/*
    * 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.revwalk;
  
  import static java.util.Objects.requireNonNull;
  import static org.eclipse.jgit.lib.Constants.OBJ_BLOB;
  import static org.eclipse.jgit.lib.Constants.OBJ_COMMIT;
  import static org.eclipse.jgit.lib.Constants.OBJ_TREE;
  
  import java.io.IOException;
  import java.text.MessageFormat;
  import java.util.ArrayList;
  import java.util.List;
  
  import org.eclipse.jgit.errors.CorruptObjectException;
  import org.eclipse.jgit.errors.IncorrectObjectTypeException;
  import org.eclipse.jgit.errors.LargeObjectException;
  import org.eclipse.jgit.errors.MissingObjectException;
  import org.eclipse.jgit.internal.JGitText;
  import org.eclipse.jgit.lib.AnyObjectId;
  import org.eclipse.jgit.lib.ObjectReader;
  import org.eclipse.jgit.lib.Repository;
  import org.eclipse.jgit.revwalk.filter.ObjectFilter;
  import org.eclipse.jgit.util.RawParseUtils;
  
  /**
   * Specialized subclass of RevWalk to include trees, blobs and tags.
   * <p>
   * Unlike RevWalk this subclass is able to remember starting roots that include
   * annotated tags, or arbitrary trees or blobs. Once commit generation is
   * complete and all commits have been popped by the application, individual
   * annotated tag, tree and blob objects can be popped through the additional
   * method {@link #nextObject()}.
   * <p>
   * Tree and blob objects reachable from interesting commits are automatically
   * scheduled for inclusion in the results of {@link #nextObject()}, returning
   * each object exactly once. Objects are sorted and returned according to the
   * the commits that reference them and the order they appear within a tree.
   * Ordering can be affected by changing the
   * {@link org.eclipse.jgit.revwalk.RevSort} used to order the commits that are
   * returned first.
   */
  public class ObjectWalk extends RevWalk {
  	private static final int ID_SZ = 20;
  	private static final int TYPE_SHIFT = 12;
  	private static final int TYPE_TREE = 0040000 >>> TYPE_SHIFT;
  	private static final int TYPE_SYMLINK = 0120000 >>> TYPE_SHIFT;
  	private static final int TYPE_FILE = 0100000 >>> TYPE_SHIFT;
  	private static final int TYPE_GITLINK = 0160000 >>> TYPE_SHIFT;
  
  	/**
  	 * Indicates a non-RevCommit is in {@link #pendingObjects}.
  	 * <p>
  	 * We can safely reuse {@link RevWalk#REWRITE} here for the same value as it
  	 * is only set on RevCommit and {@link #pendingObjects} never has RevCommit
  	 * instances inserted into it.
  	 */
  	private static final int IN_PENDING = RevWalk.REWRITE;
  
  	/**
  	 * When walking over a tree and blob graph, objects are usually marked as
  	 * seen as they are visited and this "seen" status is checked upon the next
  	 * visit. If they are already "seen" then they are not processed (returned
  	 * by {@link ObjectWalk#nextObject()}) again. However, this behavior can be
  	 * overridden by supplying a different implementation of this class.
  	 *
  	 * @since 5.4
  	 */
  	public interface VisitationPolicy {
  		/**
  		 * Whenever the rev or object walk reaches a Git object, if that object
  		 * already exists as a RevObject, this method is called to determine if
  		 * that object should be visited.
  		 *
  		 * @param o
  		 *            the object to check if it should be visited
  		 * @return true if the object should be visited
  		 */
  		boolean shouldVisit(RevObject o);
  
  		/**
  		 * Called when an object is visited.
  		 *
  		 * @param o
  		 *            the object that was visited
  		 */
  		void visited(RevObject o);
  	}
  
  	/**
  	 * The default visitation policy: causes all objects to be visited exactly
 	 * once.
 	 *
 	 * @since 5.4
 	 */
 	public static final VisitationPolicy SIMPLE_VISITATION_POLICY =
 			new VisitationPolicy() {
 		@Override
 		public boolean shouldVisit(RevObject o) {
 			return (o.flags & SEEN) == 0;
 		}
 
 		@Override
 		public void visited(RevObject o) {
 			o.flags |= SEEN;
 		}
 	};
 
 	private List<RevObject> rootObjects;
 
 	private BlockObjQueue pendingObjects;
 
 	private ObjectFilter objectFilter;
 
 	private TreeVisit freeVisit;
 
 	private TreeVisit currVisit;
 
 	private byte[] pathBuf;
 
 	private int pathLen;
 
 	private boolean boundary;
 
 	private VisitationPolicy visitationPolicy = SIMPLE_VISITATION_POLICY;
 
 	/**
 	 * Create a new revision and object walker for a given repository.
 	 *
 	 * @param repo
 	 *            the repository the walker will obtain data from.
 	 */
 	public ObjectWalk(Repository repo) {
 		this(repo.newObjectReader());
 	}
 
 	/**
 	 * Create a new revision and object walker for a given repository.
 	 *
 	 * @param or
 	 *            the reader the walker will obtain data from. The reader should
 	 *            be released by the caller when the walker is no longer
 	 *            required.
 	 */
 	public ObjectWalk(ObjectReader or) {
 		super(or);
 		setRetainBody(false);
 		rootObjects = new ArrayList<>();
 		pendingObjects = new BlockObjQueue();
 		objectFilter = ObjectFilter.ALL;
 		pathBuf = new byte[256];
 	}
 
 	/**
 	 * Create an object reachability checker that will use bitmaps if possible.
 	 *
 	 * This reachability checker accepts any object as target. For checks
 	 * exclusively between commits, see
 	 * {@link RevWalk#createReachabilityChecker()}.
 	 *
 	 * @return an object reachability checker, using bitmaps if possible.
 	 *
 	 * @throws IOException
 	 *             when the index fails to load.
 	 *
 	 * @since 5.8
 	 */
 	public ObjectReachabilityChecker createObjectReachabilityChecker()
 			throws IOException {
 		if (reader.getBitmapIndex() != null) {
 			return new BitmappedObjectReachabilityChecker(this);
 		}
 
 		return new PedestrianObjectReachabilityChecker(this);
 	}
 
 	/**
 	 * Mark an object or commit to start graph traversal from.
 	 * <p>
 	 * Callers are encouraged to use
 	 * {@link org.eclipse.jgit.revwalk.RevWalk#parseAny(AnyObjectId)} instead of
 	 * {@link org.eclipse.jgit.revwalk.RevWalk#lookupAny(AnyObjectId, int)}, as
 	 * this method requires the object to be parsed before it can be added as a
 	 * root for the traversal.
 	 * <p>
 	 * The method will automatically parse an unparsed object, but error
 	 * handling may be more difficult for the application to explain why a
 	 * RevObject is not actually valid. The object pool of this walker would
 	 * also be 'poisoned' by the invalid RevObject.
 	 * <p>
 	 * This method will automatically call
 	 * {@link org.eclipse.jgit.revwalk.RevWalk#markStart(RevCommit)} if passed
 	 * RevCommit instance, or a RevTag that directly (or indirectly) references
 	 * a RevCommit.
 	 *
 	 * @param o
 	 *            the object to start traversing from. The object passed must be
 	 *            from this same revision walker.
 	 * @throws org.eclipse.jgit.errors.MissingObjectException
 	 *             the object supplied is not available from the object
 	 *             database. This usually indicates the supplied object is
 	 *             invalid, but the reference was constructed during an earlier
 	 *             invocation to
 	 *             {@link org.eclipse.jgit.revwalk.RevWalk#lookupAny(AnyObjectId, int)}.
 	 * @throws org.eclipse.jgit.errors.IncorrectObjectTypeException
 	 *             the object was not parsed yet and it was discovered during
 	 *             parsing that it is not actually the type of the instance
 	 *             passed in. This usually indicates the caller used the wrong
 	 *             type in a
 	 *             {@link org.eclipse.jgit.revwalk.RevWalk#lookupAny(AnyObjectId, int)}
 	 *             call.
 	 * @throws java.io.IOException
 	 *             a pack file or loose object could not be read.
 	 */
 	public void markStart(RevObject o) throws MissingObjectException,
 			IncorrectObjectTypeException, IOException {
 		while (o instanceof RevTag) {
 			addObject(o);
 			o = ((RevTag) o).getObject();
 			parseHeaders(o);
 		}
 
 		if (o instanceof RevCommit)
 			super.markStart((RevCommit) o);
 		else
 			addObject(o);
 	}
 
 	/**
 	 * Mark an object to not produce in the output.
 	 * <p>
 	 * Uninteresting objects denote not just themselves but also their entire
 	 * reachable chain, back until the merge base of an uninteresting commit and
 	 * an otherwise interesting commit.
 	 * <p>
 	 * Callers are encouraged to use
 	 * {@link org.eclipse.jgit.revwalk.RevWalk#parseAny(AnyObjectId)} instead of
 	 * {@link org.eclipse.jgit.revwalk.RevWalk#lookupAny(AnyObjectId, int)}, as
 	 * this method requires the object to be parsed before it can be added as a
 	 * root for the traversal.
 	 * <p>
 	 * The method will automatically parse an unparsed object, but error
 	 * handling may be more difficult for the application to explain why a
 	 * RevObject is not actually valid. The object pool of this walker would
 	 * also be 'poisoned' by the invalid RevObject.
 	 * <p>
 	 * This method will automatically call
 	 * {@link org.eclipse.jgit.revwalk.RevWalk#markStart(RevCommit)} if passed
 	 * RevCommit instance, or a RevTag that directly (or indirectly) references
 	 * a RevCommit.
 	 *
 	 * @param o
 	 *            the object to start traversing from. The object passed must be
 	 * @throws org.eclipse.jgit.errors.MissingObjectException
 	 *             the object supplied is not available from the object
 	 *             database. This usually indicates the supplied object is
 	 *             invalid, but the reference was constructed during an earlier
 	 *             invocation to
 	 *             {@link org.eclipse.jgit.revwalk.RevWalk#lookupAny(AnyObjectId, int)}.
 	 * @throws org.eclipse.jgit.errors.IncorrectObjectTypeException
 	 *             the object was not parsed yet and it was discovered during
 	 *             parsing that it is not actually the type of the instance
 	 *             passed in. This usually indicates the caller used the wrong
 	 *             type in a
 	 *             {@link org.eclipse.jgit.revwalk.RevWalk#lookupAny(AnyObjectId, int)}
 	 *             call.
 	 * @throws java.io.IOException
 	 *             a pack file or loose object could not be read.
 	 */
 	public void markUninteresting(RevObject o) throws MissingObjectException,
 			IncorrectObjectTypeException, IOException {
 		while (o instanceof RevTag) {
 			o.flags |= UNINTERESTING;
 			if (boundary)
 				addObject(o);
 			o = ((RevTag) o).getObject();
 			parseHeaders(o);
 		}
 
 		if (o instanceof RevCommit)
 			super.markUninteresting((RevCommit) o);
 		else if (o instanceof RevTree)
 			markTreeUninteresting((RevTree) o);
 		else
 			o.flags |= UNINTERESTING;
 
 		if (o.getType() != OBJ_COMMIT && boundary)
 			addObject(o);
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public void sort(RevSort s) {
 		super.sort(s);
 		boundary = hasRevSort(RevSort.BOUNDARY);
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public void sort(RevSort s, boolean use) {
 		super.sort(s, use);
 		boundary = hasRevSort(RevSort.BOUNDARY);
 	}
 
 	/**
 	 * Get the currently configured object filter.
 	 *
 	 * @return the current filter. Never null as a filter is always needed.
 	 * @since 4.0
 	 */
 	public ObjectFilter getObjectFilter() {
 		return objectFilter;
 	}
 
 	/**
 	 * Set the object filter for this walker. This filter affects the objects
 	 * visited by {@link #nextObject()}. It does not affect the commits listed
 	 * by {@link #next()}.
 	 * <p>
 	 * If the filter returns false for an object, then that object is skipped
 	 * and objects reachable from it are not enqueued to be walked recursively.
 	 * This can be used to speed up the object walk by skipping subtrees that
 	 * are known to be uninteresting.
 	 *
 	 * @param newFilter
 	 *            the new filter. If null the special
 	 *            {@link org.eclipse.jgit.revwalk.filter.ObjectFilter#ALL}
 	 *            filter will be used instead, as it matches every object.
 	 * @since 4.0
 	 */
 	public void setObjectFilter(ObjectFilter newFilter) {
 		assertNotStarted();
 		objectFilter = newFilter != null ? newFilter : ObjectFilter.ALL;
 	}
 
 	/**
 	 * Sets the visitation policy to use during this walk.
 	 *
 	 * @param policy
 	 *            the {@code VisitationPolicy} to use
 	 * @since 5.4
 	 */
 	public void setVisitationPolicy(VisitationPolicy policy) {
 		assertNotStarted();
 		visitationPolicy = requireNonNull(policy);
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public RevCommit next() throws MissingObjectException,
 			IncorrectObjectTypeException, IOException {
 		for (;;) {
 			final RevCommit r = super.next();
 			if (r == null) {
 				return null;
 			}
 			final RevTree t = r.getTree();
 			if ((r.flags & UNINTERESTING) != 0) {
 				if (objectFilter.include(this, t)) {
 					markTreeUninteresting(t);
 				}
 				if (boundary) {
 					return r;
 				}
 				continue;
 			}
 			if (objectFilter.include(this, t)) {
 				pendingObjects.add(t);
 			}
 			return r;
 		}
 	}
 
 	/**
 	 * Skips the current tree such that {@link #nextObject()} does not return
 	 * any objects inside it. This should be called right after
 	 * {@link #nextObject()} returns the tree.
 	 *
 	 * @since 5.4
 	 */
 	public void skipTree() {
 		if (currVisit != null) {
 			currVisit.ptr = currVisit.buf.length;
 		}
 	}
 
 	/**
 	 * Pop the next most recent object.
 	 *
 	 * @return next most recent object; null if traversal is over.
 	 * @throws org.eclipse.jgit.errors.MissingObjectException
 	 *             one or more of the next objects are not available from the
 	 *             object database, but were thought to be candidates for
 	 *             traversal. This usually indicates a broken link.
 	 * @throws org.eclipse.jgit.errors.IncorrectObjectTypeException
 	 *             one or more of the objects in a tree do not match the type
 	 *             indicated.
 	 * @throws java.io.IOException
 	 *             a pack file or loose object could not be read.
 	 */
 	public RevObject nextObject() throws MissingObjectException,
 			IncorrectObjectTypeException, IOException {
 		pathLen = 0;
 
 		TreeVisit tv = currVisit;
 		while (tv != null) {
 			byte[] buf = tv.buf;
 			for (int ptr = tv.ptr; ptr < buf.length;) {
 				int startPtr = ptr;
 				ptr = findObjectId(buf, ptr);
 				idBuffer.fromRaw(buf, ptr);
 				ptr += ID_SZ;
 
 				if (!objectFilter.include(this, idBuffer)) {
 					continue;
 				}
 
 				RevObject obj = objects.get(idBuffer);
 				if (obj != null && !visitationPolicy.shouldVisit(obj))
 					continue;
 
 				int mode = parseMode(buf, startPtr, ptr, tv);
 				switch (mode >>> TYPE_SHIFT) {
 				case TYPE_FILE:
 				case TYPE_SYMLINK:
 					if (obj == null) {
 						obj = new RevBlob(idBuffer);
 						visitationPolicy.visited(obj);
 						objects.add(obj);
 						return obj;
 					}
 					if (!(obj instanceof RevBlob))
 						throw new IncorrectObjectTypeException(obj, OBJ_BLOB);
 					visitationPolicy.visited(obj);
 					if ((obj.flags & UNINTERESTING) == 0)
 						return obj;
 					if (boundary)
 						return obj;
 					continue;
 
 				case TYPE_TREE:
 					if (obj == null) {
 						obj = new RevTree(idBuffer);
 						visitationPolicy.visited(obj);
 						objects.add(obj);
 						return pushTree(obj);
 					}
 					if (!(obj instanceof RevTree))
 						throw new IncorrectObjectTypeException(obj, OBJ_TREE);
 					visitationPolicy.visited(obj);
 					if ((obj.flags & UNINTERESTING) == 0)
 						return pushTree(obj);
 					if (boundary)
 						return pushTree(obj);
 					continue;
 
 				case TYPE_GITLINK:
 					continue;
 
 				default:
 					throw new CorruptObjectException(MessageFormat.format(
 							JGitText.get().corruptObjectInvalidMode3,
 							String.format("%o", Integer.valueOf(mode)), //$NON-NLS-1$
 							idBuffer.name(),
 							RawParseUtils.decode(buf, tv.namePtr, tv.nameEnd),
 							tv.obj));
 				}
 			}
 
 			currVisit = tv.parent;
 			releaseTreeVisit(tv);
 			tv = currVisit;
 		}
 
 		for (;;) {
 			RevObject o = pendingObjects.next();
 			if (o == null) {
 				return null;
 			}
 			if (!visitationPolicy.shouldVisit(o)) {
 				continue;
 			}
 			visitationPolicy.visited(o);
 			if ((o.flags & UNINTERESTING) == 0 || boundary) {
 				if (o instanceof RevTree) {
 					// The previous while loop should have exhausted the stack
 					// of trees.
 					assert currVisit == null;
 
 					pushTree(o);
 				}
 				return o;
 			}
 		}
 	}
 
 	private static int findObjectId(byte[] buf, int ptr) {
 		// Skip over the mode and name until the NUL before the ObjectId
 		// can be located. Skip the NUL as the function returns.
 		for (;;) {
 			if (buf[++ptr] == 0) return ++ptr;
 			if (buf[++ptr] == 0) return ++ptr;
 			if (buf[++ptr] == 0) return ++ptr;
 			if (buf[++ptr] == 0) return ++ptr;
 
 			if (buf[++ptr] == 0) return ++ptr;
 			if (buf[++ptr] == 0) return ++ptr;
 			if (buf[++ptr] == 0) return ++ptr;
 			if (buf[++ptr] == 0) return ++ptr;
 
 			if (buf[++ptr] == 0) return ++ptr;
 			if (buf[++ptr] == 0) return ++ptr;
 			if (buf[++ptr] == 0) return ++ptr;
 			if (buf[++ptr] == 0) return ++ptr;
 
 			if (buf[++ptr] == 0) return ++ptr;
 			if (buf[++ptr] == 0) return ++ptr;
 			if (buf[++ptr] == 0) return ++ptr;
 			if (buf[++ptr] == 0) return ++ptr;
 		}
 	}
 
 	private static int parseMode(byte[] buf, int startPtr, int recEndPtr, TreeVisit tv) {
 		int mode = buf[startPtr] - '0';
 		for (;;) {
 			byte c = buf[++startPtr];
 			if (' ' == c)
 				break;
 			mode <<= 3;
 			mode += c - '0';
 
 			c = buf[++startPtr];
 			if (' ' == c)
 				break;
 			mode <<= 3;
 			mode += c - '0';
 
 			c = buf[++startPtr];
 			if (' ' == c)
 				break;
 			mode <<= 3;
 			mode += c - '0';
 
 			c = buf[++startPtr];
 			if (' ' == c)
 				break;
 			mode <<= 3;
 			mode += c - '0';
 
 			c = buf[++startPtr];
 			if (' ' == c)
 				break;
 			mode <<= 3;
 			mode += c - '0';
 
 			c = buf[++startPtr];
 			if (' ' == c)
 				break;
 			mode <<= 3;
 			mode += c - '0';
 
 			c = buf[++startPtr];
 			if (' ' == c)
 				break;
 			mode <<= 3;
 			mode += c - '0';
 		}
 
 		tv.ptr = recEndPtr;
 		tv.namePtr = startPtr + 1;
 		tv.nameEnd = recEndPtr - (ID_SZ + 1);
 		return mode;
 	}
 
 	/**
 	 * Verify all interesting objects are available, and reachable.
 	 * <p>
 	 * Callers should populate starting points and ending points with
 	 * {@link #markStart(RevObject)} and {@link #markUninteresting(RevObject)}
 	 * and then use this method to verify all objects between those two points
 	 * exist in the repository and are readable.
 	 * <p>
 	 * This method returns successfully if everything is connected; it throws an
 	 * exception if there is a connectivity problem. The exception message
 	 * provides some detail about the connectivity failure.
 	 *
 	 * @throws org.eclipse.jgit.errors.MissingObjectException
 	 *             one or more of the next objects are not available from the
 	 *             object database, but were thought to be candidates for
 	 *             traversal. This usually indicates a broken link.
 	 * @throws org.eclipse.jgit.errors.IncorrectObjectTypeException
 	 *             one or more of the objects in a tree do not match the type
 	 *             indicated.
 	 * @throws java.io.IOException
 	 *             a pack file or loose object could not be read.
 	 */
 	public void checkConnectivity() throws MissingObjectException,
 			IncorrectObjectTypeException, IOException {
 		for (;;) {
 			final RevCommit c = next();
 			if (c == null)
 				break;
 		}
 		for (;;) {
 			final RevObject o = nextObject();
 			if (o == null)
 				break;
 			if (o instanceof RevBlob && !reader.has(o))
 				throw new MissingObjectException(o, OBJ_BLOB);
 		}
 	}
 
 	/**
 	 * Get the current object's complete path.
 	 * <p>
 	 * This method is not very efficient and is primarily meant for debugging
 	 * and final output generation. Applications should try to avoid calling it,
 	 * and if invoked do so only once per interesting entry, where the name is
 	 * absolutely required for correct function.
 	 *
 	 * @return complete path of the current entry, from the root of the
 	 *         repository. If the current entry is in a subtree there will be at
 	 *         least one '/' in the returned string. Null if the current entry
 	 *         has no path, such as for annotated tags or root level trees.
 	 */
 	public String getPathString() {
 		if (pathLen == 0) {
 			pathLen = updatePathBuf(currVisit);
 			if (pathLen == 0)
 				return null;
 		}
 		return RawParseUtils.decode(pathBuf, 0, pathLen);
 	}
 
 	/**
 	 * @return the current traversal depth from the root tree object
 	 * @since 5.4
 	 */
 	public int getTreeDepth() {
 		if (currVisit == null) {
 			return 0;
 		}
 		return currVisit.depth;
 	}
 
 	/**
 	 * Get the current object's path hash code.
 	 * <p>
 	 * This method computes a hash code on the fly for this path, the hash is
 	 * suitable to cluster objects that may have similar paths together.
 	 *
 	 * @return path hash code; any integer may be returned.
 	 */
 	public int getPathHashCode() {
 		TreeVisit tv = currVisit;
 		if (tv == null)
 			return 0;
 
 		int nameEnd = tv.nameEnd;
 		if (nameEnd == 0) {
 			// When nameEnd == 0 the subtree is itself the current path
 			// being visited. The name hash must be obtained from its
 			// parent tree. If there is no parent, this is a root tree with
 			// a hash code of 0.
 			tv = tv.parent;
 			if (tv == null)
 				return 0;
 			nameEnd = tv.nameEnd;
 		}
 
 		byte[] buf;
 		int ptr;
 
 		if (16 <= (nameEnd - tv.namePtr)) {
 			buf = tv.buf;
 			ptr = nameEnd - 16;
 		} else {
 			nameEnd = pathLen;
 			if (nameEnd == 0) {
 				nameEnd = updatePathBuf(currVisit);
 				pathLen = nameEnd;
 			}
 			buf = pathBuf;
 			ptr = Math.max(0, nameEnd - 16);
 		}
 
 		int hash = 0;
 		for (; ptr < nameEnd; ptr++) {
 			byte c = buf[ptr];
 			if (c != ' ')
 				hash = (hash >>> 2) + (c << 24);
 		}
 		return hash;
 	}
 
 	/**
 	 * Get the internal buffer holding the current path.
 	 *
 	 * @return the internal buffer holding the current path.
 	 */
 	public byte[] getPathBuffer() {
 		if (pathLen == 0)
 			pathLen = updatePathBuf(currVisit);
 		return pathBuf;
 	}
 
 	/**
 	 * Get length of the path in {@link #getPathBuffer()}.
 	 *
 	 * @return length of the path in {@link #getPathBuffer()}.
 	 */
 	public int getPathLength() {
 		if (pathLen == 0)
 			pathLen = updatePathBuf(currVisit);
 		return pathLen;
 	}
 
 	private int updatePathBuf(TreeVisit tv) {
 		if (tv == null)
 			return 0;
 
 		// If nameEnd == 0 this tree has not yet contributed an entry.
 		// Update only for the parent, which if null will be empty.
 		int nameEnd = tv.nameEnd;
 		if (nameEnd == 0)
 			return updatePathBuf(tv.parent);
 
 		int ptr = tv.pathLen;
 		if (ptr == 0) {
 			ptr = updatePathBuf(tv.parent);
 			if (ptr == pathBuf.length)
 				growPathBuf(ptr);
 			if (ptr != 0)
 				pathBuf[ptr++] = '/';
 			tv.pathLen = ptr;
 		}
 
 		int namePtr = tv.namePtr;
 		int nameLen = nameEnd - namePtr;
 		int end = ptr + nameLen;
 		while (pathBuf.length < end)
 			growPathBuf(ptr);
 		System.arraycopy(tv.buf, namePtr, pathBuf, ptr, nameLen);
 		return end;
 	}
 
 	private void growPathBuf(int ptr) {
 		byte[] newBuf = new byte[pathBuf.length << 1];
 		System.arraycopy(pathBuf, 0, newBuf, 0, ptr);
 		pathBuf = newBuf;
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public void dispose() {
 		super.dispose();
 		pendingObjects = new BlockObjQueue();
 		currVisit = null;
 		freeVisit = null;
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	protected void reset(int retainFlags) {
 		super.reset(retainFlags);
 
 		for (RevObject obj : rootObjects)
 			obj.flags &= ~IN_PENDING;
 
 		rootObjects = new ArrayList<>();
 		pendingObjects = new BlockObjQueue();
 		currVisit = null;
 		freeVisit = null;
 	}
 
 	private void addObject(RevObject o) {
 		if ((o.flags & IN_PENDING) == 0) {
 			o.flags |= IN_PENDING;
 			rootObjects.add(o);
 			pendingObjects.add(o);
 		}
 	}
 
 	private void markTreeUninteresting(RevTree tree)
 			throws MissingObjectException, IncorrectObjectTypeException,
 			IOException {
 		if ((tree.flags & UNINTERESTING) != 0)
 			return;
 		tree.flags |= UNINTERESTING;
 
 		byte[] raw = reader.open(tree, OBJ_TREE).getCachedBytes();
 		for (int ptr = 0; ptr < raw.length;) {
 			byte c = raw[ptr];
 			int mode = c - '0';
 			for (;;) {
 				c = raw[++ptr];
 				if (' ' == c)
 					break;
 				mode <<= 3;
 				mode += c - '0';
 			}
 			while (raw[++ptr] != 0) {
 				// Skip entry name.
 			}
 			ptr++; // Skip NUL after entry name.
 
 			switch (mode >>> TYPE_SHIFT) {
 			case TYPE_FILE:
 			case TYPE_SYMLINK:
 				idBuffer.fromRaw(raw, ptr);
 				lookupBlob(idBuffer).flags |= UNINTERESTING;
 				break;
 
 			case TYPE_TREE:
 				idBuffer.fromRaw(raw, ptr);
 				markTreeUninteresting(lookupTree(idBuffer));
 				break;
 
 			case TYPE_GITLINK:
 				break;
 
 			default:
 				idBuffer.fromRaw(raw, ptr);
 				throw new CorruptObjectException(MessageFormat.format(
 						JGitText.get().corruptObjectInvalidMode3,
 						String.format("%o", Integer.valueOf(mode)), //$NON-NLS-1$
 						idBuffer.name(), "", tree)); //$NON-NLS-1$
 			}
 			ptr += ID_SZ;
 		}
 	}
 
 	private RevObject/../../../org/eclipse/jgit/revwalk/RevObject.html#RevObject">RevObject pushTree(RevObject obj) throws LargeObjectException,
 			MissingObjectException, IncorrectObjectTypeException, IOException {
 		TreeVisit tv = freeVisit;
 		if (tv != null) {
 			freeVisit = tv.parent;
 			tv.ptr = 0;
 			tv.namePtr = 0;
 			tv.nameEnd = 0;
 			tv.pathLen = 0;
 		} else {
 			tv = new TreeVisit();
 		}
 		tv.obj = obj;
 		tv.buf = reader.open(obj, OBJ_TREE).getCachedBytes();
 		tv.parent = currVisit;
 		currVisit = tv;
 		if (tv.parent == null) {
 			tv.depth = 1;
 		} else {
 			tv.depth = tv.parent.depth + 1;
 		}
 
 		return obj;
 	}
 
 	private void releaseTreeVisit(TreeVisit tv) {
 		tv.buf = null;
 		tv.parent = freeVisit;
 		freeVisit = tv;
 	}
 
 	private static class TreeVisit {
 		/** Parent tree visit that entered this tree, null if root tree. */
 		TreeVisit parent;
 
 		/** The RevTree currently being iterated through. */
 		RevObject obj;
 
 		/** Canonical encoding of the tree named by {@link #obj}. */
 		byte[] buf;
 
 		/** Index of next entry to parse in {@link #buf}. */
 		int ptr;
 
 		/** Start of the current name entry in {@link #buf}. */
 		int namePtr;
 
 		/** One past end of name, {@code nameEnd - namePtr} is the length. */
 		int nameEnd;
 
 		/** Number of bytes in the path leading up to this tree. */
 		int pathLen;
 
 		/** Number of levels deep from the root tree. 0 for root tree. */
 		int depth;
 	}
 }