From 1af7aa891910131a6a6012ef156510609417bd5e Mon Sep 17 00:00:00 2001
From: Ivan Frade <ifrade@google.com>
Date: Tue, 17 Sep 2024 13:50:59 -0700
Subject: [PATCH] DfsReader: Fallback to regular size read if size index throws

The reader can get IOException when reading the object size index, but
that index is an optimization, the size should still be available in
the pack.

Use the regular #getObjectSize() as a fallback when we get an
IOException from the object size index.

Change-Id: Ic5ec2cfc7c698aa94c6cfd5960cbab6c129f595a
---
 .../jgit/internal/storage/dfs/DfsReader.java  | 61 +++++++++++++++----
 1 file changed, 48 insertions(+), 13 deletions(-)

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsReader.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsReader.java
index 9cfcbaa5f7..62f6753e5d 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsReader.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsReader.java
@@ -511,18 +511,15 @@ public class DfsReader extends ObjectReader implements ObjectReuseAsIs {
 			throw new MissingObjectException(objectId.copy(), typeHint);
 		}
 
-		if (typeHint != Constants.OBJ_BLOB || !pack.hasObjectSizeIndex(this)) {
+		if (typeHint != Constants.OBJ_BLOB || !safeHasObjectSizeIndex(pack)) {
 			return pack.getObjectSize(this, objectId);
 		}
 
-		long sz = pack.getIndexedObjectSize(this, objectId);
+		Optional<Long> maybeSz = safeGetIndexedObjectSize(pack, objectId);
+		long sz = maybeSz.orElse(-1L);
 		if (sz >= 0) {
-			stats.objectSizeIndexHit += 1;
 			return sz;
 		}
-
-		// Object wasn't in the index
-		stats.objectSizeIndexMiss += 1;
 		return pack.getObjectSize(this, objectId);
 	}
 
@@ -541,23 +538,61 @@ public class DfsReader extends ObjectReader implements ObjectReuseAsIs {
 		}
 
 		stats.isNotLargerThanCallCount += 1;
-		if (typeHint != Constants.OBJ_BLOB || !pack.hasObjectSizeIndex(this)) {
+		if (typeHint != Constants.OBJ_BLOB || !safeHasObjectSizeIndex(pack)) {
+			return pack.getObjectSize(this, objectId) <= limit;
+		}
+
+		Optional<Long> maybeSz = safeGetIndexedObjectSize(pack, objectId);
+		if (maybeSz.isEmpty()) {
+			// Exception in object size index
 			return pack.getObjectSize(this, objectId) <= limit;
 		}
 
-		long sz = pack.getIndexedObjectSize(this, objectId);
+		long sz = maybeSz.get();
+		if (sz >= 0) {
+			return sz <= limit;
+		}
+
+		if (isLimitInsideIndexThreshold(pack, limit)) {
+			// With threshold T, not-found means object < T
+			// If limit L > T, then object < T < L
+			return true;
+		}
+
+		return pack.getObjectSize(this, objectId) <= limit;
+	}
+
+	private boolean safeHasObjectSizeIndex(DfsPackFile pack) {
+		try {
+			return pack.hasObjectSizeIndex(this);
+		} catch (IOException e) {
+			return false;
+		}
+	}
+
+	private Optional<Long> safeGetIndexedObjectSize(DfsPackFile pack,
+			AnyObjectId objectId) {
+		long sz;
+		try {
+			sz = pack.getIndexedObjectSize(this, objectId);
+		} catch (IOException e) {
+			// Do not count the exception as an index miss
+			return Optional.empty();
+		}
 		if (sz < 0) {
 			stats.objectSizeIndexMiss += 1;
 		} else {
 			stats.objectSizeIndexHit += 1;
 		}
+		return Optional.of(sz);
+	}
 
-		// Got size from index or we didn't but we are sure it should be there.
-		if (sz >= 0 || pack.getObjectSizeIndexThreshold(this) <= limit) {
-			return sz <= limit;
+	private boolean isLimitInsideIndexThreshold(DfsPackFile pack, long limit) {
+		try {
+			return pack.getObjectSizeIndexThreshold(this) <= limit;
+		} catch (IOException e) {
+			return false;
 		}
-
-		return pack.getObjectSize(this, objectId) <= limit;
 	}
 
 	private DfsPackFile findPackWithObject(AnyObjectId objectId)
-- 
2.39.5