[GitHub] [arrow] coryan commented on a change in pull request #11976: ARROW-15115: [C++] GcsFileSystem return errors if using closed streams

[GitBox]

coryan commented on a change in pull request #11976:
URL: https://github.com/apache/arrow/pull/11976#discussion_r772359773



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File path: cpp/src/arrow/filesystem/gcsfs.cc
##########
@@ -96,28 +96,29 @@ class GcsInputStream : public arrow::io::InputStream {
   // @name FileInterface
   Status Close() override {
     stream_.Close();
+    closed_ = true;
     return Status::OK();
   }
 
   Result<int64_t> Tell() const override {
-    if (!stream_) {
-      return Status::IOError("invalid stream");
-    }
+    if (closed()) return Status::Invalid("Cannot use Tell() on a closed 
stream");
     return stream_.tellg() + offset_;
   }
 
-  bool closed() const override { return !stream_.IsOpen(); }
+  bool closed() const override { return closed_ && !stream_.IsOpen(); }

Review comment:
       Yes.  zero-length objects are "born closed" in `google-cloud-cpp`.  
Probably a bug (or at least a very poorly thought API), but you can `read()` 
from them, while they  return `IsOpen() == false`.




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