]> source.dussan.org Git - jgit.git/commitdiff
reftable: create and write reftable files 47/101147/24
authorShawn Pearce <spearce@spearce.org>
Sun, 9 Jul 2017 17:38:24 +0000 (10:38 -0700)
committerShawn Pearce <spearce@spearce.org>
Thu, 17 Aug 2017 22:06:50 +0000 (15:06 -0700)
This is a simple writer to create reftable formatted files.  Follow-up
commits will add support for reading from reftable, debugging
utilities, and tests.

Change-Id: I3d520c3515c580144490b0b45433ea175a3e6e11

org.eclipse.jgit/META-INF/MANIFEST.MF
org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties
org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java
org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/BlockSizeTooSmallException.java [new file with mode: 0644]
org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/BlockWriter.java [new file with mode: 0644]
org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/ReftableConfig.java [new file with mode: 0644]
org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/ReftableConstants.java [new file with mode: 0644]
org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/ReftableOutputStream.java [new file with mode: 0644]
org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/ReftableWriter.java [new file with mode: 0644]

index 4719ceb0e58f72c73dd19f0ab54ca00ab230b46c..bbc500fe35def7908cecec9e50820bf9959ae8b5 100644 (file)
@@ -75,6 +75,7 @@ Export-Package: org.eclipse.jgit.annotations;version="4.9.0",
    org.eclipse.jgit.pgm,
    org.eclipse.jgit.pgm.test",
  org.eclipse.jgit.internal.storage.pack;version="4.9.0";x-friends:="org.eclipse.jgit.junit,org.eclipse.jgit.test,org.eclipse.jgit.pgm",
+ org.eclipse.jgit.internal.storage.reftable;version="4.9.0";x-friends:="org.eclipse.jgit.junit,org.eclipse.jgit.test,org.eclipse.jgit.pgm",
  org.eclipse.jgit.internal.storage.reftree;version="4.9.0";x-friends:="org.eclipse.jgit.junit,org.eclipse.jgit.test,org.eclipse.jgit.pgm",
  org.eclipse.jgit.lib;version="4.9.0";
   uses:="org.eclipse.jgit.revwalk,
index 22e60cbb54e7ab2a2b8f6da8e08f74f8d1a1583d..b91b18083a08066438c04d20de003dd2c171d2d7 100644 (file)
@@ -475,6 +475,7 @@ openFilesMustBeAtLeast1=Open files must be >= 1
 openingConnection=Opening connection
 operationCanceled=Operation {0} was canceled
 outputHasAlreadyBeenStarted=Output has already been started.
+overflowedReftableBlock=Overflowed reftable block
 packChecksumMismatch=Pack checksum mismatch detected for pack file {0}
 packCorruptedWhileWritingToFilesystem=Pack corrupted while writing to filesystem
 packDoesNotMatchIndex=Pack {0} does not match index
@@ -502,6 +503,7 @@ patchFormatException=Format error: {0}
 pathIsNotInWorkingDir=Path is not in working dir
 pathNotConfigured=Submodule path is not configured
 peeledLineBeforeRef=Peeled line before ref.
+peeledRefIsRequired=Peeled ref is required.
 peerDidNotSupplyACompleteObjectGraph=peer did not supply a complete object graph
 personIdentEmailNonNull=E-mail address of PersonIdent must not be null.
 personIdentNameNonNull=Name of PersonIdent must not be null.
@@ -663,6 +665,7 @@ unableToCreateNewObject=Unable to create new object: {0}
 unableToStore=Unable to store {0}.
 unableToWrite=Unable to write {0}
 unauthorized=Unauthorized
+underflowedReftableBlock=Underflowed reftable block
 unencodeableFile=Unencodable file: {0}
 unexpectedCompareResult=Unexpected metadata comparison result: {0}
 unexpectedEndOfConfigFile=Unexpected end of config file
index 610b99c14655b3a2d53c22317a96aaa33b6a6d5a..e4d7e7f6e23d893dbf59cb6bade2c68ebb794a4d 100644 (file)
@@ -534,6 +534,7 @@ public class JGitText extends TranslationBundle {
        /***/ public String openingConnection;
        /***/ public String operationCanceled;
        /***/ public String outputHasAlreadyBeenStarted;
+       /***/ public String overflowedReftableBlock;
        /***/ public String packChecksumMismatch;
        /***/ public String packCorruptedWhileWritingToFilesystem;
        /***/ public String packDoesNotMatchIndex;
@@ -561,6 +562,7 @@ public class JGitText extends TranslationBundle {
        /***/ public String pathIsNotInWorkingDir;
        /***/ public String pathNotConfigured;
        /***/ public String peeledLineBeforeRef;
+       /***/ public String peeledRefIsRequired;
        /***/ public String peerDidNotSupplyACompleteObjectGraph;
        /***/ public String personIdentEmailNonNull;
        /***/ public String personIdentNameNonNull;
@@ -722,6 +724,7 @@ public class JGitText extends TranslationBundle {
        /***/ public String unableToStore;
        /***/ public String unableToWrite;
        /***/ public String unauthorized;
+       /***/ public String underflowedReftableBlock;
        /***/ public String unencodeableFile;
        /***/ public String unexpectedCompareResult;
        /***/ public String unexpectedEndOfConfigFile;
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/BlockSizeTooSmallException.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/BlockSizeTooSmallException.java
new file mode 100644 (file)
index 0000000..cb0f988
--- /dev/null
@@ -0,0 +1,62 @@
+/*
+ * 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 java.io.IOException;
+
+/** Thrown if {@link ReftableWriter} cannot fit a reference. */
+public class BlockSizeTooSmallException extends IOException {
+       private static final long serialVersionUID = 1L;
+
+       private final int minBlockSize;
+
+       BlockSizeTooSmallException(int b) {
+               minBlockSize = b;
+       }
+
+       /** @return minimum block size in bytes reftable requires to write a ref. */
+       public int getMinimumBlockSize() {
+               return minBlockSize;
+       }
+}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/BlockWriter.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/BlockWriter.java
new file mode 100644 (file)
index 0000000..8f3e889
--- /dev/null
@@ -0,0 +1,601 @@
+/*
+ * 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 java.nio.charset.StandardCharsets.UTF_8;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.FILE_HEADER_LEN;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.INDEX_BLOCK_TYPE;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.LOG_BLOCK_TYPE;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.LOG_DATA;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.LOG_NONE;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.MAX_RESTARTS;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.OBJ_BLOCK_TYPE;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.REF_BLOCK_TYPE;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.VALUE_1ID;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.VALUE_2ID;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.VALUE_NONE;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.VALUE_SYMREF;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.VALUE_TYPE_MASK;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.reverseUpdateIndex;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableOutputStream.computeVarintSize;
+import static org.eclipse.jgit.lib.Constants.OBJECT_ID_LENGTH;
+import static org.eclipse.jgit.lib.Ref.Storage.NEW;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+import org.eclipse.jgit.internal.JGitText;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.PersonIdent;
+import org.eclipse.jgit.lib.Ref;
+import org.eclipse.jgit.util.IntList;
+import org.eclipse.jgit.util.LongList;
+import org.eclipse.jgit.util.NB;
+
+/** Formats and writes blocks for {@link ReftableWriter}. */
+class BlockWriter {
+       private final byte blockType;
+       private final byte keyType;
+       private final List<Entry> entries;
+       private final int blockLimitBytes;
+       private final int restartInterval;
+
+       private int entriesSumBytes;
+       private int restartCnt;
+
+       BlockWriter(byte type, byte kt, int bs, int ri) {
+               blockType = type;
+               keyType = kt;
+               blockLimitBytes = bs;
+               restartInterval = ri;
+               entries = new ArrayList<>(estimateEntryCount(type, kt, bs));
+       }
+
+       private static int estimateEntryCount(byte blockType, byte keyType,
+                       int blockLimitBytes) {
+               double avgBytesPerEntry;
+               switch (blockType) {
+               case REF_BLOCK_TYPE:
+               default:
+                       avgBytesPerEntry = 35.31;
+                       break;
+
+               case OBJ_BLOCK_TYPE:
+                       avgBytesPerEntry = 4.19;
+                       break;
+
+               case LOG_BLOCK_TYPE:
+                       avgBytesPerEntry = 101.14;
+                       break;
+
+               case INDEX_BLOCK_TYPE:
+                       switch (keyType) {
+                       case REF_BLOCK_TYPE:
+                       case LOG_BLOCK_TYPE:
+                       default:
+                               avgBytesPerEntry = 27.44;
+                               break;
+
+                       case OBJ_BLOCK_TYPE:
+                               avgBytesPerEntry = 11.57;
+                               break;
+                       }
+               }
+
+               int cnt = (int) (Math.ceil(blockLimitBytes / avgBytesPerEntry));
+               return Math.min(cnt, 4096);
+       }
+
+       byte blockType() {
+               return blockType;
+       }
+
+       boolean padBetweenBlocks() {
+               return padBetweenBlocks(blockType)
+                               || (blockType == INDEX_BLOCK_TYPE && padBetweenBlocks(keyType));
+       }
+
+       static boolean padBetweenBlocks(byte type) {
+               return type == REF_BLOCK_TYPE || type == OBJ_BLOCK_TYPE;
+       }
+
+       byte[] lastKey() {
+               return entries.get(entries.size() - 1).key;
+       }
+
+       int currentSize() {
+               return computeBlockBytes(0, false);
+       }
+
+       void mustAdd(Entry entry) throws BlockSizeTooSmallException {
+               if (!tryAdd(entry, true)) {
+                       // Insanely long names need a larger block size.
+                       throw blockSizeTooSmall(entry);
+               }
+       }
+
+       boolean tryAdd(Entry entry) {
+               if (entry instanceof ObjEntry
+                               && computeBlockBytes(entry.sizeBytes(), 1) > blockLimitBytes) {
+                       // If the ObjEntry has so many ref block pointers that its
+                       // encoding overflows any block, reconfigure it to tell readers to
+                       // instead scan all refs for this ObjectId. That significantly
+                       // shrinks the entry to a very small size, which may now fit into
+                       // this block.
+                       ((ObjEntry) entry).markScanRequired();
+               }
+
+               if (tryAdd(entry, true)) {
+                       return true;
+               } else if (nextShouldBeRestart()) {
+                       // It was time for another restart, but the entry doesn't fit
+                       // with its complete key, as the block is nearly full. Try to
+                       // force it to fit with prefix compression rather than waste
+                       // the tail of the block with padding.
+                       return tryAdd(entry, false);
+               }
+               return false;
+       }
+
+       private boolean tryAdd(Entry entry, boolean tryRestart) {
+               byte[] key = entry.key;
+               int prefixLen = 0;
+               boolean restart = tryRestart && nextShouldBeRestart();
+               if (!restart) {
+                       Entry priorEntry = entries.get(entries.size() - 1);
+                       byte[] prior = priorEntry.key;
+                       prefixLen = commonPrefix(prior, prior.length, key);
+                       if (prefixLen <= 5 /* "refs/" */ && keyType == REF_BLOCK_TYPE) {
+                               // Force restart points at transitions between namespaces
+                               // such as "refs/heads/" to "refs/tags/".
+                               restart = true;
+                               prefixLen = 0;
+                       } else if (prefixLen == 0) {
+                               restart = true;
+                       }
+               }
+
+               entry.restart = restart;
+               entry.prefixLen = prefixLen;
+               int entryBytes = entry.sizeBytes();
+               if (computeBlockBytes(entryBytes, restart) > blockLimitBytes) {
+                       return false;
+               }
+
+               entriesSumBytes += entryBytes;
+               entries.add(entry);
+               if (restart) {
+                       restartCnt++;
+               }
+               return true;
+       }
+
+       private boolean nextShouldBeRestart() {
+               int cnt = entries.size();
+               return (cnt == 0 || ((cnt + 1) % restartInterval) == 0)
+                               && restartCnt < MAX_RESTARTS;
+       }
+
+       private int computeBlockBytes(int entryBytes, boolean restart) {
+               return computeBlockBytes(
+                               entriesSumBytes + entryBytes,
+                               restartCnt + (restart ? 1 : 0));
+       }
+
+       private static int computeBlockBytes(int entryBytes, int restartCnt) {
+               return 4 // 4-byte block header
+                               + entryBytes
+                               + restartCnt * 3 // restart_offset
+                               + 2; // 2-byte restart_count
+       }
+
+       void writeTo(ReftableOutputStream os) throws IOException {
+               os.beginBlock(blockType);
+               IntList restarts = new IntList(restartCnt);
+               for (Entry entry : entries) {
+                       if (entry.restart) {
+                               restarts.add(os.bytesWrittenInBlock());
+                       }
+                       entry.writeKey(os);
+                       entry.writeValue(os);
+               }
+               if (restarts.size() == 0 || restarts.size() > MAX_RESTARTS) {
+                       throw new IllegalStateException();
+               }
+               for (int i = 0; i < restarts.size(); i++) {
+                       os.writeInt24(restarts.get(i));
+               }
+               os.writeInt16(restarts.size());
+               os.flushBlock();
+       }
+
+       private BlockSizeTooSmallException blockSizeTooSmall(Entry entry) {
+               // Compute size required to fit this entry by itself.
+               int min = FILE_HEADER_LEN + computeBlockBytes(entry.sizeBytes(), 1);
+               return new BlockSizeTooSmallException(min);
+       }
+
+       static int commonPrefix(byte[] a, int n, byte[] b) {
+               int len = Math.min(n, Math.min(a.length, b.length));
+               for (int i = 0; i < len; i++) {
+                       if (a[i] != b[i]) {
+                               return i;
+                       }
+               }
+               return len;
+       }
+
+       static int encodeSuffixAndType(int sfx, int valueType) {
+               return (sfx << 3) | valueType;
+       }
+
+       static int compare(
+                       byte[] a, int ai, int aLen,
+                       byte[] b, int bi, int bLen) {
+               int aEnd = ai + aLen;
+               int bEnd = bi + bLen;
+               while (ai < aEnd && bi < bEnd) {
+                       int c = (a[ai++] & 0xff) - (b[bi++] & 0xff);
+                       if (c != 0) {
+                               return c;
+                       }
+               }
+               return aLen - bLen;
+       }
+
+       static abstract class Entry {
+               static int compare(Entry ea, Entry eb) {
+                       byte[] a = ea.key;
+                       byte[] b = eb.key;
+                       return BlockWriter.compare(a, 0, a.length, b, 0, b.length);
+               }
+
+               final byte[] key;
+               int prefixLen;
+               boolean restart;
+
+               Entry(byte[] key) {
+                       this.key = key;
+               }
+
+               void writeKey(ReftableOutputStream os) {
+                       int sfxLen = key.length - prefixLen;
+                       os.writeVarint(prefixLen);
+                       os.writeVarint(encodeSuffixAndType(sfxLen, valueType()));
+                       os.write(key, prefixLen, sfxLen);
+               }
+
+               int sizeBytes() {
+                       int sfxLen = key.length - prefixLen;
+                       int sfx = encodeSuffixAndType(sfxLen, valueType());
+                       return computeVarintSize(prefixLen)
+                                       + computeVarintSize(sfx)
+                                       + sfxLen
+                                       + valueSize();
+               }
+
+               abstract byte blockType();
+               abstract int valueType();
+               abstract int valueSize();
+               abstract void writeValue(ReftableOutputStream os) throws IOException;
+       }
+
+       static class IndexEntry extends Entry {
+               private final long blockPosition;
+
+               IndexEntry(byte[] key, long blockPosition) {
+                       super(key);
+                       this.blockPosition = blockPosition;
+               }
+
+               @Override
+               byte blockType() {
+                       return INDEX_BLOCK_TYPE;
+               }
+
+               @Override
+               int valueType() {
+                       return 0;
+               }
+
+               @Override
+               int valueSize() {
+                       return computeVarintSize(blockPosition);
+               }
+
+               @Override
+               void writeValue(ReftableOutputStream os) {
+                       os.writeVarint(blockPosition);
+               }
+       }
+
+       static class RefEntry extends Entry {
+               final Ref ref;
+
+               RefEntry(Ref ref) {
+                       super(nameUtf8(ref));
+                       this.ref = ref;
+               }
+
+               @Override
+               byte blockType() {
+                       return REF_BLOCK_TYPE;
+               }
+
+               @Override
+               int valueType() {
+                       if (ref.isSymbolic()) {
+                               return VALUE_SYMREF;
+                       } else if (ref.getStorage() == NEW && ref.getObjectId() == null) {
+                               return VALUE_NONE;
+                       } else if (ref.getPeeledObjectId() != null) {
+                               return VALUE_2ID;
+                       } else {
+                               return VALUE_1ID;
+                       }
+               }
+
+               @Override
+               int valueSize() {
+                       switch (valueType()) {
+                       case VALUE_NONE:
+                               return 0;
+                       case VALUE_1ID:
+                               return OBJECT_ID_LENGTH;
+                       case VALUE_2ID:
+                               return 2 * OBJECT_ID_LENGTH;
+                       case VALUE_SYMREF:
+                               if (ref.isSymbolic()) {
+                                       int nameLen = nameUtf8(ref.getTarget()).length;
+                                       return computeVarintSize(nameLen) + nameLen;
+                               }
+                       }
+                       throw new IllegalStateException();
+               }
+
+               @Override
+               void writeValue(ReftableOutputStream os) throws IOException {
+                       switch (valueType()) {
+                       case VALUE_NONE:
+                               return;
+
+                       case VALUE_1ID: {
+                               ObjectId id1 = ref.getObjectId();
+                               if (!ref.isPeeled()) {
+                                       throw new IOException(JGitText.get().peeledRefIsRequired);
+                               } else if (id1 == null) {
+                                       throw new IOException(JGitText.get().invalidId0);
+                               }
+                               os.writeId(id1);
+                               return;
+                       }
+
+                       case VALUE_2ID: {
+                               ObjectId id1 = ref.getObjectId();
+                               ObjectId id2 = ref.getPeeledObjectId();
+                               if (!ref.isPeeled()) {
+                                       throw new IOException(JGitText.get().peeledRefIsRequired);
+                               } else if (id1 == null || id2 == null) {
+                                       throw new IOException(JGitText.get().invalidId0);
+                               }
+                               os.writeId(id1);
+                               os.writeId(id2);
+                               return;
+                       }
+
+                       case VALUE_SYMREF:
+                               if (ref.isSymbolic()) {
+                                       os.writeVarintString(ref.getTarget().getName());
+                                       return;
+                               }
+                       }
+                       throw new IllegalStateException();
+               }
+
+               private static byte[] nameUtf8(Ref ref) {
+                       return ref.getName().getBytes(UTF_8);
+               }
+       }
+
+       static class ObjEntry extends Entry {
+               final LongList blockPos;
+
+               ObjEntry(int idLen, ObjectId id, LongList blockPos) {
+                       super(key(idLen, id));
+                       this.blockPos = blockPos;
+               }
+
+               private static byte[] key(int idLen, ObjectId id) {
+                       byte[] key = new byte[OBJECT_ID_LENGTH];
+                       id.copyRawTo(key, 0);
+                       if (idLen < OBJECT_ID_LENGTH) {
+                               return Arrays.copyOf(key, idLen);
+                       }
+                       return key;
+               }
+
+               void markScanRequired() {
+                       blockPos.clear();
+               }
+
+               @Override
+               byte blockType() {
+                       return OBJ_BLOCK_TYPE;
+               }
+
+               @Override
+               int valueType() {
+                       int cnt = blockPos.size();
+                       return cnt != 0 && cnt <= VALUE_TYPE_MASK ? cnt : 0;
+               }
+
+               @Override
+               int valueSize() {
+                       int cnt = blockPos.size();
+                       if (cnt == 0) {
+                               return computeVarintSize(0);
+                       }
+
+                       int n = 0;
+                       if (cnt > VALUE_TYPE_MASK) {
+                               n += computeVarintSize(cnt);
+                       }
+                       n += computeVarintSize(blockPos.get(0));
+                       for (int j = 1; j < cnt; j++) {
+                               long prior = blockPos.get(j - 1);
+                               long b = blockPos.get(j);
+                               n += computeVarintSize(b - prior);
+                       }
+                       return n;
+               }
+
+               @Override
+               void writeValue(ReftableOutputStream os) throws IOException {
+                       int cnt = blockPos.size();
+                       if (cnt == 0) {
+                               os.writeVarint(0);
+                               return;
+                       }
+
+                       if (cnt > VALUE_TYPE_MASK) {
+                               os.writeVarint(cnt);
+                       }
+                       os.writeVarint(blockPos.get(0));
+                       for (int j = 1; j < cnt; j++) {
+                               long prior = blockPos.get(j - 1);
+                               long b = blockPos.get(j);
+                               os.writeVarint(b - prior);
+                       }
+               }
+       }
+
+       static class DeleteLogEntry extends Entry {
+               DeleteLogEntry(String refName, long updateIndex) {
+                       super(LogEntry.key(refName, updateIndex));
+               }
+
+               @Override
+               byte blockType() {
+                       return LOG_BLOCK_TYPE;
+               }
+
+               @Override
+               int valueType() {
+                       return LOG_NONE;
+               }
+
+               @Override
+               int valueSize() {
+                       return 0;
+               }
+
+               @Override
+               void writeValue(ReftableOutputStream os) {
+                       // Nothing in a delete log record.
+               }
+       }
+
+       static class LogEntry extends Entry {
+               final ObjectId oldId;
+               final ObjectId newId;
+               final long timeSecs;
+               final short tz;
+               final byte[] name;
+               final byte[] email;
+               final byte[] msg;
+
+               LogEntry(String refName, long updateIndex, PersonIdent who,
+                               ObjectId oldId, ObjectId newId, String message) {
+                       super(key(refName, updateIndex));
+
+                       this.oldId = oldId;
+                       this.newId = newId;
+                       this.timeSecs = who.getWhen().getTime() / 1000L;
+                       this.tz = (short) who.getTimeZoneOffset();
+                       this.name = who.getName().getBytes(UTF_8);
+                       this.email = who.getEmailAddress().getBytes(UTF_8);
+                       this.msg = message.getBytes(UTF_8);
+               }
+
+               static byte[] key(String ref, long index) {
+                       byte[] name = ref.getBytes(UTF_8);
+                       byte[] key = Arrays.copyOf(name, name.length + 1 + 8);
+                       NB.encodeInt64(key, key.length - 8, reverseUpdateIndex(index));
+                       return key;
+               }
+
+               @Override
+               byte blockType() {
+                       return LOG_BLOCK_TYPE;
+               }
+
+               @Override
+               int valueType() {
+                       return LOG_DATA;
+               }
+
+               @Override
+               int valueSize() {
+                       return 2 * OBJECT_ID_LENGTH
+                                       + computeVarintSize(name.length) + name.length
+                                       + computeVarintSize(email.length) + email.length
+                                       + computeVarintSize(timeSecs)
+                                       + 2 // tz
+                                       + computeVarintSize(msg.length) + msg.length;
+               }
+
+               @Override
+               void writeValue(ReftableOutputStream os) {
+                       os.writeId(oldId);
+                       os.writeId(newId);
+                       os.writeVarintString(name);
+                       os.writeVarintString(email);
+                       os.writeVarint(timeSecs);
+                       os.writeInt16(tz);
+                       os.writeVarintString(msg);
+               }
+       }
+}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/ReftableConfig.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/ReftableConfig.java
new file mode 100644 (file)
index 0000000..f7a1fbe
--- /dev/null
@@ -0,0 +1,216 @@
+/*
+ * 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.internal.storage.reftable.ReftableConstants.MAX_BLOCK_SIZE;
+
+import org.eclipse.jgit.lib.Config;
+import org.eclipse.jgit.lib.Repository;
+
+/** Configuration used by a reftable writer when constructing the stream. */
+public class ReftableConfig {
+       private int refBlockSize = 4 << 10;
+       private int logBlockSize;
+       private int restartInterval;
+       private int maxIndexLevels;
+       private boolean alignBlocks = true;
+       private boolean indexObjects = true;
+
+       /** Create a default configuration. */
+       public ReftableConfig() {
+       }
+
+       /**
+        * Create a configuration honoring the repository's settings.
+        *
+        * @param db
+        *            the repository to read settings from. The repository is not
+        *            retained by the new configuration, instead its settings are
+        *            copied during the constructor.
+        */
+       public ReftableConfig(Repository db) {
+               fromConfig(db.getConfig());
+       }
+
+       /**
+        * Create a configuration honoring settings in a {@link Config}.
+        *
+        * @param cfg
+        *            the source to read settings from. The source is not retained
+        *            by the new configuration, instead its settings are copied
+        *            during the constructor.
+        */
+       public ReftableConfig(Config cfg) {
+               fromConfig(cfg);
+       }
+
+       /**
+        * Copy an existing configuration to a new instance.
+        *
+        * @param cfg
+        *            the source configuration to copy from.
+        */
+       public ReftableConfig(ReftableConfig cfg) {
+               this.refBlockSize = cfg.refBlockSize;
+               this.logBlockSize = cfg.logBlockSize;
+               this.restartInterval = cfg.restartInterval;
+               this.maxIndexLevels = cfg.maxIndexLevels;
+               this.alignBlocks = cfg.alignBlocks;
+               this.indexObjects = cfg.indexObjects;
+       }
+
+       /** @return desired output block size for references, in bytes */
+       public int getRefBlockSize() {
+               return refBlockSize;
+       }
+
+       /**
+        * @param szBytes
+        *            desired output block size for references, in bytes.
+        */
+       public void setRefBlockSize(int szBytes) {
+               if (szBytes > MAX_BLOCK_SIZE) {
+                       throw new IllegalArgumentException();
+               }
+               refBlockSize = Math.max(0, szBytes);
+       }
+
+       /**
+        * @return desired output block size for log entries, in bytes. If 0 the
+        *         writer will default to {@code 2 * getRefBlockSize()}.
+        */
+       public int getLogBlockSize() {
+               return logBlockSize;
+       }
+
+       /**
+        * @param szBytes
+        *            desired output block size for log entries, in bytes. If 0 will
+        *            default to {@code 2 * getRefBlockSize()}.
+        */
+       public void setLogBlockSize(int szBytes) {
+               if (szBytes > MAX_BLOCK_SIZE) {
+                       throw new IllegalArgumentException();
+               }
+               logBlockSize = Math.max(0, szBytes);
+       }
+
+       /** @return number of references between binary search markers. */
+       public int getRestartInterval() {
+               return restartInterval;
+       }
+
+       /**
+        * @param interval
+        *            number of references between binary search markers. If
+        *            {@code interval} is 0 (default), the writer will select a
+        *            default value based on the block size.
+        */
+       public void setRestartInterval(int interval) {
+               restartInterval = Math.max(0, interval);
+       }
+
+       /** @return maximum depth of the index; 0 for unlimited. */
+       public int getMaxIndexLevels() {
+               return maxIndexLevels;
+       }
+
+       /**
+        * @param levels
+        *            maximum number of levels to use in indexes. Lower levels of
+        *            the index respect {@link #getRefBlockSize()}, and the highest
+        *            level may exceed that if the number of levels is limited.
+        */
+       public void setMaxIndexLevels(int levels) {
+               maxIndexLevels = Math.max(0, levels);
+       }
+
+       /** @return {@code true} if the writer should align blocks. */
+       public boolean isAlignBlocks() {
+               return alignBlocks;
+       }
+
+       /**
+        * @param align
+        *            if {@code true} blocks are written aligned to multiples of
+        *            {@link #getRefBlockSize()}. May increase file size due to NUL
+        *            padding bytes added between blocks. Default is {@code true}.
+        */
+       public void setAlignBlocks(boolean align) {
+               alignBlocks = align;
+       }
+
+       /** @return {@code true} if the writer should index object to ref. */
+       public boolean isIndexObjects() {
+               return indexObjects;
+       }
+
+       /**
+        * @param index
+        *            if {@code true} the reftable may include additional storage to
+        *            efficiently map from {@code ObjectId} to reference names. By
+        *            default, {@code true}.
+        */
+       public void setIndexObjects(boolean index) {
+               indexObjects = index;
+       }
+
+       /**
+        * Update properties by setting fields from the configuration.
+        *
+        * If a property's corresponding variable is not defined in the supplied
+        * configuration, then it is left unmodified.
+        *
+        * @param rc
+        *            configuration to read properties from.
+        */
+       public void fromConfig(Config rc) {
+               refBlockSize = rc.getInt("reftable", "blockSize", refBlockSize); //$NON-NLS-1$ //$NON-NLS-2$
+               logBlockSize = rc.getInt("reftable", "logBlockSize", logBlockSize); //$NON-NLS-1$ //$NON-NLS-2$
+               restartInterval = rc.getInt("reftable", "restartInterval", restartInterval); //$NON-NLS-1$ //$NON-NLS-2$
+               maxIndexLevels = rc.getInt("reftable", "indexLevels", maxIndexLevels); //$NON-NLS-1$ //$NON-NLS-2$
+               alignBlocks = rc.getBoolean("reftable", "alignBlocks", alignBlocks); //$NON-NLS-1$ //$NON-NLS-2$
+               indexObjects = rc.getBoolean("reftable", "indexObjects", indexObjects); //$NON-NLS-1$ //$NON-NLS-2$
+       }
+}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/ReftableConstants.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/ReftableConstants.java
new file mode 100644 (file)
index 0000000..0b89327
--- /dev/null
@@ -0,0 +1,85 @@
+/*
+ * 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;
+
+class ReftableConstants {
+       static final byte[] FILE_HEADER_MAGIC = { 'R', 'E', 'F', 'T' };
+       static final byte VERSION_1 = (byte) 1;
+
+       static final int FILE_HEADER_LEN = 24;
+       static final int FILE_FOOTER_LEN = 68;
+
+       static final byte FILE_BLOCK_TYPE = 'R';
+       static final byte REF_BLOCK_TYPE = 'r';
+       static final byte OBJ_BLOCK_TYPE = 'o';
+       static final byte LOG_BLOCK_TYPE = 'g';
+       static final byte INDEX_BLOCK_TYPE = 'i';
+
+       static final int VALUE_NONE = 0x0;
+       static final int VALUE_1ID = 0x1;
+       static final int VALUE_2ID = 0x2;
+       static final int VALUE_SYMREF = 0x3;
+       static final int VALUE_TYPE_MASK = 0x7;
+
+       static final int LOG_NONE = 0x0;
+       static final int LOG_DATA = 0x1;
+
+       static final int MAX_BLOCK_SIZE = (1 << 24) - 1;
+       static final int MAX_RESTARTS = 65535;
+
+       static boolean isFileHeaderMagic(byte[] buf, int o, int n) {
+               return (n - o) >= FILE_HEADER_MAGIC.length
+                               && buf[o + 0] == FILE_HEADER_MAGIC[0]
+                               && buf[o + 1] == FILE_HEADER_MAGIC[1]
+                               && buf[o + 2] == FILE_HEADER_MAGIC[2]
+                               && buf[o + 3] == FILE_HEADER_MAGIC[3];
+       }
+
+       static long reverseUpdateIndex(long time) {
+               return 0xffffffffffffffffL - time;
+       }
+
+       private ReftableConstants() {
+       }
+}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/ReftableOutputStream.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/ReftableOutputStream.java
new file mode 100644 (file)
index 0000000..a24619b
--- /dev/null
@@ -0,0 +1,247 @@
+/*
+ * 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 java.nio.charset.StandardCharsets.UTF_8;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.FILE_HEADER_LEN;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.INDEX_BLOCK_TYPE;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.LOG_BLOCK_TYPE;
+import static org.eclipse.jgit.lib.Constants.OBJECT_ID_LENGTH;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.util.Arrays;
+import java.util.zip.Deflater;
+import java.util.zip.DeflaterOutputStream;
+
+import org.eclipse.jgit.internal.JGitText;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.util.NB;
+import org.eclipse.jgit.util.io.CountingOutputStream;
+
+/**
+ * Wrapper to assist formatting a reftable to an {@link OutputStream}.
+ * <p>
+ * Internally buffers at block size boundaries, flushing only complete blocks to
+ * the {@code OutputStream}.
+ */
+class ReftableOutputStream extends OutputStream {
+       private final byte[] tmp = new byte[10];
+       private final CountingOutputStream out;
+       private final boolean alignBlocks;
+
+       private Deflater deflater;
+       private DeflaterOutputStream compressor;
+
+       private int blockType;
+       private int blockSize;
+       private int blockStart;
+       private byte[] blockBuf;
+       private int cur;
+       private long paddingUsed;
+
+       ReftableOutputStream(OutputStream os, int bs, boolean align) {
+               blockSize = bs;
+               blockBuf = new byte[bs];
+               alignBlocks = align;
+               out = new CountingOutputStream(os);
+       }
+
+       void setBlockSize(int bs) {
+               blockSize = bs;
+       }
+
+       @Override
+       public void write(int b) {
+               ensureBytesAvailableInBlockBuf(1);
+               blockBuf[cur++] = (byte) b;
+       }
+
+       @Override
+       public void write(byte[] b, int off, int cnt) {
+               ensureBytesAvailableInBlockBuf(cnt);
+               System.arraycopy(b, off, blockBuf, cur, cnt);
+               cur += cnt;
+       }
+
+       int bytesWrittenInBlock() {
+               return cur;
+       }
+
+       int bytesAvailableInBlock() {
+               return blockSize - cur;
+       }
+
+       long paddingUsed() {
+               return paddingUsed;
+       }
+
+       /** @return bytes flushed; excludes {@link #bytesWrittenInBlock()}. */
+       long size() {
+               return out.getCount();
+       }
+
+       static int computeVarintSize(long val) {
+               int n = 1;
+               for (; (val >>>= 7) != 0; n++) {
+                       val--;
+               }
+               return n;
+       }
+
+       void writeVarint(long val) {
+               int n = tmp.length;
+               tmp[--n] = (byte) (val & 0x7f);
+               while ((val >>>= 7) != 0) {
+                       tmp[--n] = (byte) (0x80 | (--val & 0x7F));
+               }
+               write(tmp, n, tmp.length - n);
+       }
+
+       void writeInt16(int val) {
+               ensureBytesAvailableInBlockBuf(2);
+               NB.encodeInt16(blockBuf, cur, val);
+               cur += 2;
+       }
+
+       void writeInt24(int val) {
+               ensureBytesAvailableInBlockBuf(3);
+               NB.encodeInt24(blockBuf, cur, val);
+               cur += 3;
+       }
+
+       void writeId(ObjectId id) {
+               ensureBytesAvailableInBlockBuf(OBJECT_ID_LENGTH);
+               id.copyRawTo(blockBuf, cur);
+               cur += OBJECT_ID_LENGTH;
+       }
+
+       void writeVarintString(String s) {
+               writeVarintString(s.getBytes(UTF_8));
+       }
+
+       void writeVarintString(byte[] msg) {
+               writeVarint(msg.length);
+               write(msg, 0, msg.length);
+       }
+
+       private void ensureBytesAvailableInBlockBuf(int cnt) {
+               if (cur + cnt > blockBuf.length) {
+                       int n = Math.max(cur + cnt, blockBuf.length * 2);
+                       blockBuf = Arrays.copyOf(blockBuf, n);
+               }
+       }
+
+       void flushFileHeader() throws IOException {
+               if (cur == FILE_HEADER_LEN && out.getCount() == 0) {
+                       out.write(blockBuf, 0, cur);
+                       cur = 0;
+               }
+       }
+
+       void beginBlock(byte type) {
+               blockType = type;
+               blockStart = cur;
+               cur += 4; // reserve space for 4-byte block header.
+       }
+
+       void flushBlock() throws IOException {
+               if (cur > blockSize && blockType != INDEX_BLOCK_TYPE) {
+                       throw new IOException(JGitText.get().overflowedReftableBlock);
+               }
+               NB.encodeInt32(blockBuf, blockStart, (blockType << 24) | cur);
+
+               if (blockType == LOG_BLOCK_TYPE) {
+                       // Log blocks are deflated after the block header.
+                       out.write(blockBuf, 0, 4);
+                       if (deflater != null) {
+                               deflater.reset();
+                       } else {
+                               deflater = new Deflater(Deflater.BEST_COMPRESSION);
+                               compressor = new DeflaterOutputStream(out, deflater);
+                       }
+                       compressor.write(blockBuf, 4, cur - 4);
+                       compressor.finish();
+               } else {
+                       // Other blocks are uncompressed.
+                       out.write(blockBuf, 0, cur);
+               }
+
+               cur = 0;
+               blockType = 0;
+               blockStart = 0;
+       }
+
+       void padBetweenBlocksToNextBlock() throws IOException {
+               if (alignBlocks) {
+                       long m = size() % blockSize;
+                       if (m > 0) {
+                               int pad = blockSize - (int) m;
+                               ensureBytesAvailableInBlockBuf(pad);
+                               Arrays.fill(blockBuf, 0, pad, (byte) 0);
+                               out.write(blockBuf, 0, pad);
+                               paddingUsed += pad;
+                       }
+               }
+       }
+
+       int estimatePadBetweenBlocks(int currentBlockSize) {
+               if (alignBlocks) {
+                       long m = (size() + currentBlockSize) % blockSize;
+                       return m > 0 ? blockSize - (int) m : 0;
+               }
+               return 0;
+       }
+
+       void finishFile() throws IOException {
+               // File footer doesn't need patching for the block start.
+               // Just flush what has been buffered.
+               out.write(blockBuf, 0, cur);
+               cur = 0;
+
+               if (deflater != null) {
+                       deflater.end();
+               }
+       }
+}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/ReftableWriter.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/ReftableWriter.java
new file mode 100644 (file)
index 0000000..45b759f
--- /dev/null
@@ -0,0 +1,792 @@
+/*
+ * 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 java.lang.Math.log;
+import static org.eclipse.jgit.internal.storage.reftable.BlockWriter.padBetweenBlocks;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.FILE_FOOTER_LEN;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.FILE_HEADER_LEN;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.FILE_HEADER_MAGIC;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.INDEX_BLOCK_TYPE;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.LOG_BLOCK_TYPE;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.MAX_BLOCK_SIZE;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.MAX_RESTARTS;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.OBJ_BLOCK_TYPE;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.REF_BLOCK_TYPE;
+import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.VERSION_1;
+import static org.eclipse.jgit.lib.Constants.OBJECT_ID_LENGTH;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Set;
+import java.util.zip.CRC32;
+
+import org.eclipse.jgit.annotations.Nullable;
+import org.eclipse.jgit.internal.storage.reftable.BlockWriter.DeleteLogEntry;
+import org.eclipse.jgit.internal.storage.reftable.BlockWriter.Entry;
+import org.eclipse.jgit.internal.storage.reftable.BlockWriter.IndexEntry;
+import org.eclipse.jgit.internal.storage.reftable.BlockWriter.LogEntry;
+import org.eclipse.jgit.internal.storage.reftable.BlockWriter.ObjEntry;
+import org.eclipse.jgit.internal.storage.reftable.BlockWriter.RefEntry;
+import org.eclipse.jgit.lib.AbbreviatedObjectId;
+import org.eclipse.jgit.lib.AnyObjectId;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.ObjectIdOwnerMap;
+import org.eclipse.jgit.lib.ObjectIdSubclassMap;
+import org.eclipse.jgit.lib.PersonIdent;
+import org.eclipse.jgit.lib.Ref;
+import org.eclipse.jgit.util.LongList;
+import org.eclipse.jgit.util.NB;
+
+/**
+ * Writes a reftable formatted file.
+ * <p>
+ * A reftable can be written in a streaming fashion, provided the caller sorts
+ * all references. A {@link ReftableWriter} is single-use, and not thread-safe.
+ */
+public class ReftableWriter {
+       private ReftableConfig config;
+       private int refBlockSize;
+       private int logBlockSize;
+       private int restartInterval;
+       private int maxIndexLevels;
+       private boolean alignBlocks;
+       private boolean indexObjects;
+
+       private long minUpdateIndex;
+       private long maxUpdateIndex;
+
+       private ReftableOutputStream out;
+       private ObjectIdSubclassMap<RefList> obj2ref;
+
+       private BlockWriter cur;
+       private Section refs;
+       private Section objs;
+       private Section logs;
+       private int objIdLen;
+       private Stats stats;
+
+       /** Initialize a writer with a default configuration. */
+       public ReftableWriter() {
+               this(new ReftableConfig());
+       }
+
+       /**
+        * Initialize a writer with a specific configuration.
+        *
+        * @param cfg
+        *            configuration for the writer.
+        */
+       public ReftableWriter(ReftableConfig cfg) {
+               config = cfg;
+       }
+
+       /**
+        * @param cfg
+        *            configuration for the writer.
+        * @return {@code this}
+        */
+       public ReftableWriter setConfig(ReftableConfig cfg) {
+               this.config = cfg != null ? cfg : new ReftableConfig();
+               return this;
+       }
+
+       /**
+        * @param min
+        *            the minimum update index for log entries that appear in this
+        *            reftable. This should be 1 higher than the prior reftable's
+        *            {@code maxUpdateIndex} if this table will be used in a stack.
+        * @return {@code this}
+        */
+       public ReftableWriter setMinUpdateIndex(long min) {
+               minUpdateIndex = min;
+               return this;
+       }
+
+       /**
+        * @param max
+        *            the maximum update index for log entries that appear in this
+        *            reftable. This should be at least 1 higher than the prior
+        *            reftable's {@code maxUpdateIndex} if this table will be used
+        *            in a stack.
+        * @return {@code this}
+        */
+       public ReftableWriter setMaxUpdateIndex(long max) {
+               maxUpdateIndex = max;
+               return this;
+       }
+
+       /**
+        * Begin writing the reftable.
+        *
+        * @param os
+        *            stream to write the table to. Caller is responsible for
+        *            closing the stream after invoking {@link #finish()}.
+        * @return {@code this}
+        * @throws IOException
+        *             if reftable header cannot be written.
+        */
+       public ReftableWriter begin(OutputStream os) throws IOException {
+               refBlockSize = config.getRefBlockSize();
+               logBlockSize = config.getLogBlockSize();
+               restartInterval = config.getRestartInterval();
+               maxIndexLevels = config.getMaxIndexLevels();
+               alignBlocks = config.isAlignBlocks();
+               indexObjects = config.isIndexObjects();
+
+               if (refBlockSize <= 0) {
+                       refBlockSize = 4 << 10;
+               } else if (refBlockSize > MAX_BLOCK_SIZE) {
+                       throw new IllegalArgumentException();
+               }
+               if (logBlockSize <= 0) {
+                       logBlockSize = 2 * refBlockSize;
+               }
+               if (restartInterval <= 0) {
+                       restartInterval = refBlockSize < (60 << 10) ? 16 : 64;
+               }
+
+               out = new ReftableOutputStream(os, refBlockSize, alignBlocks);
+               refs = new Section(REF_BLOCK_TYPE);
+               if (indexObjects) {
+                       obj2ref = new ObjectIdSubclassMap<>();
+               }
+               writeFileHeader();
+               return this;
+       }
+
+       /**
+        * Sort a collection of references and write them to the reftable.
+        *
+        * @param refsToPack
+        *            references to sort and write.
+        * @return {@code this}
+        * @throws IOException
+        *             if reftable cannot be written.
+        */
+       public ReftableWriter sortAndWriteRefs(Collection<Ref> refsToPack)
+                       throws IOException {
+               Iterator<RefEntry> itr = refsToPack.stream()
+                               .map(RefEntry::new)
+                               .sorted(Entry::compare)
+                               .iterator();
+               while (itr.hasNext()) {
+                       RefEntry entry = itr.next();
+                       long blockPos = refs.write(entry);
+                       indexRef(entry.ref, blockPos);
+               }
+               return this;
+       }
+
+       /**
+        * Write one reference to the reftable.
+        * <p>
+        * References must be passed in sorted order.
+        *
+        * @param ref
+        *            the reference to store.
+        * @throws IOException
+        *             if reftable cannot be written.
+        */
+       public void writeRef(Ref ref) throws IOException {
+               long blockPos = refs.write(new RefEntry(ref));
+               indexRef(ref, blockPos);
+       }
+
+       private void indexRef(Ref ref, long blockPos) {
+               if (indexObjects && !ref.isSymbolic()) {
+                       indexId(ref.getObjectId(), blockPos);
+                       indexId(ref.getPeeledObjectId(), blockPos);
+               }
+       }
+
+       private void indexId(ObjectId id, long blockPos) {
+               if (id != null) {
+                       RefList l = obj2ref.get(id);
+                       if (l == null) {
+                               l = new RefList(id);
+                               obj2ref.add(l);
+                       }
+                       l.addBlock(blockPos);
+               }
+       }
+
+       /**
+        * Write one reflog entry to the reftable.
+        * <p>
+        * Reflog entries must be written in reference name and descending
+        * {@code updateIndex} (highest first) order.
+        *
+        * @param ref
+        *            name of the reference.
+        * @param updateIndex
+        *            identifier of the transaction that created the log record. The
+        *            {@code updateIndex} must be unique within the scope of
+        *            {@code ref}, and must be within the bounds defined by
+        *            {@code minUpdateIndex <= updateIndex <= maxUpdateIndex}.
+        * @param who
+        *            committer of the reflog entry.
+        * @param oldId
+        *            prior id; pass {@link ObjectId#zeroId()} for creations.
+        * @param newId
+        *            new id; pass {@link ObjectId#zeroId()} for deletions.
+        * @param message
+        *            optional message (may be null).
+        * @throws IOException
+        *             if reftable cannot be written.
+        */
+       public void writeLog(String ref, long updateIndex, PersonIdent who,
+                       ObjectId oldId, ObjectId newId, @Nullable String message)
+                                       throws IOException {
+               String msg = message != null ? message : ""; //$NON-NLS-1$
+               beginLog();
+               logs.write(new LogEntry(ref, updateIndex, who, oldId, newId, msg));
+       }
+
+       /**
+        * Record deletion of one reflog entry in this reftable.
+        *
+        * <p>
+        * The deletion can shadow an entry stored in a lower table in the stack.
+        * This is useful for {@code refs/stash} and dropping an entry from its
+        * reflog.
+        * <p>
+        * Deletion must be properly interleaved in sorted updateIndex order with
+        * any other logs written by
+        * {@link #writeLog(String, long, PersonIdent, ObjectId, ObjectId, String)}.
+        *
+        * @param ref
+        *            the ref to delete (hide) a reflog entry from.
+        * @param updateIndex
+        *            the update index that must be hidden.
+        * @throws IOException
+        *             if reftable cannot be written.
+        */
+       public void deleteLog(String ref, long updateIndex) throws IOException {
+               beginLog();
+               logs.write(new DeleteLogEntry(ref, updateIndex));
+       }
+
+       private void beginLog() throws IOException {
+               if (logs == null) {
+                       finishRefAndObjSections(); // close prior ref blocks and their index, if present.
+                       out.flushFileHeader();
+                       out.setBlockSize(logBlockSize);
+                       logs = new Section(LOG_BLOCK_TYPE);
+               }
+       }
+
+       /**
+        * @return an estimate of the current size in bytes of the reftable, if it
+        *         was finished right now. Estimate is only accurate if
+        *         {@link ReftableConfig#setIndexObjects(boolean)} is {@code false}
+        *         and {@link ReftableConfig#setMaxIndexLevels(int)} is {@code 1}.
+        */
+       public long estimateTotalBytes() {
+               long bytes = out.size();
+               if (bytes == 0) {
+                       bytes += FILE_HEADER_LEN;
+               }
+               if (cur != null) {
+                       long curBlockPos = out.size();
+                       int sz = cur.currentSize();
+                       bytes += sz;
+
+                       IndexBuilder idx = null;
+                       if (cur.blockType() == REF_BLOCK_TYPE) {
+                               idx = refs.idx;
+                       } else if (cur.blockType() == LOG_BLOCK_TYPE) {
+                               idx = logs.idx;
+                       }
+                       if (idx != null && shouldHaveIndex(idx)) {
+                               if (idx == refs.idx) {
+                                       bytes += out.estimatePadBetweenBlocks(sz);
+                               }
+                               bytes += idx.estimateBytes(curBlockPos);
+                       }
+               }
+               bytes += FILE_FOOTER_LEN;
+               return bytes;
+       }
+
+       /**
+        * Finish writing the reftable by writing its trailer.
+        *
+        * @return {@code this}
+        * @throws IOException
+        *             if reftable cannot be written.
+        */
+       public ReftableWriter finish() throws IOException {
+               finishRefAndObjSections();
+               finishLogSection();
+               writeFileFooter();
+               out.finishFile();
+
+               stats = new Stats(this, out);
+               out = null;
+               obj2ref = null;
+               cur = null;
+               refs = null;
+               objs = null;
+               logs = null;
+               return this;
+       }
+
+       private void finishRefAndObjSections() throws IOException {
+               if (cur != null && cur.blockType() == REF_BLOCK_TYPE) {
+                       refs.finishSectionMaybeWriteIndex();
+                       if (indexObjects && !obj2ref.isEmpty() && refs.idx.bytes > 0) {
+                               writeObjBlocks();
+                       }
+                       obj2ref = null;
+               }
+       }
+
+       private void writeObjBlocks() throws IOException {
+               List<RefList> sorted = sortById(obj2ref);
+               obj2ref = null;
+               objIdLen = shortestUniqueAbbreviation(sorted);
+
+               out.padBetweenBlocksToNextBlock();
+               objs = new Section(OBJ_BLOCK_TYPE);
+               objs.entryCnt = sorted.size();
+               for (RefList l : sorted) {
+                       objs.write(new ObjEntry(objIdLen, l, l.blockPos));
+               }
+               objs.finishSectionMaybeWriteIndex();
+       }
+
+       private void finishLogSection() throws IOException {
+               if (cur != null && cur.blockType() == LOG_BLOCK_TYPE) {
+                       logs.finishSectionMaybeWriteIndex();
+               }
+       }
+
+       private boolean shouldHaveIndex(IndexBuilder idx) {
+               int threshold;
+               if (idx == refs.idx && alignBlocks) {
+                       threshold = 4;
+               } else {
+                       threshold = 1;
+               }
+               return idx.entries.size() + (cur != null ? 1 : 0) > threshold;
+       }
+
+       private void writeFileHeader() {
+               byte[] hdr = new byte[FILE_HEADER_LEN];
+               encodeHeader(hdr);
+               out.write(hdr, 0, FILE_HEADER_LEN);
+       }
+
+       private void encodeHeader(byte[] hdr) {
+               System.arraycopy(FILE_HEADER_MAGIC, 0, hdr, 0, 4);
+               int bs = alignBlocks ? refBlockSize : 0;
+               NB.encodeInt32(hdr, 4, (VERSION_1 << 24) | bs);
+               NB.encodeInt64(hdr, 8, minUpdateIndex);
+               NB.encodeInt64(hdr, 16, maxUpdateIndex);
+       }
+
+       private void writeFileFooter() {
+               int ftrLen = FILE_FOOTER_LEN;
+               byte[] ftr = new byte[ftrLen];
+               encodeHeader(ftr);
+
+               NB.encodeInt64(ftr, 24, indexPosition(refs));
+               NB.encodeInt64(ftr, 32, (firstBlockPosition(objs) << 5) | objIdLen);
+               NB.encodeInt64(ftr, 40, indexPosition(objs));
+               NB.encodeInt64(ftr, 48, firstBlockPosition(logs));
+               NB.encodeInt64(ftr, 56, indexPosition(logs));
+
+               CRC32 crc = new CRC32();
+               crc.update(ftr, 0, ftrLen - 4);
+               NB.encodeInt32(ftr, ftrLen - 4, (int) crc.getValue());
+
+               out.write(ftr, 0, ftrLen);
+       }
+
+       private static long firstBlockPosition(@Nullable Section s) {
+               return s != null ? s.firstBlockPosition : 0;
+       }
+
+       private static long indexPosition(@Nullable Section s) {
+               return s != null && s.idx != null ? s.idx.rootPosition : 0;
+       }
+
+       /** @return statistics of the last written reftable. */
+       public Stats getStats() {
+               return stats;
+       }
+
+       /** Statistics about a written reftable. */
+       public static class Stats {
+               private final int refBlockSize;
+               private final int logBlockSize;
+               private final int restartInterval;
+
+               private final long minUpdateIndex;
+               private final long maxUpdateIndex;
+
+               private final long refCnt;
+               private final long objCnt;
+               private final int objIdLen;
+               private final long logCnt;
+               private final long refBytes;
+               private final long objBytes;
+               private final long logBytes;
+               private final long paddingUsed;
+               private final long totalBytes;
+
+               private final int refIndexSize;
+               private final int refIndexLevels;
+               private final int objIndexSize;
+               private final int objIndexLevels;
+
+               Stats(ReftableWriter w, ReftableOutputStream o) {
+                       refBlockSize = w.refBlockSize;
+                       logBlockSize = w.logBlockSize;
+                       restartInterval = w.restartInterval;
+
+                       minUpdateIndex = w.minUpdateIndex;
+                       maxUpdateIndex = w.maxUpdateIndex;
+                       paddingUsed = o.paddingUsed();
+                       totalBytes = o.size();
+
+                       refCnt = w.refs.entryCnt;
+                       refBytes = w.refs.bytes;
+
+                       objCnt = w.objs != null ? w.objs.entryCnt : 0;
+                       objBytes = w.objs != null ? w.objs.bytes : 0;
+                       objIdLen = w.objIdLen;
+
+                       logCnt = w.logs != null ? w.logs.entryCnt : 0;
+                       logBytes = w.logs != null ? w.logs.bytes : 0;
+
+                       IndexBuilder refIdx = w.refs.idx;
+                       refIndexSize = refIdx.bytes;
+                       refIndexLevels = refIdx.levels;
+
+                       IndexBuilder objIdx = w.objs != null ? w.objs.idx : null;
+                       objIndexSize = objIdx != null ? objIdx.bytes : 0;
+                       objIndexLevels = objIdx != null ? objIdx.levels : 0;
+               }
+
+               /** @return number of bytes in a ref block. */
+               public int refBlockSize() {
+                       return refBlockSize;
+               }
+
+               /** @return number of bytes to compress into a log block. */
+               public int logBlockSize() {
+                       return logBlockSize;
+               }
+
+               /** @return number of references between binary search markers. */
+               public int restartInterval() {
+                       return restartInterval;
+               }
+
+               /** @return smallest update index contained in this reftable. */
+               public long minUpdateIndex() {
+                       return minUpdateIndex;
+               }
+
+               /** @return largest update index contained in this reftable. */
+               public long maxUpdateIndex() {
+                       return maxUpdateIndex;
+               }
+
+               /** @return total number of references in the reftable. */
+               public long refCount() {
+                       return refCnt;
+               }
+
+               /** @return number of unique objects in the reftable. */
+               public long objCount() {
+                       return objCnt;
+               }
+
+               /** @return total number of log records in the reftable. */
+               public long logCount() {
+                       return logCnt;
+               }
+
+               /** @return number of bytes for references, including ref index. */
+               public long refBytes() {
+                       return refBytes;
+               }
+
+               /** @return number of bytes for objects, including object index. */
+               public long objBytes() {
+                       return objBytes;
+               }
+
+               /** @return number of bytes for log, including log index. */
+               public long logBytes() {
+                       return logBytes;
+               }
+
+               /** @return total number of bytes in the reftable. */
+               public long totalBytes() {
+                       return totalBytes;
+               }
+
+               /** @return bytes of padding used to maintain block alignment. */
+               public long paddingBytes() {
+                       return paddingUsed;
+               }
+
+               /** @return number of bytes in the ref index; 0 if no index was used. */
+               public int refIndexSize() {
+                       return refIndexSize;
+               }
+
+               /** @return number of levels in the ref index. */
+               public int refIndexLevels() {
+                       return refIndexLevels;
+               }
+
+               /** @return number of bytes in the object index; 0 if no index. */
+               public int objIndexSize() {
+                       return objIndexSize;
+               }
+
+               /** @return number of levels in the object index. */
+               public int objIndexLevels() {
+                       return objIndexLevels;
+               }
+
+               /**
+                * @return number of bytes required to uniquely identify all objects in
+                *         the reftable. Unique abbreviations in hex would be
+                *         {@code 2 * objIdLength()}.
+                */
+               public int objIdLength() {
+                       return objIdLen;
+               }
+       }
+
+       private static List<RefList> sortById(ObjectIdSubclassMap<RefList> m) {
+               List<RefList> s = new ArrayList<>(m.size());
+               for (RefList l : m) {
+                       s.add(l);
+               }
+               Collections.sort(s);
+               return s;
+       }
+
+       private static int shortestUniqueAbbreviation(List<RefList> in) {
+               // Estimate minimum number of bytes necessary for unique abbreviations.
+               int bytes = Math.max(2, (int) (log(in.size()) / log(8)));
+               Set<AbbreviatedObjectId> tmp = new HashSet<>((int) (in.size() * 0.75f));
+               retry: for (;;) {
+                       int hexLen = bytes * 2;
+                       for (ObjectId id : in) {
+                               AbbreviatedObjectId a = id.abbreviate(hexLen);
+                               if (!tmp.add(a)) {
+                                       if (++bytes >= OBJECT_ID_LENGTH) {
+                                               return OBJECT_ID_LENGTH;
+                                       }
+                                       tmp.clear();
+                                       continue retry;
+                               }
+                       }
+                       return bytes;
+               }
+       }
+
+       private static class RefList extends ObjectIdOwnerMap.Entry {
+               final LongList blockPos = new LongList(2);
+
+               RefList(AnyObjectId id) {
+                       super(id);
+               }
+
+               void addBlock(long pos) {
+                       if (!blockPos.contains(pos)) {
+                               blockPos.add(pos);
+                       }
+               }
+       }
+
+       private class Section {
+               final IndexBuilder idx;
+               final long firstBlockPosition;
+
+               long entryCnt;
+               long bytes;
+
+               Section(byte keyType) {
+                       idx = new IndexBuilder(keyType);
+                       firstBlockPosition = out.size();
+               }
+
+               long write(BlockWriter.Entry entry) throws IOException {
+                       if (cur == null) {
+                               beginBlock(entry);
+                       } else if (!cur.tryAdd(entry)) {
+                               flushCurBlock();
+                               if (cur.padBetweenBlocks()) {
+                                       out.padBetweenBlocksToNextBlock();
+                               }
+                               beginBlock(entry);
+                       }
+                       entryCnt++;
+                       return out.size();
+               }
+
+               private void beginBlock(BlockWriter.Entry entry)
+                               throws BlockSizeTooSmallException {
+                       byte blockType = entry.blockType();
+                       int bs = out.bytesAvailableInBlock();
+                       cur = new BlockWriter(blockType, idx.keyType, bs, restartInterval);
+                       cur.mustAdd(entry);
+               }
+
+               void flushCurBlock() throws IOException {
+                       idx.entries.add(new IndexEntry(cur.lastKey(), out.size()));
+                       cur.writeTo(out);
+               }
+
+               void finishSectionMaybeWriteIndex() throws IOException {
+                       flushCurBlock();
+                       cur = null;
+                       if (shouldHaveIndex(idx)) {
+                               idx.writeIndex();
+                       }
+                       bytes = out.size() - firstBlockPosition;
+               }
+       }
+
+       private class IndexBuilder {
+               final byte keyType;
+               List<IndexEntry> entries = new ArrayList<>();
+               long rootPosition;
+               int bytes;
+               int levels;
+
+               IndexBuilder(byte kt) {
+                       keyType = kt;
+               }
+
+               int estimateBytes(long curBlockPos) {
+                       BlockWriter b = new BlockWriter(
+                                       INDEX_BLOCK_TYPE, keyType,
+                                       MAX_BLOCK_SIZE,
+                                       Math.max(restartInterval, entries.size() / MAX_RESTARTS));
+                       try {
+                               for (Entry e : entries) {
+                                       b.mustAdd(e);
+                               }
+                               if (cur != null) {
+                                       b.mustAdd(new IndexEntry(cur.lastKey(), curBlockPos));
+                               }
+                       } catch (BlockSizeTooSmallException e) {
+                               return b.currentSize();
+                       }
+                       return b.currentSize();
+               }
+
+               void writeIndex() throws IOException {
+                       if (padBetweenBlocks(keyType)) {
+                               out.padBetweenBlocksToNextBlock();
+                       }
+                       long startPos = out.size();
+                       writeMultiLevelIndex(entries);
+                       bytes = (int) (out.size() - startPos);
+                       entries = null;
+               }
+
+               private void writeMultiLevelIndex(List<IndexEntry> keys)
+                               throws IOException {
+                       levels = 1;
+                       while (maxIndexLevels == 0 || levels < maxIndexLevels) {
+                               keys = writeOneLevel(keys);
+                               if (keys == null) {
+                                       return;
+                               }
+                               levels++;
+                       }
+
+                       // When maxIndexLevels has restricted the writer, write one
+                       // index block with the entire remaining set of keys.
+                       BlockWriter b = new BlockWriter(
+                                       INDEX_BLOCK_TYPE, keyType,
+                                       MAX_BLOCK_SIZE,
+                                       Math.max(restartInterval, keys.size() / MAX_RESTARTS));
+                       for (Entry e : keys) {
+                               b.mustAdd(e);
+                       }
+                       rootPosition = out.size();
+                       b.writeTo(out);
+               }
+
+               private List<IndexEntry> writeOneLevel(List<IndexEntry> keys)
+                               throws IOException {
+                       Section thisLevel = new Section(keyType);
+                       for (Entry e : keys) {
+                               thisLevel.write(e);
+                       }
+                       if (!thisLevel.idx.entries.isEmpty()) {
+                               thisLevel.flushCurBlock();
+                               if (cur.padBetweenBlocks()) {
+                                       out.padBetweenBlocksToNextBlock();
+                               }
+                               cur = null;
+                               return thisLevel.idx.entries;
+                       }
+
+                       // The current block fit entire level; make it the root.
+                       rootPosition = out.size();
+                       cur.writeTo(out);
+                       cur = null;
+                       return null;
+               }
+       }
+}