Update #47 - Singleplayer lag fixes

sources/main/java/com/carrotsearch/hppc/AbstractIterator.java

@@ -0,0 +1,71 @@
+/*
+ * HPPC
+ *
+ * Copyright (C) 2010-2024 Carrot Search s.c. and contributors
+ * All rights reserved.
+ *
+ * Refer to the full license file "LICENSE.txt":
+ * https://github.com/carrotsearch/hppc/blob/master/LICENSE.txt
+ */
+package com.carrotsearch.hppc;
+
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+
+/** Simplifies the implementation of iterators a bit. Modeled loosely after Google Guava's API. */
+public abstract class AbstractIterator<E> implements Iterator<E> {
+  private static final int NOT_CACHED = 0;
+  private static final int CACHED = 1;
+  private static final int AT_END = 2;
+
+  /** Current iterator state. */
+  private int state = NOT_CACHED;
+
+  /** The next element to be returned from {@link #next()} if fetched. */
+  private E nextElement;
+
+  /** {@inheritDoc} */
+  @Override
+  public boolean hasNext() {
+    if (state == NOT_CACHED) {
+      state = CACHED;
+      nextElement = fetch();
+    }
+    return state == CACHED;
+  }
+
+  /** {@inheritDoc} */
+  @Override
+  public E next() {
+    if (!hasNext()) {
+      throw new NoSuchElementException();
+    }
+
+    state = NOT_CACHED;
+    return nextElement;
+  }
+
+  /** Default implementation throws {@link UnsupportedOperationException}. */
+  @Override
+  public void remove() {
+    throw new UnsupportedOperationException();
+  }
+
+  /**
+   * Fetch next element. The implementation must return {@link #done()} when all elements have been
+   * fetched.
+   *
+   * @return Returns the next value for the iterator or chain-calls {@link #done()}.
+   */
+  protected abstract E fetch();
+
+  /**
+   * Call when done.
+   *
+   * @return Returns a unique sentinel value to indicate end-of-iteration.
+   */
+  protected final E done() {
+    state = AT_END;
+    return null;
+  }
+}