Class CircularList

solr/core/src/java/org/apache/solr/logging/CircularList.java:28–148

FIFO Circular List. Once the size is reached, it will overwrite previous entries

 * <p>Once the size is reached, it will overwrite previous entries
 */
public class CircularList<T> implements Iterable<T> {
  private T[] data;
  private int head = 0;
  private int tail = 0;
  private int size = 0;

  @SuppressWarnings("unchecked")
  public CircularList(int size) {
    data = (T[]) new Object[size];
  }

  @SuppressWarnings("unchecked")
  public synchronized void resize(int newsize) {
    if (newsize == this.size) return;

    T[] vals = (T[]) new Object[newsize];
    int i = 0;
    if (newsize > size) {
      for (i = 0; i < size; i++) {
        vals[i] = data[convert(i)];
      }
    } else {
      int off = size - newsize;
      for (i = 0; i < newsize; i++) {
        vals[i] = data[convert(i + off)];
      }
    }
    data = vals;
    head = 0;
    tail = i;
  }

  private int convert(int index) {
    return (index + head) % data.length;
  }

  public boolean isEmpty() {
    return head == tail; // or size == 0
  }

  public int size() {
    return size;
  }

  public int getBufferSize() {
    return data.length;
  }

  private void checkIndex(int index) {
    if (index >= size || index < 0)
      throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + size);
  }

  public T get(int index) {
    checkIndex(index);
    return data[convert(index)];
  }