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Sun Java Streaming XML Parser (SJSXP) is the implementation of JSR 173.
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/*
 * ThreadLocalBufferAllocator.java
 *
 * Created on November 22, 2006, 1:58 PM
 *
 * To change this template, choose Tools | Template Manager
 * and open the template in the editor.
 */

package com.sun.xml.stream.util;

import java.lang.ref.*;

/**
 * This is a Singleton class that allows you to allocate buffer that 
 * are stored in ThreadLocal. This class stores 3 types of char 
 * buffers - small (< 128 bytes), medium (<2K) and large (> 2K) as 
 * well as three byte buffers - small, medium and large.
 * The local storage is activated on the return of the buffer. 
 * The buffer returns null if it is already allocated.
 */
public class ThreadLocalBufferAllocator {
   private static ThreadLocal tlba = new ThreadLocal();

   public static BufferAllocator getBufferAllocator() {
	SoftReference bAllocatorRef = (SoftReference) tlba.get();
	if (bAllocatorRef == null || bAllocatorRef.get() == null) { 
	    bAllocatorRef = new SoftReference(new BufferAllocator());
	    tlba.set(bAllocatorRef);
        }

	return (BufferAllocator) bAllocatorRef.get();
   }
}