/*
 * 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.
 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 nextObject(). 
 Tree and blob objects reachable from interesting commits are automatically scheduled for inclusion in the results of 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 RevSort used to order the commits that are returned first. /**
 * 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 pendingObjects. 
 We can safely reuse RevWalk.REWRITE here for the same value as it is only set on RevCommit and pendingObjects never has RevCommit instances inserted into it. /**
	 * 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 ObjectWalk.nextObject()) again. However, this behavior can be overridden by supplying a different implementation of this class. 
Since:
5.4/**
	 * 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.
Params:
o – 
           the object to check if it should be visited
Returns:
true if the object should be visited/**
		 * 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.
Params:
o – 
           the object that was visited/**
		 * 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/**
	 * 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.
Params:
repo – 
           the repository the walker will obtain data from./**
	 * 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.
Params:
or – 
           the reader the walker will obtain data from. The reader should
           be released by the caller when the walker is no longer
           required./**
	 * 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 RevWalk.createReachabilityChecker(). 
Throws:
IOException – 
            when the index fails to load.
Returns:
an object reachability checker, using bitmaps if possible.
Since:
5.8/**
	 * 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.
 Callers are encouraged to use RevWalk.parseAny(AnyObjectId) instead of RevWalk.lookupAny(AnyObjectId, int), as this method requires the object to be parsed before it can be added as a root for the traversal. 

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.
 This method will automatically call RevWalk.markStart(RevCommit) if passed RevCommit instance, or a RevTag that directly (or indirectly) references a RevCommit. 
Params:
o – 
           the object to start traversing from. The object passed must be
           from this same revision walker.
Throws:
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 RevWalk.lookupAny(AnyObjectId, int).
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 RevWalk.lookupAny(AnyObjectId, int) call.
IOException – 
            a pack file or loose object could not be read./**
	 * 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.

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.
 Callers are encouraged to use RevWalk.parseAny(AnyObjectId) instead of RevWalk.lookupAny(AnyObjectId, int), as this method requires the object to be parsed before it can be added as a root for the traversal. 

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.
 This method will automatically call RevWalk.markStart(RevCommit) if passed RevCommit instance, or a RevTag that directly (or indirectly) references a RevCommit. 
Params:
o – 
           the object to start traversing from. The object passed must be
Throws:
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 RevWalk.lookupAny(AnyObjectId, int).
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 RevWalk.lookupAny(AnyObjectId, int) call.
IOException – 
            a pack file or loose object could not be read./**
	 * 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} /** {@inheritDoc} */
	@Override
	public void sort(RevSort s) {
		super.sort(s);
		boundary = hasRevSort(RevSort.BOUNDARY);
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public void sort(RevSort s, boolean use) {
		super.sort(s, use);
		boundary = hasRevSort(RevSort.BOUNDARY);
	}

	
Get the currently configured object filter.
Returns:
the current filter. Never null as a filter is always needed.
Since:
4.0/**
	 * 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 nextObject(). It does not affect the commits listed by next(). 

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.
Params:
newFilter –  the new filter. If null the special ObjectFilter.ALL filter will be used instead, as it matches every object.
Since:
4.0/**
	 * 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.
Params:
policy –  the VisitationPolicy to use
Since:
5.4/**
	 * 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} /** {@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 nextObject() does not return any objects inside it. This should be called right after nextObject() returns the tree. 
Since:
5.4/**
	 * 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.
Throws:
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.
IncorrectObjectTypeException – 
            one or more of the objects in a tree do not match the type
            indicated.
IOException – 
            a pack file or loose object could not be read.
Returns:
next most recent object; null if traversal is over./**
	 * 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.
 Callers should populate starting points and ending points with markStart(RevObject) and markUninteresting(RevObject) and then use this method to verify all objects between those two points exist in the repository and are readable. 

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:
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.
IncorrectObjectTypeException – 
            one or more of the objects in a tree do not match the type
            indicated.
IOException – 
            a pack file or loose object could not be read./**
	 * 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.

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.
Returns:
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./**
	 * 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);
	}

	
Returns:
the current traversal depth from the root tree object
Since:
5.4/**
	 * @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.

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.
Returns:
path hash code; any integer may be returned./**
	 * 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.
Returns:
the internal buffer holding the current path./**
	 * 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 getPathBuffer(). 
Returns:
length of the path in getPathBuffer()./**
	 * 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} /** {@inheritDoc} */
	@Override
	public void dispose() {
		super.dispose();
		pendingObjects = new BlockObjQueue();
		currVisit = null;
		freeVisit = null;
	}

	
{@inheritDoc} /** {@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 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. /** Parent tree visit that entered this tree, null if root tree. */
		TreeVisit parent;

		
The RevTree currently being iterated through. /** The RevTree currently being iterated through. */
		RevObject obj;

		
Canonical encoding of the tree named by obj. /** Canonical encoding of the tree named by {@link #obj}. */
		byte[] buf;

		
Index of next entry to parse in buf. /** Index of next entry to parse in {@link #buf}. */
		int ptr;

		
Start of the current name entry in buf. /** Start of the current name entry in {@link #buf}. */
		int namePtr;

		
One past end of name, nameEnd - namePtr is the length. /** One past end of name, {@code nameEnd - namePtr} is the length. */
		int nameEnd;

		
Number of bytes in the path leading up to this tree. /** 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. /** Number of levels deep from the root tree. 0 for root tree. */
		int depth;
	}
}