readerthread.java

Reader Writer Problem to solve synchronization issues

public class ReaderThread extends Thread {

  private int tnum,rdata;		// thread number (>= zero)
//  private Integer rc;
  private static int rc;

  private Semaphore[] flags;
  private Boolean[] continuous;

  private Semaphore db;
  private Semaphore mutex;
  private Data_base dtbas; 

  private CodeWin win;
  private Gui xyz;
//  private static final String a="INITIAL",b="MUTEX",c="RC",d="DB",e="DBASE";

  public ReaderThread(int n, Semaphore[] s, Boolean[] b, int c,
			Semaphore mut,Semaphore dbas, Data_base rdtbase, 
							CodeWin w, Gui xy) 
{
    tnum = n;
    flags = s;
    continuous = b;
    rc = c;
//	System.out.println("initia rc value of "+tnum+":"+rc);
    mutex=mut;
    db=dbas;
    dtbas=rdtbase;
    win = w;
    xyz = xy;
  }

  public void run() {

    while (true) {
/*---------------------------------------------------------*/      
//         DOWN(MUTEX);
      // If we are in continuous mode and this thread's step 
      // flag is false, wait
      if (continuous[0].booleanValue() == false)
	flags[tnum].down();
      // When we get here, the step flag is true; thus we can take
      // (at least) one step

      	xyz.start_to_mutex_db(tnum);
      	win.step(tnum);
	mutex.down();
	xyz.mutex_lock(tnum);

/*---------------------------------------------------------*/      
//	RC=RC+1;
      if (continuous[0].booleanValue() == false)
	flags[tnum].down();

       rc = rc+ 1;

      xyz.rc_plus_minus(tnum,rc);
      win.step(tnum);

//	System.out.println("inc rc value of "+tnum+":"+rc);

      
/*---------------------------------------------------------*/      
//	IF(RC=1) THEN; 
      if (continuous[0].booleanValue() == false)
         flags[tnum].down();

        win.step(tnum);

      if (rc == 1) {

      if (continuous[0].booleanValue() == true)
	xyz.rc_one_zero(tnum,2);
      else
	xyz.rc_one_zero(tnum,1);

	
/*---------------------------------------------------------*/      
//	  DOWN(DB);
	if (continuous[0].booleanValue() == false)
	  flags[tnum].down();

	xyz.rc_reset();
      	xyz.rc_one_db(tnum);
	win.step(tnum);
	db.down();
      	xyz.db_lock(tnum);

/*----------*/      
//	  UP(MUTEX);
	if (continuous[0].booleanValue() == false)
	  flags[tnum].down();

	xyz.db_down_to_mutex(tnum);
	win.step(tnum);
	xyz.mutex_unlock(tnum,1);
	mutex.up();

      } else {
/*---------------------------------------------------------*/      
//	  UP(MUTEX);
	if (continuous[0].booleanValue() == false)
	  flags[tnum].down();

	xyz.rc_not_one_zero(tnum);
	win.step(tnum,2);
	xyz.mutex_unlock(tnum,1);
	mutex.up();

      }
/*---------------------------------------------------------*/      
//      READ_DB();
      if (continuous[0].booleanValue() == false)
	flags[tnum].down();

	xyz.read_dbase(tnum);
      win.step(tnum);
      rdata=dtbas.readdb();
	xyz.dbase_data(tnum,rdata);

/*---------------------------------------------------------*/      
//      DOWN(MUTEX);
      if (continuous[0].booleanValue() == false)
	flags[tnum].down();

	xyz.dbase_to_mutex(tnum);
      win.step(tnum);
      mutex.down();
	xyz.mutex_lock(tnum);

      
/*---------------------------------------------------------*/      
//	RC=RC-1;
      if (continuous[0].booleanValue() == false)
	flags[tnum].down();

//      rc = new Integer(rc.intValue() - 1);
      rc = rc - 1;

	xyz.rc_plus_minus(tnum,rc);
      win.step(tnum);

      
/*---------------------------------------------------------*/      
//	IF(RC=0)THEN;
      if (continuous[0].booleanValue() == false)
	flags[tnum].down();

      win.step(tnum);

//      if (rc.intValue() == 0) {
      if (rc == 0) {

      if (continuous[0].booleanValue() == true)
	xyz.rc_one_zero(tnum,2);
      else
	xyz.rc_one_zero(tnum,1);

	
/*---------------------------------------------------------*/      
//	  UP(DB);
	if (continuous[0].booleanValue() == false)
	  flags[tnum].down();

	xyz.rc_zero_db(tnum);
	win.step(tnum);
	xyz.db_unlock(tnum);
        db.up();

/*----------*/      
//	  UP(MUTEX);
	if (continuous[0].booleanValue() == false)
	  flags[tnum].down();

	xyz.db_up_to_mutex(tnum);
	win.step(tnum);
	xyz.mutex_unlock(tnum,2);
	mutex.up();

      } else {
/*---------------------------------------------------------*/      
//	  UP(MUTEX);
	if (continuous[0].booleanValue() == false)
	  flags[tnum].down();

	xyz.rc_not_one_zero(tnum);
	win.step(tnum,2);
	xyz.mutex_unlock(tnum,2);
	mutex.up();

      }
/*---------------------------------------------------------*/      
      if (continuous[0].booleanValue() == false)
	flags[tnum].down();
      win.step(tnum);

      yield();
    }
  }
  
}