Make possible to overwrite the object count

Right now, PackParser relies on the object count from the pack header.
However, when creating Dfs INSERT packs, the object count is not known
at the beginning of the operation. And when we append the base to a
RECEIVE pack, we can't modify the pack header for object count in most
Dfs implementations.

Make it possible to tell PackParser the expected object count by adding
a setter for expectedObjectCount, implementation can overwrite the
object count in onPackHeader function.

Change-Id: I646ca33ab2b843de84edc287abfb65803a56a927
Signed-off-by: Zhen Chen <czhen@google.com>

org.eclipse.jgit/src/org/eclipse/jgit/transport/PackParser.java

@@ -143,7 +143,7 @@ public abstract class PackParser {
 
 	private boolean expectDataAfterPackFooter;
 
-	private long objectCount;
+	private long expectedObjectCount;
 
 	private PackedObjectInfo[] entries;
 
@@ -525,15 +525,15 @@ public abstract class PackParser {
 		try {
 			readPackHeader();
 
-			entries = new PackedObjectInfo[(int) objectCount];
+			entries = new PackedObjectInfo[(int) expectedObjectCount];
 			baseById = new ObjectIdOwnerMap<>();
 			baseByPos = new LongMap<>();
 			collisionCheckObjs = new BlockList<>();
 
 			receiving.beginTask(JGitText.get().receivingObjects,
-					(int) objectCount);
+					(int) expectedObjectCount);
 			try {
-				for (int done = 0; done < objectCount; done++) {
+				for (int done = 0; done < expectedObjectCount; done++) {
 					indexOneObject();
 					receiving.update(1);
 					if (receiving.isCancelled())
@@ -557,19 +557,19 @@ public abstract class PackParser {
 				}
 				resolving.beginTask(JGitText.get().resolvingDeltas, deltaCount);
 				resolveDeltas(resolving);
-				if (entryCount < objectCount) {
+				if (entryCount < expectedObjectCount) {
 					if (!isAllowThin()) {
 						throw new IOException(MessageFormat.format(
 								JGitText.get().packHasUnresolvedDeltas,
-								Long.valueOf(objectCount - entryCount)));
+								Long.valueOf(expectedObjectCount - entryCount)));
 					}
 
 					resolveDeltasWithExternalBases(resolving);
 
-					if (entryCount < objectCount) {
+					if (entryCount < expectedObjectCount) {
 						throw new IOException(MessageFormat.format(
 								JGitText.get().packHasUnresolvedDeltas,
-								Long.valueOf(objectCount - entryCount)));
+								Long.valueOf(expectedObjectCount - entryCount)));
 					}
 				}
 				resolving.endTask();
@@ -878,7 +878,7 @@ public abstract class PackParser {
 	private void growEntries(int extraObjects) {
 		final PackedObjectInfo[] ne;
 
-		ne = new PackedObjectInfo[(int) objectCount + extraObjects];
+		ne = new PackedObjectInfo[(int) expectedObjectCount + extraObjects];
 		System.arraycopy(entries, 0, ne, 0, entryCount);
 		entries = ne;
 	}
@@ -901,9 +901,9 @@ public abstract class PackParser {
 		if (vers != 2 && vers != 3)
 			throw new IOException(MessageFormat.format(
 					JGitText.get().unsupportedPackVersion, Long.valueOf(vers)));
-		objectCount = NB.decodeUInt32(buf, p + 8);
+		final long objectCount = NB.decodeUInt32(buf, p + 8);
 		use(hdrln);
-
+		setExpectedObjectCount(objectCount);
 		onPackHeader(objectCount);
 	}
 
@@ -1260,6 +1260,22 @@ public abstract class PackParser {
 		return oe;
 	}
 
+	/**
+	 * Set the expected number of objects in the pack stream.
+	 * <p>
+	 * The object count in the pack header is not always correct for some Dfs
+	 * pack files. e.g. INSERT pack always assume 1 object in the header since
+	 * the actual object count is unknown when the pack is written.
+	 * <p>
+	 * If external implementation wants to overwrite the expectedObjectCount,
+	 * they should call this method during {@link #onPackHeader(long)}.
+	 *
+	 * @param expectedObjectCount
+	 */
+	protected void setExpectedObjectCount(long expectedObjectCount) {
+		this.expectedObjectCount = expectedObjectCount;
+	}
+
 	/**
 	 * Store bytes received from the raw stream.
 	 * <p>