package com.cokere.util;


/* this class can be used to work around Bug 4724038 in Java, which they have no intention of fixing
   see   http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4724038  for information. basically this
   The only way to unmap a byte buffer in java is wait for it to be garbage collected. And  the only
   way to 'wait' for  something to become garbage  collected is to sleep in a  loop untill it's done.
   
   This class does that. Waits in a loop (for up to a bit more then a minute, otherwise it throws an
   exception)  untill it's possible to do what you wanted to do,  but couldn't, because the file was
   mapped into a MappedByteBuffer.
   
   To use it, you basically do this:
   
   //remove all refrences to MappedByteBuffer (i.e. mybuffer = null);
   com.cokere.util.Bug4724038.workaround(new com.cokere.util.Bug4724038.FileOp(){
        public void op()throws java.io.IOException{
            //do whatever. Delete, resize, etc;
        }
    });
    
    --Chad Okere.
   
 */

public class Bug4724038 {
     
    public static void workaround(FileOp f) throws java.io.IOException{
        long sleep = 1; 
        long maxsleep = 1024*64;//A binary minute :)
        boolean success = false;
        while(!success){
            try{
                f.op();
                success = true;                
            }
            catch(java.io.IOException e){
                try{
                    Thread.sleep(sleep);
                }
                catch(Exception ex){}
                
                if(sleep > maxsleep){
                    throw e;
                }
                sleep *= 2;
                System.gc();
                System.runFinalization();                
            }
        }
    }
    
    public static abstract class FileOp{
        public abstract void op() throws java.io.IOException;
    }
}