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/*
* Copyright (C) 2025, Google LLC
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Distribution License v. 1.0 which is available at
* https://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
package org.eclipse.jgit.internal.storage.midx;
import static org.eclipse.jgit.internal.storage.midx.MultiPackIndexConstants.CHUNK_LOOKUP_WIDTH;
import static org.eclipse.jgit.internal.storage.midx.MultiPackIndexConstants.MIDX_CHUNKID_OBJECTOFFSETS;
import static org.eclipse.jgit.internal.storage.midx.MultiPackIndexConstants.MIDX_CHUNKID_OIDFANOUT;
import static org.eclipse.jgit.internal.storage.midx.MultiPackIndexConstants.MIDX_CHUNKID_OIDLOOKUP;
import static org.eclipse.jgit.internal.storage.midx.MultiPackIndexConstants.MIDX_CHUNKID_PACKNAMES;
import static org.junit.Assert.assertArrayEquals;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.eclipse.jgit.internal.storage.file.Pack;
import org.eclipse.jgit.internal.storage.file.PackFile;
import org.eclipse.jgit.internal.storage.file.PackIndex;
import org.eclipse.jgit.internal.storage.pack.PackExt;
import org.eclipse.jgit.lib.NullProgressMonitor;
import org.eclipse.jgit.test.resources.SampleDataRepositoryTestCase;
import org.eclipse.jgit.util.NB;
import org.junit.Test;
public class CgitMidxCompatibilityTest extends SampleDataRepositoryTestCase {
@Test
public void jgitMidx_verifyByCgit()
throws IOException, InterruptedException {
byte[] jgitMidxBytes = generateJGitMidx();
writeMidx(jgitMidxBytes);
assertEquals("cgit exit code", 0, run_cgit_multipackindex_verify());
}
@Test
public void compareBasicChunkSizes()
throws IOException, InterruptedException {
// We cannot compare byte-by-byte because there are optional chunks and
// it is not guaranteed what cgit and jgit will generate
byte[] jgitMidxBytes = generateJGitMidx();
assertEquals("cgit exit code", 0, run_cgit_multipackindex_write());
byte[] cgitMidxBytes = readCgitMidx();
RawMultiPackIndex jgitMidx = new RawMultiPackIndex(jgitMidxBytes);
RawMultiPackIndex cgitMidx = new RawMultiPackIndex(cgitMidxBytes);
// This is a fixed sized chunk
assertEquals(256 * 4, cgitMidx.getChunkSize(MIDX_CHUNKID_OIDFANOUT));
assertArrayEquals(cgitMidx.getRawChunk(MIDX_CHUNKID_OIDFANOUT),
jgitMidx.getRawChunk(MIDX_CHUNKID_OIDFANOUT));
assertArrayEquals(cgitMidx.getRawChunk(MIDX_CHUNKID_OIDLOOKUP),
jgitMidx.getRawChunk(MIDX_CHUNKID_OIDLOOKUP));
// The spec has changed from padding packnames to a multile of four, to
// move the packname chunk to the end of the file.
// git 2.48 pads the packs names to a multiple of 4
// jgit puts the chunk at the end
byte[] cgitPacknames = trimPadding(
cgitMidx.getRawChunk(MIDX_CHUNKID_PACKNAMES));
assertArrayEquals(cgitPacknames,
jgitMidx.getRawChunk(MIDX_CHUNKID_PACKNAMES));
assertArrayEquals(cgitMidx.getRawChunk(MIDX_CHUNKID_OBJECTOFFSETS),
jgitMidx.getRawChunk(MIDX_CHUNKID_OBJECTOFFSETS));
}
@Test
public void jgit_loadsCgitMidx()
throws IOException, InterruptedException {
assertEquals("cgit exit code", 0, run_cgit_multipackindex_write());
byte[] cgitMidxBytes = readCgitMidx();
MultiPackIndex midx = MultiPackIndexLoader
.read(new ByteArrayInputStream(cgitMidxBytes));
assertEquals(7, midx.getPackNames().length);
}
private byte[] generateJGitMidx() throws IOException {
Map<String, PackIndex> indexes = new HashMap<>();
for (Pack pack : db.getObjectDatabase().getPacks()) {
PackFile packFile = pack.getPackFile().create(PackExt.INDEX);
indexes.put(packFile.getName(), pack.getIndex());
}
MultiPackIndexWriter writer = new MultiPackIndexWriter();
ByteArrayOutputStream out = new ByteArrayOutputStream();
writer.write(NullProgressMonitor.INSTANCE, out, indexes);
return out.toByteArray();
}
private int run_cgit_multipackindex_write()
throws IOException, InterruptedException {
String[] command = new String[] { "git", "multi-pack-index", "write" };
Process proc = Runtime.getRuntime().exec(command, new String[0],
db.getDirectory());
return proc.waitFor();
}
private int run_cgit_multipackindex_verify()
throws IOException, InterruptedException {
String[] command = new String[] { "git", "multi-pack-index", "verify" };
Process proc = Runtime.getRuntime().exec(command, new String[0],
db.getDirectory());
return proc.waitFor();
}
private byte[] readCgitMidx() throws IOException {
File midx = getMIdxStandardLocation();
assertTrue("cgit multi-pack-index exists", midx.exists());
return Files.readAllBytes(midx.toPath());
}
private void writeMidx(byte[] midx) throws IOException {
File midxFile = getMIdxStandardLocation();
Files.write(midxFile.toPath(), midx);
}
private File getMIdxStandardLocation() {
return new File(db.getObjectDatabase().getPackDirectory(),
"multi-pack-index");
}
private byte[] trimPadding(byte[] data) {
// Chunk MUST have one \0, we want to remove any extra \0
int newEnd = data.length - 1;
while (newEnd - 1 >= 0 && data[newEnd - 1] == 0) {
newEnd--;
}
if (newEnd == data.length - 1) {
return data;
}
return Arrays.copyOfRange(data, 0, newEnd + 1);
}
private static class RawMultiPackIndex {
private final List<ChunkSegment> chunks;
private final byte[] midx;
private RawMultiPackIndex(byte[] midx) {
this.chunks = readChunks(midx);
this.midx = midx;
}
long getChunkSize(int chunkId) {
int chunkPos = findChunkPosition(chunks, chunkId);
return chunks.get(chunkPos + 1).offset
- chunks.get(chunkPos).offset;
}
long getOffset(int chunkId) {
return chunks.get(findChunkPosition(chunks, chunkId)).offset;
}
private long getNextOffset(int chunkId) {
return chunks.get(findChunkPosition(chunks, chunkId) + 1).offset;
}
byte[] getRawChunk(int chunkId) {
int start = (int) getOffset(chunkId);
int end = (int) getNextOffset(chunkId);
return Arrays.copyOfRange(midx, start, end);
}
private static int findChunkPosition(List<ChunkSegment> chunks,
int id) {
int chunkPos = -1;
for (int i = 0; i < chunks.size(); i++) {
if (chunks.get(i).id() == id) {
chunkPos = i;
break;
}
}
if (chunkPos == -1) {
throw new IllegalStateException("Chunk doesn't exist");
}
return chunkPos;
}
private List<ChunkSegment> readChunks(byte[] midx) {
// Read the number of "chunkOffsets" (1 byte)
int chunkCount = midx[6];
byte[] lookupBuffer = new byte[CHUNK_LOOKUP_WIDTH
* (chunkCount + 1)];
System.arraycopy(midx, 12, lookupBuffer, 0, lookupBuffer.length);
List<ChunkSegment> chunks = new ArrayList<>(chunkCount + 1);
for (int i = 0; i <= chunkCount; i++) {
// chunks[chunkCount] is just a marker, in order to record the
// length of the last chunk.
int id = NB.decodeInt32(lookupBuffer, i * 12);
long offset = NB.decodeInt64(lookupBuffer, i * 12 + 4);
chunks.add(new ChunkSegment(id, offset));
}
return chunks;
}
}
private record ChunkSegment(int id, long offset) {
}
}
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