reftable: enforce ordering for ref and log writes

Previously, the API did not enforce ordering of writes.  Misuse of
this API would lead to data effectively being lost.

Guard against that with IllegalArgumentException, and add a test.

Change-Id: I04f55c481d60532fc64d35fa32c47037a03988ae
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>

1 files changed, 24 insertions, 2 deletions

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
index f8b9ffd176..726339617d 100644
--- 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
@@ -44,6 +44,7 @@
 package org.eclipse.jgit.internal.storage.reftable;
 
 import static java.lang.Math.log;
+import static java.nio.charset.StandardCharsets.UTF_8;
 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;
@@ -108,6 +109,8 @@ public class ReftableWriter {
 	private ReftableOutputStream out;
 	private ObjectIdSubclassMap<RefList> obj2ref;
 
+	private BlockWriter.Entry lastRef;
+	private BlockWriter.Entry lastLog;
 	private BlockWriter cur;
 	private Section refs;
 	private Section objs;
@@ -120,6 +123,8 @@ public class ReftableWriter {
 	 */
 	public ReftableWriter() {
 		this(new ReftableConfig());
+		lastRef = null;
+		lastLog = null;
 	}
 
 	/**
@@ -269,10 +274,22 @@ public class ReftableWriter {
 			throw new IllegalArgumentException();
 		}
 		long d = updateIndex - minUpdateIndex;
-		long blockPos = refs.write(new RefEntry(ref, d));
+		RefEntry entry = new RefEntry(ref, d);
+		if (lastRef != null && Entry.compare(lastRef, entry) >= 0) {
+			throwIllegalEntry(lastRef, entry);
+		}
+		lastRef = entry;
+
+		long blockPos = refs.write(entry);
 		indexRef(ref, blockPos);
 	}
 
+	private void throwIllegalEntry(Entry last, Entry now) {
+		throw new IllegalArgumentException(
+			String.format("records must be increasing: last %s, this %s",
+				new String(last.key, UTF_8), new String(now.key, UTF_8)));
+	}
+
 	private void indexRef(Ref ref, long blockPos) {
 		if (indexObjects && !ref.isSymbolic()) {
 			indexId(ref.getObjectId(), blockPos);
@@ -322,7 +339,12 @@ public class ReftableWriter {
 					throws IOException {
 		String msg = message != null ? message : ""; //$NON-NLS-1$
 		beginLog();
-		logs.write(new LogEntry(ref, updateIndex, who, oldId, newId, msg));
+		LogEntry entry = new LogEntry(ref, updateIndex, who, oldId, newId, msg);
+		if (lastLog != null && Entry.compare(lastLog, entry) >= 0) {
+			throwIllegalEntry(lastLog, entry);
+		}
+		lastLog = entry;
+		logs.write(entry);
 	}
 
 	/**