org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/reftable/ReftableTest.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.reftable;

 import static org.eclipse.jgit.lib.Constants.HEAD;
 import static org.eclipse.jgit.lib.Constants.OBJECT_ID_LENGTH;
 import static org.eclipse.jgit.lib.Constants.R_HEADS;
 import static org.eclipse.jgit.lib.Ref.Storage.NEW;
 import static org.eclipse.jgit.lib.Ref.Storage.PACKED;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;

 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.List;

 import org.eclipse.jgit.internal.JGitText;
 import org.eclipse.jgit.internal.storage.io.BlockSource;
 import org.eclipse.jgit.internal.storage.reftable.ReftableWriter.Stats;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.ObjectIdRef;
 import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.SymbolicRef;
 import org.junit.Test;

 public class ReftableTest {
 	private static final String MASTER = "refs/heads/master";
 	private static final String V1_0 = "refs/tags/v1.0";

 	private Stats stats;

 	@Test
 	public void emptyTable() throws IOException {
 		byte[] table = write();
 		assertEquals(92 /* header, footer */, table.length);
 		assertEquals('R', table[0]);
 		assertEquals('E', table[1]);
 		assertEquals('F', table[2]);
 		assertEquals('T', table[3]);
 		assertEquals(0x01, table[4]);
 		assertTrue(ReftableConstants.isFileHeaderMagic(table, 0, 8));
 		assertTrue(ReftableConstants.isFileHeaderMagic(table, 24, 92));

 		Reftable t = read(table);
 		try (RefCursor rc = t.allRefs()) {
 			assertFalse(rc.next());
 		}
 		try (RefCursor rc = t.seekRef(HEAD)) {
 			assertFalse(rc.next());
 		}
 		try (RefCursor rc = t.seekRef(R_HEADS)) {
 			assertFalse(rc.next());
 		}
 		try (LogCursor rc = t.allLogs()) {
 			assertFalse(rc.next());
 		}
 	}

 	@Test
 	public void emptyVirtualTableFromRefs() throws IOException {
 		Reftable t = Reftable.from(Collections.emptyList());
 		try (RefCursor rc = t.allRefs()) {
 			assertFalse(rc.next());
 		}
 		try (RefCursor rc = t.seekRef(HEAD)) {
 			assertFalse(rc.next());
 		}
 		try (LogCursor rc = t.allLogs()) {
 			assertFalse(rc.next());
 		}
 	}

 	@Test
 	public void estimateCurrentBytesOneRef() throws IOException {
 		Ref exp = ref(MASTER, 1);
 		int expBytes = 24 + 4 + 5 + 3 + MASTER.length() + 20 + 68;

 		byte[] table;
 		ReftableConfig cfg = new ReftableConfig();
 		cfg.setIndexObjects(false);
 		ReftableWriter writer = new ReftableWriter().setConfig(cfg);
 		try (ByteArrayOutputStream buf = new ByteArrayOutputStream()) {
 			writer.begin(buf);
 			assertEquals(92, writer.estimateTotalBytes());
 			writer.writeRef(exp);
 			assertEquals(expBytes, writer.estimateTotalBytes());
 			writer.finish();
 			table = buf.toByteArray();
 		}
 		assertEquals(expBytes, table.length);
 	}

 	@SuppressWarnings("boxing")
 	@Test
 	public void estimateCurrentBytesWithIndex() throws IOException {
 		List<Ref> refs = new ArrayList<>();
 		for (int i = 1; i <= 5670; i++) {
 			refs.add(ref(String.format("refs/heads/%04d", i), i));
 		}

 		ReftableConfig cfg = new ReftableConfig();
 		cfg.setIndexObjects(false);
 		cfg.setMaxIndexLevels(1);

 		int expBytes = 139654;
 		byte[] table;
 		ReftableWriter writer = new ReftableWriter().setConfig(cfg);
 		try (ByteArrayOutputStream buf = new ByteArrayOutputStream()) {
 			writer.begin(buf);
 			writer.sortAndWriteRefs(refs);
 			assertEquals(expBytes, writer.estimateTotalBytes());
 			writer.finish();
 			stats = writer.getStats();
 			table = buf.toByteArray();
 		}
 		assertEquals(1, stats.refIndexLevels());
 		assertEquals(expBytes, table.length);
 	}

 	@Test
 	public void oneIdRef() throws IOException {
 		Ref exp = ref(MASTER, 1);
 		byte[] table = write(exp);
 		assertEquals(24 + 4 + 5 + 3 + MASTER.length() + 20 + 68, table.length);

 		ReftableReader t = read(table);
 		try (RefCursor rc = t.allRefs()) {
 			assertTrue(rc.next());
 			Ref act = rc.getRef();
 			assertNotNull(act);
 			assertEquals(PACKED, act.getStorage());
 			assertTrue(act.isPeeled());
 			assertFalse(act.isSymbolic());
 			assertEquals(exp.getName(), act.getName());
 			assertEquals(exp.getObjectId(), act.getObjectId());
 			assertNull(act.getPeeledObjectId());
 			assertFalse(rc.wasDeleted());
 			assertFalse(rc.next());
 		}
 		try (RefCursor rc = t.seekRef(MASTER)) {
 			assertTrue(rc.next());
 			Ref act = rc.getRef();
 			assertNotNull(act);
 			assertEquals(exp.getName(), act.getName());
 			assertFalse(rc.next());
 		}
 	}

 	@Test
 	public void oneTagRef() throws IOException {
 		Ref exp = tag(V1_0, 1, 2);
 		byte[] table = write(exp);
 		assertEquals(24 + 4 + 5 + 2 + V1_0.length() + 40 + 68, table.length);

 		ReftableReader t = read(table);
 		try (RefCursor rc = t.allRefs()) {
 			assertTrue(rc.next());
 			Ref act = rc.getRef();
 			assertNotNull(act);
 			assertEquals(PACKED, act.getStorage());
 			assertTrue(act.isPeeled());
 			assertFalse(act.isSymbolic());
 			assertEquals(exp.getName(), act.getName());
 			assertEquals(exp.getObjectId(), act.getObjectId());
 			assertEquals(exp.getPeeledObjectId(), act.getPeeledObjectId());
 		}
 	}

 	@Test
 	public void oneSymbolicRef() throws IOException {
 		Ref exp = sym(HEAD, MASTER);
 		byte[] table = write(exp);
 		assertEquals(
 				24 + 4 + 5 + 2 + HEAD.length() + 1 + MASTER.length() + 68,
 				table.length);

 		ReftableReader t = read(table);
 		try (RefCursor rc = t.allRefs()) {
 			assertTrue(rc.next());
 			Ref act = rc.getRef();
 			assertNotNull(act);
 			assertTrue(act.isSymbolic());
 			assertEquals(exp.getName(), act.getName());
 			assertNotNull(act.getLeaf());
 			assertEquals(MASTER, act.getTarget().getName());
 			assertNull(act.getObjectId());
 		}
 	}

 	@Test
 	public void oneDeletedRef() throws IOException {
 		String name = "refs/heads/gone";
 		Ref exp = newRef(name);
 		byte[] table = write(exp);
 		assertEquals(24 + 4 + 5 + 2 + name.length() + 68, table.length);

 		ReftableReader t = read(table);
 		try (RefCursor rc = t.allRefs()) {
 			assertFalse(rc.next());
 		}

 		t.setIncludeDeletes(true);
 		try (RefCursor rc = t.allRefs()) {
 			assertTrue(rc.next());
 			Ref act = rc.getRef();
 			assertNotNull(act);
 			assertFalse(act.isSymbolic());
 			assertEquals(name, act.getName());
 			assertEquals(NEW, act.getStorage());
 			assertNull(act.getObjectId());
 			assertTrue(rc.wasDeleted());
 		}
 	}

 	@Test
 	public void seekNotFound() throws IOException {
 		Ref exp = ref(MASTER, 1);
 		ReftableReader t = read(write(exp));
 		try (RefCursor rc = t.seekRef("refs/heads/a")) {
 			assertFalse(rc.next());
 		}
 		try (RefCursor rc = t.seekRef("refs/heads/n")) {
 			assertFalse(rc.next());
 		}
 	}

 	public void unpeeledDoesNotWrite() {
 		try {
 			write(new ObjectIdRef.Unpeeled(PACKED, MASTER, id(1)));
 			fail("expected IOException");
 		} catch (IOException e) {
 			assertEquals(JGitText.get().peeledRefIsRequired, e.getMessage());
 		}
 	}

 	@Test
 	public void nameTooLongDoesNotWrite() throws IOException {
 		try {
 			ReftableConfig cfg = new ReftableConfig();
 			cfg.setRefBlockSize(64);

 			ByteArrayOutputStream buffer = new ByteArrayOutputStream();
 			ReftableWriter writer = new ReftableWriter(cfg).begin(buffer);
 			writer.writeRef(ref("refs/heads/i-am-not-a-teapot", 1));
 			writer.finish();
 			fail("expected BlockSizeTooSmallException");
 		} catch (BlockSizeTooSmallException e) {
 			assertEquals(84, e.getMinimumBlockSize());
 		}
 	}

 	@Test
 	public void badCrc32() throws IOException {
 		byte[] table = write();
 		table[table.length - 1] = 0x42;

 		try {
 			read(table).seekRef(HEAD);
 			fail("expected IOException");
 		} catch (IOException e) {
 			assertEquals(JGitText.get().invalidReftableCRC, e.getMessage());
 		}
 	}


 	private static Ref ref(String name, int id) {
 		return new ObjectIdRef.PeeledNonTag(PACKED, name, id(id));
 	}

 	private static Ref tag(String name, int id1, int id2) {
 		return new ObjectIdRef.PeeledTag(PACKED, name, id(id1), id(id2));
 	}

 	private static Ref sym(String name, String target) {
 		return new SymbolicRef(name, newRef(target));
 	}

 	private static Ref newRef(String name) {
 		return new ObjectIdRef.Unpeeled(NEW, name, null);
 	}

 	private static ObjectId id(int i) {
 		byte[] buf = new byte[OBJECT_ID_LENGTH];
 		buf[0] = (byte) (i & 0xff);
 		buf[1] = (byte) ((i >>> 8) & 0xff);
 		buf[2] = (byte) ((i >>> 16) & 0xff);
 		buf[3] = (byte) (i >>> 24);
 		return ObjectId.fromRaw(buf);
 	}

 	private static ReftableReader read(byte[] table) {
 		return new ReftableReader(BlockSource.from(table));
 	}

 	private byte[] write(Ref... refs) throws IOException {
 		return write(Arrays.asList(refs));
 	}

 	private byte[] write(Collection<Ref> refs) throws IOException {
 		ByteArrayOutputStream buffer = new ByteArrayOutputStream();
 		stats = new ReftableWriter()
 				.begin(buffer)
 				.sortAndWriteRefs(refs)
 				.finish()
 				.getStats();
 		return buffer.toByteArray();
 	}
 }
	/*
	* 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.reftable;

	import static org.eclipse.jgit.lib.Constants.HEAD;
	import static org.eclipse.jgit.lib.Constants.OBJECT_ID_LENGTH;
	import static org.eclipse.jgit.lib.Constants.R_HEADS;
	import static org.eclipse.jgit.lib.Ref.Storage.NEW;
	import static org.eclipse.jgit.lib.Ref.Storage.PACKED;
	import static org.junit.Assert.assertEquals;
	import static org.junit.Assert.assertFalse;
	import static org.junit.Assert.assertNotNull;
	import static org.junit.Assert.assertNull;
	import static org.junit.Assert.assertTrue;
	import static org.junit.Assert.fail;

	import java.io.ByteArrayOutputStream;
	import java.io.IOException;
	import java.util.ArrayList;
	import java.util.Arrays;
	import java.util.Collection;
	import java.util.Collections;
	import java.util.List;

	import org.eclipse.jgit.internal.JGitText;
	import org.eclipse.jgit.internal.storage.io.BlockSource;
	import org.eclipse.jgit.internal.storage.reftable.ReftableWriter.Stats;
	import org.eclipse.jgit.lib.ObjectId;
	import org.eclipse.jgit.lib.ObjectIdRef;
	import org.eclipse.jgit.lib.Ref;
	import org.eclipse.jgit.lib.SymbolicRef;
	import org.junit.Test;

	public class ReftableTest {
	private static final String MASTER = "refs/heads/master";
	private static final String V1_0 = "refs/tags/v1.0";

	private Stats stats;

	@Test
	public void emptyTable() throws IOException {
	byte[] table = write();
	assertEquals(92 /* header, footer */, table.length);
	assertEquals('R', table[0]);
	assertEquals('E', table[1]);
	assertEquals('F', table[2]);
	assertEquals('T', table[3]);
	assertEquals(0x01, table[4]);
	assertTrue(ReftableConstants.isFileHeaderMagic(table, 0, 8));
	assertTrue(ReftableConstants.isFileHeaderMagic(table, 24, 92));

	Reftable t = read(table);
	try (RefCursor rc = t.allRefs()) {
	assertFalse(rc.next());
	}
	try (RefCursor rc = t.seekRef(HEAD)) {
	assertFalse(rc.next());
	}
	try (RefCursor rc = t.seekRef(R_HEADS)) {
	assertFalse(rc.next());
	}
	try (LogCursor rc = t.allLogs()) {
	assertFalse(rc.next());
	}
	}

	@Test
	public void emptyVirtualTableFromRefs() throws IOException {
	Reftable t = Reftable.from(Collections.emptyList());
	try (RefCursor rc = t.allRefs()) {
	assertFalse(rc.next());
	}
	try (RefCursor rc = t.seekRef(HEAD)) {
	assertFalse(rc.next());
	}
	try (LogCursor rc = t.allLogs()) {
	assertFalse(rc.next());
	}
	}

	@Test
	public void estimateCurrentBytesOneRef() throws IOException {
	Ref exp = ref(MASTER, 1);
	int expBytes = 24 + 4 + 5 + 3 + MASTER.length() + 20 + 68;

	byte[] table;
	ReftableConfig cfg = new ReftableConfig();
	cfg.setIndexObjects(false);
	ReftableWriter writer = new ReftableWriter().setConfig(cfg);
	try (ByteArrayOutputStream buf = new ByteArrayOutputStream()) {
	writer.begin(buf);
	assertEquals(92, writer.estimateTotalBytes());
	writer.writeRef(exp);
	assertEquals(expBytes, writer.estimateTotalBytes());
	writer.finish();
	table = buf.toByteArray();
	}
	assertEquals(expBytes, table.length);
	}

	@SuppressWarnings("boxing")
	@Test
	public void estimateCurrentBytesWithIndex() throws IOException {
	List<Ref> refs = new ArrayList<>();
	for (int i = 1; i <= 5670; i++) {
	refs.add(ref(String.format("refs/heads/%04d", i), i));
	}

	ReftableConfig cfg = new ReftableConfig();
	cfg.setIndexObjects(false);
	cfg.setMaxIndexLevels(1);

	int expBytes = 139654;
	byte[] table;
	ReftableWriter writer = new ReftableWriter().setConfig(cfg);
	try (ByteArrayOutputStream buf = new ByteArrayOutputStream()) {
	writer.begin(buf);
	writer.sortAndWriteRefs(refs);
	assertEquals(expBytes, writer.estimateTotalBytes());
	writer.finish();
	stats = writer.getStats();
	table = buf.toByteArray();
	}
	assertEquals(1, stats.refIndexLevels());
	assertEquals(expBytes, table.length);
	}

	@Test
	public void oneIdRef() throws IOException {
	Ref exp = ref(MASTER, 1);
	byte[] table = write(exp);
	assertEquals(24 + 4 + 5 + 3 + MASTER.length() + 20 + 68, table.length);

	ReftableReader t = read(table);
	try (RefCursor rc = t.allRefs()) {
	assertTrue(rc.next());
	Ref act = rc.getRef();
	assertNotNull(act);
	assertEquals(PACKED, act.getStorage());
	assertTrue(act.isPeeled());
	assertFalse(act.isSymbolic());
	assertEquals(exp.getName(), act.getName());
	assertEquals(exp.getObjectId(), act.getObjectId());
	assertNull(act.getPeeledObjectId());
	assertFalse(rc.wasDeleted());
	assertFalse(rc.next());
	}
	try (RefCursor rc = t.seekRef(MASTER)) {
	assertTrue(rc.next());
	Ref act = rc.getRef();
	assertNotNull(act);
	assertEquals(exp.getName(), act.getName());
	assertFalse(rc.next());
	}
	}

	@Test
	public void oneTagRef() throws IOException {
	Ref exp = tag(V1_0, 1, 2);
	byte[] table = write(exp);
	assertEquals(24 + 4 + 5 + 2 + V1_0.length() + 40 + 68, table.length);

	ReftableReader t = read(table);
	try (RefCursor rc = t.allRefs()) {
	assertTrue(rc.next());
	Ref act = rc.getRef();
	assertNotNull(act);
	assertEquals(PACKED, act.getStorage());
	assertTrue(act.isPeeled());
	assertFalse(act.isSymbolic());
	assertEquals(exp.getName(), act.getName());
	assertEquals(exp.getObjectId(), act.getObjectId());
	assertEquals(exp.getPeeledObjectId(), act.getPeeledObjectId());
	}
	}

	@Test
	public void oneSymbolicRef() throws IOException {
	Ref exp = sym(HEAD, MASTER);
	byte[] table = write(exp);
	assertEquals(
	24 + 4 + 5 + 2 + HEAD.length() + 1 + MASTER.length() + 68,
	table.length);

	ReftableReader t = read(table);
	try (RefCursor rc = t.allRefs()) {
	assertTrue(rc.next());
	Ref act = rc.getRef();
	assertNotNull(act);
	assertTrue(act.isSymbolic());
	assertEquals(exp.getName(), act.getName());
	assertNotNull(act.getLeaf());
	assertEquals(MASTER, act.getTarget().getName());
	assertNull(act.getObjectId());
	}
	}

	@Test
	public void oneDeletedRef() throws IOException {
	String name = "refs/heads/gone";
	Ref exp = newRef(name);
	byte[] table = write(exp);
	assertEquals(24 + 4 + 5 + 2 + name.length() + 68, table.length);

	ReftableReader t = read(table);
	try (RefCursor rc = t.allRefs()) {
	assertFalse(rc.next());
	}

	t.setIncludeDeletes(true);
	try (RefCursor rc = t.allRefs()) {
	assertTrue(rc.next());
	Ref act = rc.getRef();
	assertNotNull(act);
	assertFalse(act.isSymbolic());
	assertEquals(name, act.getName());
	assertEquals(NEW, act.getStorage());
	assertNull(act.getObjectId());
	assertTrue(rc.wasDeleted());
	}
	}

	@Test
	public void seekNotFound() throws IOException {
	Ref exp = ref(MASTER, 1);
	ReftableReader t = read(write(exp));
	try (RefCursor rc = t.seekRef("refs/heads/a")) {
	assertFalse(rc.next());
	}
	try (RefCursor rc = t.seekRef("refs/heads/n")) {
	assertFalse(rc.next());
	}
	}

	public void unpeeledDoesNotWrite() {
	try {
	write(new ObjectIdRef.Unpeeled(PACKED, MASTER, id(1)));
	fail("expected IOException");
	} catch (IOException e) {
	assertEquals(JGitText.get().peeledRefIsRequired, e.getMessage());
	}
	}

	@Test
	public void nameTooLongDoesNotWrite() throws IOException {
	try {
	ReftableConfig cfg = new ReftableConfig();
	cfg.setRefBlockSize(64);

	ByteArrayOutputStream buffer = new ByteArrayOutputStream();
	ReftableWriter writer = new ReftableWriter(cfg).begin(buffer);
	writer.writeRef(ref("refs/heads/i-am-not-a-teapot", 1));
	writer.finish();
	fail("expected BlockSizeTooSmallException");
	} catch (BlockSizeTooSmallException e) {
	assertEquals(84, e.getMinimumBlockSize());
	}
	}

	@Test
	public void badCrc32() throws IOException {
	byte[] table = write();
	table[table.length - 1] = 0x42;

	try {
	read(table).seekRef(HEAD);
	fail("expected IOException");
	} catch (IOException e) {
	assertEquals(JGitText.get().invalidReftableCRC, e.getMessage());
	}
	}


	private static Ref ref(String name, int id) {
	return new ObjectIdRef.PeeledNonTag(PACKED, name, id(id));
	}

	private static Ref tag(String name, int id1, int id2) {
	return new ObjectIdRef.PeeledTag(PACKED, name, id(id1), id(id2));
	}

	private static Ref sym(String name, String target) {
	return new SymbolicRef(name, newRef(target));
	}

	private static Ref newRef(String name) {
	return new ObjectIdRef.Unpeeled(NEW, name, null);
	}

	private static ObjectId id(int i) {
	byte[] buf = new byte[OBJECT_ID_LENGTH];
	buf[0] = (byte) (i & 0xff);
	buf[1] = (byte) ((i >>> 8) & 0xff);
	buf[2] = (byte) ((i >>> 16) & 0xff);
	buf[3] = (byte) (i >>> 24);
	return ObjectId.fromRaw(buf);
	}

	private static ReftableReader read(byte[] table) {
	return new ReftableReader(BlockSource.from(table));
	}

	private byte[] write(Ref... refs) throws IOException {
	return write(Arrays.asList(refs));
	}

	private byte[] write(Collection<Ref> refs) throws IOException {
	ByteArrayOutputStream buffer = new ByteArrayOutputStream();
	stats = new ReftableWriter()
	.begin(buffer)
	.sortAndWriteRefs(refs)
	.finish()
	.getStats();
	return buffer.toByteArray();
	}
	}