http://www.eclipse.org/jgit//org.eclipse.jgit: Repository access and algorithms (Eclipse JGit Project)
  • Eclipse Distribution License (New BSD License)
  • Andrey Loskutov
  • Christian Halstrick
  • Dave Borowitz
  • David Pursehouse
  • Gunnar Wagenknecht
  • Jonathan Nieder
  • Jonathan Tan
  • Matthias Sohn
  • Sasa Zivkov
  • Terry Parker
  • Thomas Wolf 
/*
 * Copyright (C) 2008, Google Inc.
 * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
 * 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.dircache;

import static org.eclipse.jgit.lib.FileMode.TYPE_TREE;
import static org.eclipse.jgit.util.Paths.compareSameName;

import java.io.IOException;

import org.eclipse.jgit.errors.DirCacheNameConflictException;


Generic update/editing support for DirCache. 

The different update strategies extend this class to provide their own unique
services to applications.

/**
 * Generic update/editing support for {@link DirCache}.
 * <p>
 * The different update strategies extend this class to provide their own unique
 * services to applications.
 */
abstract class BaseDirCacheEditor {
	
The cache instance this editor updates during finish(). 
/** The cache instance this editor updates during {@link #finish()}. */
	protected DirCache cache;

	
Entry table this builder will eventually replace into cache. 
 Use fastAdd(DirCacheEntry) or fastKeep(int, int) to make additions to this table. The table is automatically expanded if it is too small for a new addition. 

Typically the entries in here are sorted by their path names, just like
they are in the DirCache instance.

/**
	 * Entry table this builder will eventually replace into {@link #cache}.
	 * <p>
	 * Use {@link #fastAdd(DirCacheEntry)} or {@link #fastKeep(int, int)} to
	 * make additions to this table. The table is automatically expanded if it
	 * is too small for a new addition.
	 * <p>
	 * Typically the entries in here are sorted by their path names, just like
	 * they are in the DirCache instance.
	 */
	protected DirCacheEntry[] entries;

	
Total number of valid entries in entries. 
/** Total number of valid entries in {@link #entries}. */
	protected int entryCnt;

	
Construct a new editor.

Params:
  • dc – 
           the cache this editor will eventually update.
  • ecnt – 
           estimated number of entries the editor will have upon
           completion. This sizes the initial entry table.
/**
	 * Construct a new editor.
	 *
	 * @param dc
	 *            the cache this editor will eventually update.
	 * @param ecnt
	 *            estimated number of entries the editor will have upon
	 *            completion. This sizes the initial entry table.
	 */
	protected BaseDirCacheEditor(DirCache dc, int ecnt) {
		cache = dc;
		entries = new DirCacheEntry[ecnt];
	}

	
Get the DirCache 
Returns:the cache we will update on finish().
/**
	 * Get the {@code DirCache}
	 *
	 * @return the cache we will update on {@link #finish()}.
	 */
	public DirCache getDirCache() {
		return cache;
	}

	
Append one entry into the resulting entry list.


The entry is placed at the end of the entry list. The caller is
responsible for making sure the final table is correctly sorted.

 The entries table is automatically expanded if there is insufficient space for the new addition. 
Params:
  • newEntry – 
           the new entry to add.
/**
	 * Append one entry into the resulting entry list.
	 * <p>
	 * The entry is placed at the end of the entry list. The caller is
	 * responsible for making sure the final table is correctly sorted.
	 * <p>
	 * The {@link #entries} table is automatically expanded if there is
	 * insufficient space for the new addition.
	 *
	 * @param newEntry
	 *            the new entry to add.
	 */
	protected void fastAdd(DirCacheEntry newEntry) {
		if (entries.length == entryCnt) {
			final DirCacheEntry[] n = new DirCacheEntry[(entryCnt + 16) * 3 / 2];
			System.arraycopy(entries, 0, n, 0, entryCnt);
			entries = n;
		}
		entries[entryCnt++] = newEntry;
	}

	
Add a range of existing entries from the destination cache.


The entries are placed at the end of the entry list, preserving their
current order. The caller is responsible for making sure the final table
is correctly sorted.


This method copies from the destination cache, which has not yet been
updated with this editor's new table. So all offsets into the destination
cache are not affected by any updates that may be currently taking place
in this editor.

 The entries table is automatically expanded if there is insufficient space for the new additions. 
Params:
  • pos – 
           first entry to copy from the destination cache.
  • cnt – 
           number of entries to copy.
/**
	 * Add a range of existing entries from the destination cache.
	 * <p>
	 * The entries are placed at the end of the entry list, preserving their
	 * current order. The caller is responsible for making sure the final table
	 * is correctly sorted.
	 * <p>
	 * This method copies from the destination cache, which has not yet been
	 * updated with this editor's new table. So all offsets into the destination
	 * cache are not affected by any updates that may be currently taking place
	 * in this editor.
	 * <p>
	 * The {@link #entries} table is automatically expanded if there is
	 * insufficient space for the new additions.
	 *
	 * @param pos
	 *            first entry to copy from the destination cache.
	 * @param cnt
	 *            number of entries to copy.
	 */
	protected void fastKeep(int pos, int cnt) {
		if (entryCnt + cnt > entries.length) {
			final int m1 = (entryCnt + 16) * 3 / 2;
			final int m2 = entryCnt + cnt;
			final DirCacheEntry[] n = new DirCacheEntry[Math.max(m1, m2)];
			System.arraycopy(entries, 0, n, 0, entryCnt);
			entries = n;
		}

		cache.toArray(pos, entries, entryCnt, cnt);
		entryCnt += cnt;
	}

	
Finish this builder and update the destination DirCache. 

When this method completes this builder instance is no longer usable by
the calling application. A new builder must be created to make additional
changes to the index entries.

 After completion the DirCache returned by getDirCache() will contain all modifications. 

Note to implementors: Make sure entries is fully sorted then invoke replace() to update the DirCache with the new table. 
/**
	 * Finish this builder and update the destination
	 * {@link org.eclipse.jgit.dircache.DirCache}.
	 * <p>
	 * When this method completes this builder instance is no longer usable by
	 * the calling application. A new builder must be created to make additional
	 * changes to the index entries.
	 * <p>
	 * After completion the DirCache returned by {@link #getDirCache()} will
	 * contain all modifications.
	 * <p>
	 * <i>Note to implementors:</i> Make sure {@link #entries} is fully sorted
	 * then invoke {@link #replace()} to update the DirCache with the new table.
	 */
	public abstract void finish();

	
Update the DirCache with the contents of entries. 
 This method should be invoked only during an implementation of finish(), and only after entries is sorted. 
/**
	 * Update the DirCache with the contents of {@link #entries}.
	 * <p>
	 * This method should be invoked only during an implementation of
	 * {@link #finish()}, and only after {@link #entries} is sorted.
	 */
	protected void replace() {
		checkNameConflicts();
		if (entryCnt < entries.length / 2) {
			final DirCacheEntry[] n = new DirCacheEntry[entryCnt];
			System.arraycopy(entries, 0, n, 0, entryCnt);
			entries = n;
		}
		cache.replace(entries, entryCnt);
	}

	private void checkNameConflicts() {
		int end = entryCnt - 1;
		for (int eIdx = 0; eIdx < end; eIdx++) {
			DirCacheEntry e = entries[eIdx];
			if (e.getStage() != 0) {
				continue;
			}

			byte[] ePath = e.path;
			int prefixLen = lastSlash(ePath) + 1;

			for (int nIdx = eIdx + 1; nIdx < entryCnt; nIdx++) {
				DirCacheEntry n = entries[nIdx];
				if (n.getStage() != 0) {
					continue;
				}

				byte[] nPath = n.path;
				if (!startsWith(ePath, nPath, prefixLen)) {
					// Different prefix; this entry is in another directory.
					break;
				}

				int s = nextSlash(nPath, prefixLen);
				int m = s < nPath.length ? TYPE_TREE : n.getRawMode();
				int cmp = compareSameName(
						ePath, prefixLen, ePath.length,
						nPath, prefixLen, s, m);
				if (cmp < 0) {
					break;
				} else if (cmp == 0) {
					throw new DirCacheNameConflictException(
							e.getPathString(),
							n.getPathString());
				}
			}
		}
	}

	private static int lastSlash(byte[] path) {
		for (int i = path.length - 1; i >= 0; i--) {
			if (path[i] == '/') {
				return i;
			}
		}
		return -1;
	}

	private static int nextSlash(byte[] b, int p) {
		final int n = b.length;
		for (; p < n; p++) {
			if (b[p] == '/') {
				return p;
			}
		}
		return n;
	}

	private static boolean startsWith(byte[] a, byte[] b, int n) {
		if (b.length < n) {
			return false;
		}
		for (n--; n >= 0; n--) {
			if (a[n] != b[n]) {
				return false;
			}
		}
		return true;
	}

	
Finish, write, commit this change, and release the index lock.


If this method fails (returns false) the lock is still released.


This is a utility method for applications as the finish-write-commit
pattern is very common after using a builder to update entries.

Throws:
Returns:true if the commit was successful and the file contains the new
        data; false if the commit failed and the file remains with the
        old data.
/**
	 * Finish, write, commit this change, and release the index lock.
	 * <p>
	 * If this method fails (returns false) the lock is still released.
	 * <p>
	 * This is a utility method for applications as the finish-write-commit
	 * pattern is very common after using a builder to update entries.
	 *
	 * @return true if the commit was successful and the file contains the new
	 *         data; false if the commit failed and the file remains with the
	 *         old data.
	 * @throws java.lang.IllegalStateException
	 *             the lock is not held.
	 * @throws java.io.IOException
	 *             the output file could not be created. The caller no longer
	 *             holds the lock.
	 */
	public boolean commit() throws IOException {
		finish();
		cache.write();
		return cache.commit();
	}
}