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- /*
- * Copyright (C) 2010, Google Inc.
- * and other copyright owners as documented in the project's IP log.
- *
- * This program and the accompanying materials are made available
- * under the terms of the Eclipse Distribution License v1.0 which
- * accompanies this distribution, is reproduced below, and is
- * available at http://www.eclipse.org/org/documents/edl-v10.php
- *
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or
- * without modification, are permitted provided that the following
- * conditions are met:
- *
- * - Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- *
- * - Redistributions in binary form must reproduce the above
- * copyright notice, this list of conditions and the following
- * disclaimer in the documentation and/or other materials provided
- * with the distribution.
- *
- * - Neither the name of the Eclipse Foundation, Inc. nor the
- * names of its contributors may be used to endorse or promote
- * products derived from this software without specific prior
- * written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
- * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
- * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
- * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
- * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
- * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
- * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
- * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
- * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
- * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
- package org.eclipse.jgit.util;
-
- import java.util.Arrays;
- import java.util.Collections;
- import java.util.Iterator;
- import java.util.List;
- import java.util.NoSuchElementException;
-
- import org.eclipse.jgit.lib.Ref;
- import org.eclipse.jgit.lib.RefComparator;
-
- /**
- * Specialized variant of an ArrayList to support a {@code RefDatabase}.
- * <p>
- * This list is a hybrid of a Map<String,Ref> and of a List<Ref>. It
- * tracks reference instances by name by keeping them sorted and performing
- * binary search to locate an entry. Lookup time is O(log N), but addition and
- * removal is O(N + log N) due to the list expansion or contraction costs.
- * <p>
- * This list type is copy-on-write. Mutation methods return a new copy of the
- * list, leaving {@code this} unmodified. As a result we cannot easily implement
- * the {@link java.util.List} interface contract.
- *
- * @param <T>
- * the type of reference being stored in the collection.
- */
- public class RefList<T extends Ref> implements Iterable<Ref> {
- private static final RefList<Ref> EMPTY = new RefList<Ref>(new Ref[0], 0);
-
- /**
- * @return an empty unmodifiable reference list.
- * @param <T>
- * the type of reference being stored in the collection.
- */
- @SuppressWarnings("unchecked")
- public static <T extends Ref> RefList<T> emptyList() {
- return (RefList<T>) EMPTY;
- }
-
- private final Ref[] list;
-
- private final int cnt;
-
- RefList(Ref[] list, int cnt) {
- this.list = list;
- this.cnt = cnt;
- }
-
- /**
- * Initialize this list to use the same backing array as another list.
- *
- * @param src
- * the source list.
- */
- protected RefList(RefList<T> src) {
- this.list = src.list;
- this.cnt = src.cnt;
- }
-
- public Iterator<Ref> iterator() {
- return new Iterator<Ref>() {
- private int idx;
-
- public boolean hasNext() {
- return idx < cnt;
- }
-
- public Ref next() {
- if (idx < cnt)
- return list[idx++];
- throw new NoSuchElementException();
- }
-
- public void remove() {
- throw new UnsupportedOperationException();
- }
- };
- }
-
- /** @return this cast as an immutable, standard {@link java.util.List}. */
- public final List<Ref> asList() {
- final List<Ref> r = Arrays.asList(list).subList(0, cnt);
- return Collections.unmodifiableList(r);
- }
-
- /** @return number of items in this list. */
- public final int size() {
- return cnt;
- }
-
- /** @return true if the size of this list is 0. */
- public final boolean isEmpty() {
- return cnt == 0;
- }
-
- /**
- * Locate an entry by name.
- *
- * @param name
- * the name of the reference to find.
- * @return the index the reference is at. If the entry is not present
- * returns a negative value. The insertion position for the given
- * name can be computed from {@code -(index + 1)}.
- */
- public final int find(String name) {
- int high = cnt;
- if (high == 0)
- return -1;
- int low = 0;
- do {
- final int mid = (low + high) >>> 1;
- final int cmp = RefComparator.compareTo(list[mid], name);
- if (cmp < 0)
- low = mid + 1;
- else if (cmp == 0)
- return mid;
- else
- high = mid;
- } while (low < high);
- return -(low + 1);
- }
-
- /**
- * Determine if a reference is present.
- *
- * @param name
- * name of the reference to find.
- * @return true if the reference is present; false if it is not.
- */
- public final boolean contains(String name) {
- return 0 <= find(name);
- }
-
- /**
- * Get a reference object by name.
- *
- * @param name
- * the name of the reference.
- * @return the reference object; null if it does not exist in this list.
- */
- public final T get(String name) {
- int idx = find(name);
- return 0 <= idx ? get(idx) : null;
- }
-
- /**
- * Get the reference at a particular index.
- *
- * @param idx
- * the index to obtain. Must be {@code 0 <= idx < size()}.
- * @return the reference value, never null.
- */
- @SuppressWarnings("unchecked")
- public final T get(int idx) {
- return (T) list[idx];
- }
-
- /**
- * Obtain a builder initialized with the first {@code n} elements.
- * <p>
- * Copies the first {@code n} elements from this list into a new builder,
- * which can be used by the caller to add additional elements.
- *
- * @param n
- * the number of elements to copy.
- * @return a new builder with the first {@code n} elements already added.
- */
- public final Builder<T> copy(int n) {
- Builder<T> r = new Builder<T>(Math.max(16, n));
- r.addAll(list, 0, n);
- return r;
- }
-
- /**
- * Obtain a new copy of the list after changing one element.
- * <p>
- * This list instance is not affected by the replacement. Because this
- * method copies the entire list, it runs in O(N) time.
- *
- * @param idx
- * index of the element to change.
- * @param ref
- * the new value, must not be null.
- * @return copy of this list, after replacing {@code idx} with {@code ref} .
- */
- public final RefList<T> set(int idx, T ref) {
- Ref[] newList = new Ref[cnt];
- System.arraycopy(list, 0, newList, 0, cnt);
- newList[idx] = ref;
- return new RefList<T>(newList, cnt);
- }
-
- /**
- * Add an item at a specific index.
- * <p>
- * This list instance is not affected by the addition. Because this method
- * copies the entire list, it runs in O(N) time.
- *
- * @param idx
- * position to add the item at. If negative the method assumes it
- * was a direct return value from {@link #find(String)} and will
- * adjust it to the correct position.
- * @param ref
- * the new reference to insert.
- * @return copy of this list, after making space for and adding {@code ref}.
- */
- public final RefList<T> add(int idx, T ref) {
- if (idx < 0)
- idx = -(idx + 1);
-
- Ref[] newList = new Ref[cnt + 1];
- if (0 < idx)
- System.arraycopy(list, 0, newList, 0, idx);
- newList[idx] = ref;
- if (idx < cnt)
- System.arraycopy(list, idx, newList, idx + 1, cnt - idx);
- return new RefList<T>(newList, cnt + 1);
- }
-
- /**
- * Remove an item at a specific index.
- * <p>
- * This list instance is not affected by the addition. Because this method
- * copies the entire list, it runs in O(N) time.
- *
- * @param idx
- * position to remove the item from.
- * @return copy of this list, after making removing the item at {@code idx}.
- */
- public final RefList<T> remove(int idx) {
- if (cnt == 1)
- return emptyList();
- Ref[] newList = new Ref[cnt - 1];
- if (0 < idx)
- System.arraycopy(list, 0, newList, 0, idx);
- if (idx + 1 < cnt)
- System.arraycopy(list, idx + 1, newList, idx, cnt - (idx + 1));
- return new RefList<T>(newList, cnt - 1);
- }
-
- /**
- * Store a reference, adding or replacing as necessary.
- * <p>
- * This list instance is not affected by the store. The correct position is
- * determined, and the item is added if missing, or replaced if existing.
- * Because this method copies the entire list, it runs in O(N + log N) time.
- *
- * @param ref
- * the reference to store.
- * @return copy of this list, after performing the addition or replacement.
- */
- public final RefList<T> put(T ref) {
- int idx = find(ref.getName());
- if (0 <= idx)
- return set(idx, ref);
- return add(idx, ref);
- }
-
- @Override
- public String toString() {
- StringBuilder r = new StringBuilder();
- r.append('[');
- if (cnt > 0) {
- r.append(list[0]);
- for (int i = 1; i < cnt; i++) {
- r.append(", "); //$NON-NLS-1$
- r.append(list[i]);
- }
- }
- r.append(']');
- return r.toString();
- }
-
- /**
- * Builder to facilitate fast construction of an immutable RefList.
- *
- * @param <T>
- * type of reference being stored.
- */
- public static class Builder<T extends Ref> {
- private Ref[] list;
-
- private int size;
-
- /** Create an empty list ready for items to be added. */
- public Builder() {
- this(16);
- }
-
- /**
- * Create an empty list with at least the specified capacity.
- *
- * @param capacity
- * the new capacity.
- */
- public Builder(int capacity) {
- list = new Ref[capacity];
- }
-
- /** @return number of items in this builder's internal collection. */
- public int size() {
- return size;
- }
-
- /**
- * Get the reference at a particular index.
- *
- * @param idx
- * the index to obtain. Must be {@code 0 <= idx < size()}.
- * @return the reference value, never null.
- */
- @SuppressWarnings("unchecked")
- public T get(int idx) {
- return (T) list[idx];
- }
-
- /**
- * Remove an item at a specific index.
- *
- * @param idx
- * position to remove the item from.
- */
- public void remove(int idx) {
- System.arraycopy(list, idx + 1, list, idx, size - (idx + 1));
- size--;
- }
-
- /**
- * Add the reference to the end of the array.
- * <p>
- * References must be added in sort order, or the array must be sorted
- * after additions are complete using {@link #sort()}.
- *
- * @param ref
- */
- public void add(T ref) {
- if (list.length == size) {
- Ref[] n = new Ref[size * 2];
- System.arraycopy(list, 0, n, 0, size);
- list = n;
- }
- list[size++] = ref;
- }
-
- /**
- * Add all items from a source array.
- * <p>
- * References must be added in sort order, or the array must be sorted
- * after additions are complete using {@link #sort()}.
- *
- * @param src
- * the source array.
- * @param off
- * position within {@code src} to start copying from.
- * @param cnt
- * number of items to copy from {@code src}.
- */
- public void addAll(Ref[] src, int off, int cnt) {
- if (list.length < size + cnt) {
- Ref[] n = new Ref[Math.max(size * 2, size + cnt)];
- System.arraycopy(list, 0, n, 0, size);
- list = n;
- }
- System.arraycopy(src, off, list, size, cnt);
- size += cnt;
- }
-
- /**
- * Replace a single existing element.
- *
- * @param idx
- * index, must have already been added previously.
- * @param ref
- * the new reference.
- */
- public void set(int idx, T ref) {
- list[idx] = ref;
- }
-
- /** Sort the list's backing array in-place. */
- public void sort() {
- Arrays.sort(list, 0, size, RefComparator.INSTANCE);
- }
-
- /** @return an unmodifiable list using this collection's backing array. */
- public RefList<T> toRefList() {
- return new RefList<T>(list, size);
- }
-
- @Override
- public String toString() {
- return toRefList().toString();
- }
- }
- }
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