chore: remove cumulative crc32c check on GapicUnbufferedReadableByteChannel (#1903)

Cumulative crc32c check is only applicable to an initial offset of 0 because the
crc32c value return for a resource is for the entire resource. Instead, we continue
to perform the crc32c integrity check for each ChecksummedData which is always for the
bytes it is packed with.

Author: BenWhitehead

google-cloud-storage/src/main/java/com/google/cloud/storage/GapicUnbufferedReadableByteChannel.java

@@ -27,7 +27,6 @@
 import com.google.cloud.storage.UnbufferedReadableByteChannelSession.UnbufferedReadableByteChannel;
 import com.google.storage.v2.ChecksummedData;
 import com.google.storage.v2.Object;
-import com.google.storage.v2.ObjectChecksums;
 import com.google.storage.v2.ReadObjectRequest;
 import com.google.storage.v2.ReadObjectResponse;
 import java.io.Closeable;
@@ -50,12 +49,9 @@ final class GapicUnbufferedReadableByteChannel
 
   private boolean open = true;
   private boolean complete = false;
-  private boolean ioExceptionAlreadyThrown = false;
   private long blobOffset;
-  private Crc32cLengthKnown cumulativeCrc32c;
 
   private Object metadata;
-  private ObjectChecksums objectChecksums;
 
   private ByteBuffer leftovers;
 
@@ -110,30 +106,16 @@ public long read(ByteBuffer[] dsts, int offset, int length) throws IOException {
             result.set(metadata);
           }
         }
-        if (resp.hasObjectChecksums()) {
-          ObjectChecksums checksums = resp.getObjectChecksums();
-          if (this.objectChecksums == null) {
-            this.objectChecksums = checksums;
-          } else if (!objectChecksums.equals(checksums)) {
-            throw closeWithError(
-                String.format(
-                    "Mismatch checksums between subsequent reads. Expected %s but received %s",
-                    Crc32cValue.fmtCrc32cValue(objectChecksums.getCrc32C()),
-                    Crc32cValue.fmtCrc32cValue(checksums.getCrc32C())));
-          }
-        }
         ChecksummedData checksummedData = resp.getChecksummedData();
         ByteBuffer content = checksummedData.getContent().asReadOnlyByteBuffer();
         // very important to know whether a crc32c value is set. Without checking, protobuf will
         // happily return 0, which is a valid crc32c value.
         if (checksummedData.hasCrc32C()) {
           Crc32cLengthKnown expected =
               Crc32cValue.of(checksummedData.getCrc32C(), checksummedData.getContent().size());
-          cumulativeCrc32c = hasher.nullSafeConcat(cumulativeCrc32c, expected);
           try {
             hasher.validate(expected, content::duplicate);
           } catch (IOException e) {
-            ioExceptionAlreadyThrown = true;
             close();
             throw e;
           }
@@ -161,18 +143,6 @@ public boolean isOpen() {
 
   @Override
   public void close() throws IOException {
-    if (!ioExceptionAlreadyThrown
-        && cumulativeCrc32c != null
-        && objectChecksums != null
-        && objectChecksums.hasCrc32C()) {
-      Crc32cLengthKnown expected = Crc32cValue.of(objectChecksums.getCrc32C(), metadata.getSize());
-      if (!expected.eqValue(cumulativeCrc32c)) {
-        throw new IOException(
-            String.format(
-                "Mismatch checksum value. Expected %s actual %s",
-                expected.debugString(), cumulativeCrc32c.debugString()));
-      }
-    }
     open = false;
     iter.close();
   }
@@ -187,7 +157,6 @@ private void copy(ReadCursor c, ByteBuffer content, ByteBuffer[] dsts, int offse
   }
 
   private IOException closeWithError(String message) throws IOException {
-    ioExceptionAlreadyThrown = true;
     close();
     StorageException cause =
         new StorageException(HttpStatusCodes.STATUS_CODE_PRECONDITION_FAILED, message);

google-cloud-storage/src/test/java/com/google/cloud/storage/GapicUnbufferedReadableByteChannelTest.java

@@ -271,46 +271,6 @@ public void readObject(
     }
   }
 
-  @Test
-  public void ioException_if_crc32c_mismatch_cumulative() throws IOException, InterruptedException {
-    StorageGrpc.StorageImplBase fakeStorage =
-        new StorageGrpc.StorageImplBase() {
-          @Override
-          public void readObject(
-              ReadObjectRequest request, StreamObserver<ReadObjectResponse> responseObserver) {
-            if (request.equals(req1)) {
-              responseObserver.onNext(resp1);
-              responseObserver.onCompleted();
-            } else {
-              responseObserver.onError(apiException(Code.PERMISSION_DENIED));
-            }
-          }
-        };
-    try (FakeServer server = FakeServer.of(fakeStorage);
-        StorageClient storageClient = StorageClient.create(server.storageSettings())) {
-
-      UnbufferedReadableByteChannelSession<Object> session =
-          new UnbufferedReadSession<>(
-              ApiFutures.immediateFuture(req1),
-              (start, resultFuture) ->
-                  new GapicUnbufferedReadableByteChannel(
-                      resultFuture,
-                      storageClient
-                          .readObjectCallable()
-                          .withDefaultCallContext(
-                              contextWithRetryForCodes(StatusCode.Code.DATA_LOSS)),
-                      start,
-                      Hasher.enabled()));
-      byte[] actualBytes = new byte[40];
-      //noinspection resource
-      UnbufferedReadableByteChannel c = session.open();
-      c.read(ByteBuffer.wrap(actualBytes));
-
-      IOException ioException = assertThrows(IOException.class, c::close);
-      assertThat(ioException).hasMessageThat().contains("Mismatch checksum");
-    }
-  }
-
   @Test
   public void overRead_handledProperly() throws IOException, InterruptedException {
     StorageGrpc.StorageImplBase fakeStorage =