RDateIteratorImpl.java

// Copyright (C) 2006 Google Inc.
//
// Licensed 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 com.google.ical.iter;

import com.google.ical.values.DateValue;

/**
 * a recurrence iterator that iterates over an array of dates.
 *
 * @author mikesamuel+svn@gmail.com (Mike Samuel)
 */
final class RDateIteratorImpl implements RecurrenceIterator {
  private int i;
  private DateValue[] datesUtc;

  RDateIteratorImpl(DateValue[] datesUtc) {
    this.datesUtc = datesUtc.clone();  // defensive copy
    assert increasing(datesUtc);  // indirectly checks that not-null.
  }

  public boolean hasNext() { return i < datesUtc.length; }

  public DateValue next() { return datesUtc[i++]; }

  public void remove() { throw new UnsupportedOperationException(); }

  public void advanceTo(DateValue newStartUtc) {
    long startCmp = DateValueComparison.comparable(newStartUtc);
    while (i < datesUtc.length
           && startCmp > DateValueComparison.comparable(datesUtc[i])) {
      ++i;
    }
  }

  /** monotonically. */
  private static <C extends Comparable<C>> boolean increasing(C[] els) {
    for (int i = els.length; --i >= 1;) {
      if (els[i - 1].compareTo(els[i]) > 0) { return false; }
    }
    return true;
  }

}