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/*
* $Id: DTMStringPool.java,v 1.8 2010-11-01 04:34:38 joehw Exp $
*/
package com.sun.org.apache.xml.internal.dtm.ref;
import java.util.Vector;
import com.sun.org.apache.xml.internal.utils.IntVector;
/** DTMStringPool is an "interning" mechanism for strings. It will
* create a stable 1:1 mapping between a set of string values and a set of
* integer index values, so the integers can be used to reliably and
* uniquely identify (and when necessary retrieve) the strings.
*
* Design Priorities:
*
* - String-to-index lookup speed is critical.
* - Index-to-String lookup speed is slightly less so.
* - Threadsafety is not guaranteed at this level.
* Enforce that in the application if needed.
* - Storage efficiency is an issue but not a huge one.
* It is expected that string pools won't exceed about 2000 entries.
*
*
*
* Implementation detail: A standard Hashtable is relatively
* inefficient when looking up primitive int values, especially when
* we're already maintaining an int-to-string vector. So I'm
* maintaining a simple hash chain within this class.
*
* NOTE: There is nothing in the code that has a real dependency upon
* String. It would work with any object type that implements reliable
* .hashCode() and .equals() operations. The API enforces Strings because
* it's safer that way, but this could trivially be turned into a general
* ObjectPool if one was needed.
*
* Status: Passed basic test in main().
* */
public class DTMStringPool
{
Vector m_intToString;
static final int HASHPRIME=101;
int[] m_hashStart=new int[HASHPRIME];
IntVector m_hashChain;
public static final int NULL=-1;
/**
* Create a DTMStringPool using the given chain size
*
* @param chainSize The size of the hash chain vector
*/
public DTMStringPool(int chainSize)
{
m_intToString=new Vector();
m_hashChain=new IntVector(chainSize);
removeAllElements();
// -sb Add this to force empty strings to be index 0.
stringToIndex("");
}
public DTMStringPool()
{
this(512);
}
public void removeAllElements()
{
m_intToString.removeAllElements();
for(int i=0;i