chore: update BlobDescriptorStream logic to prevent over-read if more bytes are returned than requested

BenWhitehead · BenWhitehead · commit cbc22f22f27f · 2025-03-14T16:47:39.000-04:00
diff --git a/google-cloud-storage/src/main/java/com/google/cloud/storage/BlobDescriptorStream.java b/google-cloud-storage/src/main/java/com/google/cloud/storage/BlobDescriptorStream.java
@@ -281,8 +281,21 @@ public void onResponse(BidiReadObjectResponse response) {
           long begin = readRange.getReadOffset();
           long position = read.getReadCursor().position();
           if (begin == position) {
-            ChildRef childRef =
-                handle.borrow(r -> r.getObjectDataRanges(idx).getChecksummedData().getContent());
+            long remaining = read.getReadCursor().remaining();
+            int contentSize = content.size();
+            ChildRef childRef;
+            if (remaining >= contentSize) {
+              childRef =
+                  handle.borrow(r -> r.getObjectDataRanges(idx).getChecksummedData().getContent());
+            } else {
+              childRef =
+                  handle.borrow(
+                      r ->
+                          r.getObjectDataRanges(idx)
+                              .getChecksummedData()
+                              .getContent()
+                              .substring(0, Math.toIntExact(remaining)));
+            }
             read.accept(childRef);
           } else if (begin < position) {
             int skip = Math.toIntExact(position - begin);
diff --git a/google-cloud-storage/src/test/java/com/google/cloud/storage/ITBlobDescriptorFakeTest.java b/google-cloud-storage/src/test/java/com/google/cloud/storage/ITBlobDescriptorFakeTest.java
@@ -704,6 +704,31 @@ public void retrySettingsApplicable_objectRangeData_offset_notAligned_gt() throw
     }
   }
 
+  @Test
+  public void moreBytesReturnedThanRequested_onlyForwardsRequestedBytes() throws Exception {
+
+    ChecksummedTestContent expected = ChecksummedTestContent.of(ALL_OBJECT_BYTES, 10, 20);
+    ChecksummedTestContent content2 = ChecksummedTestContent.of(ALL_OBJECT_BYTES, 10, 21);
+    BidiReadObjectRequest req2 = read(1, 10, 20);
+    BidiReadObjectResponse res2 =
+        BidiReadObjectResponse.newBuilder()
+            .addObjectDataRanges(
+                ObjectRangeData.newBuilder()
+                    .setChecksummedData(content2.asChecksummedData())
+                    .setReadRange(getReadRange(1, 10, content2))
+                    .setRangeEnd(true)
+                    .build())
+            .build();
+
+    ImmutableMap<BidiReadObjectRequest, BidiReadObjectResponse> db =
+        ImmutableMap.<BidiReadObjectRequest, BidiReadObjectResponse>builder()
+            .put(REQ_OPEN, RES_OPEN)
+            .put(req2, res2)
+            .buildOrThrow();
+
+    runTestAgainstFakeServer(FakeStorage.from(db), RangeSpec.of(10, 20), expected);
+  }
+
   private static void runTestAgainstFakeServer(
       FakeStorage fakeStorage, RangeSpec range, ChecksummedTestContent expected) throws Exception {
 
