test: add integration to verify behavior of reader with effective len…

…gth <= 0 (#1988)

StorageReadChannel is able to detect when an effective read length is <= 0 and will return EOF without sending an RPC.

If we ever return object metadata along with a read, we will need to amend this behavior so that the metadata can be resolved.

google-cloud-storage/src/test/java/com/google/cloud/storage/it/ITStorageReadChannelTest.java

@@ -40,9 +40,14 @@
 import com.google.cloud.storage.it.runner.annotations.CrossRun;
 import com.google.cloud.storage.it.runner.annotations.Inject;
 import com.google.cloud.storage.it.runner.registry.Generator;
+import com.google.cloud.storage.it.runner.registry.ObjectsFixture;
+import com.google.common.io.ByteStreams;
+import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.nio.ByteBuffer;
+import java.nio.channels.Channels;
 import java.nio.channels.ReadableByteChannel;
+import java.nio.channels.WritableByteChannel;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.TimeUnit;
 import java.util.function.Function;
@@ -61,6 +66,8 @@ public final class ITStorageReadChannelTest {
 
   @Inject public Generator generator;
 
+  @Inject public ObjectsFixture objectsFixture;
+
   @Test
   public void storageReadChannel_getObject_returns() throws Exception {
     int _512KiB = 512 * 1024;
@@ -109,7 +116,6 @@ public void storageReadChannel_getObject_returns() throws Exception {
   }
 
   @Test
-  // @CrossRun.Exclude(transports = Transport.GRPC)
   public void storageReadChannel_shouldAllowDisablingBufferingBySettingChunkSize_lteq0()
       throws IOException {
     int _512KiB = 512 * 1024;
@@ -137,6 +143,21 @@ public void storageReadChannel_shouldAllowDisablingBufferingBySettingChunkSize_l
     }
   }
 
+  @Test
+  public void storageReadChannel_attemptToReadZeroBytes() throws IOException {
+    BlobInfo info1 = objectsFixture.getInfo1();
+    try (ReadChannel r = storage.reader(info1.getBlobId());
+        ByteArrayOutputStream baos = new ByteArrayOutputStream();
+        WritableByteChannel w = Channels.newChannel(baos)) {
+      r.setChunkSize(10);
+      r.seek(10);
+      r.limit(10);
+
+      ByteStreams.copy(r, w);
+      assertThat(baos.toByteArray()).isEmpty();
+    }
+  }
+
   @Test
   public void storageReadChannel_getObject_404() {
     BlobId id = BlobId.of(bucket.getName(), generator.randomObjectName());