);
        for ( int i = 0; i < iSize; i++ ) {
            this.vect.addElement( new Vector(this.HASH_DEPTH) );
        }
    }
    
    public int getSize()
    {
        return iSize;
    }
    
    public synchronized void add(XObj xobj)
    {
        if (xobj == null) return;
        
        Vector vectSlot;
        
        int hashSlot = (xobj.hashCode() % this.iSize);
        if ( hashSlot < 0 ) {
            hashSlot = -hashSlot;
        }
        vectSlot = (Vector) vect.elementAt( hashSlot );
        vectSlot.addElement(xobj);
    }

    public synchronized Vector elements(XObj xobj) {
        if (xobj == null) return (new Vector());
        
        Vector vectSlot;    // hash slot
        Vector elemVect = new Vector(24); // return object
        
        int hashSlot = (xobj.hashCode() % this.iSize);
        if ( hashSlot < 0 ) {
            hashSlot = -hashSlot;
        }
        
        vectSlot = (Vector) vect.elementAt( hashSlot );
        
        XObj xobj2;
        int size = vectSlot.size();
        for ( int i = (size - 1); i >= 0; i-- ) {
            xobj2 = (XObj) vectSlot.elementAt(i);
            if ( xobj.key() == xobj2.key() ) {
                elemVect.addElement(xobj2);
            }
        }
        return elemVect;
    }
    
    public synchronized boolean contains(XObj xobj)
    {
        if (xobj == null) return false;
        
        Vector vectSlot;
        
        int hashSlot = (xobj.hashCode() % this.iSize);
        if ( hashSlot < 0 ) {
            hashSlot = -hashSlot;
        }
        
        vectSlot = (Vector) vect.elementAt( hashSlot );
        return vectSlot.contains(xobj);
    }
    
    public synchronized boolean remove(XObj xobj)
    {
        if (xobj == null) return false;
        
        Vector vectSlot;

        int hashSlot = (xobj.hashCode() % this.iSize);
        if ( hashSlot < 0 ) {
            hashSlot = -hashSlot;
        }
        
        vectSlot = (Vector) vect.elementAt( hashSlot );
        return vectSlot.removeElement(xobj);
    }

    public synchronized XObj get(XObj xobj)
    {
        if (xobj == null) return null;
        
        Vector vectSlot;
        
        int hashSlot = (xobj.hashCode() % this.iSize);
        if ( hashSlot < 0 ) {
            hashSlot = -hashSlot;
        }
        
        vectSlot = (Vector) vect.elementAt( hashSlot );

        XObj xobj2;
        int size = vectSlot.size();
        for ( int i = 0; i < size; i++ ) {
            xobj2 = (XObj) vectSlot.elementAt(i);
            if ( xobj.equals(xobj2) ) {
                return xobj2;
            }
        }
        return null;
    }

    private void printStatus(String msg, int hashSlot, XObj xobj) {
        System.out.println( this.getClass() + "::" + msg + "(slot" + hashSlot + ")::" + xobj.toString() );
    }
    
    public Vector allElements() {
        Vector vectSlot = null;
        XObj xobj = null;
        Vector hashContents = new Vector(1024);
        
        for (int i = 0; i < this.iSize; i++) {    // walk down hashslots
            if ( (this.vect).size() > 0 ) {    // contains elements?
                vectSlot = (Vector) (this.vect).elementAt(i);
                
                for (int j = 0; j < vectSlot.size(); j++) {    // walk down single hash slot, adding elements.
                    xobj = (XObj) vectSlot.elementAt(j);
                    hashContents.addElement(xobj);
                }
            }
            // else contributes nothing.
        }
        
        return hashContents;
    }
    
    public synchronized void removeAll(XObj xobj)
    {
        if (xobj == null) return;
        
        Vector vectSlot;
        
        int hashSlot = (xobj.hashCode() % this.iSize);
        if ( hashSlot < 0 ) {
            hashSlot = -hashSlot;
        }
        
        vectSlot = (Vector) vect.elementAt( hashSlot );
        
        XObj xobj2;
        int size = vectSlot.size();
        for ( int i = (size - 1); i >= 0; i-- ) {
            xobj2 = (XObj) vectSlot.elementAt(i);
            if ( xobj.key() == xobj2.key() ) {
                vectSlot.removeElementAt(i);
            }
        }
    }
}