recordenumerationimpl.java

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	synchronized (recordStore.rsLock) {
	    filterAdd(recordId);
	}
    }
    

    /**
     * From the RecordListener interface.  This method is called when a
     * record in <code>recordStore</code> is deleted.
     *
     * @param recordStore the record store from which a record was deleted
     * @param recordId the record id of the deleted record
     */
    public synchronized void recordDeleted(RecordStore recordStore, 
					   int recordId)
    {
	checkDestroyed();
	/*
	 * Remove the deleted element from the records array.
	 * No resorting is required.
	 */

	int recIndex = findIndexOfRecord(recordId);
	
	if (recIndex < 0) 
	    return;  // not in the enumeration
	
	// remove this record from the enumeration
	removeRecordAtIndex(recIndex);    
    }


    /**
     * Implements RecordEnumeration.destroy() interface.  Called
     * to signal that this enumeration will no longer be used, and that
     * its resources may be collected.
     */ 
    public synchronized void destroy()
    {
	checkDestroyed();
	if (beObserver == true) {
	    recordStore.removeRecordListener(this);
	}
	filter = null;
	comparator = null;
	records = null;
	recordStore = null; // a signal that this is destroyed!
    }


    /**
     * Helper method that checks if this enumeration can be used.
     * If this enumeration has been destroyed, an exception is thrown.
     *
     * @exception IllegalStateException if RecordEnumeration has been 
     *            destroyed.
     */
    private void checkDestroyed()
    {
	if (recordStore == null)
	    throw new IllegalStateException();
    }


    /**
     * Used to add a record to an already filtered and sorted
     * <code>records</code> array.  More efficient than 
     * <code>reFilterSort</code> because it relys on 
     * <code>records</code> being in sorted order.
     *
     * First ensures that record <code>recordId</code> 
     * meets this enumeration's filter criteria.
     * If it does it is added to records as array element
     * 0.  If a comparator is defined for this enumeration,
     * the helper method <code>sortAdd</code> is called to 
     * properly position <code>recordId</code> within the ordered
     * <code>records</code> array.
     *
     * Should be called from within a 
     * synchronized (recordStore.rsLock) block.
     *
     * @param recordId the record to add to this enumeration
     */
    private void filterAdd(int recordId) {
	int insertPoint = -1;
	if (filter != null) {
	    try {
		if (!filter.matches(recordStore.getRecord(recordId)))
		    return;  // recordId filtered out
	    } catch (RecordStoreException rse) {
		return;  // recordId does not exist
	    }
	}
	// the new record has been accepted by the filter
	int[] newrecs = new int[records.length + 1];
	newrecs[0] = recordId;  // insert new record at front of list
	System.arraycopy(records, 0, newrecs, 1, records.length);
	records = newrecs;
	if (comparator != null) {  // move the new record into place
	    try {
		insertPoint = sortInsert();
	    } catch (RecordStoreException rse) {
		// NOTE: - should never be here
		// throw a RSE?  destroy record enumeration?
		System.out.println("Unexpected exception in filterAdd");
	    }
	}
	// keep index up to date as well
	if (index != NO_SUCH_RECORD && insertPoint != -1 && 
	    insertPoint < index) {
	    index++;
	}
    }


    /**
     * Helper method called by <code>filterAdd</code>.
     * Moves the posibly unsorted element zero in the
     * <code>records</code> array to its sorted position
     * within the array.
     *
     * @return index of inserted element.
     * @exception RecordStoreException if an error occurs
     *            in the comparator function.
     */
    private int sortInsert() throws RecordStoreException {
	// bubble sort the first record in records into place
	int tmp;
	int i;
	int j;
	for (i = 0, j = 1; i < records.length - 1; i++, j++) {
	    if (comparator.compare(recordStore.getRecord(records[i]),
				   recordStore.getRecord(records[j])) ==
		RecordComparator.FOLLOWS) {
		// if i follows j swap them in records
		tmp = records[i];
		records[i] = records[j];
		records[j] = tmp;
	    } else {
		break;  // done sorting if compare returns EQUALS or PRECEDES 
	    }
	}
	return i; // final index of new record in records
    }
    
    
    /**
     * Find the index in records of record <code>recordId</code> 
     * and return it.  
     *
     * @param recordId the record index to find
     * @return the index of the record, or -1.
     */
    private int findIndexOfRecord(int recordId) {
	int idx;
	int recIndex = -1;
	for (idx = records.length - 1; idx >= 0; idx--) {
	    if (records[idx] == recordId) {
		recIndex = idx;
		break;
	    }
	} 
	return recIndex;
    }


    /**
     * Internal helper method which 
     * removes the array element at index <code>recIndex</code>
     * from the internal <code>records</code> array.  
     *
     * <code>recIndex</code> should be non negative.
     *
     * @param recIndex the array element to remove.
     */
    private void removeRecordAtIndex(int recIndex) {
	int[] tmp = new int[records.length - 1];
	if (recIndex < records.length) {
	    System.arraycopy(records, 0, tmp, 0, recIndex);
	    System.arraycopy(records, recIndex + 1, tmp, 
			     recIndex, (records.length - recIndex) - 1);
	} else {
	    System.arraycopy(records, 0, tmp, 0, records.length - 1);
	}
	records = tmp;
	
	/* 
	 * If a record prior to current index was deleted
	 * update index so nothing is skipped
	 */
	if (index != NO_SUCH_RECORD && recIndex < index) {
	    index --;
	} else if (index == records.length) {
	    // last element in records removed
	    index --;
	}
    }


    /**
     * Internal helper method for filtering and sorting records if
     * necessary. Called from rebuild().
     *
     * Should be called from within a synchronized(recordStore.rsLock) block
     *
     * @param filtered array of record stores to filter and sort.
     */ 
    private void reFilterSort(int[] filtered)
    {
	int filteredIndex = 0;
	if (filter == null) {
	    /*
	     * If this enumeration doesn't have any filters, the
	     * recordId's returned by getRecordIDs should be 
	     * used as they are.
	     */
	    records = filtered;
	} else {
	    /*
	     * If a filter has been specified, filter the recordStore
	     * records to determine the subset to be used for this
	     * enumeration.
	     */
	    for (int i = 0; i < filtered.length; i++) {
		// if this record matches the filter keep it
		try {
		    if (filter.matches(recordStore.getRecord(filtered[i]))) {
			// not sure if element overlap is allowed
			if (filteredIndex != i) {
			    filtered[filteredIndex++] = filtered[i];
			} else {
			    filteredIndex++;
			}
		    }
		} catch (RecordStoreException rse) {
		    // if a record can't be found it doesn't match
		}
	    }
	    
	    records = new int[filteredIndex];
	    System.arraycopy(filtered, 0, records, 0, filteredIndex);
	}
	/*
	 * If a comparator has been specified, sort the remaining
	 * records by comparing records against each other using
	 * the comparator the application provides.
	 */
	if (comparator != null) {
	    try {
		QuickSort(records, 0, records.length - 1, comparator);
	    }
	    catch (RecordStoreException de) {
		// NOTE: - should never be here
		// throw a RSE?  destroy record enumeration?
		System.out.println("Unexpected exception in " +
				   "reFilterSort");
	    }
	}
	reset(); // reset the current index of this enumeration
    }


    /**
     * Quicksort helper function for sorting the records.
     *
     * @param a the array of recordId's to sort using comparator.
     * @param lowIndex the low bound of the range to sort.
     * @param highIndex the hight bound of the range to sort.
     * @param comparator the RecordComparator to use to compare records.
     */
    private void QuickSort(int a[], int lowIndex, int highIndex, 
			   RecordComparator comparator)
	throws RecordStoreException
    {
	/*
	 * A different sorting algorithm may be preferred, because a
	 * large recursive quicksort can consume lots of
	 * stack. Quicksort is very fast for most random sequences
	 * however...
	 */
	int left = lowIndex;	// the "left" index
	int right = highIndex;	// the "right" index

	/*
	 * First partition the data into two regions, where every
	 * element on the left side of the partition is less than
	 * every element on the right side of the element.
	 */
	if (highIndex > lowIndex) {
	    /* 
	     * Arbitrarily choose the initial pivot point to be the
	     * middle of the array.
	     */
	    int ind = (lowIndex + highIndex) / 2;
	    int pivotIndex = a[ind];
	    byte[] pivotData = recordStore.getRecord(pivotIndex);
	    
	    // loop through the array until the indices cross
	    while (left <= right) {
		/* 
		 * Starting on the left, scan right until the
		 * first element greater than or equal to the
		 * pivot element is found.
		 */
		while ((left < highIndex) && 
		       (comparator.compare(recordStore.getRecord(a[left]),
					   pivotData) ==
			RecordComparator.PRECEDES)) {
		    left++;
		}
		/*
		 * Starting on the right, scan left until the
		 * first element that is less than or equal to the
		 * pivot element is found.
		 */
		while ((right > lowIndex) && 
		      (comparator.compare(recordStore.getRecord(a[right]),
					  pivotData) ==
		       RecordComparator.FOLLOWS)) {
		    right--;
		}

		// if the indexes haven't crossed, swap the elements
		if (left <= right) {
		    int tmp = a[left];
		    a[left] = a[right];
		    a[right] = tmp;
		    left++;
		    right--;
		}
	    }
	    
	    // Sort the left side of the partition
	    if (lowIndex < right) {
		QuickSort(a, lowIndex, right, comparator);
	    }
	    // Sort the right side of the partition
	    if (left < highIndex) {
		QuickSort(a, left, highIndex, comparator);
	    }
	}
    }
}