| /* |
| * Copyright (C) 2009, Google Inc. |
| * Copyright (C) 2008, Marek Zawirski <marek.zawirski@gmail.com> |
| * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org> 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.lib; |
| |
| import java.util.Iterator; |
| import java.util.NoSuchElementException; |
| |
| /** |
| * Fast, efficient map specifically for {@link org.eclipse.jgit.lib.ObjectId} |
| * subclasses. |
| * <p> |
| * This map provides an efficient translation from any ObjectId instance to a |
| * cached subclass of ObjectId that has the same value. |
| * <p> |
| * If object instances are stored in only one map, |
| * {@link org.eclipse.jgit.lib.ObjectIdOwnerMap} is a more efficient |
| * implementation. |
| * |
| * @param <V> |
| * type of subclass of ObjectId that will be stored in the map. |
| */ |
| public class ObjectIdSubclassMap<V extends ObjectId> |
| implements Iterable<V>, ObjectIdSet { |
| private static final int INITIAL_TABLE_SIZE = 2048; |
| |
| int size; |
| |
| private int grow; |
| |
| private int mask; |
| |
| V[] table; |
| |
| /** |
| * Create an empty map. |
| */ |
| public ObjectIdSubclassMap() { |
| initTable(INITIAL_TABLE_SIZE); |
| } |
| |
| /** |
| * Remove all entries from this map. |
| */ |
| public void clear() { |
| size = 0; |
| initTable(INITIAL_TABLE_SIZE); |
| } |
| |
| /** |
| * Lookup an existing mapping. |
| * |
| * @param toFind |
| * the object identifier to find. |
| * @return the instance mapped to toFind, or null if no mapping exists. |
| */ |
| public V get(AnyObjectId toFind) { |
| final int msk = mask; |
| int i = toFind.w1 & msk; |
| final V[] tbl = table; |
| V obj; |
| |
| while ((obj = tbl[i]) != null) { |
| if (AnyObjectId.isEqual(obj, toFind)) { |
| return obj; |
| } |
| i = (i + 1) & msk; |
| } |
| return null; |
| } |
| |
| /** |
| * {@inheritDoc} |
| * <p> |
| * Returns true if this map contains the specified object. |
| */ |
| @Override |
| public boolean contains(AnyObjectId toFind) { |
| return get(toFind) != null; |
| } |
| |
| /** |
| * Store an object for future lookup. |
| * <p> |
| * An existing mapping for <b>must not</b> be in this map. Callers must |
| * first call {@link #get(AnyObjectId)} to verify there is no current |
| * mapping prior to adding a new mapping, or use |
| * {@link #addIfAbsent(ObjectId)}. |
| * |
| * @param newValue |
| * the object to store. |
| */ |
| public <Q extends V> void add(Q newValue) { |
| if (++size == grow) |
| grow(); |
| insert(newValue); |
| } |
| |
| /** |
| * Store an object for future lookup. |
| * <p> |
| * Stores {@code newValue}, but only if there is not already an object for |
| * the same object name. Callers can tell if the value is new by checking |
| * the return value with reference equality: |
| * |
| * <pre> |
| * V obj = ...; |
| * boolean wasNew = map.addIfAbsent(obj) == obj; |
| * </pre> |
| * |
| * @param newValue |
| * the object to store. |
| * @return {@code newValue} if stored, or the prior value already stored and |
| * that would have been returned had the caller used |
| * {@code get(newValue)} first. |
| */ |
| public <Q extends V> V addIfAbsent(Q newValue) { |
| final int msk = mask; |
| int i = newValue.w1 & msk; |
| final V[] tbl = table; |
| V obj; |
| |
| while ((obj = tbl[i]) != null) { |
| if (AnyObjectId.isEqual(obj, newValue)) |
| return obj; |
| i = (i + 1) & msk; |
| } |
| |
| if (++size == grow) { |
| grow(); |
| insert(newValue); |
| } else { |
| tbl[i] = newValue; |
| } |
| return newValue; |
| } |
| |
| /** |
| * Get number of objects in map |
| * |
| * @return number of objects in map |
| */ |
| public int size() { |
| return size; |
| } |
| |
| /** |
| * Whether {@link #size()} is 0. |
| * |
| * @return true if {@link #size()} is 0. |
| */ |
| public boolean isEmpty() { |
| return size == 0; |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| public Iterator<V> iterator() { |
| return new Iterator<V>() { |
| private int found; |
| |
| private int i; |
| |
| @Override |
| public boolean hasNext() { |
| return found < size; |
| } |
| |
| @Override |
| public V next() { |
| while (i < table.length) { |
| final V v = table[i++]; |
| if (v != null) { |
| found++; |
| return v; |
| } |
| } |
| throw new NoSuchElementException(); |
| } |
| |
| @Override |
| public void remove() { |
| throw new UnsupportedOperationException(); |
| } |
| }; |
| } |
| |
| private void insert(V newValue) { |
| final int msk = mask; |
| int j = newValue.w1 & msk; |
| final V[] tbl = table; |
| while (tbl[j] != null) |
| j = (j + 1) & msk; |
| tbl[j] = newValue; |
| } |
| |
| private void grow() { |
| final V[] oldTable = table; |
| final int oldSize = table.length; |
| |
| initTable(oldSize << 1); |
| for (int i = 0; i < oldSize; i++) { |
| final V obj = oldTable[i]; |
| if (obj != null) |
| insert(obj); |
| } |
| } |
| |
| private void initTable(int sz) { |
| grow = sz >> 1; |
| mask = sz - 1; |
| table = createArray(sz); |
| } |
| |
| @SuppressWarnings("unchecked") |
| private final V[] createArray(int sz) { |
| return (V[]) new ObjectId[sz]; |
| } |
| } |