AnnotationCursor.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.waveprotocol.wave.model.document;

import org.waveprotocol.wave.model.util.ReadableStringSet;

/**
 * A cursor for a set of keys over a range in an annotation set. Advancing the
 * cursor moves forward to the nearest change in value of any key, until the
 * range has been traversed.
 *
 * @author danilatos@google.com (Daniel Danilatos)
 */
public interface AnnotationCursor {

  /**
   * Proceeds to the next location and returns the keys whose values are
   * changing at that location.
   *
   * Initially, the current location is the start of the cursor's range. After
   * the first call to this method, the location will be at the first change of
   * value in the relevant key set away from the initial values at the start
   * location.
   *
   * @return the keys whose values are changing at that location
   */
  ReadableStringSet nextLocation();

  /**
   * Gets the current location of the cursor.
   *
   * @return The current location (item index into the document) of the cursor
   */
  int currentLocation();

  /**
   * @return true if there are still changes in value remaining in the range
   *         from the current location
   */
  boolean hasNext();
}