reftable: pass OutputStream at construction time

This makes the intended use of the classes more clear. It also
simplifies generic functions that write reftables: they only need a
ReftableWriter as argument, as the stream is carried within the
ReftableWriter.

Change-Id: Idbb06f89ae33100f0c0b562cc38e5b3b026d5181
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/debug/WriteReftable.java

@@ -128,9 +128,9 @@ protected void run() throws Exception {
 				cfg.setMaxIndexLevels(indexLevels);
 			}
 
-			ReftableWriter w = new ReftableWriter(cfg);
+			ReftableWriter w = new ReftableWriter(cfg, os);
 			w.setMinUpdateIndex(min(logs)).setMaxUpdateIndex(max(logs));
-			w.begin(os);
+			w.begin();
 			w.sortAndWriteRefs(refs);
 			for (LogEntry e : logs) {
 				w.writeLog(e.ref, e.updateIndex, e.who,

org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/DfsGarbageCollectorTest.java

@@ -723,7 +723,7 @@ public void leavesNonGcReftablesIfNotConfigured() throws Exception {
 
 		DfsPackDescription t1 = odb.newPack(INSERT);
 		try (DfsOutputStream out = odb.writeFile(t1, REFTABLE)) {
-			new ReftableWriter().begin(out).finish();
+			new ReftableWriter(out).begin().finish();
 			t1.addFileExt(REFTABLE);
 		}
 		odb.commitPack(Collections.singleton(t1), null);
@@ -755,7 +755,7 @@ public void prunesNonGcReftables() throws Exception {
 
 		DfsPackDescription t1 = odb.newPack(INSERT);
 		try (DfsOutputStream out = odb.writeFile(t1, REFTABLE)) {
-			new ReftableWriter().begin(out).finish();
+			new ReftableWriter(out).begin().finish();
 			t1.addFileExt(REFTABLE);
 		}
 		odb.commitPack(Collections.singleton(t1), null);
@@ -795,10 +795,10 @@ public void compactsReftables() throws Exception {
 		Ref next = new ObjectIdRef.PeeledNonTag(Ref.Storage.LOOSE,
 				"refs/heads/next", commit0.copy());
 		try (DfsOutputStream out = odb.writeFile(t1, REFTABLE)) {
-			ReftableWriter w = new ReftableWriter();
+			ReftableWriter w = new ReftableWriter(out);
 			w.setMinUpdateIndex(42);
 			w.setMaxUpdateIndex(42);
-			w.begin(out);
+			w.begin();
 			w.sortAndWriteRefs(Collections.singleton(next));
 			w.finish();
 			t1.addFileExt(REFTABLE);
@@ -877,10 +877,10 @@ public void reftableWithoutTombstoneResurrected() throws Exception {
 		Ref newNext = new ObjectIdRef.PeeledNonTag(Ref.Storage.LOOSE, NEXT,
 				commit1);
 		try (DfsOutputStream out = odb.writeFile(t1, REFTABLE)) {
-			ReftableWriter w = new ReftableWriter();
+			ReftableWriter w = new ReftableWriter(out)
-			w.setMinUpdateIndex(1);
+			.setMinUpdateIndex(1)
-			w.setMaxUpdateIndex(1);
+			.setMaxUpdateIndex(1)
-			w.begin(out);
+			.begin();
 			w.writeRef(newNext, 1);
 			w.finish();
 			t1.addFileExt(REFTABLE);
@@ -929,10 +929,10 @@ public void reftableWithTombstoneNotResurrected() throws Exception {
 		Ref newNext = new ObjectIdRef.PeeledNonTag(Ref.Storage.LOOSE, NEXT,
 				commit1);
 		try (DfsOutputStream out = odb.writeFile(t1, REFTABLE)) {
-			ReftableWriter w = new ReftableWriter();
+			ReftableWriter w = new ReftableWriter(out)
-			w.setMinUpdateIndex(1);
+			.setMinUpdateIndex(1)
-			w.setMaxUpdateIndex(1);
+			.setMaxUpdateIndex(1)
-			w.begin(out);
+			.begin();
 			w.writeRef(newNext, 1);
 			w.finish();
 			t1.addFileExt(REFTABLE);

org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/reftable/MergedReftableTest.java

@@ -297,10 +297,10 @@ public void oneTableSeek() throws IOException {
 	@Test
 	public void missedUpdate() throws IOException {
 		ByteArrayOutputStream buf = new ByteArrayOutputStream();
-		ReftableWriter writer = new ReftableWriter()
+		ReftableWriter writer = new ReftableWriter(buf)
 				.setMinUpdateIndex(1)
 				.setMaxUpdateIndex(3)
-				.begin(buf);
+				.begin();
 		writer.writeRef(ref("refs/heads/a", 1), 1);
 		writer.writeRef(ref("refs/heads/c", 3), 3);
 		writer.finish();
@@ -337,13 +337,13 @@ public void compaction() throws IOException {
 		List<Ref> delta2 = Arrays.asList(delete("refs/heads/next"));
 		List<Ref> delta3 = Arrays.asList(ref("refs/heads/master", 8));
 
-		ReftableCompactor compactor = new ReftableCompactor();
+		ByteArrayOutputStream out = new ByteArrayOutputStream();
+		ReftableCompactor compactor = new ReftableCompactor(out);
 		compactor.addAll(Arrays.asList(
 				read(write(delta1)),
 				read(write(delta2)),
 				read(write(delta3))));
-		ByteArrayOutputStream out = new ByteArrayOutputStream();
+		compactor.compact();
-		compactor.compact(out);
 		byte[] table = out.toByteArray();
 
 		ReftableReader reader = read(table);
@@ -461,10 +461,10 @@ private byte[] write(Collection<Ref> refs) throws IOException {
 	private byte[] write(Collection<Ref> refs, long updateIndex)
 			throws IOException {
 		ByteArrayOutputStream buffer = new ByteArrayOutputStream();
-		new ReftableWriter()
+		new ReftableWriter(buffer)
 				.setMinUpdateIndex(updateIndex)
 				.setMaxUpdateIndex(updateIndex)
-				.begin(buffer)
+				.begin()
 				.sortAndWriteRefs(refs)
 				.finish();
 		return buffer.toByteArray();

org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/reftable/ReftableCompactorTest.java

@@ -67,9 +67,10 @@ public class ReftableCompactorTest {
 
 	@Test
 	public void noTables() throws IOException {
-		ReftableCompactor compactor = new ReftableCompactor();
+		ReftableCompactor compactor;
 		try (ByteArrayOutputStream out = new ByteArrayOutputStream()) {
-			compactor.compact(out);
+			compactor = new ReftableCompactor(out);
+			compactor.compact();
 		}
 		Stats stats = compactor.getStats();
 		assertEquals(0, stats.minUpdateIndex());
@@ -81,10 +82,10 @@ public void noTables() throws IOException {
 	public void oneTable() throws IOException {
 		byte[] inTab;
 		try (ByteArrayOutputStream inBuf = new ByteArrayOutputStream()) {
-			ReftableWriter writer = new ReftableWriter()
+			ReftableWriter writer = new ReftableWriter(inBuf)
 				.setMinUpdateIndex(0)
 				.setMaxUpdateIndex(0)
-				.begin(inBuf);
+				.begin();
 
 			writer.writeRef(ref(MASTER, 1));
 			writer.finish();
@@ -92,10 +93,11 @@ public void oneTable() throws IOException {
 		}
 
 		byte[] outTab;
-		ReftableCompactor compactor = new ReftableCompactor();
+		ReftableCompactor compactor;
 		try (ByteArrayOutputStream outBuf = new ByteArrayOutputStream()) {
+			compactor = new ReftableCompactor(outBuf);
 			compactor.tryAddFirst(read(inTab));
-			compactor.compact(outBuf);
+			compactor.compact();
 			outTab = outBuf.toByteArray();
 		}
 		Stats stats = compactor.getStats();
@@ -116,10 +118,10 @@ public void oneTable() throws IOException {
 	public void twoTablesOneRef() throws IOException {
 		byte[] inTab1;
 		try (ByteArrayOutputStream inBuf = new ByteArrayOutputStream()) {
-			ReftableWriter writer = new ReftableWriter()
+			ReftableWriter writer = new ReftableWriter(inBuf)
 				.setMinUpdateIndex(0)
 				.setMaxUpdateIndex(0)
-				.begin(inBuf);
+				.begin();
 
 			writer.writeRef(ref(MASTER, 1));
 			writer.finish();
@@ -128,10 +130,10 @@ public void twoTablesOneRef() throws IOException {
 
 		byte[] inTab2;
 		try (ByteArrayOutputStream inBuf = new ByteArrayOutputStream()) {
-			ReftableWriter writer = new ReftableWriter()
+			ReftableWriter writer = new ReftableWriter(inBuf)
 				.setMinUpdateIndex(1)
 				.setMaxUpdateIndex(1)
-				.begin(inBuf);
+				.begin();
 
 			writer.writeRef(ref(MASTER, 2));
 			writer.finish();
@@ -139,10 +141,11 @@ public void twoTablesOneRef() throws IOException {
 		}
 
 		byte[] outTab;
-		ReftableCompactor compactor = new ReftableCompactor();
+		ReftableCompactor compactor;
 		try (ByteArrayOutputStream outBuf = new ByteArrayOutputStream()) {
+			compactor = new ReftableCompactor(outBuf);
 			compactor.addAll(Arrays.asList(read(inTab1), read(inTab2)));
-			compactor.compact(outBuf);
+			compactor.compact();
 			outTab = outBuf.toByteArray();
 		}
 		Stats stats = compactor.getStats();
@@ -163,10 +166,10 @@ public void twoTablesOneRef() throws IOException {
 	public void twoTablesTwoRefs() throws IOException {
 		byte[] inTab1;
 		try (ByteArrayOutputStream inBuf = new ByteArrayOutputStream()) {
-			ReftableWriter writer = new ReftableWriter()
+			ReftableWriter writer = new ReftableWriter(inBuf)
 				.setMinUpdateIndex(0)
 				.setMaxUpdateIndex(0)
-				.begin(inBuf);
+				.begin();
 
 			writer.writeRef(ref(MASTER, 1));
 			writer.writeRef(ref(NEXT, 2));
@@ -176,10 +179,10 @@ public void twoTablesTwoRefs() throws IOException {
 
 		byte[] inTab2;
 		try (ByteArrayOutputStream inBuf = new ByteArrayOutputStream()) {
-			ReftableWriter writer = new ReftableWriter()
+			ReftableWriter writer = new ReftableWriter(inBuf)
 				.setMinUpdateIndex(1)
 				.setMaxUpdateIndex(1)
-				.begin(inBuf);
+				.begin();
 
 			writer.writeRef(ref(MASTER, 3));
 			writer.finish();
@@ -187,10 +190,11 @@ public void twoTablesTwoRefs() throws IOException {
 		}
 
 		byte[] outTab;
-		ReftableCompactor compactor = new ReftableCompactor();
+		ReftableCompactor compactor;
 		try (ByteArrayOutputStream outBuf = new ByteArrayOutputStream()) {
+			compactor =  new ReftableCompactor(outBuf);
 			compactor.addAll(Arrays.asList(read(inTab1), read(inTab2)));
-			compactor.compact(outBuf);
+			compactor.compact();
 			outTab = outBuf.toByteArray();
 		}
 		Stats stats = compactor.getStats();
@@ -216,10 +220,10 @@ public void twoTablesTwoRefs() throws IOException {
 	public void twoTablesIncludeOneDelete() throws IOException {
 		byte[] inTab1;
 		try (ByteArrayOutputStream inBuf = new ByteArrayOutputStream()) {
-			ReftableWriter writer = new ReftableWriter()
+			ReftableWriter writer = new ReftableWriter(inBuf)
 				.setMinUpdateIndex(0)
 				.setMaxUpdateIndex(0)
-				.begin(inBuf);
+				.begin();
 
 			writer.writeRef(ref(MASTER, 1));
 			writer.finish();
@@ -228,10 +232,10 @@ public void twoTablesIncludeOneDelete() throws IOException {
 
 		byte[] inTab2;
 		try (ByteArrayOutputStream inBuf = new ByteArrayOutputStream()) {
-			ReftableWriter writer = new ReftableWriter()
+			ReftableWriter writer = new ReftableWriter(inBuf)
 				.setMinUpdateIndex(1)
 				.setMaxUpdateIndex(1)
-				.begin(inBuf);
+				.begin();
 
 			writer.writeRef(tombstone(MASTER));
 			writer.finish();
@@ -239,11 +243,12 @@ public void twoTablesIncludeOneDelete() throws IOException {
 		}
 
 		byte[] outTab;
-		ReftableCompactor compactor = new ReftableCompactor();
+		ReftableCompactor compactor;
 		try (ByteArrayOutputStream outBuf = new ByteArrayOutputStream()) {
+			compactor = new ReftableCompactor(outBuf);
 			compactor.setIncludeDeletes(true);
 			compactor.addAll(Arrays.asList(read(inTab1), read(inTab2)));
-			compactor.compact(outBuf);
+			compactor.compact();
 			outTab = outBuf.toByteArray();
 		}
 		Stats stats = compactor.getStats();
@@ -261,10 +266,10 @@ public void twoTablesIncludeOneDelete() throws IOException {
 	public void twoTablesNotIncludeOneDelete() throws IOException {
 		byte[] inTab1;
 		try (ByteArrayOutputStream inBuf = new ByteArrayOutputStream()) {
-			ReftableWriter writer = new ReftableWriter()
+			ReftableWriter writer = new ReftableWriter(inBuf)
 				.setMinUpdateIndex(0)
 				.setMaxUpdateIndex(0)
-				.begin(inBuf);
+				.begin();
 
 			writer.writeRef(ref(MASTER, 1));
 			writer.finish();
@@ -273,10 +278,10 @@ public void twoTablesNotIncludeOneDelete() throws IOException {
 
 		byte[] inTab2;
 		try (ByteArrayOutputStream inBuf = new ByteArrayOutputStream()) {
-			ReftableWriter writer = new ReftableWriter()
+			ReftableWriter writer = new ReftableWriter(inBuf)
 				.setMinUpdateIndex(1)
 				.setMaxUpdateIndex(1)
-				.begin(inBuf);
+				.begin();
 
 			writer.writeRef(tombstone(MASTER));
 			writer.finish();
@@ -284,11 +289,12 @@ public void twoTablesNotIncludeOneDelete() throws IOException {
 		}
 
 		byte[] outTab;
-		ReftableCompactor compactor = new ReftableCompactor();
+		ReftableCompactor compactor;
 		try (ByteArrayOutputStream outBuf = new ByteArrayOutputStream()) {
+			compactor = new ReftableCompactor(outBuf);
 			compactor.setIncludeDeletes(false);
 			compactor.addAll(Arrays.asList(read(inTab1), read(inTab2)));
-			compactor.compact(outBuf);
+			compactor.compact();
 			outTab = outBuf.toByteArray();
 		}
 		Stats stats = compactor.getStats();

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

@@ -137,9 +137,9 @@ public void estimateCurrentBytesOneRef() throws IOException {
 		byte[] table;
 		ReftableConfig cfg = new ReftableConfig();
 		cfg.setIndexObjects(false);
-		ReftableWriter writer = new ReftableWriter().setConfig(cfg);
 		try (ByteArrayOutputStream buf = new ByteArrayOutputStream()) {
-			writer.begin(buf);
+			ReftableWriter writer = new ReftableWriter(buf).setConfig(cfg);
+			writer.begin();
 			assertEquals(92, writer.estimateTotalBytes());
 			writer.writeRef(exp);
 			assertEquals(expBytes, writer.estimateTotalBytes());
@@ -163,9 +163,9 @@ public void estimateCurrentBytesWithIndex() throws IOException {
 
 		int expBytes = 147860;
 		byte[] table;
-		ReftableWriter writer = new ReftableWriter().setConfig(cfg);
 		try (ByteArrayOutputStream buf = new ByteArrayOutputStream()) {
-			writer.begin(buf);
+			ReftableWriter writer = new ReftableWriter(buf).setConfig(cfg);
+			writer.begin();
 			writer.sortAndWriteRefs(refs);
 			assertEquals(expBytes, writer.estimateTotalBytes());
 			writer.finish();
@@ -424,10 +424,10 @@ public void noIndexSeek() throws IOException {
 	public void invalidRefWriteOrder() throws IOException {
 		Ref master = ref(MASTER, 1);
 		Ref next = ref(NEXT, 2);
-		ReftableWriter writer = new ReftableWriter()
+		ReftableWriter writer = new ReftableWriter(new ByteArrayOutputStream())
 			.setMinUpdateIndex(1)
 			.setMaxUpdateIndex(1)
-			.begin(new ByteArrayOutputStream());
+			.begin();
 
 		writer.writeRef(next);
 		IllegalArgumentException e  = assertThrows(
@@ -438,10 +438,10 @@ public void invalidRefWriteOrder() throws IOException {
 
 	@Test
 	public void invalidReflogWriteOrderUpdateIndex() throws IOException {
-		ReftableWriter writer = new ReftableWriter()
+		ReftableWriter writer = new ReftableWriter(new ByteArrayOutputStream())
 			.setMinUpdateIndex(1)
 			.setMaxUpdateIndex(2)
-			.begin(new ByteArrayOutputStream());
+			.begin();
 		PersonIdent who = new PersonIdent("Log", "Ger", 1500079709, -8 * 60);
 		String msg = "test";
 
@@ -454,10 +454,10 @@ public void invalidReflogWriteOrderUpdateIndex() throws IOException {
 
 	@Test
 	public void invalidReflogWriteOrderName() throws IOException {
-		ReftableWriter writer = new ReftableWriter()
+		ReftableWriter writer = new ReftableWriter(new ByteArrayOutputStream())
 			.setMinUpdateIndex(1)
 			.setMaxUpdateIndex(1)
-			.begin(new ByteArrayOutputStream());
+			.begin();
 		PersonIdent who = new PersonIdent("Log", "Ger", 1500079709, -8 * 60);
 		String msg = "test";
 
@@ -476,10 +476,10 @@ public void withReflog() throws IOException {
 		String msg = "test";
 
 		ByteArrayOutputStream buffer = new ByteArrayOutputStream();
-		ReftableWriter writer = new ReftableWriter()
+		ReftableWriter writer = new ReftableWriter(buffer)
 				.setMinUpdateIndex(1)
 				.setMaxUpdateIndex(1)
-				.begin(buffer);
+				.begin();
 
 		writer.writeRef(master);
 		writer.writeRef(next);
@@ -531,8 +531,8 @@ public void reflogReader() throws IOException {
 		Ref next = ref(NEXT, 2);
 
 		ByteArrayOutputStream buffer = new ByteArrayOutputStream();
-		ReftableWriter writer = new ReftableWriter().setMinUpdateIndex(1)
+		ReftableWriter writer = new ReftableWriter(buffer).setMinUpdateIndex(1)
-				.setMaxUpdateIndex(1).begin(buffer);
+				.setMaxUpdateIndex(1).begin();
 
 		writer.writeRef(master);
 		writer.writeRef(next);
@@ -573,11 +573,11 @@ public void allRefs() throws IOException {
 		cfg.setRefBlockSize(1024);
 		cfg.setLogBlockSize(1024);
 		cfg.setAlignBlocks(true);
-		ReftableWriter writer = new ReftableWriter()
+		ReftableWriter writer = new ReftableWriter(buffer)
 				.setMinUpdateIndex(1)
 				.setMaxUpdateIndex(1)
 				.setConfig(cfg)
-				.begin(buffer);
+				.begin();
 		PersonIdent who = new PersonIdent("Log", "Ger", 1500079709, -8 * 60);
 
 		// Fill out the 1st ref block.
@@ -611,10 +611,10 @@ public void reflogSeek() throws IOException {
 		String msgNext = "test next";
 
 		ByteArrayOutputStream buffer = new ByteArrayOutputStream();
-		ReftableWriter writer = new ReftableWriter()
+		ReftableWriter writer = new ReftableWriter(buffer)
 				.setMinUpdateIndex(1)
 				.setMaxUpdateIndex(1)
-				.begin(buffer);
+				.begin();
 
 		writer.writeLog(MASTER, 1, who, ObjectId.zeroId(), id(1), msg);
 		writer.writeLog(NEXT, 1, who, ObjectId.zeroId(), id(2), msgNext);
@@ -654,10 +654,10 @@ public void reflogSeekPrefix() throws IOException {
 		PersonIdent who = new PersonIdent("Log", "Ger", 1500079709, -8 * 60);
 
 		ByteArrayOutputStream buffer = new ByteArrayOutputStream();
-		ReftableWriter writer = new ReftableWriter()
+		ReftableWriter writer = new ReftableWriter(buffer)
 			.setMinUpdateIndex(1)
 			.setMaxUpdateIndex(1)
-			.begin(buffer);
+			.begin();
 
 		writer.writeLog("branchname", 1, who, ObjectId.zeroId(), id(1), "branchname");
 
@@ -678,10 +678,10 @@ public void onlyReflog() throws IOException {
 		String msg = "test";
 
 		ByteArrayOutputStream buffer = new ByteArrayOutputStream();
-		ReftableWriter writer = new ReftableWriter()
+		ReftableWriter writer = new ReftableWriter(buffer)
 				.setMinUpdateIndex(1)
 				.setMaxUpdateIndex(1)
-				.begin(buffer);
+				.begin();
 		writer.writeLog(MASTER, 1, who, ObjectId.zeroId(), id(1), msg);
 		writer.writeLog(NEXT, 1, who, ObjectId.zeroId(), id(2), msg);
 		writer.finish();
@@ -730,8 +730,8 @@ public void logScan() throws IOException {
 		cfg.setLogBlockSize(2048);
 
 		ByteArrayOutputStream buffer = new ByteArrayOutputStream();
-		ReftableWriter writer = new ReftableWriter(cfg);
+		ReftableWriter writer = new ReftableWriter(cfg, buffer);
-		writer.setMinUpdateIndex(1).setMaxUpdateIndex(1).begin(buffer);
+		writer.setMinUpdateIndex(1).setMaxUpdateIndex(1).begin();
 
 		List<Ref> refs = new ArrayList<>();
 		for (int i = 1; i <= 5670; i++) {
@@ -850,7 +850,7 @@ public void nameTooLongDoesNotWrite() throws IOException {
 			cfg.setRefBlockSize(64);
 
 			ByteArrayOutputStream buffer = new ByteArrayOutputStream();
-			ReftableWriter writer = new ReftableWriter(cfg).begin(buffer);
+			ReftableWriter writer = new ReftableWriter(cfg, buffer).begin();
 			writer.writeRef(ref("refs/heads/i-am-not-a-teapot", 1));
 			writer.finish();
 			fail("expected BlockSizeTooSmallException");
@@ -935,8 +935,8 @@ private byte[] write(Ref... refs) throws IOException {
 
 	private byte[] write(Collection<Ref> refs) throws IOException {
 		ByteArrayOutputStream buffer = new ByteArrayOutputStream();
-		stats = new ReftableWriter()
+		stats = new ReftableWriter(buffer)
-				.begin(buffer)
+				.begin()
 				.sortAndWriteRefs(refs)
 				.finish()
 				.getStats();

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsGarbageCollector.java

@@ -744,11 +744,15 @@ private void writeReftable(DfsPackDescription pack) throws IOException {
 			return;
 		}
 
-		try (DfsReftableStack stack = DfsReftableStack.open(ctx, reftablesBefore)) {
+		try (DfsReftableStack stack = DfsReftableStack.open(ctx, reftablesBefore);
-			ReftableCompactor compact = new ReftableCompactor();
+		     DfsOutputStream out = objdb.writeFile(pack, REFTABLE)) {
+			ReftableCompactor compact = new ReftableCompactor(out);
 			compact.addAll(stack.readers());
 			compact.setIncludeDeletes(includeDeletes);
-			compactReftable(pack, compact);
+			compact.setConfig(configureReftable(reftableConfig, out));
+			compact.compact();
+			pack.addFileExt(REFTABLE);
+			pack.setReftableStats(compact.getStats());
 		}
 	}
 
@@ -773,14 +777,4 @@ private void writeReftable(DfsPackDescription pack, Collection<Ref> refs)
 			pack.setReftableStats(writer.getStats());
 		}
 	}
-
-	private void compactReftable(DfsPackDescription pack,
-			ReftableCompactor compact) throws IOException {
-		try (DfsOutputStream out = objdb.writeFile(pack, REFTABLE)) {
-			compact.setConfig(configureReftable(reftableConfig, out));
-			compact.compact(out);
-			pack.addFileExt(REFTABLE);
-			pack.setReftableStats(compact.getStats());
-		}
-	}
 }

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsPackCompactor.java

@@ -311,12 +311,16 @@ private void compactReftables(DfsReader ctx) throws IOException {
 		DfsObjDatabase objdb = repo.getObjectDatabase();
 		Collections.sort(srcReftables, objdb.reftableComparator());
 
-		try (DfsReftableStack stack = DfsReftableStack.open(ctx, srcReftables)) {
+		try (DfsReftableStack stack = DfsReftableStack.open(ctx, srcReftables);
+		     DfsOutputStream out = objdb.writeFile(outDesc, REFTABLE)) {
 			initOutDesc(objdb);
-			ReftableCompactor compact = new ReftableCompactor();
+			ReftableCompactor compact = new ReftableCompactor(out);
 			compact.addAll(stack.readers());
 			compact.setIncludeDeletes(true);
-			writeReftable(objdb, outDesc, compact);
+			compact.setConfig(configureReftable(reftableConfig, out));
+			compact.compact();
+			outDesc.addFileExt(REFTABLE);
+			outDesc.setReftableStats(compact.getStats());
 		}
 	}
 
@@ -497,16 +501,6 @@ private static void writeIndex(DfsObjDatabase objdb,
 		}
 	}
 
-	private void writeReftable(DfsObjDatabase objdb, DfsPackDescription pack,
-			ReftableCompactor compact) throws IOException {
-		try (DfsOutputStream out = objdb.writeFile(pack, REFTABLE)) {
-			compact.setConfig(configureReftable(reftableConfig, out));
-			compact.compact(out);
-			pack.addFileExt(REFTABLE);
-			pack.setReftableStats(compact.getStats());
-		}
-	}
-
 	static ReftableConfig configureReftable(ReftableConfig cfg,
 			DfsOutputStream out) {
 		int bs = out.blockSize();

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/ReftableBatchRefUpdate.java

@@ -296,9 +296,9 @@ && canCompactTopOfStack(cfg)) {
 	private ReftableWriter.Stats write(OutputStream os, ReftableConfig cfg,
 			long updateIndex, List<Ref> newRefs, List<ReceiveCommand> pending)
 			throws IOException {
-		ReftableWriter writer = new ReftableWriter(cfg)
+		ReftableWriter writer = new ReftableWriter(cfg, os)
 				.setMinUpdateIndex(updateIndex).setMaxUpdateIndex(updateIndex)
-				.begin(os).sortAndWriteRefs(newRefs);
+				.begin().sortAndWriteRefs(newRefs);
 		if (!isRefLogDisabled()) {
 			writeLog(writer, updateIndex, pending);
 		}
@@ -434,11 +434,11 @@ private ReftableWriter.Stats compactTopOfStack(OutputStream out,
 		tables.add(last);
 		tables.add(new ReftableReader(BlockSource.from(newTable)));
 
-		ReftableCompactor compactor = new ReftableCompactor();
+		ReftableCompactor compactor = new ReftableCompactor(out);
 		compactor.setConfig(cfg);
 		compactor.setIncludeDeletes(true);
 		compactor.addAll(tables);
-		compactor.compact(out);
+		compactor.compact();
 		return compactor.getStats();
 	}
 

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/Reftable.java

@@ -72,9 +72,9 @@ public static Reftable from(Collection<Ref> refs) {
 			cfg.setIndexObjects(false);
 			cfg.setAlignBlocks(false);
 			ByteArrayOutputStream buf = new ByteArrayOutputStream();
-			new ReftableWriter()
+			new ReftableWriter(buf)
 				.setConfig(cfg)
-				.begin(buf)
+				.begin()
 				.sortAndWriteRefs(refs)
 				.finish();
 			return new ReftableReader(BlockSource.from(buf.toByteArray()));

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/ReftableCompactor.java

@@ -68,7 +68,7 @@
  * {@code setOldestReflogTimeMillis(Long.MAX_VALUE)}.
  */
 public class ReftableCompactor {
-	private final ReftableWriter writer = new ReftableWriter();
+	private final ReftableWriter writer;
 	private final ArrayDeque<Reftable> tables = new ArrayDeque<>();
 
 	private long compactBytesLimit;
@@ -79,6 +79,17 @@ public class ReftableCompactor {
 	private long oldestReflogTimeMillis;
 	private Stats stats;
 
+	/**
+	 * Creates a new compactor.
+	 *
+	 * @param out
+	 *            stream to write the compacted tables to. Caller is responsible
+	 *            for closing {@code out}.
+	 */
+	public ReftableCompactor(OutputStream out) {
+		writer = new ReftableWriter(out);
+	}
+
 	/**
 	 * Set configuration for the reftable.
 	 *
@@ -225,19 +236,16 @@ private void adjustUpdateIndexes(ReftableReader reader) throws IOException {
 	/**
 	 * Write a compaction to {@code out}.
 	 *
-	 * @param out
-	 *            stream to write the compacted tables to. Caller is responsible
-	 *            for closing {@code out}.
 	 * @throws java.io.IOException
 	 *             if tables cannot be read, or cannot be written.
 	 */
-	public void compact(OutputStream out) throws IOException {
+	public void compact() throws IOException {
 		MergedReftable mr = new MergedReftable(new ArrayList<>(tables));
 		mr.setIncludeDeletes(includeDeletes);
 
 		writer.setMinUpdateIndex(Math.max(minUpdateIndex, 0));
 		writer.setMaxUpdateIndex(maxUpdateIndex);
-		writer.begin(out);
+		writer.begin();
 		mergeRefs(mr);
 		mergeLogs(mr);
 		writer.finish();

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/ReftableWriter.java

@@ -123,32 +123,25 @@ public class ReftableWriter {
 
 	/**
 	 * Initialize a writer with a default configuration.
+	 *
+	 * @param os
+	 *            output stream.
 	 */
-	public ReftableWriter() {
+	public ReftableWriter(OutputStream os) {
-		this(new ReftableConfig());
+		this(new ReftableConfig(), os);
 		lastRef = null;
 		lastLog = null;
 	}
 
-	/**
-	 * Initialize a writer with a specific configuration.
-	 *
-	 * @param cfg
-	 *            configuration for the writer.
-	 */
-	public ReftableWriter(ReftableConfig cfg) {
-		this(cfg, null);
-	}
-
 	/**
 	 * Initialize a writer with a configuration.
 	 *
 	 * @param cfg
 	 *            configuration for the writer
 	 * @param os
-	 *            output stream. Do not supply a stream to begin() on this writer.
+	 *            output stream.
 	 */
-	public ReftableWriter(ReftableConfig cfg, @Nullable OutputStream os) {
+	public ReftableWriter(ReftableConfig cfg, OutputStream os) {
 		config = cfg;
 		outputStream = os;
 	}
@@ -196,22 +189,6 @@ public ReftableWriter setMaxUpdateIndex(long max) {
 		return this;
 	}
 
-	/**
-	 * Begin writing the reftable. Should be called only once.
-	 *
-	 * @param os
-	 *            stream to write the table to. Caller is responsible for
-	 *            closing the stream after invoking {@link #finish()}.
-	 * @return {@code this}
-	 */
-	public ReftableWriter begin(OutputStream os) {
-		if (outputStream != null) {
-			throw new IllegalStateException("begin() called twice.");//$NON-NLS-1$
-		}
-		outputStream = os;
-		return begin();
-	}
-
 	/**
 	 * Begin writing the reftable. Should be called only once. Call this
 	 * if a stream was passed to the constructor.