/* * Copyright (C) 2009, Google Inc. * Copyright (C) 2009, Jonas Fonseca <[email protected]> * Copyright (C) 2008, Shawn O. Pearce <[email protected]> and others * * This program and the accompanying materials are made available under the * terms of the Eclipse Distribution License v. 1.0 which is available at * https://www.eclipse.org/org/documents/edl-v10.php. * * SPDX-License-Identifier: BSD-3-Clause */ package org.eclipse.jgit.revwalk; import java.text.MessageFormat; import java.util.AbstractList; import org.eclipse.jgit.internal.JGitText; /** * An ordered list of {@link org.eclipse.jgit.revwalk.RevObject} subclasses. * * @param <E> * type of subclass of RevObject the list is storing. */ public class RevObjectList<E extends RevObject> extends AbstractList<E> { static final int BLOCK_SHIFT = 8; static final int BLOCK_SIZE = 1 << BLOCK_SHIFT; /** * Items stored in this list. * <p> * If {@link Block#shift} = 0 this block holds the list elements; otherwise * it holds pointers to other {@link Block} instances which use a shift that * is {@link #BLOCK_SHIFT} smaller. */ protected Block contents = new Block(0); /** Current number of elements in the list. */ protected int size = 0; /** * Create an empty object list. */ public RevObjectList() { // Initialized above. } /** {@inheritDoc} */ @Override public void add(int index, E element) { if (index != size) throw new UnsupportedOperationException(MessageFormat.format( JGitText.get().unsupportedOperationNotAddAtEnd, Integer.valueOf(index))); set(index, element); size++; } /** {@inheritDoc} */ @Override @SuppressWarnings("unchecked") public E set(int index, E element) { Block s = contents; while (index >> s.shift >= BLOCK_SIZE) { s = new Block(s.shift + BLOCK_SHIFT); s.contents[0] = contents; contents = s; } while (s.shift > 0) { final int i = index >> s.shift; index -= i << s.shift; if (s.contents[i] == null) s.contents[i] = new Block(s.shift - BLOCK_SHIFT); s = (Block) s.contents[i]; } final Object old = s.contents[index]; s.contents[index] = element; return (E) old; } /** {@inheritDoc} */ @Override @SuppressWarnings("unchecked") public E get(int index) { Block s = contents; if (index >> s.shift >= 1024) return null; while (s != null && s.shift > 0) { final int i = index >> s.shift; index -= i << s.shift; s = (Block) s.contents[i]; } return s != null ? (E) s.contents[index] : null; } /** {@inheritDoc} */ @Override public int size() { return size; } /** {@inheritDoc} */ @Override public void clear() { contents = new Block(0); size = 0; } /** One level of contents, either an intermediate level or a leaf level. */ protected static class Block { final Object[] contents = new Object[BLOCK_SIZE]; final int shift; Block(int s) { shift = s; } } }