org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/ReftableBatchRefUpdate.java - sop/jgit - Git at Google

 /*
  * Copyright (C) 2017, 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.internal.storage.dfs;

 import static org.eclipse.jgit.internal.storage.pack.PackExt.REFTABLE;
 import static org.eclipse.jgit.lib.Ref.Storage.NEW;
 import static org.eclipse.jgit.lib.Ref.Storage.PACKED;
 import static org.eclipse.jgit.transport.ReceiveCommand.Result.LOCK_FAILURE;
 import static org.eclipse.jgit.transport.ReceiveCommand.Result.NOT_ATTEMPTED;
 import static org.eclipse.jgit.transport.ReceiveCommand.Result.OK;
 import static org.eclipse.jgit.transport.ReceiveCommand.Result.REJECTED_MISSING_OBJECT;
 import static org.eclipse.jgit.transport.ReceiveCommand.Result.REJECTED_NONFASTFORWARD;
 import static org.eclipse.jgit.transport.ReceiveCommand.Type.UPDATE_NONFASTFORWARD;

 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.OutputStream;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.locks.ReentrantLock;

 import org.eclipse.jgit.annotations.Nullable;
 import org.eclipse.jgit.errors.MissingObjectException;
 import org.eclipse.jgit.internal.storage.dfs.DfsObjDatabase.PackSource;
 import org.eclipse.jgit.internal.storage.io.BlockSource;
 import org.eclipse.jgit.internal.storage.pack.PackExt;
 import org.eclipse.jgit.internal.storage.reftable.RefCursor;
 import org.eclipse.jgit.internal.storage.reftable.Reftable;
 import org.eclipse.jgit.internal.storage.reftable.ReftableCompactor;
 import org.eclipse.jgit.internal.storage.reftable.ReftableConfig;
 import org.eclipse.jgit.internal.storage.reftable.ReftableReader;
 import org.eclipse.jgit.internal.storage.reftable.ReftableWriter;
 import org.eclipse.jgit.lib.AnyObjectId;
 import org.eclipse.jgit.lib.BatchRefUpdate;
 import org.eclipse.jgit.lib.Config;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.ObjectIdRef;
 import org.eclipse.jgit.lib.PersonIdent;
 import org.eclipse.jgit.lib.ProgressMonitor;
 import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.ReflogEntry;
 import org.eclipse.jgit.lib.SymbolicRef;
 import org.eclipse.jgit.revwalk.RevObject;
 import org.eclipse.jgit.revwalk.RevTag;
 import org.eclipse.jgit.revwalk.RevWalk;
 import org.eclipse.jgit.transport.ReceiveCommand;

 /** {@link BatchRefUpdate} for {@link DfsReftableDatabase}. */
 public class ReftableBatchRefUpdate extends BatchRefUpdate {
 	private static final int AVG_BYTES = 36;

 	private final DfsReftableDatabase refdb;
 	private final DfsObjDatabase odb;
 	private final ReentrantLock lock;
 	private final ReftableConfig reftableConfig;

 	/**
 	 * Initialize batch update.
 	 *
 	 * @param refdb
 	 *            database the update will modify.
 	 * @param odb
 	 *            object database to store the reftable.
 	 */
 	protected ReftableBatchRefUpdate(DfsReftableDatabase refdb,
 			DfsObjDatabase odb) {
 		super(refdb);
 		this.refdb = refdb;
 		this.odb = odb;
 		lock = refdb.getLock();

 		Config cfg = refdb.getRepository().getConfig();
 		reftableConfig = new ReftableConfig();
 		if (refdb instanceof InMemoryRepository.MemRefDatabase) {
 			reftableConfig.setAlignBlocks(false);
 			reftableConfig.setIndexObjects(false);
 		}
 		reftableConfig.fromConfig(cfg);
 	}

 	@Override
 	public void execute(RevWalk rw, ProgressMonitor pm, List<String> options) {
 		List<ReceiveCommand> pending = getPending();
 		if (pending.isEmpty()) {
 			return;
 		}
 		if (options != null) {
 			setPushOptions(options);
 		}
 		try {
 			if (!checkObjectExistence(rw, pending)) {
 				return;
 			}
 			if (!checkNonFastForwards(rw, pending)) {
 				return;
 			}

 			lock.lock();
 			try {
 				Reftable table = refdb.read();
 				if (!checkExpected(table, pending)) {
 					return;
 				}
 				if (!checkConflicting(pending)) {
 					return;
 				}
 				if (!blockUntilTimestamps(MAX_WAIT)) {
 					return;
 				}
 				applyUpdates(rw, pending);
 				for (ReceiveCommand cmd : pending) {
 					cmd.setResult(OK);
 				}
 			} finally {
 				lock.unlock();
 			}
 		} catch (IOException e) {
 			pending.get(0).setResult(LOCK_FAILURE, "io error"); //$NON-NLS-1$
 			ReceiveCommand.abort(pending);
 		}
 	}

 	private List<ReceiveCommand> getPending() {
 		return ReceiveCommand.filter(getCommands(), NOT_ATTEMPTED);
 	}

 	private boolean checkObjectExistence(RevWalk rw,
 			List<ReceiveCommand> pending) throws IOException {
 		for (ReceiveCommand cmd : pending) {
 			try {
 				if (!cmd.getNewId().equals(ObjectId.zeroId())) {
 					rw.parseAny(cmd.getNewId());
 				}
 			} catch (MissingObjectException e) {
 				// ReceiveCommand#setResult(Result) converts REJECTED to
 				// REJECTED_NONFASTFORWARD, even though that result is also
 				// used for a missing object. Eagerly handle this case so we
 				// can set the right result.
 				cmd.setResult(REJECTED_MISSING_OBJECT);
 				ReceiveCommand.abort(pending);
 				return false;
 			}
 		}
 		return true;
 	}

 	private boolean checkNonFastForwards(RevWalk rw,
 			List<ReceiveCommand> pending) throws IOException {
 		if (isAllowNonFastForwards()) {
 			return true;
 		}
 		for (ReceiveCommand cmd : pending) {
 			cmd.updateType(rw);
 			if (cmd.getType() == UPDATE_NONFASTFORWARD) {
 				cmd.setResult(REJECTED_NONFASTFORWARD);
 				ReceiveCommand.abort(pending);
 				return false;
 			}
 		}
 		return true;
 	}

 	private boolean checkConflicting(List<ReceiveCommand> pending)
 			throws IOException {
 		Set<String> names = new HashSet<>();
 		for (ReceiveCommand cmd : pending) {
 			names.add(cmd.getRefName());
 		}

 		boolean ok = true;
 		for (ReceiveCommand cmd : pending) {
 			String name = cmd.getRefName();
 			if (refdb.isNameConflicting(name)) {
 				cmd.setResult(LOCK_FAILURE);
 				ok = false;
 			} else {
 				int s = name.lastIndexOf('/');
 				while (0 < s) {
 					if (names.contains(name.substring(0, s))) {
 						cmd.setResult(LOCK_FAILURE);
 						ok = false;
 						break;
 					}
 					s = name.lastIndexOf('/', s - 1);
 				}
 			}
 		}
 		if (!ok && isAtomic()) {
 			ReceiveCommand.abort(pending);
 			return false;
 		}
 		return ok;
 	}

 	private boolean checkExpected(Reftable table, List<ReceiveCommand> pending)
 			throws IOException {
 		for (ReceiveCommand cmd : pending) {
 			Ref ref;
 			try (RefCursor rc = table.seekRef(cmd.getRefName())) {
 				ref = rc.next() ? rc.getRef() : null;
 			}
 			if (!matchOld(cmd, ref)) {
 				cmd.setResult(LOCK_FAILURE);
 				if (isAtomic()) {
 					ReceiveCommand.abort(pending);
 					return false;
 				}
 			}
 		}
 		return true;
 	}

 	private static boolean matchOld(ReceiveCommand cmd, @Nullable Ref ref) {
 		if (ref == null) {
 			return AnyObjectId.equals(ObjectId.zeroId(), cmd.getOldId())
 					&& cmd.getOldSymref() == null;
 		} else if (ref.isSymbolic()) {
 			return ref.getTarget().getName().equals(cmd.getOldSymref());
 		}
 		ObjectId id = ref.getObjectId();
 		if (id == null) {
 			id = ObjectId.zeroId();
 		}
 		return cmd.getOldId().equals(id);
 	}

 	private void applyUpdates(RevWalk rw, List<ReceiveCommand> pending)
 			throws IOException {
 		List<Ref> newRefs = toNewRefs(rw, pending);
 		long updateIndex = nextUpdateIndex();
 		Set<DfsPackDescription> prune = Collections.emptySet();
 		DfsPackDescription pack = odb.newPack(PackSource.INSERT);
 		try (DfsOutputStream out = odb.writeFile(pack, REFTABLE)) {
 			ReftableConfig cfg = DfsPackCompactor
 					.configureReftable(reftableConfig, out);

 			ReftableWriter.Stats stats;
 			if (refdb.compactDuringCommit()
 					&& newRefs.size() * AVG_BYTES <= cfg.getRefBlockSize()
 					&& canCompactTopOfStack(cfg)) {
 				ByteArrayOutputStream tmp = new ByteArrayOutputStream();
 				write(tmp, cfg, updateIndex, newRefs, pending);
 				stats = compactTopOfStack(out, cfg, tmp.toByteArray());
 				prune = toPruneTopOfStack();
 			} else {
 				stats = write(out, cfg, updateIndex, newRefs, pending);
 			}
 			pack.addFileExt(REFTABLE);
 			pack.setReftableStats(stats);
 		}

 		odb.commitPack(Collections.singleton(pack), prune);
 		odb.addReftable(pack, prune);
 		refdb.clearCache();
 	}

 	private ReftableWriter.Stats write(OutputStream os, ReftableConfig cfg,
 			long updateIndex, List<Ref> newRefs, List<ReceiveCommand> pending)
 					throws IOException {
 		ReftableWriter writer = new ReftableWriter(cfg)
 				.setMinUpdateIndex(updateIndex)
 				.setMaxUpdateIndex(updateIndex)
 				.begin(os)
 				.sortAndWriteRefs(newRefs);
 		if (!isRefLogDisabled()) {
 			writeLog(writer, updateIndex, pending);
 		}
 		writer.finish();
 		return writer.getStats();
 	}

 	private void writeLog(ReftableWriter writer, long updateIndex,
 			List<ReceiveCommand> pending) throws IOException {
 		Map<String, ReceiveCommand> cmds = new HashMap<>();
 		List<String> byName = new ArrayList<>(pending.size());
 		for (ReceiveCommand cmd : pending) {
 			cmds.put(cmd.getRefName(), cmd);
 			byName.add(cmd.getRefName());
 		}
 		Collections.sort(byName);

 		PersonIdent ident = getRefLogIdent();
 		if (ident == null) {
 			ident = new PersonIdent(refdb.getRepository());
 		}
 		for (String name : byName) {
 			ReceiveCommand cmd = cmds.get(name);
 			if (isRefLogDisabled(cmd)) {
 				continue;
 			}
 			String msg = getRefLogMessage(cmd);
 			if (isRefLogIncludingResult(cmd)) {
 				String strResult = toResultString(cmd);
 				if (strResult != null) {
 					msg = msg.isEmpty() ? strResult : msg + ": " + strResult; //$NON-NLS-1$
 				}
 			}
 			writer.writeLog(
 					name,
 					updateIndex,
 					ident,
 					cmd.getOldId(),
 					cmd.getNewId(),
 					msg);
 		}
 	}

 	private String toResultString(ReceiveCommand cmd) {
 		switch (cmd.getType()) {
 		case CREATE:
 			return ReflogEntry.PREFIX_CREATED;
 		case UPDATE:
 			// Match the behavior of a single RefUpdate. In that case, setting
 			// the force bit completely bypasses the potentially expensive
 			// isMergedInto check, by design, so the reflog message may be
 			// inaccurate.
 			//
 			// Similarly, this class bypasses the isMergedInto checks when the
 			// force bit is set, meaning we can't actually distinguish between
 			// UPDATE and UPDATE_NONFASTFORWARD when isAllowNonFastForwards()
 			// returns true.
 			return isAllowNonFastForwards()
 					? ReflogEntry.PREFIX_FORCED_UPDATE
 					: ReflogEntry.PREFIX_FAST_FORWARD;
 		case UPDATE_NONFASTFORWARD:
 			return ReflogEntry.PREFIX_FORCED_UPDATE;
 		default:
 			return null;
 		}
 	}

 	private static List<Ref> toNewRefs(RevWalk rw, List<ReceiveCommand> pending)
 			throws IOException {
 		List<Ref> refs = new ArrayList<>(pending.size());
 		for (ReceiveCommand cmd : pending) {
 			String name = cmd.getRefName();
 			ObjectId newId = cmd.getNewId();
 			String newSymref = cmd.getNewSymref();
 			if (AnyObjectId.equals(ObjectId.zeroId(), newId)
 					&& newSymref == null) {
 				refs.add(new ObjectIdRef.Unpeeled(NEW, name, null));
 				continue;
 			} else if (newSymref != null) {
 				refs.add(new SymbolicRef(name,
 						new ObjectIdRef.Unpeeled(NEW, newSymref, null)));
 				continue;
 			}

 			RevObject obj = rw.parseAny(newId);
 			RevObject peel = null;
 			if (obj instanceof RevTag) {
 				peel = rw.peel(obj);
 			}
 			if (peel != null) {
 				refs.add(new ObjectIdRef.PeeledTag(PACKED, name, newId,
 						peel.copy()));
 			} else {
 				refs.add(new ObjectIdRef.PeeledNonTag(PACKED, name, newId));
 			}
 		}
 		return refs;
 	}

 	private long nextUpdateIndex() throws IOException {
 		long updateIndex = 0;
 		for (Reftable r : refdb.stack().readers()) {
 			if (r instanceof ReftableReader) {
 				updateIndex = Math.max(
 						updateIndex,
 						((ReftableReader) r).maxUpdateIndex());
 			}
 		}
 		return updateIndex + 1;
 	}

 	private boolean canCompactTopOfStack(ReftableConfig cfg)
 			throws IOException {
 		ReftableStack stack = refdb.stack();
 		List<Reftable> readers = stack.readers();
 		if (readers.isEmpty()) {
 			return false;
 		}

 		int lastIdx = readers.size() - 1;
 		DfsReftable last = stack.files().get(lastIdx);
 		DfsPackDescription desc = last.getPackDescription();
 		if (desc.getPackSource() != PackSource.INSERT) {
 			return false;
 		}
 		for (PackExt ext : PackExt.values()) {
 			if (ext != REFTABLE && desc.hasFileExt(ext)) {
 				return false;
 			}
 		}

 		Reftable table = readers.get(lastIdx);
 		int bs = cfg.getRefBlockSize();
 		return table instanceof ReftableReader
 				&& ((ReftableReader) table).size() <= 3 * bs;
 	}

 	private ReftableWriter.Stats compactTopOfStack(OutputStream out,
 			ReftableConfig cfg, byte[] newTable) throws IOException {
 		List<Reftable> stack = refdb.stack().readers();
 		Reftable last = stack.get(stack.size() - 1);

 		List<Reftable> tables = new ArrayList<>(2);
 		tables.add(last);
 		tables.add(new ReftableReader(BlockSource.from(newTable)));

 		ReftableCompactor compactor = new ReftableCompactor();
 		compactor.setConfig(cfg);
 		compactor.addAll(tables);
 		compactor.compact(out);
 		return compactor.getStats();
 	}

 	private Set<DfsPackDescription> toPruneTopOfStack() throws IOException {
 		List<DfsReftable> stack = refdb.stack().files();
 		DfsReftable last = stack.get(stack.size() - 1);
 		return Collections.singleton(last.getPackDescription());
 	}
 }
	/*
	* Copyright (C) 2017, 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.internal.storage.dfs;

	import static org.eclipse.jgit.internal.storage.pack.PackExt.REFTABLE;
	import static org.eclipse.jgit.lib.Ref.Storage.NEW;
	import static org.eclipse.jgit.lib.Ref.Storage.PACKED;
	import static org.eclipse.jgit.transport.ReceiveCommand.Result.LOCK_FAILURE;
	import static org.eclipse.jgit.transport.ReceiveCommand.Result.NOT_ATTEMPTED;
	import static org.eclipse.jgit.transport.ReceiveCommand.Result.OK;
	import static org.eclipse.jgit.transport.ReceiveCommand.Result.REJECTED_MISSING_OBJECT;
	import static org.eclipse.jgit.transport.ReceiveCommand.Result.REJECTED_NONFASTFORWARD;
	import static org.eclipse.jgit.transport.ReceiveCommand.Type.UPDATE_NONFASTFORWARD;

	import java.io.ByteArrayOutputStream;
	import java.io.IOException;
	import java.io.OutputStream;
	import java.util.ArrayList;
	import java.util.Collections;
	import java.util.HashMap;
	import java.util.HashSet;
	import java.util.List;
	import java.util.Map;
	import java.util.Set;
	import java.util.concurrent.locks.ReentrantLock;

	import org.eclipse.jgit.annotations.Nullable;
	import org.eclipse.jgit.errors.MissingObjectException;
	import org.eclipse.jgit.internal.storage.dfs.DfsObjDatabase.PackSource;
	import org.eclipse.jgit.internal.storage.io.BlockSource;
	import org.eclipse.jgit.internal.storage.pack.PackExt;
	import org.eclipse.jgit.internal.storage.reftable.RefCursor;
	import org.eclipse.jgit.internal.storage.reftable.Reftable;
	import org.eclipse.jgit.internal.storage.reftable.ReftableCompactor;
	import org.eclipse.jgit.internal.storage.reftable.ReftableConfig;
	import org.eclipse.jgit.internal.storage.reftable.ReftableReader;
	import org.eclipse.jgit.internal.storage.reftable.ReftableWriter;
	import org.eclipse.jgit.lib.AnyObjectId;
	import org.eclipse.jgit.lib.BatchRefUpdate;
	import org.eclipse.jgit.lib.Config;
	import org.eclipse.jgit.lib.ObjectId;
	import org.eclipse.jgit.lib.ObjectIdRef;
	import org.eclipse.jgit.lib.PersonIdent;
	import org.eclipse.jgit.lib.ProgressMonitor;
	import org.eclipse.jgit.lib.Ref;
	import org.eclipse.jgit.lib.ReflogEntry;
	import org.eclipse.jgit.lib.SymbolicRef;
	import org.eclipse.jgit.revwalk.RevObject;
	import org.eclipse.jgit.revwalk.RevTag;
	import org.eclipse.jgit.revwalk.RevWalk;
	import org.eclipse.jgit.transport.ReceiveCommand;

	/** {@link BatchRefUpdate} for {@link DfsReftableDatabase}. */
	public class ReftableBatchRefUpdate extends BatchRefUpdate {
	private static final int AVG_BYTES = 36;

	private final DfsReftableDatabase refdb;
	private final DfsObjDatabase odb;
	private final ReentrantLock lock;
	private final ReftableConfig reftableConfig;

	/**
	* Initialize batch update.
	*
	* @param refdb
	* database the update will modify.
	* @param odb
	* object database to store the reftable.
	*/
	protected ReftableBatchRefUpdate(DfsReftableDatabase refdb,
	DfsObjDatabase odb) {
	super(refdb);
	this.refdb = refdb;
	this.odb = odb;
	lock = refdb.getLock();

	Config cfg = refdb.getRepository().getConfig();
	reftableConfig = new ReftableConfig();
	if (refdb instanceof InMemoryRepository.MemRefDatabase) {
	reftableConfig.setAlignBlocks(false);
	reftableConfig.setIndexObjects(false);
	}
	reftableConfig.fromConfig(cfg);
	}

	@Override
	public void execute(RevWalk rw, ProgressMonitor pm, List<String> options) {
	List<ReceiveCommand> pending = getPending();
	if (pending.isEmpty()) {
	return;
	}
	if (options != null) {
	setPushOptions(options);
	}
	try {
	if (!checkObjectExistence(rw, pending)) {
	return;
	}
	if (!checkNonFastForwards(rw, pending)) {
	return;
	}

	lock.lock();
	try {
	Reftable table = refdb.read();
	if (!checkExpected(table, pending)) {
	return;
	}
	if (!checkConflicting(pending)) {
	return;
	}
	if (!blockUntilTimestamps(MAX_WAIT)) {
	return;
	}
	applyUpdates(rw, pending);
	for (ReceiveCommand cmd : pending) {
	cmd.setResult(OK);
	}
	} finally {
	lock.unlock();
	}
	} catch (IOException e) {
	pending.get(0).setResult(LOCK_FAILURE, "io error"); //$NON-NLS-1$
	ReceiveCommand.abort(pending);
	}
	}

	private List<ReceiveCommand> getPending() {
	return ReceiveCommand.filter(getCommands(), NOT_ATTEMPTED);
	}

	private boolean checkObjectExistence(RevWalk rw,
	List<ReceiveCommand> pending) throws IOException {
	for (ReceiveCommand cmd : pending) {
	try {
	if (!cmd.getNewId().equals(ObjectId.zeroId())) {
	rw.parseAny(cmd.getNewId());
	}
	} catch (MissingObjectException e) {
	// ReceiveCommand#setResult(Result) converts REJECTED to
	// REJECTED_NONFASTFORWARD, even though that result is also
	// used for a missing object. Eagerly handle this case so we
	// can set the right result.
	cmd.setResult(REJECTED_MISSING_OBJECT);
	ReceiveCommand.abort(pending);
	return false;
	}
	}
	return true;
	}

	private boolean checkNonFastForwards(RevWalk rw,
	List<ReceiveCommand> pending) throws IOException {
	if (isAllowNonFastForwards()) {
	return true;
	}
	for (ReceiveCommand cmd : pending) {
	cmd.updateType(rw);
	if (cmd.getType() == UPDATE_NONFASTFORWARD) {
	cmd.setResult(REJECTED_NONFASTFORWARD);
	ReceiveCommand.abort(pending);
	return false;
	}
	}
	return true;
	}

	private boolean checkConflicting(List<ReceiveCommand> pending)
	throws IOException {
	Set<String> names = new HashSet<>();
	for (ReceiveCommand cmd : pending) {
	names.add(cmd.getRefName());
	}

	boolean ok = true;
	for (ReceiveCommand cmd : pending) {
	String name = cmd.getRefName();
	if (refdb.isNameConflicting(name)) {
	cmd.setResult(LOCK_FAILURE);
	ok = false;
	} else {
	int s = name.lastIndexOf('/');
	while (0 < s) {
	if (names.contains(name.substring(0, s))) {
	cmd.setResult(LOCK_FAILURE);
	ok = false;
	break;
	}
	s = name.lastIndexOf('/', s - 1);
	}
	}
	}
	if (!ok && isAtomic()) {
	ReceiveCommand.abort(pending);
	return false;
	}
	return ok;
	}

	private boolean checkExpected(Reftable table, List<ReceiveCommand> pending)
	throws IOException {
	for (ReceiveCommand cmd : pending) {
	Ref ref;
	try (RefCursor rc = table.seekRef(cmd.getRefName())) {
	ref = rc.next() ? rc.getRef() : null;
	}
	if (!matchOld(cmd, ref)) {
	cmd.setResult(LOCK_FAILURE);
	if (isAtomic()) {
	ReceiveCommand.abort(pending);
	return false;
	}
	}
	}
	return true;
	}

	private static boolean matchOld(ReceiveCommand cmd, @Nullable Ref ref) {
	if (ref == null) {
	return AnyObjectId.equals(ObjectId.zeroId(), cmd.getOldId())
	&& cmd.getOldSymref() == null;
	} else if (ref.isSymbolic()) {
	return ref.getTarget().getName().equals(cmd.getOldSymref());
	}
	ObjectId id = ref.getObjectId();
	if (id == null) {
	id = ObjectId.zeroId();
	}
	return cmd.getOldId().equals(id);
	}

	private void applyUpdates(RevWalk rw, List<ReceiveCommand> pending)
	throws IOException {
	List<Ref> newRefs = toNewRefs(rw, pending);
	long updateIndex = nextUpdateIndex();
	Set<DfsPackDescription> prune = Collections.emptySet();
	DfsPackDescription pack = odb.newPack(PackSource.INSERT);
	try (DfsOutputStream out = odb.writeFile(pack, REFTABLE)) {
	ReftableConfig cfg = DfsPackCompactor
	.configureReftable(reftableConfig, out);

	ReftableWriter.Stats stats;
	if (refdb.compactDuringCommit()
	&& newRefs.size() * AVG_BYTES <= cfg.getRefBlockSize()
	&& canCompactTopOfStack(cfg)) {
	ByteArrayOutputStream tmp = new ByteArrayOutputStream();
	write(tmp, cfg, updateIndex, newRefs, pending);
	stats = compactTopOfStack(out, cfg, tmp.toByteArray());
	prune = toPruneTopOfStack();
	} else {
	stats = write(out, cfg, updateIndex, newRefs, pending);
	}
	pack.addFileExt(REFTABLE);
	pack.setReftableStats(stats);
	}

	odb.commitPack(Collections.singleton(pack), prune);
	odb.addReftable(pack, prune);
	refdb.clearCache();
	}

	private ReftableWriter.Stats write(OutputStream os, ReftableConfig cfg,
	long updateIndex, List<Ref> newRefs, List<ReceiveCommand> pending)
	throws IOException {
	ReftableWriter writer = new ReftableWriter(cfg)
	.setMinUpdateIndex(updateIndex)
	.setMaxUpdateIndex(updateIndex)
	.begin(os)
	.sortAndWriteRefs(newRefs);
	if (!isRefLogDisabled()) {
	writeLog(writer, updateIndex, pending);
	}
	writer.finish();
	return writer.getStats();
	}

	private void writeLog(ReftableWriter writer, long updateIndex,
	List<ReceiveCommand> pending) throws IOException {
	Map<String, ReceiveCommand> cmds = new HashMap<>();
	List<String> byName = new ArrayList<>(pending.size());
	for (ReceiveCommand cmd : pending) {
	cmds.put(cmd.getRefName(), cmd);
	byName.add(cmd.getRefName());
	}
	Collections.sort(byName);

	PersonIdent ident = getRefLogIdent();
	if (ident == null) {
	ident = new PersonIdent(refdb.getRepository());
	}
	for (String name : byName) {
	ReceiveCommand cmd = cmds.get(name);
	if (isRefLogDisabled(cmd)) {
	continue;
	}
	String msg = getRefLogMessage(cmd);
	if (isRefLogIncludingResult(cmd)) {
	String strResult = toResultString(cmd);
	if (strResult != null) {
	msg = msg.isEmpty() ? strResult : msg + ": " + strResult; //$NON-NLS-1$
	}
	}
	writer.writeLog(
	name,
	updateIndex,
	ident,
	cmd.getOldId(),
	cmd.getNewId(),
	msg);
	}
	}

	private String toResultString(ReceiveCommand cmd) {
	switch (cmd.getType()) {
	case CREATE:
	return ReflogEntry.PREFIX_CREATED;
	case UPDATE:
	// Match the behavior of a single RefUpdate. In that case, setting
	// the force bit completely bypasses the potentially expensive
	// isMergedInto check, by design, so the reflog message may be
	// inaccurate.
	//
	// Similarly, this class bypasses the isMergedInto checks when the
	// force bit is set, meaning we can't actually distinguish between
	// UPDATE and UPDATE_NONFASTFORWARD when isAllowNonFastForwards()
	// returns true.
	return isAllowNonFastForwards()
	? ReflogEntry.PREFIX_FORCED_UPDATE
	: ReflogEntry.PREFIX_FAST_FORWARD;
	case UPDATE_NONFASTFORWARD:
	return ReflogEntry.PREFIX_FORCED_UPDATE;
	default:
	return null;
	}
	}

	private static List<Ref> toNewRefs(RevWalk rw, List<ReceiveCommand> pending)
	throws IOException {
	List<Ref> refs = new ArrayList<>(pending.size());
	for (ReceiveCommand cmd : pending) {
	String name = cmd.getRefName();
	ObjectId newId = cmd.getNewId();
	String newSymref = cmd.getNewSymref();
	if (AnyObjectId.equals(ObjectId.zeroId(), newId)
	&& newSymref == null) {
	refs.add(new ObjectIdRef.Unpeeled(NEW, name, null));
	continue;
	} else if (newSymref != null) {
	refs.add(new SymbolicRef(name,
	new ObjectIdRef.Unpeeled(NEW, newSymref, null)));
	continue;
	}

	RevObject obj = rw.parseAny(newId);
	RevObject peel = null;
	if (obj instanceof RevTag) {
	peel = rw.peel(obj);
	}
	if (peel != null) {
	refs.add(new ObjectIdRef.PeeledTag(PACKED, name, newId,
	peel.copy()));
	} else {
	refs.add(new ObjectIdRef.PeeledNonTag(PACKED, name, newId));
	}
	}
	return refs;
	}

	private long nextUpdateIndex() throws IOException {
	long updateIndex = 0;
	for (Reftable r : refdb.stack().readers()) {
	if (r instanceof ReftableReader) {
	updateIndex = Math.max(
	updateIndex,
	((ReftableReader) r).maxUpdateIndex());
	}
	}
	return updateIndex + 1;
	}

	private boolean canCompactTopOfStack(ReftableConfig cfg)
	throws IOException {
	ReftableStack stack = refdb.stack();
	List<Reftable> readers = stack.readers();
	if (readers.isEmpty()) {
	return false;
	}

	int lastIdx = readers.size() - 1;
	DfsReftable last = stack.files().get(lastIdx);
	DfsPackDescription desc = last.getPackDescription();
	if (desc.getPackSource() != PackSource.INSERT) {
	return false;
	}
	for (PackExt ext : PackExt.values()) {
	if (ext != REFTABLE && desc.hasFileExt(ext)) {
	return false;
	}
	}

	Reftable table = readers.get(lastIdx);
	int bs = cfg.getRefBlockSize();
	return table instanceof ReftableReader
	&& ((ReftableReader) table).size() <= 3 * bs;
	}

	private ReftableWriter.Stats compactTopOfStack(OutputStream out,
	ReftableConfig cfg, byte[] newTable) throws IOException {
	List<Reftable> stack = refdb.stack().readers();
	Reftable last = stack.get(stack.size() - 1);

	List<Reftable> tables = new ArrayList<>(2);
	tables.add(last);
	tables.add(new ReftableReader(BlockSource.from(newTable)));

	ReftableCompactor compactor = new ReftableCompactor();
	compactor.setConfig(cfg);
	compactor.addAll(tables);
	compactor.compact(out);
	return compactor.getStats();
	}

	private Set<DfsPackDescription> toPruneTopOfStack() throws IOException {
	List<DfsReftable> stack = refdb.stack().files();
	DfsReftable last = stack.get(stack.size() - 1);
	return Collections.singleton(last.getPackDescription());
	}
	}