--- /dev/null
+package jalview.datamodel;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+
+/**
+ * An iterator which iterates over a list of ranges. Works with a copy of the
+ * collection of ranges.
+ */
+public class RangeIterator implements Iterator<int[]>
+{
+ // current index in rangeList
+ private int currentPosition = 0;
+
+ // current range in rangeList
+ private int[] currentRange;
+
+ // local copy or reference to rangeList
+ private List<int[]> localRanges;
+
+ /**
+ * Unbounded constructor
+ *
+ * @param rangeList
+ * list of ranges to iterate over
+ */
+ RangeIterator(List<int[]> rangeList)
+ {
+ if (!rangeList.isEmpty())
+ {
+ int last = rangeList.get(rangeList.size() - 1)[1];
+ init(0, last, rangeList);
+ }
+ else
+ {
+ init(0, 0, rangeList);
+ }
+ }
+
+ /**
+ * Construct an iterator over rangeList bounded at [lowerBound,upperBound]
+ *
+ * @param lowerBound
+ * lower bound to iterate from
+ * @param upperBound
+ * upper bound to iterate to
+ * @param rangeList
+ * list of ranges to iterate over
+ */
+ RangeIterator(int lowerBound, int upperBound,
+ List<int[]> rangeList)
+ {
+ init(lowerBound, upperBound, rangeList);
+ }
+
+ /**
+ * Construct an iterator over rangeList bounded at [lowerBound,upperBound]
+ *
+ * @param lowerBound
+ * lower bound to iterate from
+ * @param upperBound
+ * upper bound to iterate to
+ */
+ private void init(int lowerBound, int upperBound,
+ List<int[]> rangeList)
+ {
+ int start = lowerBound;
+ int end = upperBound;
+
+ if (rangeList != null)
+ {
+ localRanges = new ArrayList<>();
+
+ // iterate until a range overlaps with [start,end]
+ int i = 0;
+ while ((i < rangeList.size()) && (rangeList.get(i)[1] < start))
+ {
+ i++;
+ }
+
+ // iterate from start to end, adding each range. Positions are
+ // absolute, and all ranges which *overlap* [start,end] are added.
+ while (i < rangeList.size() && (rangeList.get(i)[0] <= end))
+ {
+ int[] rh = rangeList.get(i);
+ int[] cp = new int[2];
+ System.arraycopy(rh, 0, cp, 0, rh.length);
+ localRanges.add(cp);
+ i++;
+ }
+ }
+ }
+
+ @Override
+ public boolean hasNext()
+ {
+ return (localRanges != null) && (currentPosition < localRanges.size());
+ }
+
+ @Override
+ public int[] next()
+ {
+ currentRange = localRanges.get(currentPosition);
+ currentPosition++;
+ return currentRange;
+ }
+
+ @Override
+ public void remove()
+ {
+ localRanges.remove(--currentPosition);
+ }
+}